Filter out empty save/restores

 WebKit will sometimes produce graphics context calls that result in
 GC::Save, GC::SetClip, GC::Restore - as they don't do any drawing, we
 can detect and filter those out which saves on the amount of state
 management done.

Change-Id: I61715b0a14adb39521c605e2562fc4ac4e70a327

2 files changed, 61 insertions, 2 deletions

diff --git a/Source/WebCore/platform/graphics/android/context/GraphicsOperationCollection.cpp b/Source/WebCore/platform/graphics/android/context/GraphicsOperationCollection.cpp
index 03a0d8f..c5be59f 100644
--- a/Source/WebCore/platform/graphics/android/context/GraphicsOperationCollection.cpp
+++ b/Source/WebCore/platform/graphics/android/context/GraphicsOperationCollection.cpp
@@ -13,6 +13,31 @@
 
 namespace WebCore {
 
+using namespace GraphicsOperation;
+
+static bool isDrawingOperation(GraphicsOperation::Operation* operation) {
+    switch (operation->type()) {
+    case Operation::DrawBitmapPatternOperation:
+    case Operation::DrawBitmapRectOperation:
+    case Operation::DrawEllipseOperation:
+    case Operation::DrawLineOperation:
+    case Operation::DrawLineForTextOperation:
+    case Operation::DrawLineForTextCheckingOperation:
+    case Operation::DrawRectOperation:
+    case Operation::FillPathOperation:
+    case Operation::FillRectOperation:
+    case Operation::FillRoundedRectOperation:
+    case Operation::StrokeArcOperation:
+    case Operation::StrokePathOperation:
+    case Operation::StrokeRectOperation:
+    case Operation::DrawComplexTextOperation:
+    case Operation::DrawTextOperation:
+        return true;
+    default:
+        return false;
+    }
+}
+
 GraphicsOperationCollection::GraphicsOperationCollection()
 {
 }
@@ -23,20 +48,51 @@ GraphicsOperationCollection::~GraphicsOperationCollection()
 
 void GraphicsOperationCollection::apply(PlatformGraphicsContext* context)
 {
+    flush();
     for (unsigned int i = 0; i < m_operations.size(); i++)
         m_operations[i]->apply(context);
 }
 
-void GraphicsOperationCollection::adoptAndAppend(GraphicsOperation::Operation* operation)
+void GraphicsOperationCollection::adoptAndAppend(GraphicsOperation::Operation* rawOp)
 {
-    m_operations.append(adoptRef(operation));
+    PassRefPtr<GraphicsOperation::Operation> operation = adoptRef(rawOp);
+    if (operation->type() == Operation::SaveOperation) {
+        // TODO: Support nested Save/Restore checking?
+        flush();
+        m_pendingOperations.append(operation);
+        return;
+    }
+    if (m_pendingOperations.size()) {
+        if (operation->type() == Operation::RestoreOperation) {
+            // We hit a Save/Restore pair without any drawing, discard
+            m_pendingOperations.clear();
+            return;
+        }
+        if (!isDrawingOperation(operation.get())) {
+            // Isn't a drawing operation, so append to pending and return
+            m_pendingOperations.append(operation);
+            return;
+        }
+        // Hit a drawing operation, so flush the pending and append to m_operations
+        flush();
+    }
+    m_operations.append(operation);
 }
 
 bool GraphicsOperationCollection::isEmpty()
 {
+    flush();
     return !m_operations.size();
 }
 
+void GraphicsOperationCollection::flush()
+{
+    if (m_pendingOperations.size()) {
+        m_operations.append(m_pendingOperations);
+        m_pendingOperations.clear();
+    }
+}
+
 } // namespace WebCore
 
 #endif // USE(ACCELERATED_COMPOSITING)
diff --git a/Source/WebCore/platform/graphics/android/context/GraphicsOperationCollection.h b/Source/WebCore/platform/graphics/android/context/GraphicsOperationCollection.h
index 246e784..e7e4ccc 100644
--- a/Source/WebCore/platform/graphics/android/context/GraphicsOperationCollection.h
+++ b/Source/WebCore/platform/graphics/android/context/GraphicsOperationCollection.h
@@ -48,6 +48,9 @@ public:
     bool isEmpty();
 
 private:
+    void flush();
+
+    Vector< RefPtr<GraphicsOperation::Operation> > m_pendingOperations;
     Vector< RefPtr<GraphicsOperation::Operation> > m_operations;
 };