1 files changed, 72 insertions, 0 deletions
diff --git a/cc/CCPriorityCalculator.cpp b/cc/CCPriorityCalculator.cpp
new file mode 100644
index 0000000..7e769f7
--- /dev/null
+++ b/cc/CCPriorityCalculator.cpp
@@ -0,0 +1,72 @@
+// Copyright 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "config.h"
+
+#include "CCPriorityCalculator.h"
+
+using namespace std;
+
+namespace WebCore {
+
+// static
+int CCPriorityCalculator::uiPriority(bool drawsToRootSurface)
+{
+    return drawsToRootSurface ? -1 : 2;
+}
+
+// static
+int CCPriorityCalculator::visiblePriority(bool drawsToRootSurface)
+{
+    return drawsToRootSurface ? 0 : 3;
+}
+
+// static
+int CCPriorityCalculator::renderSurfacePriority()
+{
+    return 1;
+}
+
+// static
+int CCPriorityCalculator::lingeringPriority(int previousPriority)
+{
+    // FIXME: We should remove this once we have priorities for all
+    //        textures (we can't currently calculate distances for
+    //        off-screen textures).
+    int lingeringPriority = 1000000;
+    return min(numeric_limits<int>::max() - 1,
+               max(lingeringPriority, previousPriority)) + 1;
+}
+
+namespace {
+unsigned manhattanDistance(const IntRect& a, const IntRect& b)
+{
+    IntRect c = unionRect(a, b);
+    int x = max(0, c.width() - a.width() - b.width() + 1);
+    int y = max(0, c.height() - a.height() - b.height() + 1);
+    return (x + y);
+}
+}
+
+int CCPriorityCalculator::priorityFromDistance(const IntRect& visibleRect, const IntRect& textureRect, bool drawsToRootSurface) const
+{
+    unsigned distance = manhattanDistance(visibleRect, textureRect);
+    if (!distance)
+        return visiblePriority(drawsToRootSurface);
+    return visiblePriority(false) + distance;
+}
+
+int CCPriorityCalculator::priorityFromDistance(unsigned pixels, bool drawsToRootSurface) const
+{
+    if (!pixels)
+        return visiblePriority(drawsToRootSurface);
+    return visiblePriority(false) + pixels;
+}
+
+int CCPriorityCalculator::priorityFromVisibility(bool visible, bool drawsToRootSurface) const
+{
+    return visible ? visiblePriority(drawsToRootSurface) : lowestPriority();
+}
+
+} // WebCore