Correct implementation of saveLayer().

Change-Id: I5375126636913e0a84f2d6bbd0ebe40d2e4f2763

8 files changed, 131 insertions, 161 deletions

diff --git a/libs/hwui/Layer.h b/libs/hwui/Layer.h
index d4db782..c527038 100644
--- a/libs/hwui/Layer.h
+++ b/libs/hwui/Layer.h
@@ -63,28 +63,19 @@ struct LayerSize {
  */
 struct Layer {
     /**
-     * Coordinates of the layer corresponding to this snapshot.
-     * Only set when the flag kFlagIsLayer is set.
+     * Coordinates of the layer.
      */
     Rect layer;
     /**
      * Name of the texture used to render the layer.
-     * Only set when the flag kFlagIsLayer is set.
      */
     GLuint texture;
     /**
-     * Name of the FBO used to render the layer.
-     * Only set when the flag kFlagIsLayer is set.
-     */
-    GLuint fbo;
-    /**
      * Opacity of the layer.
-     * Only set when the flag kFlagIsLayer is set.
      */
-    float alpha;
+    int alpha;
     /**
      * Blending mode of the layer.
-     * Only set when the flag kFlagIsLayer is set.
      */
     SkXfermode::Mode mode;
     /**
diff --git a/libs/hwui/LayerCache.cpp b/libs/hwui/LayerCache.cpp
index a204778..1a18766 100644
--- a/libs/hwui/LayerCache.cpp
+++ b/libs/hwui/LayerCache.cpp
@@ -87,7 +87,6 @@ void LayerCache::deleteLayer(Layer* layer) {
     if (layer) {
         mSize -= layer->layer.getWidth() * layer->layer.getHeight() * 4;
 
-        glDeleteFramebuffers(1, &layer->fbo);
         glDeleteTextures(1, &layer->texture);
         delete layer;
     }
@@ -99,7 +98,7 @@ void LayerCache::clear() {
     mCache.setOnEntryRemovedListener(NULL);
 }
 
-Layer* LayerCache::get(LayerSize& size, GLuint previousFbo) {
+Layer* LayerCache::get(LayerSize& size) {
     Layer* layer = mCache.remove(size);
     if (layer) {
         LAYER_LOGD("Reusing layer");
@@ -111,10 +110,6 @@ Layer* LayerCache::get(LayerSize& size, GLuint previousFbo) {
         layer = new Layer;
         layer->blend = true;
 
-        // Generate the FBO and attach the texture
-        glGenFramebuffers(1, &layer->fbo);
-        glBindFramebuffer(GL_FRAMEBUFFER, layer->fbo);
-
         // Generate the texture in which the FBO will draw
         glGenTextures(1, &layer->texture);
         glBindTexture(GL_TEXTURE_2D, layer->texture);
@@ -128,23 +123,6 @@ Layer* LayerCache::get(LayerSize& size, GLuint previousFbo) {
 
         glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, size.width, size.height, 0,
                 GL_RGBA, GL_UNSIGNED_BYTE, NULL);
-
-        // Bind texture to FBO
-        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
-                layer->texture, 0);
-
-        GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
-        if (status != GL_FRAMEBUFFER_COMPLETE) {
-            LOGE("Framebuffer incomplete (GL error code 0x%x)", status);
-
-            glBindFramebuffer(GL_FRAMEBUFFER, previousFbo);
-
-            glDeleteFramebuffers(1, &layer->fbo);
-            glDeleteTextures(1, &layer->texture);
-            delete layer;
-
-            return NULL;
-        }
     }
 
     return layer;
diff --git a/libs/hwui/LayerCache.h b/libs/hwui/LayerCache.h
index 9860994..c0c7542 100644
--- a/libs/hwui/LayerCache.h
+++ b/libs/hwui/LayerCache.h
@@ -62,10 +62,8 @@ public:
      * size of the cache goes down.
      *
      * @param size The dimensions of the desired layer
-     * @param previousFbo The name of the FBO to bind to if creating a new
-     *        layer fails
      */
-    Layer* get(LayerSize& size, GLuint previousFbo);
+    Layer* get(LayerSize& size);
     /**
      * Adds the layer to the cache. The layer will not be added if there is
      * not enough space available.
diff --git a/libs/hwui/OpenGLRenderer.cpp b/libs/hwui/OpenGLRenderer.cpp
index 6c90704..7cf70f7 100644
--- a/libs/hwui/OpenGLRenderer.cpp
+++ b/libs/hwui/OpenGLRenderer.cpp
@@ -80,6 +80,21 @@ static const Blender gBlends[] = {
         { SkXfermode::kXor_Mode,     GL_ONE_MINUS_DST_ALPHA,  GL_ONE_MINUS_SRC_ALPHA }
 };
 
+static const Blender gBlendsSwap[] = {
+        { SkXfermode::kClear_Mode,   GL_ZERO,                 GL_ZERO },
+        { SkXfermode::kSrc_Mode,     GL_ZERO,                 GL_ONE },
+        { SkXfermode::kDst_Mode,     GL_ONE,                  GL_ZERO },
+        { SkXfermode::kSrcOver_Mode, GL_ONE_MINUS_DST_ALPHA,  GL_ONE },
+        { SkXfermode::kDstOver_Mode, GL_ONE,                  GL_ONE_MINUS_SRC_ALPHA },
+        { SkXfermode::kSrcIn_Mode,   GL_ZERO,                 GL_SRC_ALPHA },
+        { SkXfermode::kDstIn_Mode,   GL_DST_ALPHA,            GL_ZERO },
+        { SkXfermode::kSrcOut_Mode,  GL_ZERO,                 GL_ONE_MINUS_SRC_ALPHA },
+        { SkXfermode::kDstOut_Mode,  GL_ONE_MINUS_DST_ALPHA,  GL_ZERO },
+        { SkXfermode::kSrcATop_Mode, GL_ONE_MINUS_DST_ALPHA,  GL_SRC_ALPHA },
+        { SkXfermode::kDstATop_Mode, GL_DST_ALPHA,            GL_ONE_MINUS_SRC_ALPHA },
+        { SkXfermode::kXor_Mode,     GL_ONE_MINUS_DST_ALPHA,  GL_ONE_MINUS_SRC_ALPHA }
+};
+
 static const GLenum gTextureUnits[] = {
         GL_TEXTURE0,
         GL_TEXTURE1,
@@ -122,8 +137,6 @@ void OpenGLRenderer::setViewport(int width, int height) {
 
     mWidth = width;
     mHeight = height;
-    mFirstSnapshot->height = height;
-    mFirstSnapshot->viewport.set(0, 0, width, height);
 }
 
 void OpenGLRenderer::prepare() {
@@ -155,14 +168,19 @@ void OpenGLRenderer::acquireContext() {
 }
 
 void OpenGLRenderer::releaseContext() {
-    glViewport(0, 0, mSnapshot->viewport.getWidth(), mSnapshot->viewport.getHeight());
+    glViewport(0, 0, mWidth, mHeight);
 
     glEnable(GL_SCISSOR_TEST);
     setScissorFromClip();
 
+    glDisable(GL_DITHER);
+
+    glBindFramebuffer(GL_FRAMEBUFFER, 0);
+
     if (mCaches.blend) {
         glEnable(GL_BLEND);
         glBlendFunc(mCaches.lastSrcMode, mCaches.lastDstMode);
+        glBlendEquation(GL_FUNC_ADD);
     } else {
         glDisable(GL_BLEND);
     }
@@ -202,17 +220,10 @@ int OpenGLRenderer::saveSnapshot(int flags) {
 bool OpenGLRenderer::restoreSnapshot() {
     bool restoreClip = mSnapshot->flags & Snapshot::kFlagClipSet;
     bool restoreLayer = mSnapshot->flags & Snapshot::kFlagIsLayer;
-    bool restoreOrtho = mSnapshot->flags & Snapshot::kFlagDirtyOrtho;
 
     sp<Snapshot> current = mSnapshot;
     sp<Snapshot> previous = mSnapshot->previous;
 
-    if (restoreOrtho) {
-        Rect& r = previous->viewport;
-        glViewport(r.left, r.top, r.right, r.bottom);
-        mOrthoMatrix.load(current->orthoMatrix);
-    }
-
     mSaveCount--;
     mSnapshot = previous;
 
@@ -253,11 +264,7 @@ int OpenGLRenderer::saveLayer(float left, float top, float right, float bottom,
         mode = SkXfermode::kSrcOver_Mode;
     }
 
-    if (alpha > 0 && !mSnapshot->invisible) {
-        createLayer(mSnapshot, left, top, right, bottom, alpha, mode, flags);
-    } else {
-        mSnapshot->invisible = true;
-    }
+    createLayer(mSnapshot, left, top, right, bottom, alpha, mode, flags);
 
     return count;
 }
@@ -278,48 +285,41 @@ bool OpenGLRenderer::createLayer(sp<Snapshot> snapshot, float left, float top,
     LAYER_LOGD("Requesting layer %fx%f", right - left, bottom - top);
     LAYER_LOGD("Layer cache size = %d", mCaches.layerCache.getSize());
 
+    // Window coordinates of the layer
     Rect bounds(left, top, right, bottom);
-    // TODO: Apply transformations and treat layers in screen coordinates
-    // mSnapshot->transform->mapRect(bounds);
+    mSnapshot->transform->mapRect(bounds);
 
-    GLuint previousFbo = snapshot->previous.get() ? snapshot->previous->fbo : 0;
     LayerSize size(bounds.getWidth(), bounds.getHeight());
 
-    Layer* layer = mCaches.layerCache.get(size, previousFbo);
+    Layer* layer = mCaches.layerCache.get(size);
     if (!layer) {
         return false;
     }
 
-    glBindFramebuffer(GL_FRAMEBUFFER, layer->fbo);
-
-    // Clear the FBO
-    glDisable(GL_SCISSOR_TEST);
-    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
-    glClear(GL_COLOR_BUFFER_BIT);
-    glEnable(GL_SCISSOR_TEST);
-
     layer->mode = mode;
-    layer->alpha = alpha / 255.0f;
+    layer->alpha = alpha;
     layer->layer.set(bounds);
 
     // Save the layer in the snapshot
     snapshot->flags |= Snapshot::kFlagIsLayer;
     snapshot->layer = layer;
-    snapshot->fbo = layer->fbo;
-    // TODO: Temporary until real layer support is implemented
-    snapshot->resetTransform(-bounds.left, -bounds.top, 0.0f);
-    // TODO: Temporary until real layer support is implemented
-    snapshot->resetClip(0.0f, 0.0f, bounds.getWidth(), bounds.getHeight());
-    snapshot->viewport.set(0.0f, 0.0f, bounds.getWidth(), bounds.getHeight());
-    snapshot->height = bounds.getHeight();
-    snapshot->flags |= Snapshot::kFlagDirtyOrtho;
-    snapshot->orthoMatrix.load(mOrthoMatrix);
 
-    setScissorFromClip();
+    // Copy the framebuffer into the layer
+    glBindTexture(GL_TEXTURE_2D, layer->texture);
+    glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, bounds.left, mHeight - bounds.bottom,
+            bounds.getWidth(), bounds.getHeight(), 0);
+
+    // Clear the framebuffer where the layer will draw
+    glScissor(bounds.left, mHeight - bounds.bottom, bounds.getWidth(), bounds.getHeight());
+    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
+    glClear(GL_COLOR_BUFFER_BIT);
 
-    // Change the ortho projection
-    glViewport(0, 0, bounds.getWidth(), bounds.getHeight());
-    mOrthoMatrix.loadOrtho(0.0f, bounds.getWidth(), bounds.getHeight(), 0.0f, -1.0f, 1.0f);
+    if (flags & SkCanvas::kClipToLayer_SaveFlag) {
+        mSnapshot->clipTransformed(bounds);
+    }
+
+    // Restore the initial clip
+    setScissorFromClip();
 
     return true;
 }
@@ -330,22 +330,32 @@ void OpenGLRenderer::composeLayer(sp<Snapshot> current, sp<Snapshot> previous) {
         return;
     }
 
-    // Unbind current FBO and restore previous one
-    // Most of the time, previous->fbo will be 0 to bind the default buffer
-    glBindFramebuffer(GL_FRAMEBUFFER, previous->fbo);
-
     // Restore the clip from the previous snapshot
     const Rect& clip = *previous->clipRect;
-    glScissor(clip.left, previous->height - clip.bottom, clip.getWidth(), clip.getHeight());
+    glScissor(clip.left, mHeight - clip.bottom, clip.getWidth(), clip.getHeight());
 
     Layer* layer = current->layer;
     const Rect& rect = layer->layer;
 
-    // FBOs are already drawn with a top-left origin, don't flip the texture
+    if (layer->alpha < 255) {
+        glEnable(GL_BLEND);
+        glBlendFuncSeparate(GL_ZERO, GL_SRC_ALPHA, GL_DST_ALPHA, GL_ZERO);
+
+        drawColorRect(rect.left, rect.top, rect.right, rect.bottom,
+                layer->alpha << 24, SkXfermode::kSrcOver_Mode, true, true);
+
+        glBlendFunc(mCaches.lastSrcMode, mCaches.lastDstMode);
+        if (!mCaches.blend) {
+            glDisable(GL_BLEND);
+        }
+    }
+
+    // Layers are already drawn with a top-left origin, don't flip the texture
     resetDrawTextureTexCoords(0.0f, 1.0f, 1.0f, 0.0f);
 
-    drawTextureRect(rect.left, rect.top, rect.right, rect.bottom,
-            layer->texture, layer->alpha, layer->mode, layer->blend);
+    drawTextureMesh(rect.left, rect.top, rect.right, rect.bottom, layer->texture,
+            1.0f, layer->mode, layer->blend, &mMeshVertices[0].position[0],
+            &mMeshVertices[0].texture[0], NULL, 0, true, true);
 
     resetDrawTextureTexCoords(0.0f, 0.0f, 1.0f, 1.0f);
 
@@ -355,7 +365,6 @@ void OpenGLRenderer::composeLayer(sp<Snapshot> current, sp<Snapshot> previous) {
     if (!mCaches.layerCache.put(size, layer)) {
         LAYER_LOGD("Deleting layer");
 
-        glDeleteFramebuffers(1, &layer->fbo);
         glDeleteTextures(1, &layer->texture);
 
         delete layer;
@@ -397,7 +406,7 @@ void OpenGLRenderer::concatMatrix(SkMatrix* matrix) {
 
 void OpenGLRenderer::setScissorFromClip() {
     const Rect& clip = *mSnapshot->clipRect;
-    glScissor(clip.left, mSnapshot->height - clip.bottom, clip.getWidth(), clip.getHeight());
+    glScissor(clip.left, mHeight - clip.bottom, clip.getWidth(), clip.getHeight());
 }
 
 const Rect& OpenGLRenderer::getClipBounds() {
@@ -405,8 +414,6 @@ const Rect& OpenGLRenderer::getClipBounds() {
 }
 
 bool OpenGLRenderer::quickReject(float left, float top, float right, float bottom) {
-    if (mSnapshot->invisible) return true;
-
     Rect r(left, top, right, bottom);
     mSnapshot->transform->mapRect(r);
     return !mSnapshot->clipRect->intersects(r);
@@ -512,7 +519,6 @@ void OpenGLRenderer::drawPatch(SkBitmap* bitmap, Res_png_9patch* patch,
 }
 
 void OpenGLRenderer::drawColor(int color, SkXfermode::Mode mode) {
-    if (mSnapshot->invisible) return;
     const Rect& clip = *mSnapshot->clipRect;
     drawColorRect(clip.left, clip.top, clip.right, clip.bottom, color, mode, true);
 }
@@ -545,10 +551,10 @@ void OpenGLRenderer::drawRect(float left, float top, float right, float bottom,
 
 void OpenGLRenderer::drawText(const char* text, int bytesCount, int count,
         float x, float y, SkPaint* paint) {
-    if (mSnapshot->invisible || text == NULL || count == 0 ||
-            (paint->getAlpha() == 0 && paint->getXfermode() == NULL)) {
+    if (text == NULL || count == 0 || (paint->getAlpha() == 0 && paint->getXfermode() == NULL)) {
         return;
     }
+    paint->setAntiAlias(true);
 
     float scaleX = paint->getTextScaleX();
     bool applyScaleX = scaleX < 0.9999f || scaleX > 1.0001f;
@@ -619,8 +625,6 @@ void OpenGLRenderer::drawText(const char* text, int bytesCount, int count,
 }
 
 void OpenGLRenderer::drawPath(SkPath* path, SkPaint* paint) {
-    if (mSnapshot->invisible) return;
-
     GLuint textureUnit = 0;
     glActiveTexture(gTextureUnits[textureUnit]);
 
@@ -778,6 +782,7 @@ void OpenGLRenderer::setupTextureAlpha8(GLuint texture, uint32_t width, uint32_t
      }
 }
 
+// Same values used by Skia
 #define kStdStrikeThru_Offset   (-6.0f / 21.0f)
 #define kStdUnderline_Offset    (1.0f / 9.0f)
 #define kStdUnderline_Thickness (1.0f / 18.0f)
@@ -830,7 +835,7 @@ void OpenGLRenderer::drawTextDecorations(const char* text, int bytesCount, float
 }
 
 void OpenGLRenderer::drawColorRect(float left, float top, float right, float bottom,
-        int color, SkXfermode::Mode mode, bool ignoreTransform) {
+        int color, SkXfermode::Mode mode, bool ignoreTransform, bool ignoreBlending) {
     // If a shader is set, preserve only the alpha
     if (mShader) {
         color |= 0x00ffffff;
@@ -854,8 +859,10 @@ void OpenGLRenderer::drawColorRect(float left, float top, float right, float bot
         mColorFilter->describe(description, mExtensions);
     }
 
-    // Setup the blending mode
-    chooseBlending(alpha < 255 || (mShader && mShader->blend()), mode, description);
+    if (!ignoreBlending) {
+        // Setup the blending mode
+        chooseBlending(alpha < 255 || (mShader && mShader->blend()), mode, description);
+    }
 
     // Build and use the appropriate shader
     useProgram(mCaches.programCache.get(description));
@@ -905,7 +912,8 @@ void OpenGLRenderer::drawTextureRect(float left, float top, float right, float b
 
 void OpenGLRenderer::drawTextureMesh(float left, float top, float right, float bottom,
         GLuint texture, float alpha, SkXfermode::Mode mode, bool blend,
-        GLvoid* vertices, GLvoid* texCoords, GLvoid* indices, GLsizei elementsCount) {
+        GLvoid* vertices, GLvoid* texCoords, GLvoid* indices, GLsizei elementsCount,
+        bool swapSrcDst, bool ignoreTransform) {
     ProgramDescription description;
     description.hasTexture = true;
     if (mColorFilter) {
@@ -915,10 +923,15 @@ void OpenGLRenderer::drawTextureMesh(float left, float top, float right, float b
     mModelView.loadTranslate(left, top, 0.0f);
     mModelView.scale(right - left, bottom - top, 1.0f);
 
-    chooseBlending(blend || alpha < 1.0f, mode, description);
+    chooseBlending(blend || alpha < 1.0f, mode, description, swapSrcDst);
 
     useProgram(mCaches.programCache.get(description));
-    mCaches.currentProgram->set(mOrthoMatrix, mModelView, *mSnapshot->transform);
+    if (!ignoreTransform) {
+        mCaches.currentProgram->set(mOrthoMatrix, mModelView, *mSnapshot->transform);
+    } else {
+        mat4 m;
+        mCaches.currentProgram->set(mOrthoMatrix, mModelView, m);
+    }
 
     // Texture
     bindTexture(texture, GL_CLAMP_TO_EDGE, GL_CLAMP_TO_EDGE, 0);
@@ -948,7 +961,7 @@ void OpenGLRenderer::drawTextureMesh(float left, float top, float right, float b
 }
 
 void OpenGLRenderer::chooseBlending(bool blend, SkXfermode::Mode mode,
-        ProgramDescription& description) {
+        ProgramDescription& description, bool swapSrcDst) {
     blend = blend || mode != SkXfermode::kSrcOver_Mode;
     if (blend) {
         if (mode < SkXfermode::kPlus_Mode) {
@@ -956,8 +969,8 @@ void OpenGLRenderer::chooseBlending(bool blend, SkXfermode::Mode mode,
                 glEnable(GL_BLEND);
             }
 
-            GLenum sourceMode = gBlends[mode].src;
-            GLenum destMode = gBlends[mode].dst;
+            GLenum sourceMode = swapSrcDst ? gBlendsSwap[mode].src : gBlends[mode].src;
+            GLenum destMode = swapSrcDst ? gBlendsSwap[mode].dst : gBlends[mode].dst;
 
             if (sourceMode != mCaches.lastSrcMode || destMode != mCaches.lastDstMode) {
                 glBlendFunc(sourceMode, destMode);
@@ -970,6 +983,7 @@ void OpenGLRenderer::chooseBlending(bool blend, SkXfermode::Mode mode,
             // the blending, turn blending off here
             if (mExtensions.hasFramebufferFetch()) {
                 description.framebufferMode = mode;
+                description.swapSrcDst = swapSrcDst;
             }
 
             if (mCaches.blend) {
diff --git a/libs/hwui/OpenGLRenderer.h b/libs/hwui/OpenGLRenderer.h
index 50f42c2..e7f933f 100644
--- a/libs/hwui/OpenGLRenderer.h
+++ b/libs/hwui/OpenGLRenderer.h
@@ -166,9 +166,11 @@ private:
      * @param color The rectangle's ARGB color, defined as a packed 32 bits word
      * @param mode The Skia xfermode to use
      * @param ignoreTransform True if the current transform should be ignored
+     * @paran ignoreBlending True if the blending is set by the caller
      */
     void drawColorRect(float left, float top, float right, float bottom,
-    		int color, SkXfermode::Mode mode, bool ignoreTransform = false);
+    		int color, SkXfermode::Mode mode, bool ignoreTransform = false,
+    		bool ignoreBlending = false);
 
     /**
      * Draws a textured rectangle with the specified texture. The specified coordinates
@@ -216,10 +218,13 @@ private:
      * @param texCoords The texture coordinates of each vertex
      * @param indices The indices of the vertices, can be NULL
      * @param elementsCount The number of elements in the mesh, required by indices
+     * @param swapSrcDst Whether or not the src and dst blending operations should be swapped
+     * @param ignoreTransform True if the current transform should be ignored
      */
     void drawTextureMesh(float left, float top, float right, float bottom, GLuint texture,
             float alpha, SkXfermode::Mode mode, bool blend,
-            GLvoid* vertices, GLvoid* texCoords, GLvoid* indices, GLsizei elementsCount = 0);
+            GLvoid* vertices, GLvoid* texCoords, GLvoid* indices, GLsizei elementsCount = 0,
+            bool swapSrcDst = false, bool ignoreTransform = false);
 
     /**
      * Prepares the renderer to draw the specified shadow.
@@ -322,8 +327,13 @@ private:
      * Enable or disable blending as necessary. This function sets the appropriate
      * blend function based on the specified xfermode.
      */
-    inline void chooseBlending(bool blend, SkXfermode::Mode mode, ProgramDescription& description);
+    inline void chooseBlending(bool blend, SkXfermode::Mode mode, ProgramDescription& description,
+            bool swapSrcDst = false);
 
+    /**
+     * Safely retrieves the mode from the specified xfermode. If the specified
+     * xfermode is null, the mode is assumed to be SkXfermode::kSrcOver_Mode.
+     */
     inline SkXfermode::Mode getXfermode(SkXfermode* mode);
 
     /**
diff --git a/libs/hwui/ProgramCache.cpp b/libs/hwui/ProgramCache.cpp
index ff65c1b..becbc22 100644
--- a/libs/hwui/ProgramCache.cpp
+++ b/libs/hwui/ProgramCache.cpp
@@ -119,6 +119,8 @@ const char* gFS_Main_FragColor =
         "    gl_FragColor = fragColor;\n";
 const char* gFS_Main_FragColor_Blend =
         "    gl_FragColor = blendFramebuffer(fragColor, gl_LastFragColor);\n";
+const char* gFS_Main_FragColor_Blend_Swap =
+        "    gl_FragColor = blendFramebuffer(gl_LastFragColor, fragColor);\n";
 const char* gFS_Main_ApplyColorOp[4] = {
         // None
         "",
@@ -376,7 +378,8 @@ String8 ProgramCache::generateFragmentShader(const ProgramDescription& descripti
         if (!blendFramebuffer) {
             shader.append(gFS_Main_FragColor);
         } else {
-            shader.append(gFS_Main_FragColor_Blend);
+            shader.append(!description.swapSrcDst ?
+                    gFS_Main_FragColor_Blend : gFS_Main_FragColor_Blend_Swap);
         }
     }
     // End the shader
diff --git a/libs/hwui/ProgramCache.h b/libs/hwui/ProgramCache.h
index 8f5304d..0a17052 100644
--- a/libs/hwui/ProgramCache.h
+++ b/libs/hwui/ProgramCache.h
@@ -35,7 +35,7 @@ namespace uirenderer {
 ///////////////////////////////////////////////////////////////////////////////
 
 // Debug
-#define DEBUG_PROGRAM_CACHE 1
+#define DEBUG_PROGRAM_CACHE 0
 
 // Debug
 #if DEBUG_PROGRAM_CACHE
@@ -44,6 +44,9 @@ namespace uirenderer {
     #define PROGRAM_LOGD(...)
 #endif
 
+/*
+ * IMPORTANT: All 32 bits are used, switch to a long.
+ */
 #define PROGRAM_KEY_TEXTURE 0x1
 #define PROGRAM_KEY_A8_TEXTURE 0x2
 #define PROGRAM_KEY_BITMAP 0x4
@@ -53,6 +56,7 @@ namespace uirenderer {
 #define PROGRAM_KEY_COLOR_LIGHTING 0x40
 #define PROGRAM_KEY_COLOR_BLEND 0x80
 #define PROGRAM_KEY_BITMAP_NPOT 0x100
+#define PROGRAM_KEY_SWAP_SRC_DST 0x2000
 
 #define PROGRAM_KEY_BITMAP_WRAPS_MASK 0x600
 #define PROGRAM_KEY_BITMAP_WRAPT_MASK 0x1800
@@ -70,6 +74,9 @@ namespace uirenderer {
 // Types
 ///////////////////////////////////////////////////////////////////////////////
 
+/*
+ * IMPORTANT: All 32 bits are used, switch to a long.
+ */
 typedef uint32_t programid;
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -95,7 +102,7 @@ struct ProgramDescription {
         shadersMode(SkXfermode::kClear_Mode), isBitmapFirst(false),
         bitmapWrapS(GL_CLAMP_TO_EDGE), bitmapWrapT(GL_CLAMP_TO_EDGE),
         colorOp(kColorNone), colorMode(SkXfermode::kClear_Mode),
-        framebufferMode(SkXfermode::kClear_Mode) {
+        framebufferMode(SkXfermode::kClear_Mode), swapSrcDst(false) {
     }
 
     // Texturing
@@ -118,6 +125,7 @@ struct ProgramDescription {
     // Framebuffer blending (requires Extensions.hasFramebufferFetch())
     // Ignored for all values < SkXfermode::kPlus_Mode
     SkXfermode::Mode framebufferMode;
+    bool swapSrcDst;
 
     inline uint32_t getEnumForWrap(GLenum wrap) const {
         switch (wrap) {
@@ -163,6 +171,7 @@ struct ProgramDescription {
                 break;
         }
         key |= (framebufferMode & PROGRAM_MAX_XFERMODE) << PROGRAM_XFERMODE_FRAMEBUFFER_SHIFT;
+        if (swapSrcDst) key |= PROGRAM_KEY_SWAP_SRC_DST;
         return key;
     }
 }; // struct ProgramDescription
diff --git a/libs/hwui/Snapshot.h b/libs/hwui/Snapshot.h
index da48243..ebedf53 100644
--- a/libs/hwui/Snapshot.h
+++ b/libs/hwui/Snapshot.h
@@ -43,7 +43,7 @@ namespace uirenderer {
  */
 class Snapshot: public LightRefBase<Snapshot> {
 public:
-    Snapshot(): invisible(false), flags(0), previous(NULL), layer(NULL), fbo(0) {
+    Snapshot(): flags(0), previous(NULL), layer(NULL) {
         transform = &mTransformRoot;
         clipRect = &mClipRectRoot;
     }
@@ -53,13 +53,7 @@ public:
      * the previous snapshot.
      */
     Snapshot(const sp<Snapshot>& s, int saveFlags):
-            height(s->height),
-            invisible(s->invisible),
-            flags(0),
-            previous(s),
-            layer(NULL),
-            fbo(s->fbo),
-            viewport(s->viewport) {
+            flags(0), previous(s), layer(NULL) {
         if (saveFlags & SkCanvas::kMatrix_SaveFlag) {
             mTransformRoot.load(*s->transform);
             transform = &mTransformRoot;
@@ -97,23 +91,30 @@ public:
          */
         kFlagIsLayer = 0x2,
         /**
-         * Indicates that this snapshot has changed the ortho matrix.
-         */
-        kFlagDirtyOrtho = 0x4,
-        /**
          * Indicates that the local clip should be recomputed.
          */
-        kFlagDirtyLocalClip = 0x8,
+        kFlagDirtyLocalClip = 0x4,
     };
 
     /**
-     * Intersects the current clip with the new clip rectangle.
+     * Modifies the current clip with the new clip rectangle and
+     * the specified operation. The specified rectangle is transformed
+     * by this snapshot's trasnformation.
      */
-    bool clip(float left, float top, float right, float bottom, SkRegion::Op op) {
-        bool clipped = false;
-
+    bool clip(float left, float top, float right, float bottom,
+            SkRegion::Op op = SkRegion::kIntersect_Op) {
         Rect r(left, top, right, bottom);
         transform->mapRect(r);
+        return clipTransformed(r, op);
+    }
+
+    /**
+     * Modifies the current clip with the new clip rectangle and
+     * the specified operation. The specified rectangle is considered
+     * already transformed.
+     */
+    bool clipTransformed(const Rect& r, SkRegion::Op op = SkRegion::kIntersect_Op) {
+        bool clipped = false;
 
         switch (op) {
             case SkRegion::kDifference_Op:
@@ -162,29 +163,6 @@ public:
         return mLocalClip;
     }
 
-    // TODO: Temporary
-    void resetTransform(float x, float y, float z) {
-        transform = &mTransformRoot;
-        transform->loadTranslate(x, y, z);
-    }
-
-    // TODO: Temporary
-    void resetClip(float left, float top, float right, float bottom) {
-        clipRect = &mClipRectRoot;
-        clipRect->set(left, top, right, bottom);
-        flags |= Snapshot::kFlagClipSet | Snapshot::kFlagDirtyLocalClip;
-    }
-
-    /**
-     * Height of the framebuffer the snapshot is rendering into.
-     */
-    int height;
-
-    /**
-     * If true, the layer won't be rendered.
-     */
-    bool invisible;
-
     /**
      * Dirty flags.
      */
@@ -199,17 +177,6 @@ public:
      * Only set when the flag kFlagIsLayer is set.
      */
     Layer* layer;
-    GLuint fbo;
-
-    /**
-     * Current viewport.
-     */
-    Rect viewport;
-
-    /**
-     * Contains the previous ortho matrix.
-     */
-    mat4 orthoMatrix;
 
     /**
      * Local transformation. Holds the current translation, scale and