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 = max (n, (uint32_t) 3);
  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         /* x-axis limits of the curve, in window space coordinates */
 112
 113         Duple w1 = item_to_window (Duple (_points.front().x, 0.0));
 114         Duple w2 = item_to_window (Duple (_points.back().x, 0.0));
 115
 116         /* clamp actual draw to area bound by points, rather than our bounding box which is slightly different */
 117
 118         context->save ();
 119         context->rectangle (draw.x0, draw.y0, draw.width(), draw.height());
 120         context->clip ();
 121
 122         /* expand drawing area by several pixels on each side to avoid cairo stroking effects at the boundary.
 123            they will still occur, but cairo's clipping will hide them.
 124         */
 125
 126         draw = draw.expand (4.0);
 127
 128         /* now clip it to the actual points in the curve */
 129
 130         if (draw.x0 < w1.x) {
 131                 draw.x0 = w1.x;
 132         }
 133
 134         if (draw.x1 >= w2.x) {
 135                 draw.x1 = w2.x;
 136         }
 137
 138         setup_outline_context (context);
 139
 140         if (_points.size() == 3) {
 141
 142                 /* straight line */
 143
 144                 Duple window_space;
 145                 Points::const_iterator it = _points.begin();
 146                 window_space = item_to_window (*it);
 147                 context->move_to (window_space.x, window_space.y);
 148                 ++it;
 149                 window_space = item_to_window (*it, false);
 150                 context->line_to (window_space.x, window_space.y);
 151                 window_space = item_to_window (_points.back(), false);
 152                 context->line_to (window_space.x, window_space.y);
 153
 154                 switch (curve_fill) {
 155                         case None:
 156                                 context->stroke();
 157                                 break;
 158                         case Inside:
 159                                 context->stroke_preserve ();
 160                                 window_space = item_to_window (Duple(_points.back().x, draw.height()));
 161                                 context->line_to (window_space.x, window_space.y);
 162                                 window_space = item_to_window (Duple(_points.front().x, draw.height()));
 163                                 context->line_to (window_space.x, window_space.y);
 164                                 context->close_path();
 165                                 setup_fill_context(context);
 166                                 context->fill ();
 167                                 break;
 168                         case Outside:
 169                                 context->stroke_preserve ();
 170                                 window_space = item_to_window (Duple(_points.back().x, 0.0));
 171                                 context->line_to (window_space.x, window_space.y);
 172                                 window_space = item_to_window (Duple(_points.front().x, 0.0));
 173                                 context->line_to (window_space.x, window_space.y);
 174                                 context->close_path();
 175                                 setup_fill_context(context);
 176                                 context->fill ();
 177                                 break;
 178                 }
 179         } else {
 180
 181                 /* curve of at least 3 points */
 182
 183                 /* find left and right-most sample */
 184                 Duple window_space;
 185                 Points::size_type left = 0;
 186                 Points::size_type right = n_samples - 1;
 187
 188                 for (Points::size_type idx = 0; idx < n_samples - 1; ++idx) {
 189                         window_space = item_to_window (Duple (samples[idx].x, 0.0));
 190                         if (window_space.x >= draw.x0) {
 191                                 break;
 192                         }
 193                         left = idx;
 194                 }
 195
 196                 for (Points::size_type idx = left; idx < n_samples - 1; ++idx) {
 197                         window_space = item_to_window (Duple (samples[idx].x, 0.0));
 198                         if (window_space.x > draw.x1) {
 199                                 right = idx;
 200                                 break;
 201                         }
 202                 }
 203
 204                 const Duple first_sample = Duple (samples[left].x, samples[left].y);
 205
 206                 /* move to the first sample's x and the draw height */
 207                 window_space = item_to_window (Duple (first_sample.x, draw.height()));
 208                 context->move_to (window_space.x, window_space.y);
 209
 210                 /* draw line to first sample and then between samples */
 211                 for (uint32_t idx = left; idx <= right; ++idx) {
 212                         window_space = item_to_window (Duple (samples[idx].x, samples[idx].y), false);
 213                         context->line_to (window_space.x, window_space.y);
 214                 }
 215
 216                 /* a redraw may have been requested between the last sample and the last point.
 217                    if so, draw a line to the last _point.
 218                 */
 219                 Duple last_sample = Duple (samples[right].x, samples[right].y);
 220
 221                 if (draw.x1 > last_sample.x) {
 222                         last_sample = Duple (_points.back().x, _points.back().y);
 223                         window_space = item_to_window (last_sample, false);
 224                         context->line_to (window_space.x, window_space.y);
 225                 }
 226
 227                 switch (curve_fill) {
 228                         case None:
 229                                 context->stroke();
 230                                 break;
 231                         case Inside:
 232                                 context->stroke_preserve ();
 233                                 /* close the frame, possibly using the last _point's x rather than samples[right].x */
 234                                 window_space = item_to_window (Duple (last_sample.x, draw.height()));
 235                                 context->line_to (window_space.x, window_space.y);
 236                                 window_space = item_to_window (Duple (first_sample.x, draw.height()));
 237                                 context->line_to (window_space.x, window_space.y);
 238                                 context->close_path();
 239                                 setup_fill_context(context);
 240                                 context->fill ();
 241                                 break;
 242                         case Outside:
 243                                 context->stroke_preserve ();
 244                                 window_space = item_to_window (Duple (last_sample.x, 0.0));
 245                                 context->line_to (window_space.x, window_space.y);
 246                                 window_space = item_to_window (Duple (first_sample.x, 0.0));
 247                                 context->line_to (window_space.x, window_space.y);
 248                                 context->close_path();
 249                                 setup_fill_context(context);
 250                                 context->fill ();
 251                                 break;
 252                 }
 253         }
 254         context->restore ();
 255
 256 #if 0
 257         /* add points */
 258         setup_outline_context (context);
 259         for (Points::const_iterator p = _points.begin(); p != _points.end(); ++p) {
 260                 Duple window_space (item_to_window (*p));
 261                 context->arc (window_space.x, window_space.y, 5.0, 0.0, 2 * M_PI);
 262                 context->stroke ();
 263         }
 264 #endif
 265 }
 266
 267 bool
 268 FramedCurve::covers (Duple const & pc) const
 269 {
 270         Duple point = window_to_item (pc);
 271
 272         /* O(N) N = number of points, and not accurate */
 273
 274         for (Points::const_iterator p = _points.begin(); p != _points.end(); ++p) {
 275
 276                 const Coord dx = point.x - (*p).x;
 277                 const Coord dy = point.y - (*p).y;
 278                 const Coord dx2 = dx * dx;
 279                 const Coord dy2 = dy * dy;
 280
 281                 if ((dx2 < 2.0 && dy2 < 2.0) || (dx2 + dy2 < 4.0)) {
 282                         return true;
 283                 }
 284         }
 285
 286         return false;
 287 }