Bug 997014 - Part 1: Improve GetSurfaceSnapshot. r=roc

content/canvas/public/nsICanvasRenderingContextInternal.h

@@ -14,8 +14,8 @@
 #include "mozilla/RefPtr.h"
 
 #define NS_ICANVASRENDERINGCONTEXTINTERNAL_IID \
-{ 0x9a6a5bdf, 0x1261, 0x4057, \
-  { 0x85, 0xcc, 0xaf, 0x97, 0x6c, 0x36, 0x99, 0xa9 } }
+{ 0xf74397d9, 0x25d9, 0x43ed, \
+  { 0xb4, 0x6a, 0xf5, 0x4e, 0xa1, 0x17, 0xae, 0x6e } }
 
 class gfxContext;
 class gfxASurface;
@@ -90,7 +90,10 @@ public:
   
   // This gets an Azure SourceSurface for the canvas, this will be a snapshot
   // of the canvas at the time it was called.
-  virtual mozilla::TemporaryRef<mozilla::gfx::SourceSurface> GetSurfaceSnapshot() = 0;
+  // If aPremultAlpha is provided, then it assumed the callee can handle
+  // un-premultiplied surfaces, and *aPremultAlpha will be set to false
+  // if one is returned.
+  virtual mozilla::TemporaryRef<mozilla::gfx::SourceSurface> GetSurfaceSnapshot(bool* aPremultAlpha = nullptr) = 0;
 
   // If this context is opaque, the backing store of the canvas should
   // be created as opaque; all compositing operators should assume the

content/canvas/src/CanvasRenderingContext2D.h

@@ -465,8 +465,14 @@ public:
                             nsIInputStream **aStream) MOZ_OVERRIDE;
   NS_IMETHOD GetThebesSurface(gfxASurface **surface) MOZ_OVERRIDE;
 
-  mozilla::TemporaryRef<mozilla::gfx::SourceSurface> GetSurfaceSnapshot() MOZ_OVERRIDE
-  { EnsureTarget(); return mTarget->Snapshot(); }
+  mozilla::TemporaryRef<mozilla::gfx::SourceSurface> GetSurfaceSnapshot(bool* aPremultAlpha = nullptr) MOZ_OVERRIDE
+  {
+    EnsureTarget();
+    if (aPremultAlpha) {
+      *aPremultAlpha = true;
+    }
+    return mTarget->Snapshot();
+  }
 
   NS_IMETHOD SetIsOpaque(bool isOpaque) MOZ_OVERRIDE;
   bool GetIsOpaque() MOZ_OVERRIDE { return mOpaque; }

content/canvas/src/WebGLContext.cpp

@@ -1376,9 +1376,56 @@ void
 WebGLContext::MakeContextCurrent() const { gl->MakeCurrent(); }
 
 mozilla::TemporaryRef<mozilla::gfx::SourceSurface>
-WebGLContext::GetSurfaceSnapshot()
+WebGLContext::GetSurfaceSnapshot(bool* aPremultAlpha)
 {
-  return nullptr;
+    if (!gl)
+        return nullptr;
+
+    nsRefPtr<gfxImageSurface> surf = new gfxImageSurface(gfxIntSize(mWidth, mHeight),
+                                                         gfxImageFormat::ARGB32);
+    if (surf->CairoStatus() != 0) {
+        return nullptr;
+    }
+
+    gl->MakeCurrent();
+    ReadScreenIntoImageSurface(gl, surf);
+
+    if (aPremultAlpha) {
+        *aPremultAlpha = true;
+    }
+    bool srcPremultAlpha = mOptions.premultipliedAlpha;
+    if (!srcPremultAlpha) {
+        if (aPremultAlpha) {
+            *aPremultAlpha = false;
+        } else {
+            gfxUtils::PremultiplyImageSurface(surf);
+            surf->MarkDirty();
+        }
+    }
+
+    RefPtr<DrawTarget> dt =
+        Factory::CreateDrawTarget(BackendType::CAIRO,
+                                  IntSize(mWidth, mHeight),
+                                  SurfaceFormat::B8G8R8A8);
+
+    if (!dt) {
+        return nullptr;
+    }
+
+    RefPtr<SourceSurface> source = gfxPlatform::GetPlatform()->GetSourceSurfaceForSurface(dt, surf);
+
+    Matrix m;
+    m.Translate(0.0, mHeight);
+    m.Scale(1.0, -1.0);
+    dt->SetTransform(m);
+
+    dt->DrawSurface(source,
+                    Rect(0, 0, mWidth, mHeight),
+                    Rect(0, 0, mWidth, mHeight),
+                    DrawSurfaceOptions(),
+                    DrawOptions(1.0f, CompositionOp::OP_SOURCE));
+
+    return dt->Snapshot();
 }
 
 //

content/canvas/src/WebGLContext.h

@@ -173,7 +173,7 @@ public:
                               const char16_t* aEncoderOptions,
                               nsIInputStream **aStream) MOZ_OVERRIDE;
     NS_IMETHOD GetThebesSurface(gfxASurface **surface) MOZ_OVERRIDE;
-    mozilla::TemporaryRef<mozilla::gfx::SourceSurface> GetSurfaceSnapshot() MOZ_OVERRIDE;
+    mozilla::TemporaryRef<mozilla::gfx::SourceSurface> GetSurfaceSnapshot(bool* aPremultAlpha) MOZ_OVERRIDE;
 
     NS_IMETHOD SetIsOpaque(bool b) MOZ_OVERRIDE { return NS_OK; };
     bool GetIsOpaque() MOZ_OVERRIDE { return false; }