libs/canvas/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/curve.h"
  25
  26 using namespace ArdourCanvas;
  27 using std::min;
  28 using std::max;
  29
  30 Curve::Curve (Canvas* c)
  31         : PolyItem (c)
  32         , n_samples (0)
  33         , points_per_segment (16)
  34         , curve_fill (None)
  35 {
  36 }
  37
  38 Curve::Curve (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 Curve::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 Curve::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 Curve::set (Points const& p)
  73 {
  74         PolyItem::set (p);
  75         interpolate ();
  76 }
  77
  78 void
  79 Curve::interpolate ()
  80 {
  81         samples.clear ();
  82         InterpolatedCurve::interpolate (_points, points_per_segment, CatmullRomCentripetal, false, samples);
  83         n_samples = samples.size();
  84 }
  85
  86 void
  87 Curve::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) const
  88 {
  89         if (!_outline || _points.size() < 2 || !_bounding_box) {
  90                 return;
  91         }
  92
  93         Rect self = item_to_window (_bounding_box.get());
  94         boost::optional<Rect> d = self.intersection (area);
  95         assert (d);
  96         Rect draw = d.get ();
  97
  98         /* Our approach is to always draw n_segments across our total size.
  99          *
 100          * This is very inefficient if we are asked to only draw a small
 101          * section of the curve. For now we rely on cairo clipping to help
 102          * with this.
 103          */
 104
 105
 106         setup_outline_context (context);
 107
 108         if (_points.size() == 2) {
 109
 110                 /* straight line */
 111
 112                 Duple window_space;
 113
 114                 window_space = item_to_window (_points.front());
 115                 context->move_to (window_space.x, window_space.y);
 116                 window_space = item_to_window (_points.back());
 117                 context->line_to (window_space.x, window_space.y);
 118
 119
 120                 switch (curve_fill) {
 121                         case None:
 122                                 context->stroke();
 123                                 break;
 124                         case Inside:
 125                                 context->stroke_preserve ();
 126                                 window_space = item_to_window (Duple(_points.back().x, draw.height()));
 127                                 context->line_to (window_space.x, window_space.y);
 128                                 window_space = item_to_window (Duple(_points.front().x, draw.height()));
 129                                 context->line_to (window_space.x, window_space.y);
 130                                 context->close_path();
 131                                 setup_fill_context(context);
 132                                 context->fill ();
 133                                 break;
 134                         case Outside:
 135                                 context->stroke_preserve ();
 136                                 window_space = item_to_window (Duple(_points.back().x, 0.0));
 137                                 context->line_to (window_space.x, window_space.y);
 138                                 window_space = item_to_window (Duple(_points.front().x, 0.0));
 139                                 context->line_to (window_space.x, window_space.y);
 140                                 context->close_path();
 141                                 setup_fill_context(context);
 142                                 context->fill ();
 143                                 break;
 144                 }
 145
 146         } else {
 147
 148                 /* curve of at least 3 points */
 149
 150                 /* x-axis limits of the curve, in window space coordinates */
 151
 152                 Duple w1 = item_to_window (Duple (_points.front().x, 0.0));
 153                 Duple w2 = item_to_window (Duple (_points.back().x, 0.0));
 154
 155                 /* clamp actual draw to area bound by points, rather than our bounding box which is slightly different */
 156
 157                 context->save ();
 158                 context->rectangle (draw.x0, draw.y0, draw.width(), draw.height());
 159                 context->clip ();
 160
 161                 /* expand drawing area by several pixels on each side to avoid cairo stroking effects at the boundary.
 162                    they will still occur, but cairo's clipping will hide them.
 163                  */
 164
 165                 draw = draw.expand (4.0);
 166
 167                 /* now clip it to the actual points in the curve */
 168
 169                 if (draw.x0 < w1.x) {
 170                         draw.x0 = w1.x;
 171                 }
 172
 173                 if (draw.x1 >= w2.x) {
 174                         draw.x1 = w2.x;
 175                 }
 176
 177                 /* find left and right-most sample */
 178                 Duple window_space;
 179                 Points::size_type left = 0;
 180                 Points::size_type right = n_samples;
 181
 182                 for (Points::size_type idx = 0; idx < n_samples - 1; ++idx) {
 183                         left = idx;
 184                         window_space = item_to_window (Duple (samples[idx].x, 0.0));
 185                         if (window_space.x >= draw.x0) break;
 186                 }
 187                 for (Points::size_type idx = n_samples; idx > left + 1; --idx) {
 188                         window_space = item_to_window (Duple (samples[idx].x, 0.0));
 189                         if (window_space.x <= draw.x1) break;
 190                         right = idx;
 191                 }
 192
 193                 /* draw line between samples */
 194                 window_space = item_to_window (Duple (samples[left].x, samples[left].y));
 195                 context->move_to (window_space.x, window_space.y);
 196                 for (uint32_t idx = left + 1; idx < right; ++idx) {
 197                         window_space = item_to_window (Duple (samples[idx].x, samples[idx].y));
 198                         context->line_to (window_space.x, window_space.y);
 199                 }
 200
 201                 switch (curve_fill) {
 202                         case None:
 203                                 context->stroke();
 204                                 break;
 205                         case Inside:
 206                                 context->stroke_preserve ();
 207                                 window_space = item_to_window (Duple (samples[right-1].x, draw.height()));
 208                                 context->line_to (window_space.x, window_space.y);
 209                                 window_space = item_to_window (Duple (samples[left].x, draw.height()));
 210                                 context->line_to (window_space.x, window_space.y);
 211                                 context->close_path();
 212                                 setup_fill_context(context);
 213                                 context->fill ();
 214                                 break;
 215                         case Outside:
 216                                 context->stroke_preserve ();
 217                                 window_space = item_to_window (Duple (samples[right-1].x, 0.0));
 218                                 context->line_to (window_space.x, window_space.y);
 219                                 window_space = item_to_window (Duple (samples[left].x, 0.0));
 220                                 context->line_to (window_space.x, window_space.y);
 221                                 context->close_path();
 222                                 setup_fill_context(context);
 223                                 context->fill ();
 224                                 break;
 225                 }
 226                 context->restore ();
 227         }
 228
 229 #if 0
 230         /* add points */
 231         setup_outline_context (context);
 232         for (Points::const_iterator p = _points.begin(); p != _points.end(); ++p) {
 233                 Duple window_space (item_to_window (*p));
 234                 context->arc (window_space.x, window_space.y, 5.0, 0.0, 2 * M_PI);
 235                 context->stroke ();
 236         }
 237 #endif
 238 }
 239
 240 bool
 241 Curve::covers (Duple const & pc) const
 242 {
 243         Duple point = window_to_item (pc);
 244
 245         /* O(N) N = number of points, and not accurate */
 246
 247         for (Points::const_iterator p = _points.begin(); p != _points.end(); ++p) {
 248
 249                 const Coord dx = point.x - (*p).x;
 250                 const Coord dy = point.y - (*p).y;
 251                 const Coord dx2 = dx * dx;
 252                 const Coord dy2 = dy * dy;
 253
 254                 if ((dx2 < 2.0 && dy2 < 2.0) || (dx2 + dy2 < 4.0)) {
 255                         return true;
 256                 }
 257         }
 258
 259         return false;
 260 }