From fb720292a321d40bc019bc036f5d909f6f72393e Mon Sep 17 00:00:00 2001
From: Nicholas Cameron <ncameron@mozilla.com>
Date: Tue, 24 Jul 2012 22:18:40 +1200
Subject: [PATCH] Bug 764125; sort out preferred and fallback Azure backends
 for all platforms (canvas and prefs). r=Bas

---
 .../src/nsCanvasRenderingContext2DAzure.cpp   | 29 ++++---------------
 modules/libpref/src/init/all.js               |  7 +++++
 2 files changed, 13 insertions(+), 23 deletions(-)

diff --git a/content/canvas/src/nsCanvasRenderingContext2DAzure.cpp b/content/canvas/src/nsCanvasRenderingContext2DAzure.cpp
index 0d9ee32b779..04358c19e1c 100644
--- a/content/canvas/src/nsCanvasRenderingContext2DAzure.cpp
+++ b/content/canvas/src/nsCanvasRenderingContext2DAzure.cpp
@@ -549,27 +549,6 @@ PRUint8 (*nsCanvasRenderingContext2DAzure::sPremultiplyTable)[256] = nsnull;
 namespace mozilla {
 namespace dom {
 
-static bool
-AzureCanvasEnabledOnPlatform()
-{
-#ifdef XP_WIN
-  if (gfxWindowsPlatform::GetPlatform()->GetRenderMode() !=
-      gfxWindowsPlatform::RENDER_DIRECT2D ||
-      !gfxWindowsPlatform::GetPlatform()->DWriteEnabled()) {
-    static bool checkedPref = false;
-    static bool preferSkia;
-    if (!checkedPref) {
-      preferSkia = Preferences::GetBool("gfx.canvas.azure.prefer-skia", false);
-      checkedPref = true;
-    }
-    return preferSkia;
-  }
-#elif !defined(XP_MACOSX) && !defined(ANDROID) && !defined(LINUX)
-  return false;
-#endif
-  return true;
-}
-
 bool
 AzureCanvasEnabled()
 {
@@ -579,7 +558,9 @@ AzureCanvasEnabled()
     azureEnabled = Preferences::GetBool("gfx.canvas.azure.enabled", false);
     checkedPref = true;
   }
-  return azureEnabled && AzureCanvasEnabledOnPlatform();
+
+  BackendType dontCare;
+  return azureEnabled && gfxPlatform::GetPlatform()->SupportsAzure(dontCare);
 }
 
 }
@@ -588,7 +569,9 @@ AzureCanvasEnabled()
 nsresult
 NS_NewCanvasRenderingContext2DAzure(nsIDOMCanvasRenderingContext2D** aResult)
 {
-  if (!AzureCanvasEnabledOnPlatform()) {
+  // XXX[nrc] remove this check when Thebes canvas is removed
+  // (because we will always support Azure)
+  if (!AzureCanvasEnabled()) {
     return NS_ERROR_NOT_AVAILABLE;
   }
 
diff --git a/modules/libpref/src/init/all.js b/modules/libpref/src/init/all.js
index d9b8eb657e8..9c076b777f9 100644
--- a/modules/libpref/src/init/all.js
+++ b/modules/libpref/src/init/all.js
@@ -225,10 +225,17 @@ pref("gfx.font_rendering.directwrite.use_gdi_table_loading", true);
 
 #ifdef XP_WIN
 pref("gfx.canvas.azure.enabled", true);
+// comma separated list of backends to use in order of preference
+// e.g., pref("gfx.canvas.azure.backends", "direct2d,skia,cairo");
+pref("gfx.canvas.azure.backends", "direct2d");
 pref("gfx.content.azure.enabled", true);
 #else
 #ifdef XP_MACOSX
 pref("gfx.canvas.azure.enabled", true);
+pref("gfx.canvas.azure.backends", "cg");
+#else
+pref("gfx.canvas.azure.enabled", false);
+pref("gfx.canvas.azure.backends", "cairo,skia");
 #endif
 #endif