Fix out-of-bounds waveform image rendering.

With large sample-rates and high-zoom-level the minimal request-size
or at least 1/10sed can exceed the max image size supported by cairo.
e.g. @192kSPS;  100ms = 19200 samples.
 * 1 sample/pixel, * 2 (left/right) = 38400px > 2^15px.

diff --git a/libs/canvas/wave_view.cc b/libs/canvas/wave_view.cc
index 94821c48dd53819814f8458bdb8fc44b8ba82412..039979c3a9f7d62277a5fd383c814c5a46f54830 100644 (file)
--- a/libs/canvas/wave_view.cc
+++ b/libs/canvas/wave_view.cc
@@ -912,10 +912,15 @@ WaveView::desired_image_width () const
         * We want at least 1 canvas width's worth, but if that
         * represents less than 1/10th of a second, use 1/10th of
         * a second instead.
+        *
+        * ..unless at high-zoom level 100ms would be more than 2^15px
+        * (cairo image limit), note that generate_image() uses twice this
+        * width (left/right of the center of the request range.
         */
 
        framecnt_t canvas_width_samples = _canvas->visible_area().width() * _samples_per_pixel;
-       const framecnt_t one_tenth_of_second = _region->session().frame_rate() / 10;
+       const framecnt_t one_tenth_of_second = std::min (_region->session().frame_rate() / 10,  (framecnt_t)floor (16383.0 / _samples_per_pixel));
+
 
        if (canvas_width_samples > one_tenth_of_second) {
                return  canvas_width_samples;
@@ -927,6 +932,7 @@ WaveView::desired_image_width () const
 void
 WaveView::queue_get_image (boost::shared_ptr<const ARDOUR::Region> region, framepos_t start, framepos_t end) const
 {
+       DEBUG_TRACE (DEBUG::WaveView, string_compose ("%1: queue image from %2 .. %3\n", name, start, end));
        boost::shared_ptr<WaveViewThreadRequest> req (new WaveViewThreadRequest);
 
        req->type = WaveViewThreadRequest::Draw;
@@ -983,13 +989,14 @@ WaveView::generate_image (boost::shared_ptr<WaveViewThreadRequest> req, bool in_
                const framepos_t center = req->start + ((req->end - req->start) / 2);
                const framecnt_t image_samples = req->width;
 
-               /* we can request data from anywhere in the Source, between 0 and its length
-                */
+               /* we can request data from anywhere in the Source, between 0 and its length */
 
                framepos_t sample_start = max (_region_start, (center - image_samples));
                framepos_t sample_end = min (center + image_samples, region_end());
                const int n_peaks = std::max (1LL, llrint (ceil ((sample_end - sample_start) / (req->samples_per_pixel))));
 
+               DEBUG_TRACE (DEBUG::WaveView, string_compose ("%1: request %2 .. %3 width: %4; render %5 .. %6 (%7)\n", name, req->start, req->end, req->width, sample_start, sample_end, n_peaks));
+
                assert (n_peaks > 0 && n_peaks < 32767);
 
                boost::scoped_array<ARDOUR::PeakData> peaks (new PeakData[n_peaks]);