From f2b9c641927bb658794993678d541d0d178ebca5 Mon Sep 17 00:00:00 2001
From: Matt Woodrow <mwoodrow@mozilla.com>
Date: Tue, 13 May 2014 14:20:26 +1200
Subject: [PATCH] Bug 1006198 - Add PremultiplyDataSurface. r=nical

---
 gfx/layers/CopyableCanvasLayer.cpp |  6 ++--
 gfx/thebes/gfxUtils.cpp            | 46 ++++++++++++++++++++++++++++++
 gfx/thebes/gfxUtils.h              |  1 +
 3 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/gfx/layers/CopyableCanvasLayer.cpp b/gfx/layers/CopyableCanvasLayer.cpp
index c3c7c4b4781c..9fe89f487654 100644
--- a/gfx/layers/CopyableCanvasLayer.cpp
+++ b/gfx/layers/CopyableCanvasLayer.cpp
@@ -21,7 +21,7 @@
 #include "nsISupportsImpl.h"            // for gfxContext::AddRef, etc
 #include "nsRect.h"                     // for nsIntRect
 #include "nsSize.h"                     // for nsIntSize
-#include "LayerUtils.h"
+#include "gfxUtils.h"
 
 using namespace mozilla::gfx;
 using namespace mozilla::gl;
@@ -126,7 +126,7 @@ CopyableCanvasLayer::UpdateTarget(DrawTarget* aDestTarget)
             Factory::CreateWrappingDataSourceSurface(destData, destStride, destSize, destFormat);
           mGLContext->Screen()->Readback(sharedSurf, data);
           if (needsPremult) {
-            PremultiplySurface(data);
+              gfxUtils::PremultiplyDataSurface(data);
           }
           aDestTarget->ReleaseBits(destData);
           return;
@@ -144,7 +144,7 @@ CopyableCanvasLayer::UpdateTarget(DrawTarget* aDestTarget)
       // Readback handles Flush/MarkDirty.
       mGLContext->Screen()->Readback(sharedSurf, data);
       if (needsPremult) {
-        PremultiplySurface(data);
+        gfxUtils::PremultiplyDataSurface(data);
       }
       resultSurf = data;
     }
diff --git a/gfx/thebes/gfxUtils.cpp b/gfx/thebes/gfxUtils.cpp
index 68d30ed2333d..cc9078fbee18 100644
--- a/gfx/thebes/gfxUtils.cpp
+++ b/gfx/thebes/gfxUtils.cpp
@@ -89,6 +89,52 @@ gfxUtils::PremultiplyImageSurface(gfxImageSurface *aSourceSurface,
     }
 }
 
+void
+gfxUtils::PremultiplyDataSurface(DataSourceSurface *aSurface)
+{
+    // Only premultiply ARGB32
+    if (aSurface->GetFormat() != SurfaceFormat::B8G8R8A8) {
+        return;
+    }
+
+    DataSourceSurface::MappedSurface map;
+    if (!aSurface->Map(DataSourceSurface::MapType::READ_WRITE, &map)) {
+        return;
+    }
+    MOZ_ASSERT(map.mStride == aSurface->GetSize().width * 4,
+               "Source surface stride isn't tightly packed");
+
+    uint8_t *src = map.mData;
+    uint8_t *dst = map.mData;
+
+    uint32_t dim = aSurface->GetSize().width * aSurface->GetSize().height;
+    for (uint32_t i = 0; i < dim; ++i) {
+#ifdef IS_LITTLE_ENDIAN
+        uint8_t b = *src++;
+        uint8_t g = *src++;
+        uint8_t r = *src++;
+        uint8_t a = *src++;
+
+        *dst++ = PremultiplyValue(a, b);
+        *dst++ = PremultiplyValue(a, g);
+        *dst++ = PremultiplyValue(a, r);
+        *dst++ = a;
+#else
+        uint8_t a = *src++;
+        uint8_t r = *src++;
+        uint8_t g = *src++;
+        uint8_t b = *src++;
+
+        *dst++ = a;
+        *dst++ = PremultiplyValue(a, r);
+        *dst++ = PremultiplyValue(a, g);
+        *dst++ = PremultiplyValue(a, b);
+#endif
+    }
+
+    aSurface->Unmap();
+}
+
 void
 gfxUtils::UnpremultiplyImageSurface(gfxImageSurface *aSourceSurface,
                                     gfxImageSurface *aDestSurface)
diff --git a/gfx/thebes/gfxUtils.h b/gfx/thebes/gfxUtils.h
index 3e68d7614c8b..c94fbf3741ed 100644
--- a/gfx/thebes/gfxUtils.h
+++ b/gfx/thebes/gfxUtils.h
@@ -42,6 +42,7 @@ public:
      */
     static void PremultiplyImageSurface(gfxImageSurface *aSourceSurface,
                                         gfxImageSurface *aDestSurface = nullptr);
+    static void PremultiplyDataSurface(DataSourceSurface *aSurface);
     static void UnpremultiplyImageSurface(gfxImageSurface *aSurface,
                                           gfxImageSurface *aDestSurface = nullptr);
     static mozilla::TemporaryRef<DataSourceSurface> UnpremultiplyDataSurface(DataSourceSurface* aSurface);