Bug 1034345 (Part 2) - Implement OptimalImageSizeForDest for RasterImage. r=tn

--HG--
extra : rebase_source : 63c58e8df2c992f9550b481530e41938e8672ad1

image/src/RasterImage.cpp

@@ -59,6 +59,7 @@ using namespace gfx;
 using namespace layers;
 
 namespace image {
+using std::ceil;
 
 // a mask for flags that will affect the decoding
 #define DECODE_FLAGS_MASK (imgIContainer::FLAG_DECODE_NO_PREMULTIPLY_ALPHA | imgIContainer::FLAG_DECODE_NO_COLORSPACE_CONVERSION)
@@ -2586,6 +2587,39 @@ RasterImage::ScalingDone(ScaleRequest* request, ScaleStatus status)
   }
 }
 
+void
+RasterImage::RequestScale(imgFrame* aFrame, gfxSize aScale)
+{
+  // We can't store more than one scaled version of an image right now, so if
+  // there's more than one instance of this image, bail.
+  if (mLockCount != 1) {
+    return;
+  }
+
+  // We also can't scale if we can't lock the image data for this frame.
+  if (NS_FAILED(aFrame->LockImageData())) {
+    aFrame->UnlockImageData();
+    return;
+  }
+
+  // If we have an outstanding request, signal it to stop (if it can).
+  if (mScaleRequest) {
+    mScaleRequest->stopped = true;
+  }
+
+  nsRefPtr<ScaleRunner> runner = new ScaleRunner(this, aScale, aFrame);
+  if (runner->IsOK()) {
+    if (!sScaleWorkerThread) {
+      NS_NewNamedThread("Image Scaler", getter_AddRefs(sScaleWorkerThread));
+      ClearOnShutdown(&sScaleWorkerThread);
+    }
+
+    sScaleWorkerThread->Dispatch(runner, NS_DISPATCH_NORMAL);
+  }
+
+  aFrame->UnlockImageData();
+}
+
 bool
 RasterImage::DrawWithPreDownscaleIfNeeded(imgFrame *aFrame,
                                           gfxContext *aContext,
@@ -2636,27 +2670,8 @@ RasterImage::DrawWithPreDownscaleIfNeeded(imgFrame *aFrame,
 
     // If we're not waiting for exactly this result, and there's only one
     // instance of this image on this page, ask for a scale.
-    if (needScaleReq && mLockCount == 1) {
-      if (NS_FAILED(frame->LockImageData())) {
-        frame->UnlockImageData();
-        return false;
-      }
-
-      // If we have an outstanding request, signal it to stop (if it can).
-      if (mScaleRequest) {
-        mScaleRequest->stopped = true;
-      }
-
-      nsRefPtr<ScaleRunner> runner = new ScaleRunner(this, scale, frame);
-      if (runner->IsOK()) {
-        if (!sScaleWorkerThread) {
-          NS_NewNamedThread("Image Scaler", getter_AddRefs(sScaleWorkerThread));
-          ClearOnShutdown(&sScaleWorkerThread);
-        }
-
-        sScaleWorkerThread->Dispatch(runner, NS_DISPATCH_NORMAL);
-      }
-      frame->UnlockImageData();
+    if (needScaleReq) {
+      RequestScale(frame, scale);
     }
   }
 
@@ -3656,5 +3671,45 @@ RasterImage::FrameNeededWorker::Run()
   return NS_OK;
 }
 
+nsIntSize
+RasterImage::OptimalImageSizeForDest(const gfxSize& aDest, uint32_t aWhichFrame,
+                                     GraphicsFilter aFilter, uint32_t aFlags)
+{
+  MOZ_ASSERT(aDest.width >= 0 || ceil(aDest.width) <= INT32_MAX ||
+             aDest.height >= 0 || ceil(aDest.height) <= INT32_MAX,
+             "Unexpected destination size");
+
+  if (mSize.IsEmpty()) {
+    return nsIntSize(0, 0);
+  }
+
+  nsIntSize destSize(ceil(aDest.width), ceil(aDest.height));
+  gfxSize scale(double(destSize.width) / mSize.width,
+                double(destSize.height) / mSize.height);
+
+  if (CanScale(aFilter, scale, aFlags)) {
+    if (mScaleResult.scale == scale) {
+      if (mScaleResult.status == SCALE_DONE) {
+        return destSize;  // We have an existing HQ scale for this size.
+      } else if (mScaleResult.status == SCALE_PENDING) {
+        return mSize;     // We're waiting for exactly this result.
+      }
+    }
+
+    // If there's only one instance of this image on this page, ask for a scale.
+    uint32_t frameIndex = aWhichFrame == FRAME_FIRST ? 0
+                                                     : GetCurrentImgFrameIndex();
+
+    imgFrame* frame = GetDrawableImgFrame(frameIndex);
+    if (frame) {
+      RequestScale(frame, scale);
+    }
+  }
+
+  // We either can't HQ scale to this size or the scaled version isn't ready
+  // yet. Use our intrinsic size for now.
+  return mSize;
+}
+
 } // namespace image
 } // namespace mozilla

image/src/RasterImage.h

@@ -329,6 +329,9 @@ public:
   // Decode strategy
 
 private:
+  // Initiates an HQ scale for the given frame, if possible.
+  void RequestScale(imgFrame* aFrame, gfxSize aScale);
+
   already_AddRefed<imgStatusTracker> CurrentStatusTracker()
   {
     mDecodingMonitor.AssertCurrentThreadIn();