viewport.cpp

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/***************************************************************************
 *   Copyright (C) 2015 by David S. Register                               *
 *                                                                         *
 *   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, see <https://www.gnu.org/licenses/>. *
 **************************************************************************/
 
// Must come before any GL includes:
#include "gl_headers.h"
 
#include <vector>
 
#ifndef __WXMSW__
#include <signal.h>
#include <setjmp.h>
#endif
 
#if defined(__ANDROID__)
#include <GLES2/gl2.h>
#elif defined(__WXQT__) || defined(__WXGTK__)
#include <GL/glew.h>
#endif
 
// For compilers that support precompilation, includes "wx.h".
#include <wx/wxprec.h>
#ifndef WX_PRECOMP
#include <wx/wx.h>
#endif
 
#include <wx/aui/aui.h>
#include <wx/clipbrd.h>
#include <wx/graphics.h>
#include <wx/image.h>
#include <wx/listbook.h>
#include <wx/listimpl.cpp>
 
#ifdef __VISUALC__
#include <wx/msw/msvcrt.h>
#endif
 
#include "model/ais_decoder.h"
#include "model/ais_target_data.h"
#include "model/cutil.h"
#include "model/geodesic.h"
#include "model/multiplexer.h"
#include "model/routeman.h"
#include "model/select.h"
#include "model/select_item.h"
 
#include "ais.h"
#include "ais_target_alert_dlg.h"
#include "chartdb.h"
#include "chartimg.h"
#include "chcanv.h"
#include "ch_info_win.h"
#include "cm93.h"  // for chart outline draw
#include "concanv.h"
#include "config.h"
#include "dychart.h"
#include "font_mgr.h"
#include "gl_texture_descr.h"
#include "gshhs.h"
#include "kml.h"
#include "navutil.h"
#include "ocpndc.h"
#include "ocpn_pixel.h"
#include "ocpn_platform.h"
#include "ocpn_region.h"
#include "pluginmanager.h"
#include "quilt.h"
#include "routemanagerdialog.h"
#include "s52plib.h"
#include "s57chart.h"  // for ArrayOfS57Obj
#include "send_to_gps_dlg.h"
#include "styles.h"
#include "tcmgr.h"
#include "tc_win.h"
#include "thumbwin.h"
#include "tide_time.h"
#include "timers.h"
#include "track_prop_dlg.h"
#include "undo.h"
 
#ifdef ocpnUSE_GL
#include "gl_chart_canvas.h"
#endif
 
// FIXME (leamas) find new home
ColorScheme global_color_scheme = GLOBAL_COLOR_SCHEME_DAY;
 
//------------------------------------------------------------------------------
//    ViewPort Implementation
//------------------------------------------------------------------------------
ViewPort::ViewPort() {
  bValid = false;
  skew = 0.;
  view_scale_ppm = 1;
  rotation = 0.;
  tilt = 0.;
  b_quilt = false;
  pix_height = pix_width = 0;
  b_MercatorProjectionOverride = false;
  lat0_cache = NAN;
  m_projection_type = PROJECTION_MERCATOR;
  m_displayScale = 1.0;
}
 
void ViewPort::SetPixelScale(double scale) { m_displayScale = scale; }
 
// TODO: eliminate the use of this function
wxPoint ViewPort::GetPixFromLL(double lat, double lon) {
  wxPoint2DDouble p = GetDoublePixFromLL(lat, lon);
  if (wxFinite(p.m_x) && wxFinite(p.m_y)) {
    if ((abs(p.m_x) < 1e6) && (abs(p.m_y) < 1e6))
      return wxPoint(wxRound(p.m_x), wxRound(p.m_y));
  }
  return wxPoint(INVALID_COORD, INVALID_COORD);
}
 
wxPoint2DDouble ViewPort::GetDoublePixFromLL(double lat, double lon) {
  double easting = 0;
  double northing = 0;
  double xlon = lon;
 
  /*  Make sure lon and lon0 are same phase */
  if (xlon * clon < 0.) {
    if (xlon < 0.)
      xlon += 360.;
    else
      xlon -= 360.;
  }
 
  if (fabs(xlon - clon) > 180.) {
    if (xlon > clon)
      xlon -= 360.;
    else
      xlon += 360.;
  }
 
  // update cache of trig functions used for projections
  if (clat != lat0_cache) {
    lat0_cache = clat;
    switch (m_projection_type) {
      case PROJECTION_MERCATOR:
      case PROJECTION_WEB_MERCATOR:
        cache0 = toSMcache_y30(clat);
        break;
      case PROJECTION_POLAR:
        cache0 = toPOLARcache_e(clat);
        break;
      case PROJECTION_ORTHOGRAPHIC:
      case PROJECTION_STEREOGRAPHIC:
      case PROJECTION_GNOMONIC:
        cache_phi0(clat, &cache0, &cache1);
        break;
    }
  }
 
  switch (m_projection_type) {
    case PROJECTION_MERCATOR:
    case PROJECTION_WEB_MERCATOR:
      toSMcache(lat, xlon, cache0, clon, &easting, &northing);
      break;
 
    case PROJECTION_TRANSVERSE_MERCATOR:
      //    We calculate northings as referenced to the equator
      //    And eastings as though the projection point is midscreen.
 
      double tmeasting, tmnorthing;
      double tmceasting, tmcnorthing;
      toTM(clat, clon, 0., clon, &tmceasting, &tmcnorthing);
      toTM(lat, xlon, 0., clon, &tmeasting, &tmnorthing);
 
      northing = tmnorthing - tmcnorthing;
      easting = tmeasting - tmceasting;
      break;
 
    case PROJECTION_POLYCONIC:
 
      //    We calculate northings as referenced to the equator
      //    And eastings as though the projection point is midscreen.
      double pceasting, pcnorthing;
      toPOLY(clat, clon, 0., clon, &pceasting, &pcnorthing);
 
      double peasting, pnorthing;
      toPOLY(lat, xlon, 0., clon, &peasting, &pnorthing);
 
      easting = peasting;
      northing = pnorthing - pcnorthing;
      break;
 
    case PROJECTION_ORTHOGRAPHIC:
      toORTHO(lat, xlon, cache0, cache1, clon, &easting, &northing);
      break;
 
    case PROJECTION_POLAR:
      toPOLAR(lat, xlon, cache0, clat, clon, &easting, &northing);
      break;
 
    case PROJECTION_STEREOGRAPHIC:
      toSTEREO(lat, xlon, cache0, cache1, clon, &easting, &northing);
      break;
 
    case PROJECTION_GNOMONIC:
      toGNO(lat, xlon, cache0, cache1, clon, &easting, &northing);
      break;
 
    case PROJECTION_EQUIRECTANGULAR:
      toEQUIRECT(lat, xlon, clat, clon, &easting, &northing);
      break;
 
    default:
      printf("unhandled projection\n");
  }
 
  if (!wxFinite(easting) || !wxFinite(northing))
    return wxPoint2DDouble(easting, northing);
 
  double epix = easting * view_scale_ppm;
  double npix = northing * view_scale_ppm;
  double dxr = epix;
  double dyr = npix;
 
  //    Apply VP Rotation
  double angle = rotation;
 
  if (angle) {
    dxr = epix * cos(angle) + npix * sin(angle);
    dyr = npix * cos(angle) - epix * sin(angle);
  }
  double x = (pix_width / 2.0) + dxr;
  double y = (pix_height / 2.0) - dyr;
  if (!g_bopengl) {
    // Convert from physical to logical pixels when not using OpenGL.
    // This ensures that the viewport corner coordinates remain the
    // same in OpenGL and no-OpenGL mode (especially in MacOS).
    x /= m_displayScale;
    y /= m_displayScale;
  }
  return wxPoint2DDouble(x, y);
}
 
void ViewPort::GetLLFromPix(const wxPoint2DDouble &p, double *lat,
                            double *lon) {
  // Calculate distance from the center of the viewport to the given point in
  // physical pixels.
  double dx = p.m_x - (pix_width / 2.0);
  double dy = (pix_height / 2.0) - p.m_y;
 
  double xpr = dx;
  double ypr = dy;
 
  //    Apply VP Rotation
  double angle = rotation;
 
  if (angle) {
    xpr = (dx * cos(angle)) - (dy * sin(angle));
    ypr = (dy * cos(angle)) + (dx * sin(angle));
  }
  double d_east = xpr / view_scale_ppm;
  double d_north = ypr / view_scale_ppm;
 
  double slat = 0.0, slon = 0.0;
  switch (m_projection_type) {
    case PROJECTION_MERCATOR:
    case PROJECTION_WEB_MERCATOR:
      // TODO  This could be fromSM_ECC to better match some Raster charts
      //      However, it seems that cm93 (and S57) prefer no eccentricity
      //      correction Think about it....
      fromSM(d_east, d_north, clat, clon, &slat, &slon);
      break;
 
    case PROJECTION_TRANSVERSE_MERCATOR: {
      double tmceasting, tmcnorthing;
      toTM(clat, clon, 0., clon, &tmceasting, &tmcnorthing);
 
      fromTM(d_east, d_north + tmcnorthing, 0., clon, &slat, &slon);
    } break;
 
    case PROJECTION_POLYCONIC: {
      double polyeasting, polynorthing;
      toPOLY(clat, clon, 0., clon, &polyeasting, &polynorthing);
 
      fromPOLY(d_east, d_north + polynorthing, 0., clon, &slat, &slon);
    } break;
 
    case PROJECTION_ORTHOGRAPHIC:
      fromORTHO(d_east, d_north, clat, clon, &slat, &slon);
      break;
 
    case PROJECTION_POLAR:
      fromPOLAR(d_east, d_north, clat, clon, &slat, &slon);
      break;
 
    case PROJECTION_STEREOGRAPHIC:
      fromSTEREO(d_east, d_north, clat, clon, &slat, &slon);
      break;
 
    case PROJECTION_GNOMONIC:
      fromGNO(d_east, d_north, clat, clon, &slat, &slon);
      break;
 
    case PROJECTION_EQUIRECTANGULAR:
      fromEQUIRECT(d_east, d_north, clat, clon, &slat, &slon);
      break;
 
    default:
      printf("unhandled projection\n");
  }
 
  *lat = slat;
 
  if (slon < -180.)
    slon += 360.;
  else if (slon > 180.)
    slon -= 360.;
  *lon = slon;
}
 
LLRegion ViewPort::GetLLRegion(const OCPNRegion &region) {
  // todo: for these projecetions, improve this calculation by using the
  //       method in SetBoxes here
#ifndef ocpnUSE_GL
  return LLRegion(GetBBox());
#else
 
  if (!glChartCanvas::CanClipViewport(*this)) return LLRegion(GetBBox());
 
  OCPNRegionIterator it(region);
  LLRegion r;
  while (it.HaveRects()) {
    wxRect rect = it.GetRect();
 
    int x1 = rect.x, y1 = rect.y, x2 = x1 + rect.width, y2 = y1 + rect.height;
    int p[8] = {x1, y1, x2, y1, x2, y2, x1, y2};
    double pll[2896];  //  Max splits is 180, ((180 *  2)  + 2) * 8 = 2896.
    int j;
 
    /* if the viewport is rotated, we must split the segments as straight lines
       in lat/lon coordinates map to curves in projected coordinate space */
    if (fabs(rotation) >= 0.0001) {
      j = 0;
      double lastlat, lastlon;
      int li = 6;
      GetLLFromPix(wxPoint(p[li], p[li + 1]), &lastlat, &lastlon);
      for (int i = 0; i < 8; i += 2) {
        double lat, lon;
        GetLLFromPix(wxPoint(p[i], p[i + 1]), &lat, &lon);
 
        // use 2 degree grid
        double grid = 2;
        int lat_splits = floor(fabs(lat - lastlat) / grid);
        double lond = fabs(lon - lastlon);
        int lon_splits = floor((lond > 180 ? 360 - lond : lond) / grid);
        int splits = wxMax(lat_splits, lon_splits) + 1;
 
        for (int k = 1; k < splits; k++) {
          float d = (float)k / splits;
          GetLLFromPix(wxPoint((1 - d) * p[li] + d * p[i],
                               (1 - d) * p[li + 1] + d * p[i + 1]),
                       pll + j, pll + j + 1);
          j += 2;
        }
        pll[j++] = lat;
        pll[j++] = lon;
        li = i;
        lastlat = lat, lastlon = lon;
      }
    } else {
      j = 8;
      for (int i = 0; i < j; i += 2)
        GetLLFromPix(wxPoint(p[i], p[i + 1]), pll + i, pll + i + 1);
    }
 
    // resolve (this works even if rectangle crosses both 0 and 180)
    for (int i = 0; i < j; i += 2) {
      if (pll[i + 1] <= clon - 180)
        pll[i + 1] += 360;
      else if (pll[i + 1] >= clon + 180)
        pll[i + 1] -= 360;
    }
 
    r.Union(LLRegion(j / 2, pll));
    it.NextRect();
  }
  return r;
#endif
}
 
struct ContourRegion {
  double maxlat;
  bool subtract;
  OCPNRegion r;
};
 
OCPNRegion ViewPort::GetVPRegionIntersect(const OCPNRegion &region,
                                          const LLRegion &llregion,
                                          int chart_native_scale) {
  double rotation_save = rotation;
  rotation = 0;
 
  std::list<ContourRegion> cregions;
  for (auto i = llregion.contours.begin(); i != llregion.contours.end(); i++) {
    float *contour_points = new float[2 * i->size()];
    int idx = 0;
    for (auto j = i->begin(); j != i->end(); j++) {
      contour_points[idx++] = j->y;
      contour_points[idx++] = j->x;
    }
 
    double total = 0, maxlat = -90;
    int pl = idx - 2;
    double x0 = contour_points[0] - contour_points[pl + 0];
    double y0 = contour_points[1] - contour_points[pl + 1];
    // determine winding direction of this contour
    for (int p = 0; p < idx; p += 2) {
      maxlat = wxMax(maxlat, contour_points[p]);
      int pn = p < idx - 2 ? p + 2 : 0;
      double x1 = contour_points[pn + 0] - contour_points[p + 0];
      double y1 = contour_points[pn + 1] - contour_points[p + 1];
      total += x1 * y0 - x0 * y1;
      x0 = x1, y0 = y1;
    }
 
    ContourRegion s;
    s.maxlat = maxlat;
    s.subtract = total < 0;
    s.r = GetVPRegionIntersect(region, i->size(), contour_points,
                               chart_native_scale, NULL);
    delete[] contour_points;
 
    std::list<ContourRegion>::iterator k = cregions.begin();
    while (k != cregions.end()) {
      if (k->maxlat < s.maxlat) break;
      k++;
    }
    cregions.insert(k, s);
  }
 
  OCPNRegion r;
  for (std::list<ContourRegion>::iterator k = cregions.begin();
       k != cregions.end(); k++) {
    if (k->r.Ok()) {
      if (k->subtract)
        r.Subtract(k->r);
      else
        r.Union(k->r);
    }
  }
 
  rotation = rotation_save;
  return r;
}
 
OCPNRegion ViewPort::GetVPRegionIntersect(const OCPNRegion &Region, int nPoints,
                                          float *llpoints,
                                          int chart_native_scale,
                                          wxPoint *ppoints) {
  //  Calculate the intersection between a given OCPNRegion (Region) and a
  //  polygon specified by lat/lon points.
 
  //    If the viewpoint is highly overzoomed wrt to chart native scale, the
  //    polygon region may be huge. This can be very expensive, and lead to
  //    crashes on some platforms (gtk in particular) So, look for this case and
  //    handle appropriately with respect to the given Region
 
  if (chart_scale < chart_native_scale / 10) {
    //    Scan the points one-by-one, so that we can get min/max to make a bbox
    float *pfp = llpoints;
    float lon_max = -10000.;
    float lon_min = 10000.;
    float lat_max = -10000.;
    float lat_min = 10000.;
 
    for (int ip = 0; ip < nPoints; ip++) {
      lon_max = wxMax(lon_max, pfp[1]);
      lon_min = wxMin(lon_min, pfp[1]);
      lat_max = wxMax(lat_max, pfp[0]);
      lat_min = wxMin(lat_min, pfp[0]);
 
      pfp += 2;
    }
 
    LLBBox chart_box;
    chart_box.Set(lat_min, lon_min, lat_max, lon_max);
 
    //    Case:  vpBBox is completely outside the chart box, or vice versa
    //    Return an empty region
    if (chart_box.IntersectOut(vpBBox)) return OCPNRegion();
 
    //    Case:  vpBBox is completely inside the chart box
    //      Note that this test is not perfect, and will fail for some charts.
    //      The chart coverage may be  essentially triangular, and the viewport
    //      box may be in the "cut off" segment of the chart_box, and not
    //      actually exhibit any true overlap.  Results will be reported
    //      incorrectly. How to fix: maybe scrub the chart points and see if it
    //      is likely that a region may be safely built and intersection tested.
 
    if (chart_box.IntersectIn(vpBBox)) return Region;
 
    wxPoint p1 = GetPixFromLL(lat_max, lon_min);  // upper left
    wxPoint p2 = GetPixFromLL(lat_min, lon_max);  // lower right
 
    OCPNRegion r(p1, p2);
    r.Intersect(Region);
    return r;
  }
 
  //    More "normal" case
 
  wxPoint *pp;
 
  //    Use the passed point buffer if available
  if (ppoints == NULL)
    pp = new wxPoint[nPoints];
  else
    pp = ppoints;
 
  float *pfp = llpoints;
 
  wxPoint p = GetPixFromLL(pfp[0], pfp[1]);
  int poly_x_max = INVALID_COORD, poly_y_max = INVALID_COORD,
      poly_x_min = INVALID_COORD, poly_y_min = INVALID_COORD;
 
  bool valid = false;
  int npPoints = 0;
  for (int ip = 0; ip < nPoints; ip++) {
    wxPoint p = GetPixFromLL(pfp[0], pfp[1]);
    if (p.x == INVALID_COORD) continue;
 
    pp[npPoints++] = p;
 
    if (valid) {
      poly_x_max = wxMax(poly_x_max, p.x);
      poly_y_max = wxMax(poly_y_max, p.y);
      poly_x_min = wxMin(poly_x_min, p.x);
      poly_y_min = wxMin(poly_y_min, p.y);
    } else {
      poly_x_max = p.x;
      poly_y_max = p.y;
      poly_x_min = p.x;
      poly_y_min = p.y;
      valid = true;
    }
    pfp += 2;
  }
 
  if (!valid) {
    if (ppoints == NULL) delete[] pp;
    return OCPNRegion();  // empty;
  }
 
  //  We want to avoid processing regions with very large rectangle counts,
  //  so make some tests for special cases
 
  float_2Dpt p0, p1, p2, p3;
 
  //  First, calculate whether any segment of the input polygon intersects the
  //  specified Region
  int nrect = 0;
  bool b_intersect = false;
  OCPNRegionIterator screen_region_it1(Region);
  while (screen_region_it1.HaveRects()) {
    wxRect rect = screen_region_it1.GetRect();
 
    double lat, lon;
 
    //  The screen region corners
    GetLLFromPix(wxPoint(rect.x, rect.y), &lat, &lon);
    p0.y = lat;
    p0.x = lon;
 
    GetLLFromPix(wxPoint(rect.x + rect.width, rect.y), &lat, &lon);
    p1.y = lat;
    p1.x = lon;
 
    GetLLFromPix(wxPoint(rect.x + rect.width, rect.y + rect.height), &lat,
                 &lon);
    p2.y = lat;
    p2.x = lon;
 
    GetLLFromPix(wxPoint(rect.x, rect.y + rect.height), &lat, &lon);
    p3.y = lat;
    p3.x = lon;
 
    for (int i = 0; i < npPoints - 1; i++) {
      //  Quick check on y dimension
      int y0 = pp[i].y;
      int y1 = pp[i + 1].y;
 
      if (((y0 < rect.y) && (y1 < rect.y)) ||
          ((y0 > rect.y + rect.height) && (y1 > rect.y + rect.height)))
        continue;  // both ends of line outside of box, top or bottom
 
      //  Look harder
      float_2Dpt f0;
      f0.y = llpoints[i * 2];
      f0.x = llpoints[(i * 2) + 1];
      float_2Dpt f1;
      f1.y = llpoints[(i + 1) * 2];
      f1.x = llpoints[((i + 1) * 2) + 1];
      b_intersect |= Intersect_FL(p0, p1, f0, f1) != 0;
      if (b_intersect) break;
      b_intersect |= Intersect_FL(p1, p2, f0, f1) != 0;
      if (b_intersect) break;
      b_intersect |= Intersect_FL(p2, p3, f0, f1) != 0;
      if (b_intersect) break;
      b_intersect |= Intersect_FL(p3, p0, f0, f1) != 0;
      if (b_intersect) break;
 
      //  Must check the case where the input polygon has been pre-normalized,
      //  eg (0 < lon < 360), as cm93
      f0.x -= 360.;
      f1.x -= 360.;
      b_intersect |= Intersect_FL(p0, p1, f0, f1) != 0;
      if (b_intersect) break;
      b_intersect |= Intersect_FL(p1, p2, f0, f1) != 0;
      if (b_intersect) break;
      b_intersect |= Intersect_FL(p2, p3, f0, f1) != 0;
      if (b_intersect) break;
      b_intersect |= Intersect_FL(p3, p0, f0, f1) != 0;
      if (b_intersect) break;
    }
 
    // Check segment, last point back to first point
    if (!b_intersect) {
      float_2Dpt f0;
      f0.y = llpoints[(nPoints - 1) * 2];
      f0.x = llpoints[((nPoints - 1) * 2) + 1];
      float_2Dpt f1;
      f1.y = llpoints[0];
      f1.x = llpoints[1];
      b_intersect |= Intersect_FL(p0, p1, f0, f1) != 0;
      b_intersect |= Intersect_FL(p1, p2, f0, f1) != 0;
      b_intersect |= Intersect_FL(p2, p3, f0, f1) != 0;
      b_intersect |= Intersect_FL(p3, p0, f0, f1) != 0;
 
      f0.x -= 360.;
      f1.x -= 360.;
      b_intersect |= Intersect_FL(p0, p1, f0, f1) != 0;
      b_intersect |= Intersect_FL(p1, p2, f0, f1) != 0;
      b_intersect |= Intersect_FL(p2, p3, f0, f1) != 0;
      b_intersect |= Intersect_FL(p3, p0, f0, f1) != 0;
    }
 
    screen_region_it1.NextRect();
    nrect++;
  }
 
  //  If there is no itersection, we need to consider the case where
  //  the subject polygon is entirely within the Region
  bool b_contained = false;
  if (!b_intersect) {
    OCPNRegionIterator screen_region_it2(Region);
    while (screen_region_it2.HaveRects()) {
      wxRect rect = screen_region_it2.GetRect();
 
      for (int i = 0; i < npPoints - 1; i++) {
        int x0 = pp[i].x;
        int y0 = pp[i].y;
 
        if ((x0 < rect.x) || (x0 > rect.x + rect.width) || (y0 < rect.y) ||
            (y0 > rect.y + rect.height))
          continue;
 
        b_contained = true;
        break;
      }
      screen_region_it2.NextRect();
    }
  }
 
#if 1
  // and here is the payoff
  if (!b_contained && !b_intersect) {
    //  Two cases to consider
    wxRect rpoly(poly_x_min, poly_y_min, poly_x_max - poly_x_min,
                 poly_y_max - poly_y_min);
    wxRect rRegion = Region.GetBox();
    if (rpoly.Contains(rRegion)) {
      //  subject poygon may be large enough to fully encompass the target
      //  Region, but it might not, especially for irregular or concave charts.
      //  So we cannot directly shortcut here
      //  Better check....
 
#if 1
      if (nrect == 1) {  // most common case
        // If the subject polygon contains the center of the target rectangle,
        // then the intersection must be the target rectangle
        float rlat = (p0.y + p2.y) / 2.;
        float rlon = (p0.x + p1.x) / 2.;
 
        if (G_PtInPolygon_FL((float_2Dpt *)llpoints, nPoints, rlon, rlat)) {
          if (NULL == ppoints) delete[] pp;
          return Region;
        }
        rlon += 360.;
        if (G_PtInPolygon_FL((float_2Dpt *)llpoints, nPoints, rlon, rlat)) {
          if (NULL == ppoints) delete[] pp;
          return Region;
        }
 
        //  otherwise, there is no intersection
        else {
          if (NULL == ppoints) delete[] pp;
          wxRegion r;
          return r;
        }
      }
 
#endif
 
    } else {
      //  Subject polygon is entirely outside of target Region
      //  so the intersection must be empty.
      if (NULL == ppoints) delete[] pp;
      wxRegion r;
      return r;
    }
  } else if (b_contained && !b_intersect) {
    //  subject polygon is entirely withing the target Region,
    //  so the intersection is the subject polygon
    OCPNRegion r = OCPNRegion(npPoints, pp);
    if (NULL == ppoints) delete[] pp;
    return r;
  }
 
#endif
 
#ifdef __WXGTK__
  sigaction(SIGSEGV, NULL,
            &sa_all_old);  // save existing action for this signal
 
  struct sigaction temp;
  sigaction(SIGSEGV, NULL, &temp);  // inspect existing action for this signal
 
  temp.sa_handler = catch_signals;  // point to my handler
  sigemptyset(&temp.sa_mask);       // make the blocking set
  // empty, so that all
  // other signals will be
  // unblocked during my handler
  temp.sa_flags = 0;
  sigaction(SIGSEGV, &temp, NULL);
 
  if (sigsetjmp(env, 1))  //  Something in the below code block faulted....
  {
    sigaction(SIGSEGV, &sa_all_old, NULL);  // reset signal handler
 
    return Region;
 
  }
 
  else {
    OCPNRegion r = OCPNRegion(npPoints, pp);
    if (NULL == ppoints) delete[] pp;
 
    sigaction(SIGSEGV, &sa_all_old, NULL);  // reset signal handler
    r.Intersect(Region);
    return r;
  }
 
#else
  OCPNRegion r = OCPNRegion(npPoints, pp);
 
  if (NULL == ppoints) delete[] pp;
 
  r.Intersect(Region);
  return r;
 
#endif
}
 
wxRect ViewPort::GetVPRectIntersect(size_t n, float *llpoints) {
  //  Calculate the intersection between the currect VP screen
  //  and the bounding box of a polygon specified by lat/lon points.
 
  float *pfp = llpoints;
 
  BoundingBox point_box;
  for (unsigned int ip = 0; ip < n; ip++) {
    point_box.Expand(pfp[1], pfp[0]);
    pfp += 2;
  }
 
  wxPoint pul = GetPixFromLL(point_box.GetMaxY(), point_box.GetMinX());
  wxPoint plr = GetPixFromLL(point_box.GetMinY(), point_box.GetMaxX());
 
  OCPNRegion r(pul, plr);
  OCPNRegion rs(rv_rect);
 
  r.Intersect(rs);
 
  return r.GetBox();
}
 
void ViewPort::SetBoxes() {
  // In the case where canvas rotation is applied, we need to define a larger
  // "virtual" pixel window size to ensure that enough chart data is fatched
  // and available to fill the rotated screen.
  rv_rect = wxRect(0, 0, pix_width, pix_height);
 
  //  Specify the minimum required rectangle in unrotated screen space which
  //  will supply full screen data after specified rotation
  if ((fabs(skew) > .0001) || (fabs(rotation) > .0001)) {
    double rotator = rotation;
    double lpixh = pix_height;
    double lpixw = pix_width;
 
    lpixh = wxMax(lpixh,
                  (fabs(pix_height * cos(skew)) + fabs(pix_width * sin(skew))));
    lpixw = wxMax(lpixw,
                  (fabs(pix_width * cos(skew)) + fabs(pix_height * sin(skew))));
 
    int dy = wxRound(fabs(lpixh * cos(rotator)) + fabs(lpixw * sin(rotator)));
    int dx = wxRound(fabs(lpixw * cos(rotator)) + fabs(lpixh * sin(rotator)));
 
    //  It is important for MSW build that viewport pixel dimensions be
    //  multiples of 4.....
    if (dy % 4) dy += 4 - (dy % 4);
    if (dx % 4) dx += 4 - (dx % 4);
 
    int inflate_x = wxMax((dx - pix_width) / 2, 0);
    int inflate_y = wxMax((dy - pix_height) / 2, 0);
 
    //  Grow the source rectangle appropriately
    rv_rect.Inflate(inflate_x, inflate_y);
  }
 
  //  Compute Viewport lat/lon reference points for co-ordinate hit testing
 
  //  This must be done in unrotated space with respect to full unrotated screen
  //  space calculated above
  double rotation_save = rotation;
  SetRotationAngle(0.0);
 
  wxPoint ul(rv_rect.x, rv_rect.y);  // Upper left.
  wxPoint lr(rv_rect.x + rv_rect.width,
             rv_rect.y + rv_rect.height);  // Lower right.
  double dlat_min, dlat_max, dlon_min, dlon_max;
 
  bool hourglass = false;
  switch (m_projection_type) {
    case PROJECTION_TRANSVERSE_MERCATOR:
    case PROJECTION_STEREOGRAPHIC:
    case PROJECTION_GNOMONIC:
      hourglass = true;
      // fall through
    case PROJECTION_POLYCONIC:
    case PROJECTION_POLAR:
    case PROJECTION_ORTHOGRAPHIC: {
      double d;
 
      if (clat > 0) {  // north polar
        wxPoint u(rv_rect.x + rv_rect.width / 2, rv_rect.y);
        wxPoint ur(rv_rect.x + rv_rect.width, rv_rect.y);
        GetLLFromPix(ul, &d, &dlon_min);
        GetLLFromPix(ur, &d, &dlon_max);
        GetLLFromPix(lr, &dlat_min, &d);
        GetLLFromPix(u, &dlat_max, &d);
 
        if (fabs(fabs(d - clon) - 180) < 1) {  // the pole is onscreen
          dlat_max = 90;
          dlon_min = -180;
          dlon_max = 180;
        } else if (std::isnan(dlat_max))
          dlat_max = 90;
 
        if (hourglass) {
          // near equator, center may be less
          wxPoint l(rv_rect.x + rv_rect.width / 2, rv_rect.y + rv_rect.height);
          double dlat_min2;
          GetLLFromPix(l, &dlat_min2, &d);
          dlat_min = wxMin(dlat_min, dlat_min2);
        }
 
        if (std::isnan(dlat_min))  //  world is off-screen
          dlat_min = clat - 90;
      } else {  // south polar
        wxPoint l(rv_rect.x + rv_rect.width / 2, rv_rect.y + rv_rect.height);
        wxPoint ll(rv_rect.x, rv_rect.y + rv_rect.height);
        GetLLFromPix(ul, &dlat_max, &d);
        GetLLFromPix(lr, &d, &dlon_max);
        GetLLFromPix(ll, &d, &dlon_min);
        GetLLFromPix(l, &dlat_min, &d);
 
        if (fabs(fabs(d - clon) - 180) < 1) {  // the pole is onscreen
          dlat_min = -90;
          dlon_min = -180;
          dlon_max = 180;
        } else if (std::isnan(dlat_min))
          dlat_min = -90;
 
        if (hourglass) {
          // near equator, center may be less
          wxPoint u(rv_rect.x + rv_rect.width / 2, rv_rect.y);
          double dlat_max2;
          GetLLFromPix(u, &dlat_max2, &d);
          dlat_max = wxMax(dlat_max, dlat_max2);
        }
 
        if (std::isnan(dlat_max))  //  world is off-screen
          dlat_max = clat + 90;
      }
 
      if (std::isnan(dlon_min)) {
        // if neither pole is visible, but left and right of the screen are in
        // space we can avoid drawing the far side of the earth
        if (dlat_max < 90 && dlat_min > -90) {
          dlon_min =
              clon - 90 -
              fabs(clat);  // this logic is not optimal, is it always correct?
          dlon_max = clon + 90 + fabs(clat);
        } else {
          dlon_min = -180;
          dlon_max = 180;
        }
      }
    } break;
 
    default:  // works for mercator and equirectangular
    {
      GetLLFromPix(ul, &dlat_max, &dlon_min);
      GetLLFromPix(lr, &dlat_min, &dlon_max);
    }
  }
 
  if (clon < dlon_min)
    dlon_min -= 360;
  else if (clon > dlon_max)
    dlon_max += 360;
 
  //  Set the viewport lat/lon bounding box appropriately
  vpBBox.Set(dlat_min, dlon_min, dlat_max, dlon_max);
 
  // Restore the rotation angle
  SetRotationAngle(rotation_save);
}
 
void ViewPort::SetBBoxDirect(double latmin, double lonmin, double latmax,
                             double lonmax) {
  vpBBox.Set(latmin, lonmin, latmax, lonmax);
}
bool ViewPort::ContainsIDL() {
  if ((vpBBox.GetMinLon() <= -180.) && (vpBBox.GetMaxLon() > -180.))
    return true;
  if ((vpBBox.GetMinLon() <= 180.) && (vpBBox.GetMaxLon() > 180.)) return true;
  return false;
}
 
ViewPort ViewPort::BuildExpandedVP(int width, int height) {
  ViewPort new_vp = *this;
 
  new_vp.pix_width = width;
  new_vp.pix_height = height;
  new_vp.SetBoxes();
 
  return new_vp;
}
 
void ViewPort::SetVPTransformMatrix() {
  mat4x4 m;
  mat4x4_identity(m);
  mat4x4_scale_aniso((float(*)[4])vp_matrix_transform, m,
                     2.0 / (float)pix_width, -2.0 / (float)pix_height, 1.0);
  mat4x4_translate_in_place((float(*)[4])vp_matrix_transform, -pix_width / 2,
                            -pix_height / 2, 0);
}