libs/canvas/curve.cc

   1 /*
   2  * Copyright (C) 2013-2017 Paul Davis <paul@linuxaudiosystems.com>
   3  * Copyright (C) 2014-2015 Robin Gareus <robin@gareus.org>
   4  * Copyright (C) 2016 Nick Mainsbridge <mainsbridge@gmail.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with this program; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19  */
  20
  21 #include <cmath>
  22 #include <exception>
  23 #include <algorithm>
  24
  25 #include "canvas/curve.h"
  26
  27 using namespace ArdourCanvas;
  28 using std::min;
  29 using std::max;
  30
  31 Curve::Curve (Canvas* c)
  32         : PolyItem (c)
  33         , n_samples (0)
  34         , points_per_segment (16)
  35         , curve_fill (None)
  36 {
  37 }
  38
  39 Curve::Curve (Item* parent)
  40         : PolyItem (parent)
  41         , n_samples (0)
  42         , points_per_segment (16)
  43         , curve_fill (None)
  44 {
  45 }
  46
  47 /** When rendering the curve, we will always draw a fixed number of straight
  48  * line segments to span the x-axis extent of the curve. More segments:
  49  * smoother visual rendering. Less rendering: closer to a visibily poly-line
  50  * render.
  51  */
  52 void
  53 Curve::set_points_per_segment (uint32_t n)
  54 {
  55         /* this only changes our appearance rather than the bounding box, so we
  56            just need to schedule a redraw rather than notify the parent of any
  57            changes
  58         */
  59         points_per_segment = n;
  60         interpolate ();
  61         redraw ();
  62 }
  63
  64 void
  65 Curve::compute_bounding_box () const
  66 {
  67         PolyItem::compute_bounding_box ();
  68
  69         /* possibly add extents of any point indicators here if we ever do that */
  70 }
  71
  72 void
  73 Curve::set (Points const& p)
  74 {
  75         PolyItem::set (p);
  76         interpolate ();
  77 }
  78
  79 void
  80 Curve::interpolate ()
  81 {
  82         samples.clear ();
  83         InterpolatedCurve::interpolate (_points, points_per_segment, CatmullRomCentripetal, false, samples);
  84         n_samples = samples.size();
  85 }
  86
  87 void
  88 Curve::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) const
  89 {
  90         if (!_outline || _points.size() < 2 || !_bounding_box) {
  91                 return;
  92         }
  93
  94         Rect self = item_to_window (_bounding_box);
  95         Rect d = self.intersection (area);
  96         assert (d);
  97         Rect draw = d;
  98
  99         /* Our approach is to always draw n_segments across our total size.
 100          *
 101          * This is very inefficient if we are asked to only draw a small
 102          * section of the curve. For now we rely on cairo clipping to help
 103          * with this.
 104          */
 105
 106
 107         setup_outline_context (context);
 108
 109         if (_points.size() == 2) {
 110
 111                 /* straight line */
 112
 113                 Duple window_space;
 114
 115                 window_space = item_to_window (_points.front());
 116                 context->move_to (window_space.x, window_space.y);
 117                 window_space = item_to_window (_points.back());
 118                 context->line_to (window_space.x, window_space.y);
 119
 120
 121                 switch (curve_fill) {
 122                         case None:
 123                                 context->stroke();
 124                                 break;
 125                         case Inside:
 126                                 context->stroke_preserve ();
 127                                 window_space = item_to_window (Duple(_points.back().x, draw.height()));
 128                                 context->line_to (window_space.x, window_space.y);
 129                                 window_space = item_to_window (Duple(_points.front().x, draw.height()));
 130                                 context->line_to (window_space.x, window_space.y);
 131                                 context->close_path();
 132                                 setup_fill_context(context);
 133                                 context->fill ();
 134                                 break;
 135                         case Outside:
 136                                 context->stroke_preserve ();
 137                                 window_space = item_to_window (Duple(_points.back().x, 0.0));
 138                                 context->line_to (window_space.x, window_space.y);
 139                                 window_space = item_to_window (Duple(_points.front().x, 0.0));
 140                                 context->line_to (window_space.x, window_space.y);
 141                                 context->close_path();
 142                                 setup_fill_context(context);
 143                                 context->fill ();
 144                                 break;
 145                 }
 146
 147         } else {
 148
 149                 /* curve of at least 3 points */
 150
 151                 /* x-axis limits of the curve, in window space coordinates */
 152
 153                 Duple w1 = item_to_window (Duple (_points.front().x, 0.0));
 154                 Duple w2 = item_to_window (Duple (_points.back().x, 0.0));
 155
 156                 /* clamp actual draw to area bound by points, rather than our bounding box which is slightly different */
 157
 158                 context->save ();
 159                 context->rectangle (draw.x0, draw.y0, draw.width(), draw.height());
 160                 context->clip ();
 161
 162                 /* expand drawing area by several pixels on each side to avoid cairo stroking effects at the boundary.
 163                    they will still occur, but cairo's clipping will hide them.
 164                  */
 165
 166                 draw = draw.expand (4.0);
 167
 168                 /* now clip it to the actual points in the curve */
 169
 170                 if (draw.x0 < w1.x) {
 171                         draw.x0 = w1.x;
 172                 }
 173
 174                 if (draw.x1 >= w2.x) {
 175                         draw.x1 = w2.x;
 176                 }
 177
 178                 /* find left and right-most sample */
 179                 Duple window_space;
 180                 Points::size_type left = 0;
 181                 Points::size_type right = n_samples;
 182
 183                 for (Points::size_type idx = 0; idx < n_samples - 1; ++idx) {
 184                         left = idx;
 185                         window_space = item_to_window (Duple (samples[idx].x, 0.0));
 186                         if (window_space.x >= draw.x0) break;
 187                 }
 188                 for (Points::size_type idx = n_samples; idx > left + 1; --idx) {
 189                         window_space = item_to_window (Duple (samples[idx].x, 0.0));
 190                         if (window_space.x <= draw.x1) break;
 191                         right = idx;
 192                 }
 193
 194                 /* draw line between samples */
 195                 window_space = item_to_window (Duple (samples[left].x, samples[left].y));
 196                 context->move_to (window_space.x, window_space.y);
 197                 for (uint32_t idx = left + 1; idx < right; ++idx) {
 198                         window_space = item_to_window (Duple (samples[idx].x, samples[idx].y));
 199                         context->line_to (window_space.x, window_space.y);
 200                 }
 201
 202                 switch (curve_fill) {
 203                         case None:
 204                                 context->stroke();
 205                                 break;
 206                         case Inside:
 207                                 context->stroke_preserve ();
 208                                 window_space = item_to_window (Duple (samples[right-1].x, draw.height()));
 209                                 context->line_to (window_space.x, window_space.y);
 210                                 window_space = item_to_window (Duple (samples[left].x, draw.height()));
 211                                 context->line_to (window_space.x, window_space.y);
 212                                 context->close_path();
 213                                 setup_fill_context(context);
 214                                 context->fill ();
 215                                 break;
 216                         case Outside:
 217                                 context->stroke_preserve ();
 218                                 window_space = item_to_window (Duple (samples[right-1].x, 0.0));
 219                                 context->line_to (window_space.x, window_space.y);
 220                                 window_space = item_to_window (Duple (samples[left].x, 0.0));
 221                                 context->line_to (window_space.x, window_space.y);
 222                                 context->close_path();
 223                                 setup_fill_context(context);
 224                                 context->fill ();
 225                                 break;
 226                 }
 227                 context->restore ();
 228         }
 229
 230 #if 0
 231         /* add points */
 232         setup_outline_context (context);
 233         for (Points::const_iterator p = _points.begin(); p != _points.end(); ++p) {
 234                 Duple window_space (item_to_window (*p));
 235                 context->arc (window_space.x, window_space.y, 5.0, 0.0, 2 * M_PI);
 236                 context->stroke ();
 237         }
 238 #endif
 239 }
 240
 241 bool
 242 Curve::covers (Duple const & pc) const
 243 {
 244         Duple point = window_to_item (pc);
 245
 246         /* O(N) N = number of points, and not accurate */
 247
 248         for (Points::const_iterator p = _points.begin(); p != _points.end(); ++p) {
 249
 250                 const Coord dx = point.x - (*p).x;
 251                 const Coord dy = point.y - (*p).y;
 252                 const Coord dx2 = dx * dx;
 253                 const Coord dy2 = dy * dy;
 254
 255                 if ((dx2 < 2.0 && dy2 < 2.0) || (dx2 + dy2 < 4.0)) {
 256                         return true;
 257                 }
 258         }
 259
 260         return false;
 261 }