diff -r 000000000000 -r 6474c204b198 widget/gonk/HwcUtils.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/widget/gonk/HwcUtils.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,147 @@
+/*
+ * Copyright (c) 2013 The Linux Foundation. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <android/log.h>
+#include "HwcUtils.h"
+#include "gfxUtils.h"
+
+#define LOG_TAG "HwcUtils"
+
+#if (LOG_NDEBUG == 0)
+#define LOGD(args...) __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, ## args)
+#else
+#define LOGD(args...) ((void)0)
+#endif
+
+#define LOGE(args...) __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, ## args)
+
+
+namespace mozilla {
+
+/* Utility functions for HwcComposer */
+
+
+
+/* static */ bool
+HwcUtils::PrepareLayerRects(nsIntRect aVisible, const gfxMatrix& aTransform,
+                            nsIntRect aClip, nsIntRect aBufferRect,
+                            bool aYFlipped,
+                            hwc_rect_t* aSourceCrop, hwc_rect_t* aVisibleRegionScreen) {
+
+    gfxRect visibleRect(aVisible);
+    gfxRect clip(aClip);
+    gfxRect visibleRectScreen = aTransform.TransformBounds(visibleRect);
+    // |clip| is guaranteed to be integer
+    visibleRectScreen.IntersectRect(visibleRectScreen, clip);
+
+    if (visibleRectScreen.IsEmpty()) {
+        LOGD("Skip layer");
+        return false;
+    }
+
+    gfxMatrix inverse(aTransform);
+    inverse.Invert();
+    gfxRect crop = inverse.TransformBounds(visibleRectScreen);
+
+    //clip to buffer size
+    crop.IntersectRect(crop, aBufferRect);
+    crop.Round();
+
+    if (crop.IsEmpty()) {
+        LOGD("Skip layer");
+        return false;
+    }
+
+    //propagate buffer clipping back to visible rect
+    visibleRectScreen = aTransform.TransformBounds(crop);
+    visibleRectScreen.Round();
+
+    // Map from layer space to buffer space
+    crop -= aBufferRect.TopLeft();
+    if (aYFlipped) {
+        crop.y = aBufferRect.height - (crop.y + crop.height);
+    }
+
+    aSourceCrop->left = crop.x;
+    aSourceCrop->top  = crop.y;
+    aSourceCrop->right  = crop.x + crop.width;
+    aSourceCrop->bottom = crop.y + crop.height;
+
+    aVisibleRegionScreen->left = visibleRectScreen.x;
+    aVisibleRegionScreen->top  = visibleRectScreen.y;
+    aVisibleRegionScreen->right  = visibleRectScreen.x + visibleRectScreen.width;
+    aVisibleRegionScreen->bottom = visibleRectScreen.y + visibleRectScreen.height;
+
+    return true;
+}
+
+/* static */ bool
+HwcUtils::PrepareVisibleRegion(const nsIntRegion& aVisible,
+                               const gfxMatrix& aTransform,
+                               nsIntRect aClip, nsIntRect aBufferRect,
+                               RectVector* aVisibleRegionScreen) {
+
+    nsIntRegionRectIterator rect(aVisible);
+    bool isVisible = false;
+    while (const nsIntRect* visibleRect = rect.Next()) {
+        hwc_rect_t visibleRectScreen;
+        gfxRect screenRect;
+
+        screenRect.IntersectRect(gfxRect(*visibleRect), aBufferRect);
+        screenRect = aTransform.TransformBounds(screenRect);
+        screenRect.IntersectRect(screenRect, aClip);
+        screenRect.Round();
+        if (screenRect.IsEmpty()) {
+            continue;
+        }
+        visibleRectScreen.left = screenRect.x;
+        visibleRectScreen.top  = screenRect.y;
+        visibleRectScreen.right  = screenRect.XMost();
+        visibleRectScreen.bottom = screenRect.YMost();
+        aVisibleRegionScreen->push_back(visibleRectScreen);
+        isVisible = true;
+    }
+
+    return isVisible;
+}
+
+/* static */ bool
+HwcUtils::CalculateClipRect(const gfxMatrix& aTransform,
+                            const nsIntRect* aLayerClip,
+                            nsIntRect aParentClip, nsIntRect* aRenderClip) {
+
+    *aRenderClip = aParentClip;
+
+    if (!aLayerClip) {
+        return true;
+    }
+
+    if (aLayerClip->IsEmpty()) {
+        return false;
+    }
+
+    nsIntRect clip = *aLayerClip;
+
+    gfxRect r(clip);
+    gfxRect trClip = aTransform.TransformBounds(r);
+    trClip.Round();
+    gfxUtils::GfxRectToIntRect(trClip, &clip);
+
+    aRenderClip->IntersectRect(*aRenderClip, clip);
+    return true;
+}
+
+} // namespace mozilla