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 (Inside)
  35 {
  36 }
  37
  38 FramedCurve::FramedCurve (Item* parent)
  39         : PolyItem (parent)
  40         , n_samples (0)
  41         , points_per_segment (16)
  42         , curve_fill (Inside)
  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         if (_points.size() == 3) {
  89                 samples.push_back (curve_points.front());
  90                 samples.push_back (curve_points.back());
  91                 n_samples = 2;
  92         } else {
  93
  94                 InterpolatedCurve::interpolate (curve_points, points_per_segment, CatmullRomCentripetal, false, samples);
  95                 n_samples = samples.size();
  96         }
  97 }
  98
  99 void
 100 FramedCurve::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) const
 101 {
 102         if (!_outline || _points.size() < 3 || !_bounding_box) {
 103                 return;
 104         }
 105
 106         Rect self = item_to_window (_bounding_box.get());
 107         boost::optional<Rect> d = self.intersection (area);
 108         assert (d);
 109         Rect draw = d.get ();
 110
 111         /* Our approach is to always draw n_segments across our total size.
 112          *
 113          * This is very inefficient if we are asked to only draw a small
 114          * section of the curve. For now we rely on cairo clipping to help
 115          * with this.
 116          */
 117
 118         /* x-axis limits of the curve, in window space coordinates */
 119
 120         Duple w1 = item_to_window (Duple (_points.front().x, 0.0));
 121         Duple w2 = item_to_window (Duple (_points.back().x, 0.0));
 122
 123         /* clamp actual draw to area bound by points, rather than our bounding box which is slightly different */
 124
 125         context->save ();
 126         context->rectangle (draw.x0, draw.y0, draw.width(), draw.height());
 127         context->clip ();
 128
 129         /* expand drawing area by several pixels on each side to avoid cairo stroking effects at the boundary.
 130            they will still occur, but cairo's clipping will hide them.
 131         */
 132
 133         draw = draw.expand (4.0);
 134
 135         /* now clip it to the actual points in the curve */
 136
 137         if (draw.x0 < w1.x) {
 138                 draw.x0 = w1.x;
 139         }
 140
 141         if (draw.x1 >= w2.x) {
 142                 draw.x1 = w2.x;
 143         }
 144
 145         setup_outline_context (context);
 146
 147         if (_points.size() == 3) {
 148
 149                 /* straight line */
 150
 151                 Duple window_space;
 152                 Points::const_iterator it = _points.begin();
 153                 window_space = item_to_window (*it);
 154                 context->move_to (window_space.x, window_space.y);
 155                 ++it;
 156                 window_space = item_to_window (*it, false);
 157                 context->line_to (window_space.x, window_space.y);
 158                 window_space = item_to_window (_points.back(), false);
 159                 context->line_to (window_space.x, window_space.y);
 160
 161                 switch (curve_fill) {
 162                         case None:
 163                                 context->stroke();
 164                                 break;
 165                         case Inside:
 166                                 context->stroke_preserve ();
 167                                 window_space = item_to_window (Duple(_points.back().x, draw.height()));
 168                                 context->line_to (window_space.x, window_space.y);
 169                                 window_space = item_to_window (Duple(_points.front().x, draw.height()));
 170                                 context->line_to (window_space.x, window_space.y);
 171                                 context->close_path();
 172                                 setup_fill_context(context);
 173                                 context->fill ();
 174                                 break;
 175                         case Outside:
 176                                 context->stroke_preserve ();
 177                                 window_space = item_to_window (Duple(_points.back().x, 0.0));
 178                                 context->line_to (window_space.x, window_space.y);
 179                                 window_space = item_to_window (Duple(_points.front().x, 0.0));
 180                                 context->line_to (window_space.x, window_space.y);
 181                                 context->close_path();
 182                                 setup_fill_context(context);
 183                                 context->fill ();
 184                                 break;
 185                 }
 186         } else {
 187
 188                 /* curve of at least 3 points */
 189
 190                 /* find left and right-most sample */
 191                 Duple window_space;
 192                 Points::size_type left = 0;
 193                 Points::size_type right = n_samples - 1;
 194
 195                 for (Points::size_type idx = 0; idx < n_samples - 1; ++idx) {
 196                         window_space = item_to_window (Duple (samples[idx].x, 0.0));
 197                         if (window_space.x >= draw.x0) {
 198                                 break;
 199                         }
 200                         left = idx;
 201                 }
 202
 203                 for (Points::size_type idx = left; idx < n_samples - 1; ++idx) {
 204                         window_space = item_to_window (Duple (samples[idx].x, 0.0));
 205                         if (window_space.x > draw.x1) {
 206                                 right = idx;
 207                                 break;
 208                         }
 209                 }
 210
 211                 const Duple first_sample = Duple (samples[left].x, samples[left].y);
 212
 213                 /* move to the first sample's x and the draw height */
 214                 window_space = item_to_window (Duple (first_sample.x, draw.height()));
 215                 context->move_to (window_space.x, window_space.y);
 216
 217                 /* draw line to first sample and then between samples */
 218                 for (uint32_t idx = left; idx <= right; ++idx) {
 219                         window_space = item_to_window (Duple (samples[idx].x, samples[idx].y), false);
 220                         context->line_to (window_space.x, window_space.y);
 221                 }
 222
 223                 /* a redraw may have been requested between the last sample and the last point.
 224                    if so, draw a line to the last _point.
 225                 */
 226                 Duple last_sample = Duple (samples[right].x, samples[right].y);
 227
 228                 if (draw.x1 > last_sample.x) {
 229                         last_sample = Duple (_points.back().x, _points.back().y);
 230                         window_space = item_to_window (last_sample, false);
 231                         context->line_to (window_space.x, window_space.y);
 232                 }
 233
 234                 switch (curve_fill) {
 235                         case None:
 236                                 context->stroke();
 237                                 break;
 238                         case Inside:
 239                                 context->stroke_preserve ();
 240                                 /* close the frame, possibly using the last _point's x rather than samples[right].x */
 241                                 window_space = item_to_window (Duple (last_sample.x, draw.height()));
 242                                 context->line_to (window_space.x, window_space.y);
 243                                 window_space = item_to_window (Duple (first_sample.x, draw.height()));
 244                                 context->line_to (window_space.x, window_space.y);
 245                                 context->close_path();
 246                                 setup_fill_context(context);
 247                                 context->fill ();
 248                                 break;
 249                         case Outside:
 250                                 context->stroke_preserve ();
 251                                 window_space = item_to_window (Duple (last_sample.x, 0.0));
 252                                 context->line_to (window_space.x, window_space.y);
 253                                 window_space = item_to_window (Duple (first_sample.x, 0.0));
 254                                 context->line_to (window_space.x, window_space.y);
 255                                 context->close_path();
 256                                 setup_fill_context(context);
 257                                 context->fill ();
 258                                 break;
 259                 }
 260         }
 261         context->restore ();
 262
 263 #if 0
 264         /* add points */
 265         setup_outline_context (context);
 266         for (Points::const_iterator p = _points.begin(); p != _points.end(); ++p) {
 267                 Duple window_space (item_to_window (*p));
 268                 context->arc (window_space.x, window_space.y, 5.0, 0.0, 2 * M_PI);
 269                 context->stroke ();
 270         }
 271 #endif
 272 }
 273
 274 bool
 275 FramedCurve::covers (Duple const & pc) const
 276 {
 277         Duple point = window_to_item (pc);
 278
 279         /* O(N) N = number of points, and not accurate */
 280
 281         for (Points::const_iterator p = _points.begin(); p != _points.end(); ++p) {
 282
 283                 const Coord dx = point.x - (*p).x;
 284                 const Coord dy = point.y - (*p).y;
 285                 const Coord dx2 = dx * dx;
 286                 const Coord dy2 = dy * dy;
 287
 288                 if ((dx2 < 2.0 && dy2 < 2.0) || (dx2 + dy2 < 4.0)) {
 289                         return true;
 290                 }
 291         }
 292
 293         return false;
 294 }