From 34ea3f441fa25709a105c6e52bc58d11695124a3 Mon Sep 17 00:00:00 2001
From: Matt Woodrow <mwoodrow@mozilla.com>
Date: Sat, 1 Mar 2014 08:51:17 +1300
Subject: [PATCH] Bug 971720 - Adjust the source pattern transform when masking
 with RotatedBuffer to take the mask transform into account. r=roc

---
 gfx/layers/RotatedBuffer.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/gfx/layers/RotatedBuffer.cpp b/gfx/layers/RotatedBuffer.cpp
index 2f4063e0a783..866900261eca 100644
--- a/gfx/layers/RotatedBuffer.cpp
+++ b/gfx/layers/RotatedBuffer.cpp
@@ -125,17 +125,24 @@ RotatedBuffer::DrawBufferQuadrant(gfx::DrawTarget* aTarget,
   }
 
   if (aMask) {
+    Matrix oldTransform = aTarget->GetTransform();
+
     // Transform from user -> buffer space.
     Matrix transform;
     transform.Translate(quadrantTranslation.x, quadrantTranslation.y);
 
+    Matrix inverseMask = *aMaskTransform;
+    inverseMask.Invert();
+
+    transform *= oldTransform;
+    transform *= inverseMask;
+
 #ifdef MOZ_GFX_OPTIMIZE_MOBILE
     SurfacePattern source(snapshot, ExtendMode::CLAMP, transform, Filter::POINT);
 #else
     SurfacePattern source(snapshot, ExtendMode::CLAMP, transform);
 #endif
 
-    Matrix oldTransform = aTarget->GetTransform();
     aTarget->SetTransform(*aMaskTransform);
     aTarget->MaskSurface(source, aMask, Point(0, 0), DrawOptions(aOpacity, aOperator));
     aTarget->SetTransform(oldTransform);