From 69a6c4d747bb6f5d673f2c7505d393d20a75748a Mon Sep 17 00:00:00 2001
From: nick_m <mainsbridge@gmail.com>
Date: Sun, 22 Mar 2015 00:31:32 +1100
Subject: [PATCH] Provide an image if there are no peaks.

---
 libs/canvas/canvas/wave_view.h |  1 +
 libs/canvas/wave_view.cc       | 41 ++++++++++++++++++++++++++++++++--
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/libs/canvas/canvas/wave_view.h b/libs/canvas/canvas/wave_view.h
index 4820a3696e..4b6d6c5627 100644
--- a/libs/canvas/canvas/wave_view.h
+++ b/libs/canvas/canvas/wave_view.h
@@ -203,6 +203,7 @@ private:
 	void get_image (Cairo::RefPtr<Cairo::ImageSurface>& image, framepos_t start, framepos_t end, double& image_offset) const;
 
         ArdourCanvas::Coord y_extent (double, bool) const;
+	void draw_absent_image (Cairo::RefPtr<Cairo::ImageSurface>&, ARDOUR::PeakData*, int) const;
 	void draw_image (Cairo::RefPtr<Cairo::ImageSurface>&, ARDOUR::PeakData*, int) const;
 };
 
diff --git a/libs/canvas/wave_view.cc b/libs/canvas/wave_view.cc
index e559756e68..64b5975700 100644
--- a/libs/canvas/wave_view.cc
+++ b/libs/canvas/wave_view.cc
@@ -349,6 +349,38 @@ WaveView::y_extent (double s, bool /*round_to_lower_edge*/) const
 	}
 }
 
+void
+WaveView::draw_absent_image (Cairo::RefPtr<Cairo::ImageSurface>& image, PeakData* _peaks, int n_peaks) const
+{
+	Cairo::RefPtr<Cairo::ImageSurface> stripe = Cairo::ImageSurface::create (Cairo::FORMAT_A8, n_peaks, _height);
+
+	Cairo::RefPtr<Cairo::Context> stripe_context = Cairo::Context::create (stripe);
+	stripe_context->set_antialias (Cairo::ANTIALIAS_NONE);
+
+	uint32_t stripe_separation = 150;
+	double start = - floor (_height / stripe_separation) * stripe_separation;
+	int stripe_x = 0;
+
+	while (start < n_peaks) {
+
+		stripe_context->move_to (start, 0);
+		stripe_x = start + _height;
+		stripe_context->line_to (stripe_x, _height);
+		start += stripe_separation;
+	}
+
+	stripe_context->set_source_rgba (1.0, 1.0, 1.0, 1.0);
+	stripe_context->set_line_cap (Cairo::LINE_CAP_SQUARE);
+	stripe_context->set_line_width(50);
+	stripe_context->stroke();
+
+	Cairo::RefPtr<Cairo::Context> context = Cairo::Context::create (image);
+
+	context->set_source_rgba (1.0, 1.0, 0.0, 0.3);
+	context->mask (stripe, 0, 0);
+	context->fill ();
+}
+
 struct LineTips {
 	double top;
 	double bot;
@@ -761,14 +793,19 @@ WaveView::get_image (Cairo::RefPtr<Cairo::ImageSurface>& image, framepos_t start
 
 	boost::scoped_array<ARDOUR::PeakData> peaks (new PeakData[n_peaks]);
 
-	_region->read_peaks (peaks.get(), n_peaks,
+	framecnt_t peaks_read;
+	peaks_read = _region->read_peaks (peaks.get(), n_peaks,
 			     sample_start, sample_end - sample_start,
 			     _channel,
 			     _samples_per_pixel);
 
 	image = Cairo::ImageSurface::create (Cairo::FORMAT_ARGB32, n_peaks, _height);
 
-	draw_image (image, peaks.get(), n_peaks);
+	if (peaks_read > 0) {
+		draw_image (image, peaks.get(), n_peaks);
+	} else {
+		draw_absent_image (image, peaks.get(), n_peaks);
+	}
 
 	_image_cache[_region->audio_source ()].push_back (CacheEntry (_channel, _height, _region_amplitude, _fill_color, sample_start,  sample_end, image));