From d97c2034f7d0aa88fbe176d0a2d0d7ed33ce4f99 Mon Sep 17 00:00:00 2001
From: Chris Lord <chrislord.net@gmail.com>
Date: Fri, 3 Oct 2014 13:22:32 +1300
Subject: [PATCH] Bug 1006797 - Only apply the window render offset when
 actually rendering to the window. r=nical

---
 gfx/layers/opengl/CompositingRenderTargetOGL.cpp |  3 ++-
 gfx/layers/opengl/CompositingRenderTargetOGL.h   |  4 +++-
 gfx/layers/opengl/CompositorOGL.cpp              | 14 +++++++++++---
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/gfx/layers/opengl/CompositingRenderTargetOGL.cpp b/gfx/layers/opengl/CompositingRenderTargetOGL.cpp
index f56881cb2693..2f75e6649baa 100644
--- a/gfx/layers/opengl/CompositingRenderTargetOGL.cpp
+++ b/gfx/layers/opengl/CompositingRenderTargetOGL.cpp
@@ -92,6 +92,8 @@ CompositingRenderTargetOGL::InitializeImpl()
     NS_ERROR(msg.get());
   }
 
+  mInitParams.mStatus = InitParams::INITIALIZED;
+
   mCompositor->PrepareViewport(mInitParams.mSize);
   mGL->fScissor(0, 0, mInitParams.mSize.width, mInitParams.mSize.height);
   if (mInitParams.mInit == INIT_MODE_CLEAR) {
@@ -99,7 +101,6 @@ CompositingRenderTargetOGL::InitializeImpl()
     mGL->fClear(LOCAL_GL_COLOR_BUFFER_BIT);
   }
 
-  mInitParams.mStatus = InitParams::INITIALIZED;
 }
 
 }
diff --git a/gfx/layers/opengl/CompositingRenderTargetOGL.h b/gfx/layers/opengl/CompositingRenderTargetOGL.h
index a08066ff4140..76186da9c7ce 100644
--- a/gfx/layers/opengl/CompositingRenderTargetOGL.h
+++ b/gfx/layers/opengl/CompositingRenderTargetOGL.h
@@ -84,7 +84,7 @@ public:
                         const gfx::IntSize& aSize)
   {
     RefPtr<CompositingRenderTargetOGL> result
-      = new CompositingRenderTargetOGL(aCompositor, gfx::IntPoint(0, 0), 0, 0);
+      = new CompositingRenderTargetOGL(aCompositor, gfx::IntPoint(), 0, 0);
     result->mInitParams = InitParams(aSize, 0, INIT_MODE_NONE);
     result->mInitParams.mStatus = InitParams::INITIALIZED;
     return result.forget();
@@ -112,6 +112,8 @@ public:
    */
   void BindRenderTarget();
 
+  bool IsWindow() { return GetFBO() == 0; }
+
   GLuint GetFBO() const
   {
     MOZ_ASSERT(mInitParams.mStatus == InitParams::INITIALIZED);
diff --git a/gfx/layers/opengl/CompositorOGL.cpp b/gfx/layers/opengl/CompositorOGL.cpp
index 8202261bc626..6c4c09b04ee8 100644
--- a/gfx/layers/opengl/CompositorOGL.cpp
+++ b/gfx/layers/opengl/CompositorOGL.cpp
@@ -593,7 +593,10 @@ CompositorOGL::PrepareViewport(const gfx::IntSize& aSize)
     viewMatrix.PreScale(1.0f, -1.0f);
   }
 
-  if (!mTarget) {
+  MOZ_ASSERT(mCurrentRenderTarget, "No destination");
+  // If we're drawing directly to the window then we want to offset
+  // drawing by the render offset.
+  if (!mTarget && mCurrentRenderTarget->IsWindow()) {
     viewMatrix.PreTranslate(mRenderOffset.x, mRenderOffset.y);
   }
 
@@ -660,8 +663,8 @@ CompositorOGL::SetRenderTarget(CompositingRenderTarget *aSurface)
   CompositingRenderTargetOGL* surface
     = static_cast<CompositingRenderTargetOGL*>(aSurface);
   if (mCurrentRenderTarget != surface) {
-    surface->BindRenderTarget();
     mCurrentRenderTarget = surface;
+    surface->BindRenderTarget();
   }
 }
 
@@ -1019,9 +1022,14 @@ CompositorOGL::DrawQuad(const Rect& aRect,
     js::ProfileEntry::Category::GRAPHICS);
 
   MOZ_ASSERT(mFrameInProgress, "frame not started");
+  MOZ_ASSERT(mCurrentRenderTarget, "No destination");
 
   Rect clipRect = aClipRect;
-  if (!mTarget) {
+  // aClipRect is in destination coordinate space (after all
+  // transforms and offsets have been applied) so if our
+  // drawing is going to be shifted by mRenderOffset then we need
+  // to shift the clip rect by the same amount.
+  if (!mTarget && mCurrentRenderTarget->IsWindow()) {
     clipRect.MoveBy(mRenderOffset.x, mRenderOffset.y);
   }
   IntRect intClipRect;