Copied from Debian.

From 03a820b173ed1fdef6ff14b4468f5dbc02ff59be Mon Sep 17 00:00:00 2001
From: Heiko Lewin <heiko.lewin@worldiety.de>
Date: Tue, 15 Dec 2020 16:48:19 +0100
Subject: [PATCH] Fix mask usage in image-compositor

[trimmed test case, since not used in Debian build]

---
 src/cairo-image-compositor.c                |   8 ++--

--- cairo-1.16.0.orig/src/cairo-image-compositor.c
+++ cairo-1.16.0/src/cairo-image-compositor.c
@@ -2601,14 +2601,14 @@ _inplace_src_spans (void *abstract_rende
 		    unsigned num_spans)
 {
     cairo_image_span_renderer_t *r = abstract_renderer;
-    uint8_t *m;
+    uint8_t *m, *base = (uint8_t*)pixman_image_get_data(r->mask);
     int x0;
 
     if (num_spans == 0)
 	return CAIRO_STATUS_SUCCESS;
 
     x0 = spans[0].x;
-    m = r->_buf;
+    m = base;
     do {
 	int len = spans[1].x - spans[0].x;
 	if (len >= r->u.composite.run_length && spans[0].coverage == 0xff) {
@@ -2646,7 +2646,7 @@ _inplace_src_spans (void *abstract_rende
 				      spans[0].x, y,
 				      spans[1].x - spans[0].x, h);
 
-	    m = r->_buf;
+	    m = base;
 	    x0 = spans[1].x;
 	} else if (spans[0].coverage == 0x0) {
 	    if (spans[0].x != x0) {
@@ -2675,7 +2675,7 @@ _inplace_src_spans (void *abstract_rende
 #endif
 	    }
 
-	    m = r->_buf;
+	    m = base;
 	    x0 = spans[1].x;
 	} else {
 	    *m++ = spans[0].coverage;
><a href='/guix/diff/.gitignore?id=537f9642ebeabca09bcbd9b0b788162c5bb71eb6'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/.gitignore'>
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<div class='path'>path: <a href='/guix/log/?id=537f9642ebeabca09bcbd9b0b788162c5bb71eb6'>root</a>/<a href='/guix/log/.gitignore?id=537f9642ebeabca09bcbd9b0b788162c5bb71eb6'>.gitignore</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/.gitignore?id=537f9642ebeabca09bcbd9b0b788162c5bb71eb6&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-10-22 20:35:15 -0400'>2023-10-22</span></td><td><a href='/guix/commit/.gitignore?id=4cf4dcb8b31274a8dfba6bae3a6826a1b521da3f'>teams: Adjust shebang to use 'guix repl'.</a><span class='msg-avail'>...<span class='msg-tooltip'>This ensures the correct Guix dependencies are always available for the
script.

* etc/teams.scm.in: Rename to...
* etc/teams.scm: ... this.  Adjust shebang.
* .gitignore: No longer ignore it.
* configure.ac: Do not process it with AC_CONFIG_FILES.

Reported-by: Clément Lassieur &lt;clement@lassieur.org&gt;
Fixes: https://issues.guix.gnu.org/66605
Change-Id: I7a01750c6c5f0696b6c36b1e6caa9389d9e6822c
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2023-04-24 15:32:54 +0100'>2023-04-24</span></td><td><a href='/guix/commit/.gitignore?id=23f11afacdfe755ffa514a8cbf93ba1121b9db0d'>Add mumi config.</a><span class='msg-avail'>...<span class='msg-tooltip'>* .mumi/config: New file.
* .gitignore: Add .mumi/current-issue.
</span></span></td><td>Arun Isaac</td></tr>
<tr><td><span title='2022-07-03 14:12:32 +0200'>2022-07-03</span></td><td><a href='/guix/commit/.gitignore?id=4eaf90470f466b3fdab87f6961cb18bb348d433f'>etc: Add teams.scm.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/teams.scm.in: New file.
* configure.ac: Generate executable.
* .gitignore: Ignore generated file.
</span></span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2022-06-05 21:27:53 +0200'>2022-06-05</span></td><td><a href='/guix/commit/.gitignore?id=4d47c2c723927ad4ad4142bd517c6ccc03c27528'>gitignore: Add .DS_Store.</a><span class='msg-avail'>...<span class='msg-tooltip'>Ignore MacOS specific file: https://en.wikipedia.org/wiki/.DS_Store

Signed-off-by: Mathieu Othacehe &lt;othacehe@gnu.org&gt;
</span></span></td><td>Pavel Shlyak</td></tr>