From: Carl Hetherington <cth@carlh.net>
Date: Thu, 23 Sep 2021 21:54:13 +0000 (+0200)
Subject: Check that the image used to make a Cairo::ImageSurface is the right alignment and... 
X-Git-Tag: v2.15.163~1^2~2
X-Git-Url: https://git.carlh.net/gitweb/?a=commitdiff_plain;ds=sidebyside;h=6e1ceb315f01a233e8c449e649fa44551aa30491;p=dcpomatic.git

Check that the image used to make a Cairo::ImageSurface is the right alignment and pixel format.
---

diff --git a/src/lib/render_text.cc b/src/lib/render_text.cc
index 76c0fb79d..94b412856 100644
--- a/src/lib/render_text.cc
+++ b/src/lib/render_text.cc
@@ -93,7 +93,9 @@ set_source_rgba (Cairo::RefPtr<Cairo::Context> context, dcp::Colour colour, floa
 static shared_ptr<Image>
 create_image (dcp::Size size)
 {
-	/* FFmpeg BGRA means first byte blue, second byte green, third byte red, fourth byte alpha */
+	/* FFmpeg BGRA means first byte blue, second byte green, third byte red, fourth byte alpha.
+	 * This must be COMPACT as we're using it with Cairo::ImageSurface::create
+	 */
 	auto image = make_shared<Image>(AV_PIX_FMT_BGRA, size, Image::Alignment::COMPACT);
 	image->make_black ();
 	return image;
@@ -103,6 +105,11 @@ create_image (dcp::Size size)
 static Cairo::RefPtr<Cairo::ImageSurface>
 create_surface (shared_ptr<Image> image)
 {
+	/* XXX: I don't think it's guaranteed that format_stride_for_width will return a stride without any padding,
+	 * so it's lucky that this works.
+	 */
+	DCPOMATIC_ASSERT (image->alignment() == Image::Alignment::COMPACT);
+	DCPOMATIC_ASSERT (image->pixel_format() == AV_PIX_FMT_BGRA);
 	return Cairo::ImageSurface::create (
 		image->data()[0],
 		Cairo::FORMAT_ARGB32,