libs/canvas/framed_curve.cc

   1 /*
   2     Copyright (C) 2013 Paul Davis
   3
   4     This program is free software; you can redistribute it and/or modify
   5     it under the terms of the GNU General Public License as published by
   6     the Free Software Foundation; either version 2 of the License, or
   7     (at your option) any later version.
   8
   9     This program is distributed in the hope that it will be useful,
  10     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12     GNU General Public License for more details.
  13
  14     You should have received a copy of the GNU General Public License
  15     along with this program; if not, write to the Free Software
  16     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17
  18 */
  19
  20 #include <cmath>
  21 #include <exception>
  22 #include <algorithm>
  23
  24 #include "canvas/framed_curve.h"
  25
  26 using namespace ArdourCanvas;
  27 using std::min;
  28 using std::max;
  29
  30 FramedCurve::FramedCurve (Canvas* c)
  31         : PolyItem (c)
  32         , n_samples (0)
  33         , points_per_segment (16)
  34         , curve_fill (None)
  35 {
  36 }
  37
  38 FramedCurve::FramedCurve (Item* parent)
  39         : PolyItem (parent)
  40         , n_samples (0)
  41         , points_per_segment (16)
  42         , curve_fill (None)
  43 {
  44 }
  45
  46 /** When rendering the curve, we will always draw a fixed number of straight
  47  * line segments to span the x-axis extent of the curve. More segments:
  48  * smoother visual rendering. Less rendering: closer to a visibily poly-line
  49  * render.
  50  */
  51 void
  52 FramedCurve::set_points_per_segment (uint32_t n)
  53 {
  54         /* this only changes our appearance rather than the bounding box, so we
  55            just need to schedule a redraw rather than notify the parent of any
  56            changes
  57         */
  58         points_per_segment = n;
  59         interpolate ();
  60         redraw ();
  61 }
  62
  63 void
  64 FramedCurve::compute_bounding_box () const
  65 {
  66         PolyItem::compute_bounding_box ();
  67
  68         /* possibly add extents of any point indicators here if we ever do that */
  69 }
  70
  71 void
  72 FramedCurve::set (Points const& p)
  73 {
  74         PolyItem::set (p);
  75         interpolate ();
  76 }
  77
  78 void
  79 FramedCurve::interpolate ()
  80 {
  81         Points curve_points = _points;
  82
  83         if (curve_points.size()) {
  84                 curve_points.erase (curve_points.begin());
  85         }
  86         samples.clear ();
  87
  88         InterpolatedCurve::interpolate (curve_points, points_per_segment, CatmullRomCentripetal, false, samples);
  89         n_samples = samples.size();
  90 }
  91
  92 void
  93 FramedCurve::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) const
  94 {
  95         if (!_outline || _points.size() < 3 || !_bounding_box) {
  96                 return;
  97         }
  98
  99         Rect self = item_to_window (_bounding_box.get());
 100         boost::optional<Rect> d = self.intersection (area);
 101         assert (d);
 102         Rect draw = d.get ();
 103
 104         /* Our approach is to always draw n_segments across our total size.
 105          *
 106          * This is very inefficient if we are asked to only draw a small
 107          * section of the curve. For now we rely on cairo clipping to help
 108          * with this.
 109          */
 110
 111
 112         setup_outline_context (context);
 113
 114         if (_points.size() == 3) {
 115
 116                 /* straight line */
 117
 118                 Duple window_space;
 119                 Points::const_iterator it = _points.begin();
 120                 window_space = item_to_window (*it);
 121                 context->move_to (window_space.x, window_space.y);
 122                 ++it;
 123                 window_space = item_to_window (*it);
 124                 context->line_to (window_space.x, window_space.y);
 125                 window_space = item_to_window (_points.back());
 126                 context->line_to (window_space.x, window_space.y);
 127
 128                 switch (curve_fill) {
 129                         case None:
 130                                 context->stroke();
 131                                 break;
 132                         case Inside:
 133                                 context->stroke_preserve ();
 134                                 window_space = item_to_window (Duple(_points.back().x, draw.height()));
 135                                 context->line_to (window_space.x, window_space.y);
 136                                 window_space = item_to_window (Duple(_points.back().x, draw.height()));
 137                                 context->line_to (window_space.x, window_space.y);
 138                                 context->close_path();
 139                                 setup_fill_context(context);
 140                                 context->fill ();
 141                                 break;
 142                         case Outside:
 143                                 context->stroke_preserve ();
 144                                 window_space = item_to_window (Duple(_points.back().x, 0.0));
 145                                 context->line_to (window_space.x, window_space.y);
 146                                 window_space = item_to_window (Duple(_points.front().x, 0.0));
 147                                 context->line_to (window_space.x, window_space.y);
 148                                 context->close_path();
 149                                 setup_fill_context(context);
 150                                 context->fill ();
 151                                 break;
 152                 }
 153
 154         } else {
 155
 156                 /* curve of at least 3 points */
 157
 158                 /* x-axis limits of the curve, in window space coordinates */
 159
 160                 Duple w1 = item_to_window (Duple (_points.front().x, 0.0));
 161                 Duple w2 = item_to_window (Duple (_points.back().x, 0.0));
 162
 163                 /* clamp actual draw to area bound by points, rather than our bounding box which is slightly different */
 164
 165                 context->save ();
 166                 context->rectangle (draw.x0, draw.y0, draw.width(), draw.height());
 167                 context->clip ();
 168
 169                 /* expand drawing area by several pixels on each side to avoid cairo stroking effects at the boundary.
 170                    they will still occur, but cairo's clipping will hide them.
 171                  */
 172
 173                 draw = draw.expand (4.0);
 174
 175                 /* now clip it to the actual points in the curve */
 176
 177                 if (draw.x0 < w1.x) {
 178                         draw.x0 = w1.x;
 179                 }
 180
 181                 if (draw.x1 >= w2.x) {
 182                         draw.x1 = w2.x;
 183                 }
 184
 185                 /* find left and right-most sample */
 186                 Duple window_space;
 187                 Points::size_type left = 0;
 188                 Points::size_type right = n_samples;
 189
 190                 for (Points::size_type idx = 0; idx < n_samples - 1; ++idx) {
 191                         left = idx;
 192                         window_space = item_to_window (Duple (samples[idx].x, 0.0));
 193                         if (window_space.x >= draw.x0) break;
 194                 }
 195                 for (Points::size_type idx = n_samples; idx > left + 1; --idx) {
 196                         window_space = item_to_window (Duple (samples[idx].x, 0.0));
 197                         if (window_space.x <= draw.x1) break;
 198                         right = idx;
 199                 }
 200
 201                 /* draw line between samples */
 202                 window_space = item_to_window (Duple (samples[left].x, samples[left].y));
 203                 context->move_to (window_space.x, window_space.y);
 204                 for (uint32_t idx = left + 1; idx < right; ++idx) {
 205                         window_space = item_to_window (Duple (samples[idx].x, samples[idx].y), false);
 206                         context->line_to (window_space.x, window_space.y);
 207                 }
 208
 209                 switch (curve_fill) {
 210                         case None:
 211                                 context->stroke();
 212                                 break;
 213                         case Inside:
 214                                 context->stroke_preserve ();
 215                                 window_space = item_to_window (Duple (samples[right-1].x, draw.height()));
 216                                 context->line_to (window_space.x, window_space.y);
 217                                 window_space = item_to_window (Duple (samples[left].x, draw.height()));
 218                                 context->line_to (window_space.x, window_space.y);
 219                                 context->close_path();
 220                                 setup_fill_context(context);
 221                                 context->fill ();
 222                                 break;
 223                         case Outside:
 224                                 context->stroke_preserve ();
 225                                 window_space = item_to_window (Duple (samples[right-1].x, 0.0));
 226                                 context->line_to (window_space.x, window_space.y);
 227                                 window_space = item_to_window (Duple (samples[left].x, 0.0));
 228                                 context->line_to (window_space.x, window_space.y);
 229                                 context->close_path();
 230                                 setup_fill_context(context);
 231                                 context->fill ();
 232                                 break;
 233                 }
 234                 context->restore ();
 235         }
 236
 237 #if 0
 238         /* add points */
 239         setup_outline_context (context);
 240         for (Points::const_iterator p = _points.begin(); p != _points.end(); ++p) {
 241                 Duple window_space (item_to_window (*p));
 242                 context->arc (window_space.x, window_space.y, 5.0, 0.0, 2 * M_PI);
 243                 context->stroke ();
 244         }
 245 #endif
 246 }
 247
 248 bool
 249 FramedCurve::covers (Duple const & pc) const
 250 {
 251         Duple point = window_to_item (pc);
 252
 253         /* O(N) N = number of points, and not accurate */
 254
 255         for (Points::const_iterator p = _points.begin(); p != _points.end(); ++p) {
 256
 257                 const Coord dx = point.x - (*p).x;
 258                 const Coord dy = point.y - (*p).y;
 259                 const Coord dx2 = dx * dx;
 260                 const Coord dy2 = dy * dy;
 261
 262                 if ((dx2 < 2.0 && dy2 < 2.0) || (dx2 + dy2 < 4.0)) {
 263                         return true;
 264                 }
 265         }
 266
 267         return false;
 268 }