From 215d41a87d53a8cdaead3f5d38210ab2584ef0cc Mon Sep 17 00:00:00 2001
From: Nicolas Silva <nsilva@mozilla.com>
Date: Wed, 3 Sep 2014 13:52:14 +0200
Subject: [PATCH] Bug 1061209 - disable basic layers OMTC except on linux and
 e10s. r=mattwoodrow

---
 widget/xpwidgets/nsBaseWidget.cpp | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/widget/xpwidgets/nsBaseWidget.cpp b/widget/xpwidgets/nsBaseWidget.cpp
index b9afd2ffe26..43984a6d99c 100644
--- a/widget/xpwidgets/nsBaseWidget.cpp
+++ b/widget/xpwidgets/nsBaseWidget.cpp
@@ -872,6 +872,19 @@ nsBaseWidget::GetPreferredCompositorBackends(nsTArray<LayersBackend>& aHints)
   aHints.AppendElement(LayersBackend::LAYERS_BASIC);
 }
 
+static void
+RemoveBasicBackend(nsTArray<LayersBackend>& aHints)
+{
+#ifndef XP_WIN
+  for (size_t i = 0; i < aHints.Length(); ++i) {
+    if (aHints[i] == LayersBackend::LAYERS_BASIC &&
+        !Preferences::GetBool("layers.offmainthreadcomposition.force-basic", false)) {
+      aHints[i] = LayersBackend::LAYERS_NONE;
+    }
+  }
+#endif
+}
+
 void nsBaseWidget::CreateCompositor(int aWidth, int aHeight)
 {
   MOZ_ASSERT(gfxPlatform::UsesOffMainThreadCompositing(),
@@ -901,6 +914,12 @@ void nsBaseWidget::CreateCompositor(int aWidth, int aHeight)
   nsTArray<LayersBackend> backendHints;
   GetPreferredCompositorBackends(backendHints);
 
+#ifndef MOZ_X11
+  if (!mRequireOffMainThreadCompositing) {
+    RemoveBasicBackend(backendHints);
+  }
+#endif
+
   bool success = false;
   if (!backendHints.IsEmpty()) {
     shadowManager = mCompositorChild->SendPLayerTransactionConstructor(