source: git/src/gfxcore.cc @ 9c37beb

//
//  gfxcore.cc
//
//  Core drawing code for Aven.
//
//  Copyright (C) 2000-2003,2005,2006 Mark R. Shinwell
//  Copyright (C) 2001-2003,2004,2005,2006,2007,2010,2011 Olly Betts
//  Copyright (C) 2005 Martin Green
//
//  This program is free software; you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation; either version 2 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program; if not, write to the Free Software
//  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
//

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <assert.h>
#include <float.h>

#include "aven.h"
#include "date.h"
#include "gfxcore.h"
#include "mainfrm.h"
#include "message.h"
#include "useful.h"
#include "printwx.h"
#include "guicontrol.h"
#include "moviemaker.h"

#include <wx/confbase.h>
#include <wx/image.h>

#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define MAX3(a, b, c) ((a) > (b) ? MAX(a, c) : MAX(b, c))

// Values for m_SwitchingTo
#define PLAN 1
#define ELEVATION 2
#define NORTH 3
#define EAST 4
#define SOUTH 5
#define WEST 6

// Any error value higher than this is clamped to this.
#define MAX_ERROR 12.0

// How many bins per letter height to use when working out non-overlapping
// labels.
const unsigned int QUANTISE_FACTOR = 2;

#include "avenpal.h"

static const int COMPASS_OFFSET_X = 60;
static const int COMPASS_OFFSET_Y = 80;
static const int INDICATOR_BOX_SIZE = 60;
static const int INDICATOR_GAP = 2;
static const int INDICATOR_MARGIN = 5;
static const int INDICATOR_OFFSET_X = 15;
static const int INDICATOR_OFFSET_Y = 15;
static const int INDICATOR_RADIUS = INDICATOR_BOX_SIZE / 2 - INDICATOR_MARGIN;
static const int CLINO_OFFSET_X = 6 + INDICATOR_OFFSET_X +
                                  INDICATOR_BOX_SIZE + INDICATOR_GAP;
static const int COLOUR_KEY_OFFSET_X = 16;
static const int COLOUR_KEY_OFFSET_Y = 16;
static const int COLOUR_KEY_EXTRA_LEFT_MARGIN = 2;
static const int COLOUR_KEY_BLOCK_WIDTH = 20;
static const int COLOUR_KEY_BLOCK_HEIGHT = 16;
static const int COLOUR_KEY_MARGIN = 6;
static const int TICK_LENGTH = 4;
static const int SCALE_BAR_OFFSET_X = 15;
static const int SCALE_BAR_OFFSET_Y = 12;
static const int SCALE_BAR_HEIGHT = 12;

static const gla_colour TEXT_COLOUR = col_GREEN;
static const gla_colour HERE_COLOUR = col_WHITE;
static const gla_colour NAME_COLOUR = col_GREEN;

#define HITTEST_SIZE 20

// vector for lighting angle
static const Vector3 light(.577, .577, .577);

BEGIN_EVENT_TABLE(GfxCore, wxGLCanvas)
    EVT_PAINT(GfxCore::OnPaint)
    EVT_LEFT_DOWN(GfxCore::OnLButtonDown)
    EVT_LEFT_UP(GfxCore::OnLButtonUp)
    EVT_MIDDLE_DOWN(GfxCore::OnMButtonDown)
    EVT_MIDDLE_UP(GfxCore::OnMButtonUp)
    EVT_RIGHT_DOWN(GfxCore::OnRButtonDown)
    EVT_RIGHT_UP(GfxCore::OnRButtonUp)
    EVT_MOUSEWHEEL(GfxCore::OnMouseWheel)
    EVT_MOTION(GfxCore::OnMouseMove)
    EVT_LEAVE_WINDOW(GfxCore::OnLeaveWindow)
    EVT_SIZE(GfxCore::OnSize)
    EVT_IDLE(GfxCore::OnIdle)
    EVT_CHAR(GfxCore::OnKeyPress)
END_EVENT_TABLE()

GfxCore::GfxCore(MainFrm* parent, wxWindow* parent_win, GUIControl* control) :
    GLACanvas(parent_win, 100),
    m_Scale(0.0),
    m_ScaleBarWidth(0),
    m_Control(control),
    m_LabelGrid(NULL),
    m_Parent(parent),
    m_DoneFirstShow(false),
    m_TiltAngle(0.0),
    m_PanAngle(0.0),
    m_Rotating(false),
    m_RotationStep(0.0),
    m_SwitchingTo(0),
    m_Crosses(false),
    m_Legs(true),
    m_Names(false),
    m_Scalebar(true),
    m_ColourKey(true),
    m_OverlappingNames(false),
    m_Compass(true),
    m_Clino(true),
    m_Tubes(false),
    m_XSize(0),
    m_YSize(0),
    m_ColourBy(COLOUR_BY_DEPTH),
    m_HaveData(false),
    m_MouseOutsideCompass(false),
    m_MouseOutsideElev(false),
    m_Surface(false),
    m_Entrances(false),
    m_FixedPts(false),
    m_ExportedPts(false),
    m_Grid(false),
    m_BoundingBox(false),
    m_Degrees(false),
    m_Metric(false),
    m_HitTestGridValid(false),
    m_here_is_temporary(false),
    presentation_mode(0),
    pres_reverse(false),
    pres_speed(0.0),
    movie(NULL),
    current_cursor(GfxCore::CURSOR_DEFAULT)
{
    AddQuad = &GfxCore::AddQuadrilateralDepth;
    AddPoly = &GfxCore::AddPolylineDepth;
    wxConfigBase::Get()->Read(wxT("metric"), &m_Metric, true);
    wxConfigBase::Get()->Read(wxT("degrees"), &m_Degrees, true);
    m_here.Invalidate();
    m_there.Invalidate();

    // Initialise grid for hit testing.
    m_PointGrid = new list<LabelInfo*>[HITTEST_SIZE * HITTEST_SIZE];

    m_Pens = new GLAPen[NUM_COLOUR_BANDS + 1];
    for (int pen = 0; pen < NUM_COLOUR_BANDS + 1; ++pen) {
        m_Pens[pen].SetColour(REDS[pen] / 255.0,
                              GREENS[pen] / 255.0,
                              BLUES[pen] / 255.0);
    }
}

GfxCore::~GfxCore()
{
    TryToFreeArrays();

    delete[] m_Pens;
    delete[] m_PointGrid;
}

void GfxCore::TryToFreeArrays()
{
    // Free up any memory allocated for arrays.
    delete[] m_LabelGrid;
    m_LabelGrid = NULL;
}

//
//  Initialisation methods
//

void GfxCore::Initialise(bool same_file)
{
    // Initialise the view from the parent holding the survey data.

    TryToFreeArrays();

    m_DoneFirstShow = false;

    m_HitTestGridValid = false;
    m_here_is_temporary = true;
    m_here.Invalidate();
    m_there.Invalidate();

    m_MouseOutsideCompass = m_MouseOutsideElev = false;

    if (!same_file) {
        // Apply default parameters unless reloading the same file.
        DefaultParameters();

        // Set the initial scale.
        SetScale(1.0);
    }

    switch (m_ColourBy) {
        case COLOUR_BY_DEPTH:
            if (m_Parent->GetDepthExtent() == 0.0) {
                SetColourBy(COLOUR_BY_NONE);
            }
            break;
        case COLOUR_BY_DATE:
            if (!HasDateInformation()) {
                SetColourBy(COLOUR_BY_NONE);
            }
            break;
        case COLOUR_BY_ERROR:
            if (!m_Parent->HasErrorInformation()) {
                SetColourBy(COLOUR_BY_NONE);
            }
            break;
    }

    m_HaveData = true;

    ForceRefresh();
}

void GfxCore::FirstShow()
{
    GLACanvas::FirstShow();

    const unsigned int quantise(GetFontSize() / QUANTISE_FACTOR);
    list<LabelInfo*>::iterator pos = m_Parent->GetLabelsNC();
    while (pos != m_Parent->GetLabelsNCEnd()) {
        LabelInfo* label = *pos++;
        // Calculate and set the label width for use when plotting
        // none-overlapping labels.
        int ext_x;
        GLACanvas::GetTextExtent(label->GetText(), &ext_x, NULL);
        label->set_width(unsigned(ext_x) / quantise + 1);
    }

    SetBackgroundColour(0.0, 0.0, 0.0);

    // Set diameter of the viewing volume.
    SetVolumeDiameter(sqrt(sqrd(m_Parent->GetXExtent()) +
                           sqrd(m_Parent->GetYExtent()) +
                           sqrd(m_Parent->GetZExtent())));

    // Update our record of the client area size and centre.
    GetClientSize(&m_XSize, &m_YSize);

    m_DoneFirstShow = true;
}

//
//  Recalculating methods
//

void GfxCore::SetScale(Double scale)
{
    // Fill the plot data arrays with screen coordinates, scaling the survey
    // to a particular absolute scale.

    if (scale < 0.05) {
        scale = 0.05;
    } else if (scale > 6144.0) {
        scale = 6144.0;
    }

    m_Scale = scale;
    m_HitTestGridValid = false;
    if (m_here_is_temporary) SetHere();

    GLACanvas::SetScale(scale);
}

bool GfxCore::HasUndergroundLegs() const
{
    return m_Parent->HasUndergroundLegs();
}

bool GfxCore::HasSurfaceLegs() const
{
    return m_Parent->HasSurfaceLegs();
}

bool GfxCore::HasTubes() const
{
    return m_Parent->HasTubes();
}

void GfxCore::UpdateBlobs()
{
    InvalidateList(LIST_BLOBS);
}

//
//  Event handlers
//

void GfxCore::OnLeaveWindow(wxMouseEvent& event) {
    SetHere();
    ClearCoords();
}

void GfxCore::OnIdle(wxIdleEvent& event)
{
    // Handle an idle event.
    if (Animate()) {
        ForceRefresh();
        event.RequestMore();
    }
}

void GfxCore::OnPaint(wxPaintEvent&)
{
    // Redraw the window.

    // Get a graphics context.
    wxPaintDC dc(this);

    assert(GetContext());

    if (m_HaveData) {
        // Make sure we're initialised.
        bool first_time = !m_DoneFirstShow;
        if (first_time) {
            FirstShow();
        }

        StartDrawing();

        // Clear the background.
        Clear();

        // Set up model transformation matrix.
        SetDataTransform();

        timer.Start(); // reset timer

        if (m_Legs || m_Tubes) {
            if (m_Tubes) {
                EnableSmoothPolygons(true); // FIXME: allow false for wireframe view
                DrawList(LIST_TUBES);
                DisableSmoothPolygons();
            }

            // Draw the underground legs.  Do this last so that anti-aliasing
            // works over polygons.
            SetColour(col_GREEN);
            DrawList(LIST_UNDERGROUND_LEGS);
        }

        if (m_Surface) {
            // Draw the surface legs.
            DrawList(LIST_SURFACE_LEGS);
        }

        DrawList(LIST_BLOBS);

        if (m_BoundingBox) {
            DrawShadowedBoundingBox();
        }
        if (m_Grid) {
            // Draw the grid.
            DrawList(LIST_GRID);
        }

        if (m_Crosses) {
            DrawList(LIST_CROSSES);
        }

        SetIndicatorTransform();

        // Draw station names.
        if (m_Names /*&& !m_Control->MouseDown() && !Animating()*/) {
            SetColour(NAME_COLOUR);

            if (m_OverlappingNames) {
                SimpleDrawNames();
            } else {
                NattyDrawNames();
            }
        }

        if (MeasuringLineActive()) {
            // Draw "here" and "there".
            double hx, hy;
            SetColour(HERE_COLOUR);
            if (m_here.IsValid()) {
                double dummy;
                Transform(m_here, &hx, &hy, &dummy);
                if (!m_here_is_temporary) DrawRing(hx, hy);
            }
            if (m_there.IsValid()) {
                double tx, ty;
                double dummy;
                Transform(m_there, &tx, &ty, &dummy);
                if (m_here.IsValid()) {
                    BeginLines();
                    PlaceIndicatorVertex(hx, hy);
                    PlaceIndicatorVertex(tx, ty);
                    EndLines();
                }
                BeginBlobs();
                DrawBlob(tx, ty);
                EndBlobs();
            }
        }

        // Draw indicators.
        //
        // There's no advantage in generating an OpenGL list for the
        // indicators since they change with almost every redraw (and
        // sometimes several times between redraws).  This way we avoid
        // the need to track when to update the indicator OpenGL list,
        // and also avoid indicator update bugs when we don't quite get this
        // right...
        DrawIndicators();

        FinishDrawing();

        drawtime = timer.Time();
    } else {
        dc.SetBackground(wxSystemSettings::GetColour(wxSYS_COLOUR_WINDOWFRAME));
        dc.Clear();
    }
}

void GfxCore::DrawBoundingBox()
{
    const Vector3 v = 0.5 * m_Parent->GetExtent();

    SetColour(col_BLUE);
    EnableDashedLines();
    BeginPolyline();
    PlaceVertex(-v.GetX(), -v.GetY(), v.GetZ());
    PlaceVertex(-v.GetX(), v.GetY(), v.GetZ());
    PlaceVertex(v.GetX(), v.GetY(), v.GetZ());
    PlaceVertex(v.GetX(), -v.GetY(), v.GetZ());
    PlaceVertex(-v.GetX(), -v.GetY(), v.GetZ());
    EndPolyline();
    BeginPolyline();
    PlaceVertex(-v.GetX(), -v.GetY(), -v.GetZ());
    PlaceVertex(-v.GetX(), v.GetY(), -v.GetZ());
    PlaceVertex(v.GetX(), v.GetY(), -v.GetZ());
    PlaceVertex(v.GetX(), -v.GetY(), -v.GetZ());
    PlaceVertex(-v.GetX(), -v.GetY(), -v.GetZ());
    EndPolyline();
    BeginLines();
    PlaceVertex(-v.GetX(), -v.GetY(), v.GetZ());
    PlaceVertex(-v.GetX(), -v.GetY(), -v.GetZ());
    PlaceVertex(-v.GetX(), v.GetY(), v.GetZ());
    PlaceVertex(-v.GetX(), v.GetY(), -v.GetZ());
    PlaceVertex(v.GetX(), v.GetY(), v.GetZ());
    PlaceVertex(v.GetX(), v.GetY(), -v.GetZ());
    PlaceVertex(v.GetX(), -v.GetY(), v.GetZ());
    PlaceVertex(v.GetX(), -v.GetY(), -v.GetZ());
    EndLines();
    DisableDashedLines();
}

void GfxCore::DrawShadowedBoundingBox()
{
    const Vector3 v = 0.5 * m_Parent->GetExtent();

    DrawBoundingBox();

    PolygonOffset(true);
    SetColour(col_DARK_GREY);
    BeginQuadrilaterals();
    PlaceVertex(-v.GetX(), -v.GetY(), -v.GetZ());
    PlaceVertex(-v.GetX(), v.GetY(), -v.GetZ());
    PlaceVertex(v.GetX(), v.GetY(), -v.GetZ());
    PlaceVertex(v.GetX(), -v.GetY(), -v.GetZ());
    EndQuadrilaterals();
    PolygonOffset(false);

    DrawList(LIST_SHADOW);
}

void GfxCore::DrawGrid()
{
    // Draw the grid.
    SetColour(col_RED);

    // Calculate the extent of the survey, in metres across the screen plane.
    Double m_across_screen = SurveyUnitsAcrossViewport();
    // Calculate the length of the scale bar in metres.
    //--move this elsewhere
    Double size_snap = pow(10.0, floor(log10(0.75 * m_across_screen)));
    Double t = m_across_screen * 0.75 / size_snap;
    if (t >= 5.0) {
        size_snap *= 5.0;
    }
    else if (t >= 2.0) {
        size_snap *= 2.0;
    }

    Double grid_size = size_snap * 0.1;
    Double edge = grid_size * 2.0;
    Double grid_z = -m_Parent->GetZExtent() * 0.5 - grid_size;
    Double left = -m_Parent->GetXExtent() * 0.5 - edge;
    Double right = m_Parent->GetXExtent() * 0.5 + edge;
    Double bottom = -m_Parent->GetYExtent() * 0.5 - edge;
    Double top = m_Parent->GetYExtent() * 0.5 + edge;
    int count_x = (int) ceil((right - left) / grid_size);
    int count_y = (int) ceil((top - bottom) / grid_size);
    Double actual_right = left + count_x*grid_size;
    Double actual_top = bottom + count_y*grid_size;

    BeginLines();

    for (int xc = 0; xc <= count_x; xc++) {
        Double x = left + xc*grid_size;

        PlaceVertex(x, bottom, grid_z);
        PlaceVertex(x, actual_top, grid_z);
    }

    for (int yc = 0; yc <= count_y; yc++) {
        Double y = bottom + yc*grid_size;
        PlaceVertex(left, y, grid_z);
        PlaceVertex(actual_right, y, grid_z);
    }

    EndLines();
}

int GfxCore::GetClinoOffset() const
{
    return m_Compass ? CLINO_OFFSET_X : INDICATOR_OFFSET_X;
}

void GfxCore::DrawTick(int angle_cw)
{
    const Double theta = rad(angle_cw);
    const wxCoord length1 = INDICATOR_RADIUS;
    const wxCoord length0 = length1 + TICK_LENGTH;
    wxCoord x0 = wxCoord(length0 * sin(theta));
    wxCoord y0 = wxCoord(length0 * cos(theta));
    wxCoord x1 = wxCoord(length1 * sin(theta));
    wxCoord y1 = wxCoord(length1 * cos(theta));

    PlaceIndicatorVertex(x0, y0);
    PlaceIndicatorVertex(x1, y1);
}

void GfxCore::DrawArrow(gla_colour col1, gla_colour col2) {
    Vector3 p1(0, INDICATOR_RADIUS, 0);
    Vector3 p2(INDICATOR_RADIUS/2, INDICATOR_RADIUS*-.866025404, 0); // 150deg
    Vector3 p3(-INDICATOR_RADIUS/2, INDICATOR_RADIUS*-.866025404, 0); // 210deg
    Vector3 pc(0, 0, 0);

    DrawTriangle(col_LIGHT_GREY, col1, p2, p1, pc);
    DrawTriangle(col_LIGHT_GREY, col2, p3, p1, pc);
}

void GfxCore::DrawCompass() {
    // Ticks.
    BeginLines();
    for (int angle = 315; angle > 0; angle -= 45) {
        DrawTick(angle);
    }
    SetColour(col_GREEN);
    DrawTick(0);
    EndLines();

    // Compass background.
    DrawCircle(col_LIGHT_GREY_2, col_GREY, 0, 0, INDICATOR_RADIUS);

    // Compass arrow.
    DrawArrow(col_INDICATOR_1, col_INDICATOR_2);
}

// Draw the non-rotating background to the clino.
void GfxCore::DrawClinoBack() {
    BeginLines();
    for (int angle = 0; angle <= 180; angle += 90) {
        DrawTick(angle);
    }

    SetColour(col_GREY);
    PlaceIndicatorVertex(0, INDICATOR_RADIUS);
    PlaceIndicatorVertex(0, -INDICATOR_RADIUS);
    PlaceIndicatorVertex(0, 0);
    PlaceIndicatorVertex(INDICATOR_RADIUS, 0);

    EndLines();
}

void GfxCore::DrawClino() {
    // Ticks.
    SetColour(col_GREEN);
    BeginLines();
    DrawTick(0);
    EndLines();

    // Clino background.
    DrawSemicircle(col_LIGHT_GREY_2, col_GREY, 0, 0, INDICATOR_RADIUS, 0);

    // Elevation arrow.
    DrawArrow(col_INDICATOR_2, col_INDICATOR_1);
}

void GfxCore::Draw2dIndicators()
{
    // Draw the compass and elevation indicators.

    const int centre_y = INDICATOR_BOX_SIZE / 2 + INDICATOR_OFFSET_Y;

    const int comp_centre_x = GetCompassXPosition();

    if (m_Compass && !m_Parent->IsExtendedElevation()) {
        // If the user is dragging the compass with the pointer outside the
        // compass, we snap to 45 degree multiples, and the ticks go white.
        SetColour(m_MouseOutsideCompass ? col_WHITE : col_LIGHT_GREY_2);
        DrawList2D(LIST_COMPASS, comp_centre_x, centre_y, -m_PanAngle);
    }

    const int elev_centre_x = GetClinoXPosition();

    if (m_Clino) {
        // If the user is dragging the clino with the pointer outside the
        // clino, we snap to 90 degree multiples, and the ticks go white.
        SetColour(m_MouseOutsideElev ? col_WHITE : col_LIGHT_GREY_2);
        DrawList2D(LIST_CLINO_BACK, elev_centre_x, centre_y, 0);
        DrawList2D(LIST_CLINO, elev_centre_x, centre_y, 90 + m_TiltAngle);
    }

    SetColour(TEXT_COLOUR);

    static int triple_zero_width = 0;
    static int height = 0;
    if (!triple_zero_width) {
        GetTextExtent(wxT("000"), &triple_zero_width, &height);
    }
    const int y_off = INDICATOR_OFFSET_Y + INDICATOR_BOX_SIZE + height / 2;

    if (m_Compass && !m_Parent->IsExtendedElevation()) {
        wxString str;
        int value;
        if (m_Degrees) {
            value = int(m_PanAngle);
        } else {
            value = int(m_PanAngle * 200.0 / 180.0);
        }
        str.Printf(wxT("%03d"), value);
        DrawIndicatorText(comp_centre_x - triple_zero_width / 2, y_off, str);

        str = wmsg(/*Facing*/203);
        int w;
        GetTextExtent(str, &w, NULL);
        DrawIndicatorText(comp_centre_x - w / 2, y_off + height, str);
    }

    if (m_Clino) {
        int angle;
        wxString str;
        int width;
        if (m_Degrees) {
            static int zero_zero_width = 0;
            if (!zero_zero_width) {
                GetTextExtent(wxT("00"), &zero_zero_width, NULL);
            }
            width = zero_zero_width;
            angle = int(-m_TiltAngle);
            str = angle ? wxString::Format(wxT("%+03d"), angle) : wxT("00");
        } else {
            width = triple_zero_width;
            angle = int(-m_TiltAngle * 200.0 / 180.0);
            str = angle ? wxString::Format(wxT("%+04d"), angle) : wxT("000");
        }

        // Adjust horizontal position so the left of the first digit is
        // always in the same place.
        int sign_offset = 0;
        if (angle < 0) {
            static int minus_width = 0;
            if (!minus_width) {
                GetTextExtent(wxT("-"), &minus_width, NULL);
            }
            sign_offset = minus_width + 1;
        } else if (angle > 0) {
            static int plus_width = 0;
            if (!plus_width) {
                GetTextExtent(wxT("+"), &plus_width, NULL);
            }
            sign_offset = plus_width + 1;
        }
        DrawIndicatorText(elev_centre_x - sign_offset - width / 2, y_off, str);

        str = wmsg(/*Elevation*/118);
        int w;
        GetTextExtent(str, &w, NULL);
        DrawIndicatorText(elev_centre_x - w / 2, y_off + height, str);
    }
}

void GfxCore::NattyDrawNames()
{
    // Draw station names, without overlapping.

    const unsigned int quantise(GetFontSize() / QUANTISE_FACTOR);
    const unsigned int quantised_x = m_XSize / quantise;
    const unsigned int quantised_y = m_YSize / quantise;
    const size_t buffer_size = quantised_x * quantised_y;

    if (!m_LabelGrid) m_LabelGrid = new char[buffer_size];

    memset((void*) m_LabelGrid, 0, buffer_size);

    list<LabelInfo*>::const_iterator label = m_Parent->GetLabels();
    for ( ; label != m_Parent->GetLabelsEnd(); ++label) {
        if (!((m_Surface && (*label)->IsSurface()) ||
              (m_Legs && (*label)->IsUnderground()) ||
              (!(*label)->IsSurface() && !(*label)->IsUnderground()))) {
            // if this station isn't to be displayed, skip to the next
            // (last case is for stns with no legs attached)
            continue;
        }

        double x, y, z;

        Transform(**label, &x, &y, &z);
        // Check if the label is behind us (in perspective view).
        if (z <= 0.0 || z >= 1.0) continue;

        // Apply a small shift so that translating the view doesn't make which
        // labels are displayed change as the resulting twinkling effect is
        // distracting.
        double tx, ty, tz;
        Transform(Vector3(), &tx, &ty, &tz);
        tx -= floor(tx / quantise) * quantise;
        ty -= floor(ty / quantise) * quantise;

        tx = x - tx;
        if (tx < 0) continue;

        ty = y - ty;
        if (ty < 0) continue;

        unsigned int iy = unsigned(ty) / quantise;
        if (iy >= quantised_y) continue;
        unsigned int width = (*label)->get_width();
        unsigned int ix = unsigned(tx) / quantise;
        if (ix + width >= quantised_x) continue;

        char * test = m_LabelGrid + ix + iy * quantised_x;
        if (memchr(test, 1, width)) continue;

        x += 3;
        y -= GetFontSize() / 2;
        DrawIndicatorText((int)x, (int)y, (*label)->GetText());

        if (iy > QUANTISE_FACTOR) iy = QUANTISE_FACTOR;
        test -= quantised_x * iy;
        iy += 4;
        while (--iy && test < m_LabelGrid + buffer_size) {
            memset(test, 1, width);
            test += quantised_x;
        }
    }
}

void GfxCore::SimpleDrawNames()
{
    // Draw all station names, without worrying about overlaps
    list<LabelInfo*>::const_iterator label = m_Parent->GetLabels();
    for ( ; label != m_Parent->GetLabelsEnd(); ++label) {
        if (!((m_Surface && (*label)->IsSurface()) ||
              (m_Legs && (*label)->IsUnderground()) ||
              (!(*label)->IsSurface() && !(*label)->IsUnderground()))) {
            // if this station isn't to be displayed, skip to the next
            // (last case is for stns with no legs attached)
            continue;
        }

        double x, y, z;
        Transform(**label, &x, &y, &z);

        // Check if the label is behind us (in perspective view).
        if (z <= 0) continue;

        x += 3;
        y -= GetFontSize() / 2;
        DrawIndicatorText((int)x, (int)y, (*label)->GetText());
    }
}

void GfxCore::DrawColourKey(int num_bands, const wxString & other)
{
    int total_block_height =
        COLOUR_KEY_BLOCK_HEIGHT * (num_bands == 1 ? num_bands : num_bands - 1);
    if (!other.empty()) total_block_height += COLOUR_KEY_BLOCK_HEIGHT * 2;

    const int top = -(total_block_height + COLOUR_KEY_MARGIN);

    int size = 0;
    if (!other.empty()) GetTextExtent(other, &size, NULL);
    int band;
    for (band = 0; band < num_bands; ++band) {
        int x;
        GetTextExtent(key_legends[band], &x, NULL);
        if (x > size) size = x;
    }

    int left = -COLOUR_KEY_BLOCK_WIDTH - COLOUR_KEY_MARGIN - size;

    DrawRectangle(col_BLACK, col_DARK_GREY,
                  left - COLOUR_KEY_MARGIN - COLOUR_KEY_EXTRA_LEFT_MARGIN,
                  top - COLOUR_KEY_MARGIN * 2,
                  COLOUR_KEY_BLOCK_WIDTH + size + COLOUR_KEY_MARGIN * 3 +
                      COLOUR_KEY_EXTRA_LEFT_MARGIN,
                  total_block_height + COLOUR_KEY_MARGIN*4);

    int y = top;

    if (!other.empty()) {
        DrawShadedRectangle(GetSurfacePen(), GetSurfacePen(), left, y,
                COLOUR_KEY_BLOCK_WIDTH, COLOUR_KEY_BLOCK_HEIGHT);
        y += COLOUR_KEY_BLOCK_HEIGHT * 2;
    }

    if (num_bands == 1) {
        DrawShadedRectangle(GetPen(0), GetPen(0), left, y,
                            COLOUR_KEY_BLOCK_WIDTH, COLOUR_KEY_BLOCK_HEIGHT);
    } else {
        for (band = 0; band < num_bands - 1; ++band) {
            DrawShadedRectangle(GetPen(band), GetPen(band + 1), left, y,
                                COLOUR_KEY_BLOCK_WIDTH, COLOUR_KEY_BLOCK_HEIGHT);
            y += COLOUR_KEY_BLOCK_HEIGHT;
        }
    }

    y = top - GetFontSize() / 2;
    left += COLOUR_KEY_BLOCK_WIDTH + 5;

    SetColour(TEXT_COLOUR);
    if (!other.empty()) {
        y += COLOUR_KEY_BLOCK_HEIGHT / 2;
        DrawIndicatorText(left, y, other);
        y += COLOUR_KEY_BLOCK_HEIGHT * 2 - COLOUR_KEY_BLOCK_HEIGHT / 2;
    }

    if (num_bands == 1) {
        y += COLOUR_KEY_BLOCK_HEIGHT / 2;
        DrawIndicatorText(left, y, key_legends[0]);
    } else {
        for (band = 0; band < GetNumColourBands(); ++band) {
            DrawIndicatorText(left, y, key_legends[band]);
            y += COLOUR_KEY_BLOCK_HEIGHT;
        }
    }
}

void GfxCore::DrawDepthKey()
{
    for (int band = 0; band < GetNumColourBands(); ++band) {
        Double z = m_Parent->GetDepthMin() + m_Parent->GetOffset().GetZ() +
                   m_Parent->GetDepthExtent() * band / (GetNumColourBands() - 1);
        key_legends[band] = FormatLength(z, false);
    }

    DrawColourKey(GetNumColourBands(), wxString());
}

void GfxCore::DrawDateKey()
{
    int num_bands;
    if (m_Parent->GetDateExtent() == 0) {
        num_bands = 1;
    } else {
        num_bands = GetNumColourBands();
    }
    for (int band = 0; band < num_bands; ++band) {
        int y, m, d;
        int days = m_Parent->GetDateMin();
        if (band)
            days += m_Parent->GetDateExtent() * band / (num_bands - 1);
        ymd_from_days_since_1900(days, &y, &m, &d);
        key_legends[band].Printf(wxT("%04d-%02d-%02d"), y, m, d);
    }
    wxString other;
    if (!m_Parent->HasCompleteDateInfo()) {
        other = wmsg(/*Undated*/221);
    }

    DrawColourKey(num_bands, other);
}

void GfxCore::DrawErrorKey()
{
    for (int band = 0; band < GetNumColourBands(); ++band) {
        double E = MAX_ERROR * band / (GetNumColourBands() - 1);
        key_legends[band].Printf(wxT("%.2f"), E);
    }

    // Always show the "Not in loop" legend for now (FIXME).
    DrawColourKey(GetNumColourBands(), wmsg(/*Not in loop*/290));
}

wxString GfxCore::FormatLength(Double size_snap, bool scalebar)
{
    wxString str;
    bool negative = (size_snap < 0.0);

    if (negative) {
        size_snap = -size_snap;
    }

    if (size_snap == 0.0) {
        str = wxT("0");
    } else if (m_Metric) {
#ifdef SILLY_UNITS
        if (size_snap < 1e-12) {
            str.Printf(wxT("%.3gpm"), size_snap * 1e12);
        } else if (size_snap < 1e-9) {
            str.Printf(wxT("%.fpm"), size_snap * 1e12);
        } else if (size_snap < 1e-6) {
            str.Printf(wxT("%.fnm"), size_snap * 1e9);
        } else if (size_snap < 1e-3) {
            str.Printf(wxT("%.fum"), size_snap * 1e6);
#else
        if (size_snap < 1e-3) {
            str.Printf(wxT("%.3gmm"), size_snap * 1e3);
#endif
        } else if (size_snap < 1e-2) {
            str.Printf(wxT("%.fmm"), size_snap * 1e3);
        } else if (size_snap < 1.0) {
            str.Printf(wxT("%.fcm"), size_snap * 100.0);
        } else if (size_snap < 1e3) {
            str.Printf(wxT("%.fm"), size_snap);
#ifdef SILLY_UNITS
        } else if (size_snap < 1e6) {
            str.Printf(wxT("%.fkm"), size_snap * 1e-3);
        } else if (size_snap < 1e9) {
            str.Printf(wxT("%.fMm"), size_snap * 1e-6);
        } else {
            str.Printf(wxT("%.fGm"), size_snap * 1e-9);
#else
        } else {
            str.Printf(scalebar ? wxT("%.fkm") : wxT("%.2fkm"), size_snap * 1e-3);
#endif
        }
    } else {
        size_snap /= METRES_PER_FOOT;
        if (scalebar) {
            Double inches = size_snap * 12;
            if (inches < 1.0) {
                str.Printf(wxT("%.3gin"), inches);
            } else if (size_snap < 1.0) {
                str.Printf(wxT("%.fin"), inches);
            } else if (size_snap < 5279.5) {
                str.Printf(wxT("%.fft"), size_snap);
            } else {
                str.Printf(wxT("%.f miles"), size_snap / 5280.0);
            }
        } else {
            str.Printf(wxT("%.fft"), size_snap);
        }
    }

    return negative ? wxString(wxT("-")) + str : str;
}

void GfxCore::DrawScaleBar()
{
    // Draw the scalebar.
    if (GetPerspective()) return;

    // Calculate how many metres of survey are currently displayed across the
    // screen.
    Double across_screen = SurveyUnitsAcrossViewport();

    double f = double(GetClinoXPosition() - INDICATOR_BOX_SIZE / 2 - SCALE_BAR_OFFSET_X) / m_XSize;
    if (f > 0.75) {
        f = 0.75;
    } else if (f < 0.5) {
        // Stop it getting squeezed to nothing.
        // FIXME: In this case we should probably move the compass and clino up
        // to make room rather than letting stuff overlap.
        f = 0.5;
    }

    // Convert to imperial measurements if required.
    Double multiplier = 1.0;
    if (!m_Metric) {
        across_screen /= METRES_PER_FOOT;
        multiplier = METRES_PER_FOOT;
        if (across_screen >= 5280.0 / f) {
            across_screen /= 5280.0;
            multiplier *= 5280.0;
        }
    }

    // Calculate the length of the scale bar.
    Double size_snap = pow(10.0, floor(log10(f * across_screen)));
    Double t = across_screen * f / size_snap;
    if (t >= 5.0) {
        size_snap *= 5.0;
    } else if (t >= 2.0) {
        size_snap *= 2.0;
    }

    if (!m_Metric) size_snap *= multiplier;

    // Actual size of the thing in pixels:
    int size = int((size_snap / SurveyUnitsAcrossViewport()) * m_XSize);
    m_ScaleBarWidth = size;

    // Draw it...
    const int end_y = SCALE_BAR_OFFSET_Y + SCALE_BAR_HEIGHT;
    int interval = size / 10;

    gla_colour col = col_WHITE;
    for (int ix = 0; ix < 10; ix++) {
        int x = SCALE_BAR_OFFSET_X + int(ix * ((Double) size / 10.0));

        DrawRectangle(col, col, x, end_y, interval + 2, SCALE_BAR_HEIGHT);

        col = (col == col_WHITE) ? col_GREY : col_WHITE;
    }

    // Add labels.
    wxString str = FormatLength(size_snap);

    int text_width, text_height;
    GetTextExtent(str, &text_width, &text_height);
    const int text_y = end_y - text_height + 1;
    SetColour(TEXT_COLOUR);
    DrawIndicatorText(SCALE_BAR_OFFSET_X, text_y, wxT("0"));
    DrawIndicatorText(SCALE_BAR_OFFSET_X + size - text_width, text_y, str);
}

bool GfxCore::CheckHitTestGrid(const wxPoint& point, bool centre)
{
    if (Animating()) return false;

    if (point.x < 0 || point.x >= m_XSize ||
        point.y < 0 || point.y >= m_YSize) {
        return false;
    }

    SetDataTransform();

    if (!m_HitTestGridValid) CreateHitTestGrid();

    int grid_x = (point.x * (HITTEST_SIZE - 1)) / m_XSize;
    int grid_y = (point.y * (HITTEST_SIZE - 1)) / m_YSize;

    LabelInfo *best = NULL;
    int dist_sqrd = 25;
    int square = grid_x + grid_y * HITTEST_SIZE;
    list<LabelInfo*>::iterator iter = m_PointGrid[square].begin();

    while (iter != m_PointGrid[square].end()) {
        LabelInfo *pt = *iter++;

        double cx, cy, cz;

        Transform(*pt, &cx, &cy, &cz);

        cy = m_YSize - cy;

        int dx = point.x - int(cx);
        int ds = dx * dx;
        if (ds >= dist_sqrd) continue;
        int dy = point.y - int(cy);

        ds += dy * dy;
        if (ds >= dist_sqrd) continue;

        dist_sqrd = ds;
        best = pt;

        if (ds == 0) break;
    }

    if (best) {
        m_Parent->ShowInfo(best);
        if (centre) {
            // FIXME: allow Ctrl-Click to not set there or something?
            CentreOn(*best);
            WarpPointer(m_XSize / 2, m_YSize / 2);
            SetThere(*best);
            m_Parent->SelectTreeItem(best);
        }
    } else {
        // Left-clicking not on a survey cancels the measuring line.
        if (centre) {
            ClearTreeSelection();
        } else {
            m_Parent->ShowInfo(best);
            double x, y, z;
            ReverseTransform(point.x, m_YSize - point.y, &x, &y, &z);
            SetHere(Point(Vector3(x, y, z)));
            m_here_is_temporary = true;
        }
    }

    return best;
}

void GfxCore::OnSize(wxSizeEvent& event)
{
    // Handle a change in window size.
    InvalidateList(LIST_SCALE_BAR);

    wxSize size = event.GetSize();

    if (size.GetWidth() <= 0 || size.GetHeight() <= 0) {
        // Before things are fully initialised, we sometimes get a bogus
        // resize message...
        // FIXME have changes in MainFrm cured this?  It still happens with
        // 1.0.32 and wxGTK 2.5.2 (load a file from the command line).
        // With 1.1.6 and wxGTK 2.4.2 we only get negative sizes if MainFrm
        // is resized such that the GfxCore window isn't visible.
        //printf("OnSize(%d,%d)\n", size.GetWidth(), size.GetHeight());
        return;
    }

    wxGLCanvas::OnSize(event);

    m_XSize = size.GetWidth();
    m_YSize = size.GetHeight();

    if (m_DoneFirstShow) {
        TryToFreeArrays();

        m_HitTestGridValid = false;

        ForceRefresh();
    }
}

void GfxCore::DefaultParameters()
{
    // Set default viewing parameters.

    m_Surface = false;
    if (!m_Parent->HasUndergroundLegs()) {
        if (m_Parent->HasSurfaceLegs()) {
            // If there are surface legs, but no underground legs, turn
            // surface surveys on.
            m_Surface = true;
        } else {
            // If there are no legs (e.g. after loading a .pos file), turn
            // crosses on.
            m_Crosses = true;
        }
    }

    m_PanAngle = 0.0;
    if (m_Parent->IsExtendedElevation()) {
        m_TiltAngle = 0.0;
    } else {
        m_TiltAngle = 90.0;
    }

    SetRotation(m_PanAngle, m_TiltAngle);
    SetTranslation(Vector3());

    m_RotationStep = 30.0;
    m_Rotating = false;
    m_SwitchingTo = 0;
    m_Entrances = false;
    m_FixedPts = false;
    m_ExportedPts = false;
    m_Grid = false;
    m_BoundingBox = false;
    m_Tubes = false;
    if (GetPerspective()) TogglePerspective();
}

void GfxCore::Defaults()
{
    // Restore default scale, rotation and translation parameters.
    DefaultParameters();
    SetScale(1.0);

    // Invalidate all the cached lists.
    GLACanvas::FirstShow();

    ForceRefresh();
}

// return: true if animation occured (and ForceRefresh() needs to be called)
bool GfxCore::Animate()
{
    if (!Animating()) return false;

    // Don't show pointer coordinates while animating.
    // FIXME : only do this when we *START* animating!  Use a static copy
    // of the value of "Animating()" last time we were here to track this?
    // MainFrm now checks if we're trying to clear already cleared labels
    // and just returns, but it might be simpler to check here!
    ClearCoords();
    m_Parent->ShowInfo(NULL);

    static double last_t = 0;
    double t;
    if (movie) {
        ReadPixels(movie->GetWidth(), movie->GetHeight(), movie->GetBuffer());
        movie->AddFrame();
        t = 1.0 / 25.0; // 25 frames per second
    } else {
        t = timer.Time() * 1.0e-3;
        if (t == 0) t = 0.001;
        else if (t > 1.0) t = 1.0;
        if (last_t > 0) t = (t + last_t) / 2;
        last_t = t;
    }

    if (presentation_mode == PLAYING && pres_speed != 0.0) {
        t *= fabs(pres_speed);
        while (t >= next_mark_time) {
            t -= next_mark_time;
            this_mark_total = 0;
            PresentationMark prev_mark = next_mark;
            if (prev_mark.angle < 0) prev_mark.angle += 360.0;
            else if (prev_mark.angle >= 360.0) prev_mark.angle -= 360.0;
            if (pres_reverse)
                next_mark = m_Parent->GetPresMark(MARK_PREV);
            else
                next_mark = m_Parent->GetPresMark(MARK_NEXT);
            if (!next_mark.is_valid()) {
                SetView(prev_mark);
                presentation_mode = 0;
                delete movie;
                movie = NULL;
                break;
            }

            double tmp = (pres_reverse ? prev_mark.time : next_mark.time);
            if (tmp > 0) {
                next_mark_time = tmp;
            } else {
                double d = (next_mark - prev_mark).magnitude();
                // FIXME: should ignore component of d which is unseen in
                // non-perspective mode?
                next_mark_time = sqrd(d / 30.0);
                double a = next_mark.angle - prev_mark.angle;
                if (a > 180.0) {
                    next_mark.angle -= 360.0;
                    a = 360.0 - a;
                } else if (a < -180.0) {
                    next_mark.angle += 360.0;
                    a += 360.0;
                } else {
                    a = fabs(a);
                }
                next_mark_time += sqrd(a / 60.0);
                double ta = fabs(next_mark.tilt_angle - prev_mark.tilt_angle);
                next_mark_time += sqrd(ta / 60.0);
                double s = fabs(log(next_mark.scale) - log(prev_mark.scale));
                next_mark_time += sqrd(s / 2.0);
                next_mark_time = sqrt(next_mark_time);
                // was: next_mark_time = max(max(d / 30, s / 2), max(a, ta) / 60);
                //printf("*** %.6f from (\nd: %.6f\ns: %.6f\na: %.6f\nt: %.6f )\n",
                //       next_mark_time, d/30.0, s/2.0, a/60.0, ta/60.0);
                if (tmp < 0) next_mark_time /= -tmp;
            }
        }

        if (presentation_mode) {
            // Advance position towards next_mark
            double p = t / next_mark_time;
            double q = 1 - p;
            PresentationMark here = GetView();
            if (next_mark.angle < 0) {
                if (here.angle >= next_mark.angle + 360.0)
                    here.angle -= 360.0;
            } else if (next_mark.angle >= 360.0) {
                if (here.angle <= next_mark.angle - 360.0)
                    here.angle += 360.0;
            }
            here.assign(q * here + p * next_mark);
            here.angle = q * here.angle + p * next_mark.angle;
            if (here.angle < 0) here.angle += 360.0;
            else if (here.angle >= 360.0) here.angle -= 360.0;
            here.tilt_angle = q * here.tilt_angle + p * next_mark.tilt_angle;
            here.scale = exp(q * log(here.scale) + p * log(next_mark.scale));
            SetView(here);
            this_mark_total += t;
            next_mark_time -= t;
        }
    }

    // When rotating...
    if (m_Rotating) {
        TurnCave(m_RotationStep * t);
    }

    if (m_SwitchingTo == PLAN) {
        // When switching to plan view...
        TiltCave(90.0 * t);
        if (m_TiltAngle == 90.0) {
            m_SwitchingTo = 0;
        }
    } else if (m_SwitchingTo == ELEVATION) {
        // When switching to elevation view...
        if (fabs(m_TiltAngle) < 90.0 * t) {
            m_SwitchingTo = 0;
            TiltCave(-m_TiltAngle);
        } else if (m_TiltAngle < 0.0) {
            TiltCave(90.0 * t);
        } else {
            TiltCave(-90.0 * t);
        }
    } else if (m_SwitchingTo) {
        int angle = (m_SwitchingTo - NORTH) * 90;
        double diff = angle - m_PanAngle;
        if (diff < -180) diff += 360;
        if (diff > 180) diff -= 360;
        double move = 90.0 * t;
        if (move >= fabs(diff)) {
            TurnCave(diff);
            m_SwitchingTo = 0;
        } else if (diff < 0) {
            TurnCave(-move);
        } else {
            TurnCave(move);
        }
    }

    return true;
}

// How much to allow around the box - this is because of the ring shape
// at one end of the line.
static const int HIGHLIGHTED_PT_SIZE = 2; // FIXME: tie in to blob and ring size
#define MARGIN (HIGHLIGHTED_PT_SIZE * 2 + 1)
void GfxCore::RefreshLine(const Point &a, const Point &b, const Point &c)
{
    // Best of all might be to copy the window contents before we draw the
    // line, then replace each time we redraw.

    // Calculate the minimum rectangle which includes the old and new
    // measuring lines to minimise the redraw time
    int l = INT_MAX, r = INT_MIN, u = INT_MIN, d = INT_MAX;
    double X, Y, Z;
    if (a.IsValid()) {
        if (!Transform(a, &X, &Y, &Z)) {
            printf("oops\n");
        } else {
            int x = int(X);
            int y = m_YSize - 1 - int(Y);
            l = x - MARGIN;
            r = x + MARGIN;
            u = y + MARGIN;
            d = y - MARGIN;
        }
    }
    if (b.IsValid()) {
        if (!Transform(b, &X, &Y, &Z)) {
            printf("oops\n");
        } else {
            int x = int(X);
            int y = m_YSize - 1 - int(Y);
            l = min(l, x - MARGIN);
            r = max(r, x + MARGIN);
            u = max(u, y + MARGIN);
            d = min(d, y - MARGIN);
        }
    }
    if (c.IsValid()) {
        if (!Transform(c, &X, &Y, &Z)) {
            printf("oops\n");
        } else {
            int x = int(X);
            int y = m_YSize - 1 - int(Y);
            l = min(l, x - MARGIN);
            r = max(r, x + MARGIN);
            u = max(u, y + MARGIN);
            d = min(d, y - MARGIN);
        }
    }
    const wxRect R(l, d, r - l, u - d);
    Refresh(false, &R);
}

void GfxCore::SetHere()
{
    if (!m_here.IsValid()) return;
    bool line_active = MeasuringLineActive();
    Point old = m_here;
    m_here.Invalidate();
    if (line_active || MeasuringLineActive())
        RefreshLine(old, m_there, m_here);
}

void GfxCore::SetHere(const Point &p)
{
    bool line_active = MeasuringLineActive();
    Point old = m_here;
    m_here = p;
    if (line_active || MeasuringLineActive())
        RefreshLine(old, m_there, m_here);
    m_here_is_temporary = false;
}

void GfxCore::SetThere()
{
    if (!m_there.IsValid()) return;
    Point old = m_there;
    m_there.Invalidate();
    RefreshLine(m_here, old, m_there);
}

void GfxCore::SetThere(const Point &p)
{
    Point old = m_there;
    m_there = p;
    RefreshLine(m_here, old, m_there);
}

void GfxCore::CreateHitTestGrid()
{
    // Clear hit-test grid.
    for (int i = 0; i < HITTEST_SIZE * HITTEST_SIZE; i++) {
        m_PointGrid[i].clear();
    }

    // Fill the grid.
    list<LabelInfo*>::const_iterator pos = m_Parent->GetLabels();
    list<LabelInfo*>::const_iterator end = m_Parent->GetLabelsEnd();
    while (pos != end) {
        LabelInfo* label = *pos++;

        if (!((m_Surface && label->IsSurface()) ||
              (m_Legs && label->IsUnderground()) ||
              (!label->IsSurface() && !label->IsUnderground()))) {
            // if this station isn't to be displayed, skip to the next
            // (last case is for stns with no legs attached)
            continue;
        }

        // Calculate screen coordinates.
        double cx, cy, cz;
        Transform(*label, &cx, &cy, &cz);
        if (cx < 0 || cx >= m_XSize) continue;
        if (cy < 0 || cy >= m_YSize) continue;

        cy = m_YSize - cy;

        // On-screen, so add to hit-test grid...
        int grid_x = int((cx * (HITTEST_SIZE - 1)) / m_XSize);
        int grid_y = int((cy * (HITTEST_SIZE - 1)) / m_YSize);

        m_PointGrid[grid_x + grid_y * HITTEST_SIZE].push_back(label);
    }

    m_HitTestGridValid = true;
}

//
//  Methods for controlling the orientation of the survey
//

void GfxCore::TurnCave(Double angle)
{
    // Turn the cave around its z-axis by a given angle.

    m_PanAngle += angle;
    if (m_PanAngle >= 360.0) {
        m_PanAngle -= 360.0;
    } else if (m_PanAngle < 0.0) {
        m_PanAngle += 360.0;
    }

    m_HitTestGridValid = false;
    if (m_here_is_temporary) SetHere();

    SetRotation(m_PanAngle, m_TiltAngle);
}

void GfxCore::TurnCaveTo(Double angle)
{
    timer.Start(drawtime);
    int new_switching_to = ((int)angle) / 90 + NORTH;
    if (new_switching_to == m_SwitchingTo) {
        // A second order to switch takes us there right away
        TurnCave(angle - m_PanAngle);
        m_SwitchingTo = 0;
        ForceRefresh();
    } else {
        m_SwitchingTo = new_switching_to;
    }
}

void GfxCore::TiltCave(Double tilt_angle)
{
    // Tilt the cave by a given angle.
    if (m_TiltAngle + tilt_angle > 90.0) {
        m_TiltAngle = 90.0;
    } else if (m_TiltAngle + tilt_angle < -90.0) {
        m_TiltAngle = -90.0;
    } else {
        m_TiltAngle += tilt_angle;
    }

    m_HitTestGridValid = false;
    if (m_here_is_temporary) SetHere();

    SetRotation(m_PanAngle, m_TiltAngle);
}

void GfxCore::TranslateCave(int dx, int dy)
{
    AddTranslationScreenCoordinates(dx, dy);
    m_HitTestGridValid = false;

    if (m_here_is_temporary) SetHere();

    ForceRefresh();
}

void GfxCore::DragFinished()
{
    m_MouseOutsideCompass = m_MouseOutsideElev = false;
    ForceRefresh();
}

void GfxCore::ClearCoords()
{
    m_Parent->ClearCoords();
}

void GfxCore::SetCoords(wxPoint point)
{
    // We can't work out 2D coordinates from a perspective view, and it
    // doesn't really make sense to show coordinates while we're animating.
    if (GetPerspective() || Animating()) return;

    // Update the coordinate or altitude display, given the (x, y) position in
    // window coordinates.  The relevant display is updated depending on
    // whether we're in plan or elevation view.

    double cx, cy, cz;

    SetDataTransform();
    ReverseTransform(point.x, m_YSize - 1 - point.y, &cx, &cy, &cz);

    if (ShowingPlan()) {
        m_Parent->SetCoords(cx + m_Parent->GetOffset().GetX(),
                            cy + m_Parent->GetOffset().GetY());
    } else if (ShowingElevation()) {
        m_Parent->SetAltitude(cz + m_Parent->GetOffset().GetZ());
    } else {
        m_Parent->ClearCoords();
    }
}

int GfxCore::GetCompassXPosition() const
{
    // Return the x-coordinate of the centre of the compass in window
    // coordinates.
    return m_XSize - INDICATOR_OFFSET_X - INDICATOR_BOX_SIZE / 2;
}

int GfxCore::GetClinoXPosition() const
{
    // Return the x-coordinate of the centre of the compass in window
    // coordinates.
    return m_XSize - GetClinoOffset() - INDICATOR_BOX_SIZE / 2;
}

int GfxCore::GetIndicatorYPosition() const
{
    // Return the y-coordinate of the centre of the indicators in window
    // coordinates.
    return m_YSize - INDICATOR_OFFSET_Y - INDICATOR_BOX_SIZE / 2;
}

int GfxCore::GetIndicatorRadius() const
{
    // Return the radius of each indicator.
    return (INDICATOR_BOX_SIZE - INDICATOR_MARGIN * 2) / 2;
}

bool GfxCore::PointWithinCompass(wxPoint point) const
{
    // Determine whether a point (in window coordinates) lies within the
    // compass.
    if (!ShowingCompass()) return false;

    glaCoord dx = point.x - GetCompassXPosition();
    glaCoord dy = point.y - GetIndicatorYPosition();
    glaCoord radius = GetIndicatorRadius();

    return (dx * dx + dy * dy <= radius * radius);
}

bool GfxCore::PointWithinClino(wxPoint point) const
{
    // Determine whether a point (in window coordinates) lies within the clino.
    if (!ShowingClino()) return false;

    glaCoord dx = point.x - GetClinoXPosition();
    glaCoord dy = point.y - GetIndicatorYPosition();
    glaCoord radius = GetIndicatorRadius();

    return (dx * dx + dy * dy <= radius * radius);
}

bool GfxCore::PointWithinScaleBar(wxPoint point) const
{
    // Determine whether a point (in window coordinates) lies within the scale
    // bar.
    if (!ShowingScaleBar()) return false;

    return (point.x >= SCALE_BAR_OFFSET_X &&
            point.x <= SCALE_BAR_OFFSET_X + m_ScaleBarWidth &&
            point.y <= m_YSize - SCALE_BAR_OFFSET_Y - SCALE_BAR_HEIGHT &&
            point.y >= m_YSize - SCALE_BAR_OFFSET_Y - SCALE_BAR_HEIGHT*2);
}

void GfxCore::SetCompassFromPoint(wxPoint point)
{
    // Given a point in window coordinates, set the heading of the survey.  If
    // the point is outside the compass, it snaps to 45 degree intervals;
    // otherwise it operates as normal.

    wxCoord dx = point.x - GetCompassXPosition();
    wxCoord dy = point.y - GetIndicatorYPosition();
    wxCoord radius = GetIndicatorRadius();

    double angle = deg(atan2(double(dx), double(dy))) - 180.0;
    if (dx * dx + dy * dy <= radius * radius) {
        TurnCave(angle - m_PanAngle);
        m_MouseOutsideCompass = false;
    } else {
        TurnCave(int(angle / 45.0) * 45.0 - m_PanAngle);
        m_MouseOutsideCompass = true;
    }

    ForceRefresh();
}

void GfxCore::SetClinoFromPoint(wxPoint point)
{
    // Given a point in window coordinates, set the elevation of the survey.
    // If the point is outside the clino, it snaps to 90 degree intervals;
    // otherwise it operates as normal.

    glaCoord dx = point.x - GetClinoXPosition();
    glaCoord dy = point.y - GetIndicatorYPosition();
    glaCoord radius = GetIndicatorRadius();

    if (dx >= 0 && dx * dx + dy * dy <= radius * radius) {
        TiltCave(deg(atan2(double(dy), double(dx))) - m_TiltAngle);
        m_MouseOutsideElev = false;
    } else if (dy >= INDICATOR_MARGIN) {
        TiltCave(90.0 - m_TiltAngle);
        m_MouseOutsideElev = true;
    } else if (dy <= -INDICATOR_MARGIN) {
        TiltCave(-90.0 - m_TiltAngle);
        m_MouseOutsideElev = true;
    } else {
        TiltCave(-m_TiltAngle);
        m_MouseOutsideElev = true;
    }

    ForceRefresh();
}

void GfxCore::SetScaleBarFromOffset(wxCoord dx)
{
    // Set the scale of the survey, given an offset as to how much the mouse has
    // been dragged over the scalebar since the last scale change.

    SetScale((m_ScaleBarWidth + dx) * m_Scale / m_ScaleBarWidth);
    ForceRefresh();
}

void GfxCore::RedrawIndicators()
{
    // Redraw the compass and clino indicators.

    const wxRect r(m_XSize - INDICATOR_OFFSET_X - INDICATOR_BOX_SIZE*2 -
                     INDICATOR_GAP,
                   m_YSize - INDICATOR_OFFSET_Y - INDICATOR_BOX_SIZE,
                   INDICATOR_BOX_SIZE*2 + INDICATOR_GAP,
                   INDICATOR_BOX_SIZE);

    Refresh(false, &r);
}

void GfxCore::StartRotation()
{
    // Start the survey rotating.

    m_Rotating = true;
    timer.Start(drawtime);
}

void GfxCore::ToggleRotation()
{
    // Toggle the survey rotation on/off.

    if (m_Rotating) {
        StopRotation();
    } else {
        StartRotation();
    }
}

void GfxCore::StopRotation()
{
    // Stop the survey rotating.

    m_Rotating = false;
    ForceRefresh();
}

bool GfxCore::IsExtendedElevation() const
{
    return m_Parent->IsExtendedElevation();
}

void GfxCore::ReverseRotation()
{
    // Reverse the direction of rotation.

    m_RotationStep = -m_RotationStep;
}

void GfxCore::RotateSlower(bool accel)
{
    // Decrease the speed of rotation, optionally by an increased amount.

    m_RotationStep /= accel ? 1.44 : 1.2;
    if (m_RotationStep < 1.0) {
        m_RotationStep = 1.0;
    }
}

void GfxCore::RotateFaster(bool accel)
{
    // Increase the speed of rotation, optionally by an increased amount.

    m_RotationStep *= accel ? 1.44 : 1.2;
    if (m_RotationStep > 450.0) {
        m_RotationStep = 450.0;
    }
}

void GfxCore::SwitchToElevation()
{
    // Perform an animated switch to elevation view.

    switch (m_SwitchingTo) {
        case 0:
            timer.Start(drawtime);
            m_SwitchingTo = ELEVATION;
            break;

        case PLAN:
            m_SwitchingTo = ELEVATION;
            break;

        case ELEVATION:
            // a second order to switch takes us there right away
            TiltCave(-m_TiltAngle);
            m_SwitchingTo = 0;
            ForceRefresh();
    }
}

void GfxCore::SwitchToPlan()
{
    // Perform an animated switch to plan view.

    switch (m_SwitchingTo) {
        case 0:
            timer.Start(drawtime);
            m_SwitchingTo = PLAN;
            break;

        case ELEVATION:
            m_SwitchingTo = PLAN;
            break;

        case PLAN:
            // A second order to switch takes us there right away
            TiltCave(90.0 - m_TiltAngle);
            m_SwitchingTo = 0;
            ForceRefresh();
    }
}

void GfxCore::SetViewTo(Double xmin, Double xmax, Double ymin, Double ymax, Double zmin, Double zmax)
{

    SetTranslation(-Vector3((xmin + xmax) / 2, (ymin + ymax) / 2, (zmin + zmax) / 2));
    Double scale = HUGE_VAL;
    const Vector3 ext = m_Parent->GetExtent();
    if (xmax > xmin) {
        Double s = ext.GetX() / (xmax - xmin);
        if (s < scale) scale = s;
    }
    if (ymax > ymin) {
        Double s = ext.GetY() / (ymax - ymin);
        if (s < scale) scale = s;
    }
    if (!ShowingPlan() && zmax > zmin) {
        Double s = ext.GetZ() / (zmax - zmin);
        if (s < scale) scale = s;
    }
    if (scale != HUGE_VAL) SetScale(scale);
    ForceRefresh();
}

bool GfxCore::CanRaiseViewpoint() const
{
    // Determine if the survey can be viewed from a higher angle of elevation.

    return GetPerspective() ? (m_TiltAngle > -90.0) : (m_TiltAngle < 90.0);
}

bool GfxCore::CanLowerViewpoint() const
{
    // Determine if the survey can be viewed from a lower angle of elevation.

    return GetPerspective() ? (m_TiltAngle < 90.0) : (m_TiltAngle > -90.0);
}

bool GfxCore::HasDepth() const
{
    return m_Parent->GetDepthExtent() == 0.0;
}

bool GfxCore::HasErrorInformation() const
{
    return m_Parent->HasErrorInformation();
}

bool GfxCore::HasDateInformation() const
{
    return m_Parent->GetDateMin() >= 0;
}

bool GfxCore::ShowingPlan() const
{
    // Determine if the survey is in plan view.

    return (m_TiltAngle == 90.0);
}

bool GfxCore::ShowingElevation() const
{
    // Determine if the survey is in elevation view.

    return (m_TiltAngle == 0.0);
}

bool GfxCore::ShowingMeasuringLine() const
{
    // Determine if the measuring line is being shown.

    return (m_there.IsValid() && m_here.IsValid());
}

void GfxCore::ToggleFlag(bool* flag, int update)
{
    *flag = !*flag;
    if (update == UPDATE_BLOBS) {
        UpdateBlobs();
    } else if (update == UPDATE_BLOBS_AND_CROSSES) {
        UpdateBlobs();
        InvalidateList(LIST_CROSSES);
    }
    ForceRefresh();
}

int GfxCore::GetNumEntrances() const
{
    return m_Parent->GetNumEntrances();
}

int GfxCore::GetNumFixedPts() const
{
    return m_Parent->GetNumFixedPts();
}

int GfxCore::GetNumExportedPts() const
{
    return m_Parent->GetNumExportedPts();
}

void GfxCore::ClearTreeSelection()
{
    m_Parent->ClearTreeSelection();
}

void GfxCore::CentreOn(const Point &p)
{
    SetTranslation(-p);
    m_HitTestGridValid = false;

    ForceRefresh();
}

void GfxCore::ForceRefresh()
{
    Refresh(false);
}

void GfxCore::GenerateList(unsigned int l)
{
    assert(m_HaveData);

    switch (l) {
        case LIST_COMPASS:
            DrawCompass();
            break;
        case LIST_CLINO:
            DrawClino();
            break;
        case LIST_CLINO_BACK:
            DrawClinoBack();
            break;
        case LIST_SCALE_BAR:
            DrawScaleBar();
            break;
        case LIST_DEPTH_KEY:
            DrawDepthKey();
            break;
        case LIST_DATE_KEY:
            DrawDateKey();
            break;
        case LIST_ERROR_KEY:
            DrawErrorKey();
            break;
        case LIST_UNDERGROUND_LEGS:
            GenerateDisplayList();
            break;
        case LIST_TUBES:
            GenerateDisplayListTubes();
            break;
        case LIST_SURFACE_LEGS:
            GenerateDisplayListSurface();
            break;
        case LIST_BLOBS:
            GenerateBlobsDisplayList();
            break;
        case LIST_CROSSES: {
            BeginCrosses();
            SetColour(col_LIGHT_GREY);
            list<LabelInfo*>::const_iterator pos = m_Parent->GetLabels();
            while (pos != m_Parent->GetLabelsEnd()) {
                const LabelInfo* label = *pos++;

                if ((m_Surface && label->IsSurface()) ||
                    (m_Legs && label->IsUnderground()) ||
                    (!label->IsSurface() && !label->IsUnderground())) {
                    // Check if this station should be displayed
                    // (last case is for stns with no legs attached)
                    DrawCross(label->GetX(), label->GetY(), label->GetZ());
                }
            }
            EndCrosses();
            break;
        }
        case LIST_GRID:
            DrawGrid();
            break;
        case LIST_SHADOW:
            GenerateDisplayListShadow();
            break;
        default:
            assert(false);
            break;
    }
}

void GfxCore::ToggleSmoothShading()
{
    GLACanvas::ToggleSmoothShading();
    InvalidateList(LIST_TUBES);
    ForceRefresh();
}

void GfxCore::GenerateDisplayList()
{
    // Generate the display list for the underground legs.
    list<traverse>::const_iterator trav = m_Parent->traverses_begin();
    list<traverse>::const_iterator tend = m_Parent->traverses_end();
    while (trav != tend) {
        (this->*AddPoly)(*trav);
        ++trav;
    }
}

void GfxCore::GenerateDisplayListTubes()
{
    // Generate the display list for the tubes.
    list<vector<XSect> >::const_iterator trav = m_Parent->tubes_begin();
    list<vector<XSect> >::const_iterator tend = m_Parent->tubes_end();
    while (trav != tend) {
        SkinPassage(*trav);
        ++trav;
    }
}

void GfxCore::GenerateDisplayListSurface()
{
    // Generate the display list for the surface legs.
    EnableDashedLines();
    list<traverse>::const_iterator trav = m_Parent->surface_traverses_begin();
    list<traverse>::const_iterator tend = m_Parent->surface_traverses_end();
    while (trav != tend) {
        if (m_ColourBy == COLOUR_BY_ERROR) {
            AddPolylineError(*trav);
        } else {
            AddPolyline(*trav);
        }
        ++trav;
    }
    DisableDashedLines();
}

void GfxCore::GenerateDisplayListShadow()
{
    SetColour(col_BLACK);
    list<traverse>::const_iterator trav = m_Parent->traverses_begin();
    list<traverse>::const_iterator tend = m_Parent->traverses_end();
    while (trav != tend) {
        AddPolylineShadow(*trav);
        ++trav;
    }
}

// Plot blobs.
void GfxCore::GenerateBlobsDisplayList()
{
    if (!(m_Entrances || m_FixedPts || m_ExportedPts ||
          m_Parent->GetNumHighlightedPts()))
        return;

    // Plot blobs.
    gla_colour prev_col = col_BLACK; // not a colour used for blobs
    list<LabelInfo*>::const_iterator pos = m_Parent->GetLabels();
    BeginBlobs();
    while (pos != m_Parent->GetLabelsEnd()) {
        const LabelInfo* label = *pos++;

        // When more than one flag is set on a point:
        // search results take priority over entrance highlighting
        // which takes priority over fixed point
        // highlighting, which in turn takes priority over exported
        // point highlighting.

        if (!((m_Surface && label->IsSurface()) ||
              (m_Legs && label->IsUnderground()) ||
              (!label->IsSurface() && !label->IsUnderground()))) {
            // if this station isn't to be displayed, skip to the next
            // (last case is for stns with no legs attached)
            continue;
        }

        gla_colour col;

        if (label->IsHighLighted()) {
            col = col_YELLOW;
        } else if (m_Entrances && label->IsEntrance()) {
            col = col_GREEN;
        } else if (m_FixedPts && label->IsFixedPt()) {
            col = col_RED;
        } else if (m_ExportedPts && label->IsExportedPt()) {
            col = col_TURQUOISE;
        } else {
            continue;
        }

        // Stations are sorted by blob type, so colour changes are infrequent.
        if (col != prev_col) {
            SetColour(col);
            prev_col = col;
        }
        DrawBlob(label->GetX(), label->GetY(), label->GetZ());
    }
    EndBlobs();
}

void GfxCore::DrawIndicators()
{
    // Draw colour key.
    if (m_ColourKey) {
        if (m_ColourBy == COLOUR_BY_DEPTH && m_Parent->GetDepthExtent() != 0.0) {
            DrawList2D(LIST_DEPTH_KEY, m_XSize - COLOUR_KEY_OFFSET_X,
                       m_YSize - COLOUR_KEY_OFFSET_Y, 0);
        } else if (m_ColourBy == COLOUR_BY_DATE && HasDateInformation()) {
            DrawList2D(LIST_DATE_KEY, m_XSize - COLOUR_KEY_OFFSET_X,
                       m_YSize - COLOUR_KEY_OFFSET_Y, 0);
        } else if (m_ColourBy == COLOUR_BY_ERROR && m_Parent->HasErrorInformation()) {
            DrawList2D(LIST_ERROR_KEY, m_XSize - COLOUR_KEY_OFFSET_X,
                       m_YSize - COLOUR_KEY_OFFSET_Y, 0);
        }
    }

    // Draw compass or elevation/heading indicators.
    if (m_Compass || m_Clino) {
        if (!m_Parent->IsExtendedElevation()) Draw2dIndicators();
    }

    // Draw scalebar.
    if (m_Scalebar) {
        DrawList2D(LIST_SCALE_BAR, 0, 0, 0);
    }
}

void GfxCore::PlaceVertexWithColour(const Vector3 & v,
                                    glaTexCoord tex_x, glaTexCoord tex_y,
                                    Double factor)
{
    SetColour(GetSurfacePen(), factor); // FIXME : assumes surface pen is white!
    PlaceVertex(v, tex_x, tex_y);
}

void GfxCore::SetDepthColour(Double z, Double factor) {
    // Set the drawing colour based on the altitude.
    Double z_ext = m_Parent->GetDepthExtent();
    assert(z_ext > 0);

    z -= m_Parent->GetDepthMin();
    // points arising from tubes may be slightly outside the limits...
    if (z < 0) z = 0;
    if (z > z_ext) z = z_ext;

    Double how_far = z / z_ext;
    assert(how_far >= 0.0);
    assert(how_far <= 1.0);

    int band = int(floor(how_far * (GetNumColourBands() - 1)));
    GLAPen pen1 = GetPen(band);
    if (band < GetNumColourBands() - 1) {
        const GLAPen& pen2 = GetPen(band + 1);

        Double interval = z_ext / (GetNumColourBands() - 1);
        Double into_band = z / interval - band;

//      printf("%g z_offset=%g interval=%g band=%d\n", into_band,
//             z_offset, interval, band);
        // FIXME: why do we need to clamp here?  Is it because the walls can
        // extend further up/down than the centre-line?
        if (into_band < 0.0) into_band = 0.0;
        if (into_band > 1.0) into_band = 1.0;
        assert(into_band >= 0.0);
        assert(into_band <= 1.0);

        pen1.Interpolate(pen2, into_band);
    }
    SetColour(pen1, factor);
}

void GfxCore::PlaceVertexWithDepthColour(const Vector3 &v, Double factor)
{
    SetDepthColour(v.GetZ(), factor);
    PlaceVertex(v);
}

void GfxCore::PlaceVertexWithDepthColour(const Vector3 &v,
                                         glaTexCoord tex_x, glaTexCoord tex_y,
                                         Double factor)
{
    SetDepthColour(v.GetZ(), factor);
    PlaceVertex(v, tex_x, tex_y);
}

void GfxCore::SplitLineAcrossBands(int band, int band2,
                                   const Vector3 &p, const Vector3 &q,
                                   Double factor)
{
    const int step = (band < band2) ? 1 : -1;
    for (int i = band; i != band2; i += step) {
        const Double z = GetDepthBoundaryBetweenBands(i, i + step);

        // Find the intersection point of the line p -> q
        // with the plane parallel to the xy-plane with z-axis intersection z.
        assert(q.GetZ() - p.GetZ() != 0.0);

        const Double t = (z - p.GetZ()) / (q.GetZ() - p.GetZ());
//      assert(0.0 <= t && t <= 1.0);           FIXME: rounding problems!

        const Double x = p.GetX() + t * (q.GetX() - p.GetX());
        const Double y = p.GetY() + t * (q.GetY() - p.GetY());

        PlaceVertexWithDepthColour(Vector3(x, y, z), factor);
    }
}

int GfxCore::GetDepthColour(Double z) const
{
    // Return the (0-based) depth colour band index for a z-coordinate.
    Double z_ext = m_Parent->GetDepthExtent();
    assert(z_ext > 0);
    z -= m_Parent->GetDepthMin();
    z += z_ext / 2;
    return int(z / z_ext * (GetNumColourBands() - 1));
}

Double GfxCore::GetDepthBoundaryBetweenBands(int a, int b) const
{
    // Return the z-coordinate of the depth colour boundary between
    // two adjacent depth colour bands (specified by 0-based indices).

    assert((a == b - 1) || (a == b + 1));
    if (GetNumColourBands() == 1) return 0;

    int band = (a > b) ? a : b; // boundary N lies on the bottom of band N.
    Double z_ext = m_Parent->GetDepthExtent();
    return (z_ext * band / (GetNumColourBands() - 1)) - z_ext / 2
        + m_Parent->GetDepthMin();
}

void GfxCore::AddPolyline(const traverse & centreline)
{
    BeginPolyline();
    SetColour(GetSurfacePen());
    vector<PointInfo>::const_iterator i = centreline.begin();
    PlaceVertex(*i);
    ++i;
    while (i != centreline.end()) {
        PlaceVertex(*i);
        ++i;
    }
    EndPolyline();
}

void GfxCore::AddPolylineShadow(const traverse & centreline)
{
    BeginPolyline();
    const double z = -0.5 * m_Parent->GetZExtent();
    vector<PointInfo>::const_iterator i = centreline.begin();
    PlaceVertex(i->GetX(), i->GetY(), z);
    ++i;
    while (i != centreline.end()) {
        PlaceVertex(i->GetX(), i->GetY(), z);
        ++i;
    }
    EndPolyline();
}

void GfxCore::AddPolylineDepth(const traverse & centreline)
{
    BeginPolyline();
    vector<PointInfo>::const_iterator i, prev_i;
    i = centreline.begin();
    int band0 = GetDepthColour(i->GetZ());
    PlaceVertexWithDepthColour(*i);
    prev_i = i;
    ++i;
    while (i != centreline.end()) {
        int band = GetDepthColour(i->GetZ());
        if (band != band0) {
            SplitLineAcrossBands(band0, band, *prev_i, *i);
            band0 = band;
        }
        PlaceVertexWithDepthColour(*i);
        prev_i = i;
        ++i;
    }
    EndPolyline();
}

void GfxCore::AddQuadrilateral(const Vector3 &a, const Vector3 &b,
                               const Vector3 &c, const Vector3 &d)
{
    Vector3 normal = (a - c) * (d - b);
    normal.normalise();
    Double factor = dot(normal, light) * .3 + .7;
    glaTexCoord w(ceil(((b - a).magnitude() + (d - c).magnitude()) * .5));
    glaTexCoord h(ceil(((b - c).magnitude() + (d - a).magnitude()) * .5));
    // FIXME: should plot triangles instead to avoid rendering glitches.
    BeginQuadrilaterals();
    PlaceVertexWithColour(a, 0, 0, factor);
    PlaceVertexWithColour(b, w, 0, factor);
    PlaceVertexWithColour(c, w, h, factor);
    PlaceVertexWithColour(d, 0, h, factor);
    EndQuadrilaterals();
}

void GfxCore::AddQuadrilateralDepth(const Vector3 &a, const Vector3 &b,
                                    const Vector3 &c, const Vector3 &d)
{
    Vector3 normal = (a - c) * (d - b);
    normal.normalise();
    Double factor = dot(normal, light) * .3 + .7;
    int a_band, b_band, c_band, d_band;
    a_band = GetDepthColour(a.GetZ());
    a_band = min(max(a_band, 0), GetNumColourBands());
    b_band = GetDepthColour(b.GetZ());
    b_band = min(max(b_band, 0), GetNumColourBands());
    c_band = GetDepthColour(c.GetZ());
    c_band = min(max(c_band, 0), GetNumColourBands());
    d_band = GetDepthColour(d.GetZ());
    d_band = min(max(d_band, 0), GetNumColourBands());
    // All this splitting is incorrect - we need to make a separate polygon
    // for each depth band...
    glaTexCoord w(ceil(((b - a).magnitude() + (d - c).magnitude()) * .5));
    glaTexCoord h(ceil(((b - c).magnitude() + (d - a).magnitude()) * .5));
    BeginPolygon();
////    PlaceNormal(normal);
    PlaceVertexWithDepthColour(a, 0, 0, factor);
    if (a_band != b_band) {
        SplitLineAcrossBands(a_band, b_band, a, b, factor);
    }
    PlaceVertexWithDepthColour(b, w, 0, factor);
    if (b_band != c_band) {
        SplitLineAcrossBands(b_band, c_band, b, c, factor);
    }
    PlaceVertexWithDepthColour(c, w, h, factor);
    if (c_band != d_band) {
        SplitLineAcrossBands(c_band, d_band, c, d, factor);
    }
    PlaceVertexWithDepthColour(d, 0, h, factor);
    if (d_band != a_band) {
        SplitLineAcrossBands(d_band, a_band, d, a, factor);
    }
    EndPolygon();
}

void GfxCore::SetColourFromDate(int date, Double factor)
{
    // Set the drawing colour based on a date.

    if (date == -1) {
        // Undated.
        SetColour(GetSurfacePen(), factor);
        return;
    }

    int date_offset = date - m_Parent->GetDateMin();
    if (date_offset == 0) {
        // Earliest date - handle as a special case for the single date case.
        SetColour(GetPen(0), factor);
        return;
    }

    int date_ext = m_Parent->GetDateExtent();
    Double how_far = (Double)date_offset / date_ext;
    assert(how_far >= 0.0);
    assert(how_far <= 1.0);

    int band = int(floor(how_far * (GetNumColourBands() - 1)));
    GLAPen pen1 = GetPen(band);
    if (band < GetNumColourBands() - 1) {
        const GLAPen& pen2 = GetPen(band + 1);

        Double interval = date_ext / (GetNumColourBands() - 1);
        Double into_band = date_offset / interval - band;

//      printf("%g z_offset=%g interval=%g band=%d\n", into_band,
//             z_offset, interval, band);
        // FIXME: why do we need to clamp here?  Is it because the walls can
        // extend further up/down than the centre-line?
        if (into_band < 0.0) into_band = 0.0;
        if (into_band > 1.0) into_band = 1.0;
        assert(into_band >= 0.0);
        assert(into_band <= 1.0);

        pen1.Interpolate(pen2, into_band);
    }
    SetColour(pen1, factor);
}

void GfxCore::AddPolylineDate(const traverse & centreline)
{
    BeginPolyline();
    vector<PointInfo>::const_iterator i, prev_i;
    i = centreline.begin();
    int date = i->GetDate();
    SetColourFromDate(date, 1.0);
    PlaceVertex(*i);
    prev_i = i;
    while (++i != centreline.end()) {
        int newdate = i->GetDate();
        if (newdate != date) {
            EndPolyline();
            BeginPolyline();
            date = newdate;
            SetColourFromDate(date, 1.0);
            PlaceVertex(*prev_i);
        }
        PlaceVertex(*i);
        prev_i = i;
    }
    EndPolyline();
}

static int static_date_hack; // FIXME

void GfxCore::AddQuadrilateralDate(const Vector3 &a, const Vector3 &b,
                                   const Vector3 &c, const Vector3 &d)
{
    Vector3 normal = (a - c) * (d - b);
    normal.normalise();
    Double factor = dot(normal, light) * .3 + .7;
    int w = int(ceil(((b - a).magnitude() + (d - c).magnitude()) / 2));
    int h = int(ceil(((b - c).magnitude() + (d - a).magnitude()) / 2));
    // FIXME: should plot triangles instead to avoid rendering glitches.
    BeginQuadrilaterals();
////    PlaceNormal(normal);
    SetColourFromDate(static_date_hack, factor);
    PlaceVertex(a, 0, 0);
    PlaceVertex(b, w, 0);
    PlaceVertex(c, w, h);
    PlaceVertex(d, 0, h);
    EndQuadrilaterals();
}

static double static_E_hack; // FIXME

void GfxCore::SetColourFromError(double E, Double factor)
{
    // Set the drawing colour based on an error value.

    if (E < 0) {
        SetColour(GetSurfacePen(), factor);
        return;
    }

    Double how_far = E / MAX_ERROR;
    assert(how_far >= 0.0);
    if (how_far > 1.0) how_far = 1.0;

    int band = int(floor(how_far * (GetNumColourBands() - 1)));
    GLAPen pen1 = GetPen(band);
    if (band < GetNumColourBands() - 1) {
        const GLAPen& pen2 = GetPen(band + 1);

        Double interval = MAX_ERROR / (GetNumColourBands() - 1);
        Double into_band = E / interval - band;

//      printf("%g z_offset=%g interval=%g band=%d\n", into_band,
//             z_offset, interval, band);
        // FIXME: why do we need to clamp here?  Is it because the walls can
        // extend further up/down than the centre-line?
        if (into_band < 0.0) into_band = 0.0;
        if (into_band > 1.0) into_band = 1.0;
        assert(into_band >= 0.0);
        assert(into_band <= 1.0);

        pen1.Interpolate(pen2, into_band);
    }
    SetColour(pen1, factor);
}

void GfxCore::AddQuadrilateralError(const Vector3 &a, const Vector3 &b,
                                    const Vector3 &c, const Vector3 &d)
{
    Vector3 normal = (a - c) * (d - b);
    normal.normalise();
    Double factor = dot(normal, light) * .3 + .7;
    int w = int(ceil(((b - a).magnitude() + (d - c).magnitude()) / 2));
    int h = int(ceil(((b - c).magnitude() + (d - a).magnitude()) / 2));
    // FIXME: should plot triangles instead to avoid rendering glitches.
    BeginQuadrilaterals();
////    PlaceNormal(normal);
    SetColourFromError(static_E_hack, factor);
    PlaceVertex(a, 0, 0);
    PlaceVertex(b, w, 0);
    PlaceVertex(c, w, h);
    PlaceVertex(d, 0, h);
    EndQuadrilaterals();
}

void GfxCore::AddPolylineError(const traverse & centreline)
{
    BeginPolyline();
    SetColourFromError(centreline.E, 1.0);
    vector<PointInfo>::const_iterator i;
    for(i = centreline.begin(); i != centreline.end(); ++i) {
        PlaceVertex(*i);
    }
    EndPolyline();
}

void
GfxCore::SkinPassage(const vector<XSect> & centreline)
{
    assert(centreline.size() > 1);
    Vector3 U[4];
    XSect prev_pt_v;
    Vector3 last_right(1.0, 0.0, 0.0);

//  FIXME: it's not simple to set the colour of a tube based on error...
//    static_E_hack = something...
    vector<XSect>::const_iterator i = centreline.begin();
    vector<XSect>::size_type segment = 0;
    while (i != centreline.end()) {
        // get the coordinates of this vertex
        const XSect & pt_v = *i++;

        double z_pitch_adjust = 0.0;
        bool cover_end = false;

        Vector3 right, up;

        const Vector3 up_v(0.0, 0.0, 1.0);

        if (segment == 0) {
            assert(i != centreline.end());
            // first segment

            // get the coordinates of the next vertex
            const XSect & next_pt_v = *i;

            // calculate vector from this pt to the next one
            Vector3 leg_v = next_pt_v - pt_v;

            // obtain a vector in the LRUD plane
            right = leg_v * up_v;
            if (right.magnitude() == 0) {
                right = last_right;
                // Obtain a second vector in the LRUD plane,
                // perpendicular to the first.
                //up = right * leg_v;
                up = up_v;
            } else {
                last_right = right;
                up = up_v;
            }

            cover_end = true;
            static_date_hack = next_pt_v.GetDate();
        } else if (segment + 1 == centreline.size()) {
            // last segment

            // Calculate vector from the previous pt to this one.
            Vector3 leg_v = pt_v - prev_pt_v;

            // Obtain a horizontal vector in the LRUD plane.
            right = leg_v * up_v;
            if (right.magnitude() == 0) {
                right = Vector3(last_right.GetX(), last_right.GetY(), 0.0);
                // Obtain a second vector in the LRUD plane,
                // perpendicular to the first.
                //up = right * leg_v;
                up = up_v;
            } else {
                last_right = right;
                up = up_v;
            }

            cover_end = true;
            static_date_hack = pt_v.GetDate();
        } else {
            assert(i != centreline.end());
            // Intermediate segment.

            // Get the coordinates of the next vertex.
            const XSect & next_pt_v = *i;

            // Calculate vectors from this vertex to the
            // next vertex, and from the previous vertex to
            // this one.
            Vector3 leg1_v = pt_v - prev_pt_v;
            Vector3 leg2_v = next_pt_v - pt_v;

            // Obtain horizontal vectors perpendicular to
            // both legs, then normalise and average to get
            // a horizontal bisector.
            Vector3 r1 = leg1_v * up_v;
            Vector3 r2 = leg2_v * up_v;
            r1.normalise();
            r2.normalise();
            right = r1 + r2;
            if (right.magnitude() == 0) {
                // This is the "mid-pitch" case...
                right = last_right;
            }
            if (r1.magnitude() == 0) {
                Vector3 n = leg1_v;
                n.normalise();
                z_pitch_adjust = n.GetZ();
                //up = Vector3(0, 0, leg1_v.GetZ());
                //up = right * up;
                up = up_v;

                // Rotate pitch section to minimise the
                // "tortional stress" - FIXME: use
                // triangles instead of rectangles?
                int shift = 0;
                Double maxdotp = 0;

                // Scale to unit vectors in the LRUD plane.
                right.normalise();
                up.normalise();
                Vector3 vec = up - right;
                for (int orient = 0; orient <= 3; ++orient) {
                    Vector3 tmp = U[orient] - prev_pt_v;
                    tmp.normalise();
                    Double dotp = dot(vec, tmp);
                    if (dotp > maxdotp) {
                        maxdotp = dotp;
                        shift = orient;
                    }
                }
                if (shift) {
                    if (shift != 2) {
                        Vector3 temp(U[0]);
                        U[0] = U[shift];
                        U[shift] = U[2];
                        U[2] = U[shift ^ 2];
                        U[shift ^ 2] = temp;
                    } else {
                        swap(U[0], U[2]);
                        swap(U[1], U[3]);
                    }
                }
#if 0
                // Check that the above code actually permuted
                // the vertices correctly.
                shift = 0;
                maxdotp = 0;
                for (int j = 0; j <= 3; ++j) {
                    Vector3 tmp = U[j] - prev_pt_v;
                    tmp.normalise();
                    Double dotp = dot(vec, tmp);
                    if (dotp > maxdotp) {
                        maxdotp = dotp + 1e-6; // Add small tolerance to stop 45 degree offset cases being flagged...
                        shift = j;
                    }
                }
                if (shift) {
                    printf("New shift = %d!\n", shift);
                    shift = 0;
                    maxdotp = 0;
                    for (int j = 0; j <= 3; ++j) {
                        Vector3 tmp = U[j] - prev_pt_v;
                        tmp.normalise();
                        Double dotp = dot(vec, tmp);
                        printf("    %d : %.8f\n", j, dotp);
                    }
                }
#endif
            } else if (r2.magnitude() == 0) {
                Vector3 n = leg2_v;
                n.normalise();
                z_pitch_adjust = n.GetZ();
                //up = Vector3(0, 0, leg2_v.GetZ());
                //up = right * up;
                up = up_v;
            } else {
                up = up_v;
            }
            last_right = right;
            static_date_hack = pt_v.GetDate();
        }

        // Scale to unit vectors in the LRUD plane.
        right.normalise();
        up.normalise();

        if (z_pitch_adjust != 0) up += Vector3(0, 0, fabs(z_pitch_adjust));

        Double l = fabs(pt_v.GetL());
        Double r = fabs(pt_v.GetR());
        Double u = fabs(pt_v.GetU());
        Double d = fabs(pt_v.GetD());

        // Produce coordinates of the corners of the LRUD "plane".
        Vector3 v[4];
        v[0] = pt_v - right * l + up * u;
        v[1] = pt_v + right * r + up * u;
        v[2] = pt_v + right * r - up * d;
        v[3] = pt_v - right * l - up * d;

        if (segment > 0) {
            (this->*AddQuad)(v[0], v[1], U[1], U[0]);
            (this->*AddQuad)(v[2], v[3], U[3], U[2]);
            (this->*AddQuad)(v[1], v[2], U[2], U[1]);
            (this->*AddQuad)(v[3], v[0], U[0], U[3]);
        }

        if (cover_end) {
            (this->*AddQuad)(v[3], v[2], v[1], v[0]);
        }

        prev_pt_v = pt_v;
        U[0] = v[0];
        U[1] = v[1];
        U[2] = v[2];
        U[3] = v[3];

        ++segment;
    }
}

void GfxCore::FullScreenMode()
{
    m_Parent->ViewFullScreen();
}

bool GfxCore::IsFullScreen() const
{
    return m_Parent->IsFullScreen();
}

void
GfxCore::MoveViewer(double forward, double up, double right)
{
    double cT = cos(rad(m_TiltAngle));
    double sT = sin(rad(m_TiltAngle));
    double cP = cos(rad(m_PanAngle));
    double sP = sin(rad(m_PanAngle));
    Vector3 v_forward(cT * sP, cT * cP, -sT);
    Vector3 v_up(-sT * sP, -sT * cP, -cT);
    Vector3 v_right(-cP, sP, 0);
    assert(fabs(dot(v_forward, v_up)) < 1e-6);
    assert(fabs(dot(v_forward, v_right)) < 1e-6);
    assert(fabs(dot(v_right, v_up)) < 1e-6);
    Vector3 move = v_forward * forward + v_up * up + v_right * right;
    AddTranslation(-move);
    // Show current position.
    m_Parent->SetCoords(m_Parent->GetOffset() - GetTranslation());
    ForceRefresh();
}

PresentationMark GfxCore::GetView() const
{
    return PresentationMark(GetTranslation() + m_Parent->GetOffset(),
                            m_PanAngle, m_TiltAngle, m_Scale);
}

void GfxCore::SetView(const PresentationMark & p)
{
    m_SwitchingTo = 0;
    SetTranslation(p - m_Parent->GetOffset());
    m_PanAngle = p.angle;
    m_TiltAngle = p.tilt_angle;
    SetRotation(m_PanAngle, m_TiltAngle);
    SetScale(p.scale);
    ForceRefresh();
}

void GfxCore::PlayPres(double speed, bool change_speed) {
    if (!change_speed || presentation_mode == 0) {
        if (speed == 0.0) {
            presentation_mode = 0;
            return;
        }
        presentation_mode = PLAYING;
        next_mark = m_Parent->GetPresMark(MARK_FIRST);
        SetView(next_mark);
        next_mark_time = 0; // There already!
        this_mark_total = 0;
        pres_reverse = (speed < 0);
    }

    if (change_speed) pres_speed = speed;

    if (speed != 0.0) {
        bool new_pres_reverse = (speed < 0);
        if (new_pres_reverse != pres_reverse) {
            pres_reverse = new_pres_reverse;
            if (pres_reverse) {
                next_mark = m_Parent->GetPresMark(MARK_PREV);
            } else {
                next_mark = m_Parent->GetPresMark(MARK_NEXT);
            }
            swap(this_mark_total, next_mark_time);
        }
    }
}

void GfxCore::SetColourBy(int colour_by) {
    m_ColourBy = colour_by;
    switch (colour_by) {
        case COLOUR_BY_DEPTH:
            AddQuad = &GfxCore::AddQuadrilateralDepth;
            AddPoly = &GfxCore::AddPolylineDepth;
            break;
        case COLOUR_BY_DATE:
            AddQuad = &GfxCore::AddQuadrilateralDate;
            AddPoly = &GfxCore::AddPolylineDate;
            break;
        case COLOUR_BY_ERROR:
            AddQuad = &GfxCore::AddQuadrilateralError;
            AddPoly = &GfxCore::AddPolylineError;
            break;
        default: // case COLOUR_BY_NONE:
            AddQuad = &GfxCore::AddQuadrilateral;
            AddPoly = &GfxCore::AddPolyline;
            break;
    }

    InvalidateList(LIST_UNDERGROUND_LEGS);
    InvalidateList(LIST_SURFACE_LEGS);
    InvalidateList(LIST_TUBES);

    ForceRefresh();
}

bool GfxCore::ExportMovie(const wxString & fnm)
{
    int width;
    int height;
    GetSize(&width, &height);
    // Round up to next multiple of 2 (required by ffmpeg).
    width += (width & 1);
    height += (height & 1);

    movie = new MovieMaker();

    // FIXME: This should really use fn_str() - currently we probably can't
    // save to a Unicode path on wxmsw.
    if (!movie->Open(fnm.mb_str(), width, height)) {
        wxGetApp().ReportError(wxString(movie->get_error_string(), wxConvUTF8));
        delete movie;
        movie = NULL;
        return false;
    }

    PlayPres(1);
    return true;
}

void
GfxCore::OnPrint(const wxString &filename, const wxString &title,
                 const wxString &datestamp)
{
    svxPrintDlg * p;
    p = new svxPrintDlg(m_Parent, filename, title, datestamp,
                        m_PanAngle, m_TiltAngle,
                        m_Names, m_Crosses, m_Legs, m_Surface,
                        true);
    p->Show(TRUE);
}

void
GfxCore::OnExport(const wxString &filename, const wxString &title)
{
    svxPrintDlg * p;
    p = new svxPrintDlg(m_Parent, filename, title, wxString(),
                        m_PanAngle, m_TiltAngle,
                        m_Names, m_Crosses, m_Legs, m_Surface,
                        false);
    p->Show(TRUE);
}

static wxCursor
make_cursor(const unsigned char * bits, const unsigned char * mask,
            int hotx, int hoty)
{
#if defined __WXMSW__ || defined __WXMAC__
    wxBitmap cursor_bitmap(reinterpret_cast<const char *>(bits), 32, 32);
    wxBitmap mask_bitmap(reinterpret_cast<const char *>(mask), 32, 32);
    cursor_bitmap.SetMask(new wxMask(mask_bitmap));
    wxImage cursor_image = cursor_bitmap.ConvertToImage();
    cursor_image.SetOption(wxIMAGE_OPTION_CUR_HOTSPOT_X, hotx);
    cursor_image.SetOption(wxIMAGE_OPTION_CUR_HOTSPOT_Y, hoty);
    return wxCursor(cursor_image);
#else
    return wxCursor((const char *)bits, 32, 32, hotx, hoty,
                    (const char *)mask, wxWHITE, wxBLACK);
#endif
}

const
#include "hand.xbm"
const
#include "handmask.xbm"

const
#include "brotate.xbm"
const
#include "brotatemask.xbm"

const
#include "vrotate.xbm"
const
#include "vrotatemask.xbm"

const
#include "rotate.xbm"
const
#include "rotatemask.xbm"

const
#include "rotatezoom.xbm"
const
#include "rotatezoommask.xbm"

void
GfxCore::SetCursor(GfxCore::cursor new_cursor)
{
    // Check if we're already showing that cursor.
    if (current_cursor == new_cursor) return;

    current_cursor = new_cursor;
    switch (current_cursor) {
        case GfxCore::CURSOR_DEFAULT:
            GLACanvas::SetCursor(wxNullCursor);
            break;
        case GfxCore::CURSOR_POINTING_HAND:
            GLACanvas::SetCursor(wxCursor(wxCURSOR_HAND));
            break;
        case GfxCore::CURSOR_DRAGGING_HAND:
            GLACanvas::SetCursor(make_cursor(hand_bits, handmask_bits, 12, 18));
            break;
        case GfxCore::CURSOR_HORIZONTAL_RESIZE:
            GLACanvas::SetCursor(wxCursor(wxCURSOR_SIZEWE));
            break;
        case GfxCore::CURSOR_ROTATE_HORIZONTALLY:
            GLACanvas::SetCursor(make_cursor(rotate_bits, rotatemask_bits, 15, 15));
            break;
        case GfxCore::CURSOR_ROTATE_VERTICALLY:
            GLACanvas::SetCursor(make_cursor(vrotate_bits, vrotatemask_bits, 15, 15));
            break;
        case GfxCore::CURSOR_ROTATE_EITHER_WAY:
            GLACanvas::SetCursor(make_cursor(brotate_bits, brotatemask_bits, 15, 15));
            break;
        case GfxCore::CURSOR_ZOOM:
            GLACanvas::SetCursor(wxCursor(wxCURSOR_MAGNIFIER));
            break;
        case GfxCore::CURSOR_ZOOM_ROTATE:
            GLACanvas::SetCursor(make_cursor(rotatezoom_bits, rotatezoommask_bits, 15, 15));
            break;
    }
}

bool GfxCore::MeasuringLineActive() const
{
    if (Animating()) return false;
    return (m_here.IsValid() && !m_here_is_temporary) || m_there.IsValid();
}

bool GfxCore::HandleRClick(wxPoint point)
{
    if (PointWithinCompass(point)) {
        // Pop up menu.
        wxMenu menu;
        menu.Append(menu_ORIENT_MOVE_NORTH, wmsg(/*View &North*/240));
        menu.Append(menu_ORIENT_MOVE_EAST, wmsg(/*View &East*/241));
        menu.Append(menu_ORIENT_MOVE_SOUTH, wmsg(/*View &South*/242));
        menu.Append(menu_ORIENT_MOVE_WEST, wmsg(/*View &West*/243));
        menu.AppendSeparator();
        menu.AppendCheckItem(menu_IND_COMPASS, wmsg(/*&Hide Compass*/344));
        menu.AppendCheckItem(menu_CTL_DEGREES, wmsg(/*&Degrees*/343));
        menu.Connect(wxEVT_COMMAND_MENU_SELECTED, (wxObjectEventFunction)&MainFrm::ProcessEvent, NULL, m_Parent);
        PopupMenu(&menu);
        return true;
    }

    if (PointWithinClino(point)) {
        // Pop up menu.
        wxMenu menu;
        menu.Append(menu_ORIENT_PLAN, wmsg(/*&Plan View*/248));
        menu.Append(menu_ORIENT_ELEVATION, wmsg(/*Ele&vation*/249));
        menu.AppendSeparator();
        menu.AppendCheckItem(menu_IND_CLINO, wmsg(/*&Hide Clino*/384));
        menu.AppendCheckItem(menu_CTL_DEGREES, wmsg(/*&Degrees*/343));
        menu.Connect(wxEVT_COMMAND_MENU_SELECTED, (wxObjectEventFunction)&MainFrm::ProcessEvent, NULL, m_Parent);
        PopupMenu(&menu);
        return true;
    }

    if (PointWithinScaleBar(point)) {
        // Pop up menu.
        wxMenu menu;
        menu.AppendCheckItem(menu_IND_SCALE_BAR, wmsg(/*&Hide scale bar*/385));
        menu.AppendCheckItem(menu_CTL_METRIC, wmsg(/*&Metric*/342));
        menu.Connect(wxEVT_COMMAND_MENU_SELECTED, (wxObjectEventFunction)&MainFrm::ProcessEvent, NULL, m_Parent);
        PopupMenu(&menu);
        return true;
    }

#if 0 // FIXME: Don't yet have PointWithinColourKey() method.
    if (PointWithinColourKey(point)) {
        // Pop up menu.
        wxMenu menu;
        menu.AppendCheckItem(menu_IND_COLOUR_KEY, wmsg(/*&Hide colour key*/386));
        menu.Connect(wxEVT_COMMAND_MENU_SELECTED, (wxObjectEventFunction)&MainFrm::OnToggleMetric, NULL, m_Parent);
        PopupMenu(&menu);
        return true;
    }
#endif

    return false;
}