Bug 539165. Fix single and multi-stop solid gradients by multiplying by the alpha component. r=roc

This cairo commit that caused the problem: 2d790daa957471670f4ae0d3b22da89e4ee7111f.
It was merged into mozilla-central with 1effb72d30cf

gfx/cairo/README

@@ -64,6 +64,8 @@ quartz-first-stop.patch: return the first stop for negative positions on the gra
 
 quartz-glyph-extents.patch: bug 534260; work around incorrect glyph extents returned by quartz for anomalous empty glyphs
 
+premultiply-alpha-solid-gradients.patch: bug 539165; multiply the solid color by the alpha component before using it for a solid surface
+
 ==== pixman patches ====
 
 pixman-neon.patch: add ARM NEON optimized compositing functions

gfx/cairo/cairo/src/cairo-pattern.c

@@ -2262,8 +2262,17 @@ _cairo_pattern_acquire_surface (const cairo_pattern_t	   *pattern,
 
 	    if (src->n_stops)
 	    {
+		cairo_color_t color;
+
+		/* multiply by alpha */
+		_cairo_color_init_rgba (&color,
+			src->stops->color.red,
+			src->stops->color.green,
+			src->stops->color.blue,
+			src->stops->color.alpha);
+
 		_cairo_pattern_init_solid (&solid,
-					   &src->stops->color,
+					   &color,
 					   CAIRO_CONTENT_COLOR_ALPHA);
 	    }
 	    else
@@ -2295,9 +2304,17 @@ _cairo_pattern_acquire_surface (const cairo_pattern_t	   *pattern,
 	    }
 	    if (i == src->n_stops) {
 		cairo_solid_pattern_t solid;
+		cairo_color_t color;
+
+		/* multiply by alpha */
+		_cairo_color_init_rgba (&color,
+			src->stops->color.red,
+			src->stops->color.green,
+			src->stops->color.blue,
+			src->stops->color.alpha);
 
 		_cairo_pattern_init_solid (&solid,
-					   &src->stops->color,
+					   &color,
 					   CAIRO_CONTENT_COLOR_ALPHA);
 
 		status =

gfx/cairo/premultiply-alpha-solid-gradients.patch

@@ -0,0 +1,46 @@
+Fix single and multi-stop solid gradients by multiplying by the alpha component. r=roc
+
+This cairo commit that caused the problem: 2d790daa957471670f4ae0d3b22da89e4ee7111f.
+It was merged into mozilla-central with 1effb72d30cf
+
+diff --git a/gfx/cairo/cairo/src/cairo-pattern.c b/gfx/cairo/cairo/src/cairo-pattern.c
+--- a/gfx/cairo/cairo/src/cairo-pattern.c
++++ b/gfx/cairo/cairo/src/cairo-pattern.c
+@@ -2262,8 +2262,17 @@ _cairo_pattern_acquire_surface (const ca
+ 
+ 	    if (src->n_stops)
+ 	    {
++		cairo_color_t color;
++
++		/* multiply by alpha */
++		_cairo_color_init_rgba (&color,
++			src->stops->color.red,
++			src->stops->color.green,
++			src->stops->color.blue,
++			src->stops->color.alpha);
++
+ 		_cairo_pattern_init_solid (&solid,
+-					   &src->stops->color,
++					   &color,
+ 					   CAIRO_CONTENT_COLOR_ALPHA);
+ 	    }
+ 	    else
+@@ -2295,9 +2304,17 @@ _cairo_pattern_acquire_surface (const ca
+ 	    }
+ 	    if (i == src->n_stops) {
+ 		cairo_solid_pattern_t solid;
++		cairo_color_t color;
++
++		/* multiply by alpha */
++		_cairo_color_init_rgba (&color,
++			src->stops->color.red,
++			src->stops->color.green,
++			src->stops->color.blue,
++			src->stops->color.alpha);
+ 
+ 		_cairo_pattern_init_solid (&solid,
+-					   &src->stops->color,
++					   &color,
+ 					   CAIRO_CONTENT_COLOR_ALPHA);
+ 
+ 		status =

layout/reftests/svg/opacity-and-gradient-02-ref.svg

@@ -0,0 +1,34 @@
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/licenses/publicdomain/
+-->
+<svg xmlns="http://www.w3.org/2000/svg" version="1.1">
+
+  <title>Testcase for opacity on elements referencing a gradient</title>
+
+  <!-- From https://bugzilla.mozilla.org/show_bug.cgi?id=539165 -->
+
+  <defs>
+    <linearGradient id="lime" gradientUnits="userSpaceOnUse">
+      <stop stop-color="lime"/>
+    </linearGradient>
+    <!-- OS X doesn't draw solid gradients as a solid color so we need to use
+         a gradient fill below
+      -->
+    <linearGradient id="red" gradientUnits="userSpaceOnUse">
+      <stop stop-color="red"/>
+    </linearGradient>
+ </defs>
+
+  <rect width="100%" height="100%" fill="url(#lime)"/>
+
+  <!-- test 'opacity' -->
+  <rect width="25%" height="100%" fill="url(#red)" opacity="1"/>
+  
+  <!-- test 'fill-opacity' -->
+  <rect x="25%" width="25%" height="100%" fill="url(#red)" opacity="0.5"/>
+
+  <!-- test 'fill-opacity' -->
+  <rect x="50%" width="25%" height="100%" fill="url(#red)" opacity="0.5"/>
+
+</svg>

layout/reftests/svg/opacity-and-gradient-02.svg

@@ -0,0 +1,42 @@
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/licenses/publicdomain/
+-->
+<svg xmlns="http://www.w3.org/2000/svg" version="1.1">
+
+  <title>Testcase for opacity on elements referencing a gradient</title>
+
+  <!-- From https://bugzilla.mozilla.org/show_bug.cgi?id=539165 -->
+
+  <defs>
+    <linearGradient id="lime" gradientUnits="userSpaceOnUse">
+      <stop stop-color="lime"/>
+    </linearGradient>
+    <linearGradient id="red" gradientUnits="userSpaceOnUse">
+      <stop stop-color="red"/>
+    </linearGradient>
+    <linearGradient id="red2" gradientUnits="userSpaceOnUse">
+      <stop stop-color="red" offset="0%"/>
+      <stop stop-color="red" offset="100%"/>
+    </linearGradient>
+    <linearGradient id="redgreen" gradientUnits="userSpaceOnUse">
+      <stop stop-color="red" offset="0%"/>
+      <stop stop-color="lime" offset="100%"/>
+    </linearGradient>
+  </defs>
+
+  <rect width="100%" height="100%" fill="url(#lime)"/>
+
+  <!-- test 'opacity' -->
+  <rect width="25%" height="100%" fill="red" opacity="1"/>
+  
+  <!-- test 'fill-opacity' -->
+  <rect x="25%" width="25%" height="100%" fill="url(#red)" fill-opacity="0.5"/>
+
+  <!-- test 'fill-opacity' -->
+  <rect x="50%" width="25%" height="100%" fill="url(#red2)" fill-opacity="0.5"/>
+  
+  <!-- test 'fill-opacity' -->
+  <rect x="75%" width="25%" height="100%" fill="url(#redgreen)" fill-opacity="0"/>
+
+</svg>

layout/reftests/svg/reftest.list

@@ -101,6 +101,7 @@ fails == inline-in-xul-basic-01.xul pass.svg
 == objectBoundingBox-and-pattern-01b.svg objectBoundingBox-and-pattern-01-ref.svg
 == objectBoundingBox-and-pattern-01c.svg objectBoundingBox-and-pattern-01-ref.svg
 fails-if(http.oscpu.match(/Mac\x20OS\x20X\x2010\.4$/)) == opacity-and-gradient-01.svg pass.svg # fails on OS X 10.4 (bug 379610)
+== opacity-and-gradient-02.svg opacity-and-gradient-02-ref.svg
 == opacity-and-pattern-01.svg pass.svg
 == path-01.svg path-01-ref.svg
 == pattern-live-01a.svg pattern-live-01-ref.svg