From 16b9a30655d658a44bf7de316e76481303a408e8 Mon Sep 17 00:00:00 2001 From: Simon McVittie Date: Thu, 2 Sep 2021 22:34:14 +0100 Subject: [PATCH] reftest-compare: Treat colour channels as undefined if alpha is zero If the alpha channel is zero, it doesn't matter what the values of the red, green and blue channels are: the pixel is still fully transparent. On most architectures, fully transparent pixels end up all-zeroes (fully transparent black), matching what's in the reference PNG file; but on mips*el the blend-difference and blend-normal tests get all-ones (fully transparent white) and a test failure. Resolves: https://gitlab.gnome.org/GNOME/gtk/-/issues/4227 Signed-off-by: Simon McVittie --- testsuite/reftests/reftest-compare.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/testsuite/reftests/reftest-compare.c b/testsuite/reftests/reftest-compare.c index 5c682e1591..5bccb697b8 100644 --- a/testsuite/reftests/reftest-compare.c +++ b/testsuite/reftests/reftest-compare.c @@ -104,7 +104,12 @@ buffer_diff_core (const guchar *buf_a, /* check if the pixels are the same */ if (row_a[x] == row_b[x]) continue; - + + /* even if they're not literally the same, fully-transparent + * pixels are effectively the same regardless of colour */ + if ((row_a[x] & 0xff000000) == 0 && (row_b[x] & 0xff000000) == 0) + continue; + if (diff == NULL) { diff = cairo_image_surface_create (CAIRO_FORMAT_RGB24,