/frameworks/base/libs/hwui/OpenGLRenderer.cpp

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * 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.
 */

#define LOG_TAG "OpenGLRenderer"

#include <stdlib.h>
#include <stdint.h>
#include <sys/types.h>

#include <SkCanvas.h>
#include <SkPathMeasure.h>
#include <SkTypeface.h>

#include <utils/Log.h>
#include <utils/StopWatch.h>

#include <private/hwui/DrawGlInfo.h>

#include <ui/Rect.h>

#include "OpenGLRenderer.h"
#include "DisplayListRenderer.h"
#include "PathRenderer.h"
#include "Properties.h"
#include "Vector.h"

namespace android {
namespace uirenderer {

///////////////////////////////////////////////////////////////////////////////
// Defines
///////////////////////////////////////////////////////////////////////////////

#define RAD_TO_DEG (180.0f / 3.14159265f)
#define MIN_ANGLE 0.001f

#define ALPHA_THRESHOLD 0

#define FILTER(paint) (!paint || paint->isFilterBitmap() ? GL_LINEAR : GL_NEAREST)

///////////////////////////////////////////////////////////////////////////////
// Globals
///////////////////////////////////////////////////////////////////////////////

/**
 * Structure mapping Skia xfermodes to OpenGL blending factors.
 */
struct Blender {
    SkXfermode::Mode mode;
    GLenum src;
    GLenum dst;
}; // struct Blender

// In this array, the index of each Blender equals the value of the first
// entry. For instance, gBlends[1] == gBlends[SkXfermode::kSrc_Mode]
static const Blender gBlends[] = {
    { SkXfermode::kClear_Mode,    GL_ZERO,                GL_ONE_MINUS_SRC_ALPHA },
    { SkXfermode::kSrc_Mode,      GL_ONE,                 GL_ZERO },
    { SkXfermode::kDst_Mode,      GL_ZERO,                GL_ONE },
    { SkXfermode::kSrcOver_Mode,  GL_ONE,                 GL_ONE_MINUS_SRC_ALPHA },
    { SkXfermode::kDstOver_Mode,  GL_ONE_MINUS_DST_ALPHA, GL_ONE },
    { SkXfermode::kSrcIn_Mode,    GL_DST_ALPHA,           GL_ZERO },
    { SkXfermode::kDstIn_Mode,    GL_ZERO,                GL_SRC_ALPHA },
    { SkXfermode::kSrcOut_Mode,   GL_ONE_MINUS_DST_ALPHA, GL_ZERO },
    { SkXfermode::kDstOut_Mode,   GL_ZERO,                GL_ONE_MINUS_SRC_ALPHA },
    { SkXfermode::kSrcATop_Mode,  GL_DST_ALPHA,           GL_ONE_MINUS_SRC_ALPHA },
    { SkXfermode::kDstATop_Mode,  GL_ONE_MINUS_DST_ALPHA, GL_SRC_ALPHA },
    { SkXfermode::kXor_Mode,      GL_ONE_MINUS_DST_ALPHA, GL_ONE_MINUS_SRC_ALPHA },
    { SkXfermode::kPlus_Mode,     GL_ONE,                 GL_ONE },
    { SkXfermode::kMultiply_Mode, GL_ZERO,                GL_SRC_COLOR },
    { SkXfermode::kScreen_Mode,   GL_ONE,                 GL_ONE_MINUS_SRC_COLOR }
};

// This array contains the swapped version of each SkXfermode. For instance
// this array's SrcOver blending mode is actually DstOver. You can refer to
// createLayer() for more information on the purpose of this array.
static const Blender gBlendsSwap[] = {
    { SkXfermode::kClear_Mode,    GL_ONE_MINUS_DST_ALPHA, 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 },
    { SkXfermode::kPlus_Mode,     GL_ONE,                 GL_ONE },
    { SkXfermode::kMultiply_Mode, GL_DST_COLOR,           GL_ZERO },
    { SkXfermode::kScreen_Mode,   GL_ONE_MINUS_DST_COLOR, GL_ONE }
};

///////////////////////////////////////////////////////////////////////////////
// Constructors/destructor
///////////////////////////////////////////////////////////////////////////////
static int EnableDither = 0;
char* GetProgramName(char* buf, int size)
{
    char procName[64];
    pid_t pid = getpid();

    FILE* fp = NULL;
    snprintf(procName, sizeof(procName), "/proc/%i/cmdline", pid);
    fp = fopen(procName, "r");
    if(fp)
    {
        fread(buf, 1, size, fp);
        fclose(fp);
        fp = NULL;
    }
    else
    {
        ALOGD("%s : %d : open file %s failed \n", __FUNCTION__, __LINE__, procName);
    }

    return buf;
}

OpenGLRenderer::OpenGLRenderer(): mCaches(Caches::getInstance()) {
    mShader = NULL;
    mColorFilter = NULL;
    mHasShadow = false;
    mHasDrawFilter = false;
    mOrientation = -1;

    memcpy(mMeshVertices, gMeshVertices, sizeof(gMeshVertices));

    mFirstSnapshot = new Snapshot;

    mScissorOptimizationDisabled = false;
    char property[PROPERTY_VALUE_MAX];
    property_get("ro.sf.lcdc_composer", property, NULL) > 0;

    char exeName[64] = {0};
    GetProgramName(exeName, 64 - 1);
    if( ((0 == strcmp("com.android.browser", exeName)) ||
         (0 == strcmp("com.android.launcher", exeName))) &&
        !strcmp(property, "1"))
    {
        EnableDither = 1;
    } else {
        EnableDither = 0;
    }
}

OpenGLRenderer::~OpenGLRenderer() {
    // The context has already been destroyed at this point, do not call
    // GL APIs. All GL state should be kept in Caches.h
}

void OpenGLRenderer::initProperties() {
    char property[PROPERTY_VALUE_MAX];
    if (property_get(PROPERTY_DISABLE_SCISSOR_OPTIMIZATION, property, "false")) {
        mScissorOptimizationDisabled = !strcasecmp(property, "true");
        INIT_LOGD("  Scissor optimization %s",
                mScissorOptimizationDisabled ? "disabled" : "enabled");
    } else {
        INIT_LOGD("  Scissor optimization enabled");
    }
}

///////////////////////////////////////////////////////////////////////////////
// Setup
///////////////////////////////////////////////////////////////////////////////

bool OpenGLRenderer::isDeferred() {
    return false;
}

bool OpenGLRenderer::queryHWRenderEngine(const char* property) {
    //get gpu renderer, make sure gl context has created.
    const char *renderer = (const char *)glGetString(GL_RENDERER);
    if (renderer != NULL) {
        if (!strcmp(property, "debug.hwui.render_dirty_regions")) {
            if (!strcmp(renderer, "Mali-400 MP")) {
                return false;
            } else if (!strcmp(renderer, "PowerVR SGX 540")) {
                return true;
            }
        }
    }
    return false;
}

void OpenGLRenderer::setOrientation(int orientation) {
    //ALOGD("setOrientation: %d", orientation);
    mOrientation = orientation;
}

void OpenGLRenderer::setViewport(int width, int height) {
    initViewport(width, height);

    if(EnableDither)
        glEnable(GL_DITHER);
    else
    glDisable(GL_DITHER);

    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

    glEnableVertexAttribArray(Program::kBindingPosition);
}

void OpenGLRenderer::initViewport(int width, int height) {
    mOrthoMatrix.loadOrtho(0, width, height, 0, -1, 1);

    mWidth = width;
    mHeight = height;

    mFirstSnapshot->height = height;
    mFirstSnapshot->viewport.set(0, 0, width, height);
}

status_t OpenGLRenderer::prepare(bool opaque) {
    if (mOrientation != -1 && mOrientation % 2 == 1) {
        return prepareDirty(0.0f, 0.0f, mHeight, mWidth, opaque);
    } else {
    return prepareDirty(0.0f, 0.0f, mWidth, mHeight, opaque);
    }
}

status_t OpenGLRenderer::prepareDirty(float left, float top, float right, float bottom,
        bool opaque) {
    mCaches.clearGarbage();

    mSnapshot = new Snapshot(mFirstSnapshot,
            SkCanvas::kMatrix_SaveFlag | SkCanvas::kClip_SaveFlag);
    mSnapshot->fbo = getTargetFbo();
    int convertLeft = left;
    int convertTop = top;
    int convertRight = right;
    int convertBottom = bottom;

    switch (mOrientation) {
    case 3:
        rotate(-90);
        translate(-mHeight, 0);

        left = convertTop;
        bottom = mHeight - convertLeft;
        right = convertBottom;
        top = mHeight - convertRight;
        break;

    case 1:
	    rotate(90);
	    translate(0, -mWidth);
		left = mWidth - convertBottom;
		bottom = convertRight;
		right = mWidth - convertTop;
		top = convertLeft;
        break;
    case 2:
        rotate(180);
        translate(-mWidth, -mHeight);

        left = mWidth - convertRight;
        bottom = mHeight - convertTop;
        right = mWidth - convertLeft;
        top = mHeight - convertBottom;
        break;
    }
    mSaveCount = 1;

    mSnapshot->setClip(left, top, right, bottom);
    mDirtyClip = true;

    updateLayers();

    // If we know that we are going to redraw the entire framebuffer,
    // perform a discard to let the driver know we don't need to preserve
    // the back buffer for this frame.
    if (mCaches.extensions.hasDiscardFramebuffer() &&
            left <= 0.0f && top <= 0.0f && right >= mWidth && bottom >= mHeight) {
        const GLenum attachments[] = { getTargetFbo() == 0 ? GL_COLOR_EXT : GL_COLOR_ATTACHMENT0 };
        glDiscardFramebufferEXT(GL_FRAMEBUFFER, 1, attachments);
    }

    syncState();

    // Functors break the tiling extension in pretty spectacular ways
    // This ensures we don't use tiling when a functor is going to be
    // invoked during the frame
    mSuppressTiling = mCaches.hasRegisteredFunctors();

    mTilingSnapshot = mSnapshot;
    startTiling(mTilingSnapshot, true);

    debugOverdraw(true, true);

    return clear(left, top, right, bottom, opaque);
}

status_t OpenGLRenderer::clear(float left, float top, float right, float bottom, bool opaque) {
    if (!opaque) {
        mCaches.enableScissor();
        mCaches.setScissor(left, mSnapshot->height - bottom, right - left, bottom - top);
        glClear(GL_COLOR_BUFFER_BIT);
        return DrawGlInfo::kStatusDrew;
    }

    mCaches.resetScissor();
    return DrawGlInfo::kStatusDone;
}

void OpenGLRenderer::syncState() {
    glViewport(0, 0, mWidth, mHeight);

    if (mCaches.blend) {
        glEnable(GL_BLEND);
    } else {
        glDisable(GL_BLEND);
    }
}

void OpenGLRenderer::startTiling(const sp<Snapshot>& s, bool opaque) {
    if (!mSuppressTiling) {
        Rect* clip = mTilingSnapshot->clipRect;
        if (s->flags & Snapshot::kFlagIsFboLayer) {
            clip = s->clipRect;
        }

        mCaches.startTiling(clip->left, s->height - clip->bottom,
                clip->right - clip->left, clip->bottom - clip->top, opaque);
    }
}

void OpenGLRenderer::endTiling() {
    if (!mSuppressTiling) mCaches.endTiling();
}

void OpenGLRenderer::finish() {
    renderOverdraw();
    endTiling();

    if (!suppressErrorChecks()) {
#if DEBUG_OPENGL
        GLenum status = GL_NO_ERROR;
        while ((status = glGetError()) != GL_NO_ERROR) {
            ALOGD("GL error from OpenGLRenderer: 0x%x", status);
            switch (status) {
                case GL_INVALID_ENUM:
                    ALOGE("  GL_INVALID_ENUM");
                    break;
                case GL_INVALID_VALUE:
                    ALOGE("  GL_INVALID_VALUE");
                    break;
                case GL_INVALID_OPERATION:
                    ALOGE("  GL_INVALID_OPERATION");
                    break;
                case GL_OUT_OF_MEMORY:
                    ALOGE("  Out of memory!");
                    break;
            }
        }
#endif

#if DEBUG_MEMORY_USAGE
        mCaches.dumpMemoryUsage();
#else
        if (mCaches.getDebugLevel() & kDebugMemory) {
            mCaches.dumpMemoryUsage();
        }
#endif
    }
}

void OpenGLRenderer::interrupt() {
    if (mCaches.currentProgram) {
        if (mCaches.currentProgram->isInUse()) {
            mCaches.currentProgram->remove();
            mCaches.currentProgram = NULL;
        }
    }
    mCaches.unbindMeshBuffer();
    mCaches.unbindIndicesBuffer();
    mCaches.resetVertexPointers();
    mCaches.disbaleTexCoordsVertexArray();
    debugOverdraw(false, false);
}

void OpenGLRenderer::resume() {
    sp<Snapshot> snapshot = (mSnapshot != NULL) ? mSnapshot : mFirstSnapshot;
    glViewport(0, 0, snapshot->viewport.getWidth(), snapshot->viewport.getHeight());
    glBindFramebuffer(GL_FRAMEBUFFER, snapshot->fbo);
    debugOverdraw(true, false);

    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

    mCaches.scissorEnabled = glIsEnabled(GL_SCISSOR_TEST);
    mCaches.enableScissor();
    mCaches.resetScissor();
    dirtyClip();

    mCaches.activeTexture(0);

    mCaches.blend = true;
    glEnable(GL_BLEND);
    glBlendFunc(mCaches.lastSrcMode, mCaches.lastDstMode);
    glBlendEquation(GL_FUNC_ADD);
}

void OpenGLRenderer::resumeAfterLayer() {
    sp<Snapshot> snapshot = (mSnapshot != NULL) ? mSnapshot : mFirstSnapshot;
    glViewport(0, 0, snapshot->viewport.getWidth(), snapshot->viewport.getHeight());
    glBindFramebuffer(GL_FRAMEBUFFER, snapshot->fbo);
    debugOverdraw(true, false);

    mCaches.resetScissor();
    dirtyClip();
}

void OpenGLRenderer::detachFunctor(Functor* functor) {
    mFunctors.remove(functor);
}

void OpenGLRenderer::attachFunctor(Functor* functor) {
    mFunctors.add(functor);
}

status_t OpenGLRenderer::invokeFunctors(Rect& dirty) {
    status_t result = DrawGlInfo::kStatusDone;
    size_t count = mFunctors.size();

    if (count > 0) {
        interrupt();
        SortedVector<Functor*> functors(mFunctors);
        mFunctors.clear();

        DrawGlInfo info;
        info.clipLeft = 0;
        info.clipTop = 0;
        info.clipRight = 0;
        info.clipBottom = 0;
        info.isLayer = false;
        info.width = 0;
        info.height = 0;
        memset(info.transform, 0, sizeof(float) * 16);

        for (size_t i = 0; i < count; i++) {
            Functor* f = functors.itemAt(i);
            result |= (*f)(DrawGlInfo::kModeProcess, &info);

            if (result & DrawGlInfo::kStatusDraw) {
                Rect localDirty(info.dirtyLeft, info.dirtyTop, info.dirtyRight, info.dirtyBottom);
                dirty.unionWith(localDirty);
            }

            if (result & DrawGlInfo::kStatusInvoke) {
                mFunctors.add(f);
            }
        }
        resume();
    }

    return result;
}

status_t OpenGLRenderer::callDrawGLFunction(Functor* functor, Rect& dirty) {
    interrupt();
    detachFunctor(functor);

    mCaches.enableScissor();
    if (mDirtyClip) {
        setScissorFromClip();
    }

    Rect clip(*mSnapshot->clipRect);
    clip.snapToPixelBoundaries();

    // Since we don't know what the functor will draw, let's dirty
    // tne entire clip region
    if (hasLayer()) {
        dirtyLayerUnchecked(clip, getRegion());
    }

    DrawGlInfo info;
    info.clipLeft = clip.left;
    info.clipTop = clip.top;
    info.clipRight = clip.right;
    info.clipBottom = clip.bottom;
    info.isLayer = hasLayer();
    info.width = getSnapshot()->viewport.getWidth();
    info.height = getSnapshot()->height;
    getSnapshot()->transform->copyTo(&info.transform[0]);

    status_t result = (*functor)(DrawGlInfo::kModeDraw, &info) | DrawGlInfo::kStatusDrew;

    if (result != DrawGlInfo::kStatusDone) {
        Rect localDirty(info.dirtyLeft, info.dirtyTop, info.dirtyRight, info.dirtyBottom);
        dirty.unionWith(localDirty);

        if (result & DrawGlInfo::kStatusInvoke) {
            mFunctors.add(functor);
        }
    }

    resume();
    return result;
}

///////////////////////////////////////////////////////////////////////////////
// Debug
///////////////////////////////////////////////////////////////////////////////

void OpenGLRenderer::startMark(const char* name) const {
    mCaches.startMark(0, name);
}

void OpenGLRenderer::endMark() const {
    mCaches.endMark();
}

void OpenGLRenderer::debugOverdraw(bool enable, bool clear) {
    if (mCaches.debugOverdraw && getTargetFbo() == 0) {
        if (clear) {
            mCaches.disableScissor();
            mCaches.stencil.clear();
        }
        if (enable) {
            mCaches.stencil.enableDebugWrite();
        } else {
            mCaches.stencil.disable();
        }
    }
}

void OpenGLRenderer::renderOverdraw() {
    if (mCaches.debugOverdraw && getTargetFbo() == 0) {
        const Rect* clip = mTilingSnapshot->clipRect;

        mCaches.enableScissor();
        mCaches.setScissor(clip->left, mTilingSnapshot->height - clip->bottom,
                clip->right - clip->left, clip->bottom - clip->top);

        mCaches.stencil.enableDebugTest(2);
        drawColor(0x2f0000ff, SkXfermode::kSrcOver_Mode);
        mCaches.stencil.enableDebugTest(3);
        drawColor(0x2f00ff00, SkXfermode::kSrcOver_Mode);
        mCaches.stencil.enableDebugTest(4);
        drawColor(0x3fff0000, SkXfermode::kSrcOver_Mode);
        mCaches.stencil.enableDebugTest(4, true);
        drawColor(0x7fff0000, SkXfermode::kSrcOver_Mode);
        mCaches.stencil.disable();
    }
}

///////////////////////////////////////////////////////////////////////////////
// Layers
///////////////////////////////////////////////////////////////////////////////

bool OpenGLRenderer::updateLayer(Layer* layer, bool inFrame) {
    if (layer->deferredUpdateScheduled && layer->renderer && layer->displayList) {
        OpenGLRenderer* renderer = layer->renderer;
        Rect& dirty = layer->dirtyRect;

        if (inFrame) {
            endTiling();
            debugOverdraw(false, false);
        }
        int ori = mOrientation;
        if (mOrientation != -1) {
            renderer->setOrientation(0);
        }
        renderer->setViewport(layer->layer.getWidth(), layer->layer.getHeight());
        renderer->prepareDirty(dirty.left, dirty.top, dirty.right, dirty.bottom, !layer->isBlend());
        renderer->drawDisplayList(layer->displayList, dirty, DisplayList::kReplayFlag_ClipChildren);
        renderer->finish();
        renderer->setOrientation(ori);

        if (inFrame) {
            resumeAfterLayer();
            startTiling(mSnapshot);
        }

        dirty.setEmpty();
        layer->deferredUpdateScheduled = false;
        layer->renderer = NULL;
        layer->displayList = NULL;

        return true;
    }

    return false;
}

void OpenGLRenderer::updateLayers() {
    int count = mLayerUpdates.size();
    if (count > 0) {
        startMark("Layer Updates");

        // Note: it is very important to update the layers in reverse order
        for (int i = count - 1; i >= 0; i--) {
            Layer* layer = mLayerUpdates.itemAt(i);
            updateLayer(layer, false);
            mCaches.resourceCache.decrementRefcount(layer);
        }
        mLayerUpdates.clear();

        glBindFramebuffer(GL_FRAMEBUFFER, getTargetFbo());
        endMark();
    }
}

void OpenGLRenderer::pushLayerUpdate(Layer* layer) {
    if (layer) {
        mLayerUpdates.push_back(layer);
        mCaches.resourceCache.incrementRefcount(layer);
    }
}

void OpenGLRenderer::clearLayerUpdates() {
    size_t count = mLayerUpdates.size();
    if (count > 0) {
        mCaches.resourceCache.lock();
        for (size_t i = 0; i < count; i++) {
            mCaches.resourceCache.decrementRefcountLocked(mLayerUpdates.itemAt(i));
        }
        mCaches.resourceCache.unlock();
        mLayerUpdates.clear();
    }
}

///////////////////////////////////////////////////////////////////////////////
// State management
///////////////////////////////////////////////////////////////////////////////

int OpenGLRenderer::getSaveCount() const {
    return mSaveCount;
}

int OpenGLRenderer::save(int flags) {
    return saveSnapshot(flags);
}

void OpenGLRenderer::restore() {
    if (mSaveCount > 1) {
        restoreSnapshot();
    }
}

void OpenGLRenderer::restoreToCount(int saveCount) {
    if (saveCount < 1) saveCount = 1;

    while (mSaveCount > saveCount) {
        restoreSnapshot();
    }
}

int OpenGLRenderer::saveSnapshot(int flags) {
    mSnapshot = new Snapshot(mSnapshot, flags);
    return mSaveCount++;
}

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;

    if (restoreClip) {
        dirtyClip();
    }

    if (restoreLayer) {
        composeLayer(current, previous);
    }

    return restoreClip;
}

///////////////////////////////////////////////////////////////////////////////
// Layers
///////////////////////////////////////////////////////////////////////////////

int OpenGLRenderer::saveLayer(float left, float top, float right, float bottom,
        SkPaint* p, int flags) {
    const GLuint previousFbo = mSnapshot->fbo;
    const int count = saveSnapshot(flags);

    if (!mSnapshot->isIgnored()) {
        int alpha = 255;
        SkXfermode::Mode mode;

        if (p) {
            alpha = p->getAlpha();
            mode = getXfermode(p->getXfermode());
        } else {
            mode = SkXfermode::kSrcOver_Mode;
        }

        createLayer(left, top, right, bottom, alpha, mode, flags, previousFbo);
    }

    return count;
}

int OpenGLRenderer::saveLayerAlpha(float left, float top, float right, float bottom,
        int alpha, int flags) {
    if (alpha >= 255) {
        return saveLayer(left, top, right, bottom, NULL, flags);
    } else {
        SkPaint paint;
        paint.setAlpha(alpha);
        return saveLayer(left, top, right, bottom, &paint, flags);
    }
}

/**
 * Layers are viewed by Skia are slightly different than layers in image editing
 * programs (for instance.) When a layer is created, previously created layers
 * and the frame buffer still receive every drawing command. For instance, if a
 * layer is created and a shape intersecting the bounds of the layers and the
 * framebuffer is draw, the shape will be drawn on both (unless the layer was
 * created with the SkCanvas::kClipToLayer_SaveFlag flag.)
 *
 * A way to implement layers is to create an FBO for each layer, backed by an RGBA
 * texture. Unfortunately, this is inefficient as it requires every primitive to
 * be drawn n + 1 times, where n is the number of active layers. In practice this
 * means, for every primitive:
 *   - Switch active frame buffer
 *   - Change viewport, clip and projection matrix
 *   - Issue the drawing
 *
 * Switching rendering target n + 1 times per drawn primitive is extremely costly.
 * To avoid this, layers are implemented in a different way here, at least in the
 * general case. FBOs are used, as an optimization, when the "clip to layer" flag
 * is set. When this flag is set we can redirect all drawing operations into a
 * single FBO.
 *
 * This implementation relies on the frame buffer being at least RGBA 8888. When
 * a layer is created, only a texture is created, not an FBO. The content of the
 * frame buffer contained within the layer's bounds is copied into this texture
 * using glCopyTexImage2D(). The layer's region is then cleared(1) in the frame
 * buffer and drawing continues as normal. This technique therefore treats the
 * frame buffer as a scratch buffer for the layers.
 *
 * To compose the layers back onto the frame buffer, each layer texture
 * (containing the original frame buffer data) is drawn as a simple quad over
 * the frame buffer. The trick is that the quad is set as the composition
 * destination in the blending equation, and the frame buffer becomes the source
 * of the composition.
 *
 * Drawing layers with an alpha value requires an extra step before composition.
 * An empty quad is drawn over the layer's region in the frame buffer. This quad
 * is drawn with the rgba color (0,0,0,alpha). The alpha value offered by the
 * quad is used to multiply the colors in the frame buffer. This is achieved by
 * changing the GL blend functions for the GL_FUNC_ADD blend equation to
 * GL_ZERO, GL_SRC_ALPHA.
 *
 * Because glCopyTexImage2D() can be slow, an alternative implementation might
 * be use to draw a single clipped layer. The implementation described above
 * is correct in every case.
 *
 * (1) The frame buffer is actually not cleared right away. To allow the GPU
 *     to potentially optimize series of calls to glCopyTexImage2D, the frame
 *     buffer is left untouched until the first drawing operation. Only when
 *     something actually gets drawn are the layers regions cleared.
 */
bool OpenGLRenderer::createLayer(float left, float top, float right, float bottom,
        int alpha, SkXfermode::Mode mode, int flags, GLuint previousFbo) {
    LAYER_LOGD("Requesting layer %.2fx%.2f", right - left, bottom - top);
    LAYER_LOGD("Layer cache size = %d", mCaches.layerCache.getSize());

    const bool fboLayer = flags & SkCanvas::kClipToLayer_SaveFlag;

    // Window coordinates of the layer
    Rect clip;
    Rect bounds(left, top, right, bottom);
    Rect untransformedBounds(bounds);
    mSnapshot->transform->mapRect(bounds);

    // Layers only make sense if they are in the framebuffer's bounds
    if (bounds.intersect(*mSnapshot->clipRect)) {
        // We cannot work with sub-pixels in this case
        bounds.snapToPixelBoundaries();

        // When the layer is not an FBO, we may use glCopyTexImage so we
        // need to make sure the layer does not extend outside the bounds
        // of the framebuffer
        if (!bounds.intersect(mSnapshot->previous->viewport)) {
            bounds.setEmpty();
        } else if (fboLayer) {
            clip.set(bounds);
            mat4 inverse;
            inverse.loadInverse(*mSnapshot->transform);
            inverse.mapRect(clip);
            clip.snapToPixelBoundaries();
            if (clip.intersect(untransformedBounds)) {
                clip.translate(-left, -top);
                bounds.set(untransformedBounds);
            } else {
                clip.setEmpty();
            }
        }
    } else {
        bounds.setEmpty();
    }

    if (bounds.isEmpty() || bounds.getWidth() > mCaches.maxTextureSize ||
            bounds.getHeight() > mCaches.maxTextureSize ||
            (fboLayer && clip.isEmpty())) {
        mSnapshot->empty = fboLayer;
    } else {
        mSnapshot->invisible = mSnapshot->invisible || (alpha <= ALPHA_THRESHOLD && fboLayer);
    }

    // Bail out if we won't draw in this snapshot
    if (mSnapshot->invisible || mSnapshot->empty) {
        return false;
    }

    mCaches.activeTexture(0);
    Layer* layer = mCaches.layerCache.get(bounds.getWidth(), bounds.getHeight());
    if (!layer) {
        return false;
    }

    layer->setAlpha(alpha, mode);
    layer->layer.set(bounds);
    layer->texCoords.set(0.0f, bounds.getHeight() / float(layer->getHeight()),
            bounds.getWidth() / float(layer->getWidth()), 0.0f);
    layer->setColorFilter(mColorFilter);
    layer->setBlend(true);
    layer->setDirty(false);

    // Save the layer in the snapshot
    mSnapshot->flags |= Snapshot::kFlagIsLayer;
    mSnapshot->layer = layer;

    if (fboLayer) {
        return createFboLayer(layer, bounds, clip, previousFbo);
    } else {
        // Copy the framebuffer into the layer
        layer->bindTexture();
        if (!bounds.isEmpty()) {
            if (layer->isEmpty()) {
                glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,
                        bounds.left, mSnapshot->height - bounds.bottom,
                        layer->getWidth(), layer->getHeight(), 0);
                layer->setEmpty(false);
            } else {
                glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, bounds.left,
                        mSnapshot->height - bounds.bottom, bounds.getWidth(), bounds.getHeight());
            }

            // Enqueue the buffer coordinates to clear the corresponding region later
            mLayers.push(new Rect(bounds));
        }
    }

    return true;
}

bool OpenGLRenderer::createFboLayer(Layer* layer, Rect& bounds, Rect& clip, GLuint previousFbo) {
    layer->setFbo(mCaches.fboCache.get());

    mSnapshot->region = &mSnapshot->layer->region;
    mSnapshot->flags |= Snapshot::kFlagFboTarget;

    mSnapshot->flags |= Snapshot::kFlagIsFboLayer;
    mSnapshot->fbo = layer->getFbo();
    mSnapshot->resetTransform(-bounds.left, -bounds.top, 0.0f);
    mSnapshot->resetClip(clip.left, clip.top, clip.right, clip.bottom);
    mSnapshot->viewport.set(0.0f, 0.0f, bounds.getWidth(), bounds.getHeight());
    mSnapshot->height = bounds.getHeight();
    mSnapshot->flags |= Snapshot::kFlagDirtyOrtho;
    mSnapshot->orthoMatrix.load(mOrthoMatrix);

    endTiling();
    debugOverdraw(false, false);
    // Bind texture to FBO
    glBindFramebuffer(GL_FRAMEBUFFER, layer->getFbo());
    layer->bindTexture();

    // Initialize the texture if needed
    if (layer->isEmpty()) {
        layer->allocateTexture(GL_RGBA, GL_UNSIGNED_BYTE);
        layer->setEmpty(false);
    }

    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
            layer->getTexture(), 0);

    startTiling(mSnapshot);

    // Clear the FBO, expand the clear region by 1 to get nice bilinear filtering
    mCaches.enableScissor();
    mCaches.setScissor(clip.left - 1.0f, bounds.getHeight() - clip.bottom - 1.0f,
            clip.getWidth() + 2.0f, clip.getHeight() + 2.0f);
    glClear(GL_COLOR_BUFFER_BIT);

    dirtyClip();

    // 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);

    return true;
}

/**
 * Read the documentation of createLayer() before doing anything in this method.
 */
void OpenGLRenderer::composeLayer(sp<Snapshot> current, sp<Snapshot> previous) {
    if (!current->layer) {
        ALOGE("Attempting to compose a layer that does not exist");
        return;
    }

    const bool fboLayer = current->flags & Snapshot::kFlagIsFboLayer;

    if (fboLayer) {
        endTiling();

        // Detach the texture from the FBO
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, 0, 0);
        // Unbind current FBO and restore previous one
        glBindFramebuffer(GL_FRAMEBUFFER, previous->fbo);
        debugOverdraw(true, false);

        startTiling(previous);
    }

    Layer* layer = current->layer;
    const Rect& rect = layer->layer;

    if (!fboLayer && layer->getAlpha() < 255) {
        drawColorRect(rect.left, rect.top, rect.right, rect.bottom,
                layer->getAlpha() << 24, SkXfermode::kDstIn_Mode, true);
        // Required below, composeLayerRect() will divide by 255
        layer->setAlpha(255);
    }

    mCaches.unbindMeshBuffer();

    mCaches.activeTexture(0);

    // When the layer is stored in an FBO, we can save a bit of fillrate by
    // drawing only the dirty region
    if (fboLayer) {
        dirtyLayer(rect.left, rect.top, rect.right, rect.bottom, *previous->transform);
        if (layer->getColorFilter()) {
            setupColorFilter(layer->getColorFilter());
        }
        composeLayerRegion(layer, rect);
        if (layer->getColorFilter()) {
            resetColorFilter();
        }
    } else if (!rect.isEmpty()) {
        dirtyLayer(rect.left, rect.top, rect.right, rect.bottom);
        composeLayerRect(layer, rect, true);
    }

    if (fboLayer) {
        // Note: No need to use glDiscardFramebufferEXT() since we never
        //       create/compose layers that are not on screen with this
        //       code path
        // See LayerRenderer::destroyLayer(Layer*)

        // Put the FBO name back in the cache, if it doesn't fit, it will be destroyed
        mCaches.fboCache.put(current->fbo);
        layer->setFbo(0);
    }

    dirtyClip();

    // Failing to add the layer to the cache should happen only if the layer is too large
    if (!mCaches.layerCache.put(layer)) {
        LAYER_LOGD("Deleting layer");
        Caches::getInstance().resourceCache.decrementRefcount(layer);
    }
}

void OpenGLRenderer::drawTextureLayer(Layer* layer, const Rect& rect) {
    float alpha = layer->getAlpha() / 255.0f;

    setupDraw();
    if (layer->getRenderTarget() == GL_TEXTURE_2D) {
        setupDrawWithTexture();
    } else {
        setupDrawWithExternalTexture();
    }
    setupDrawTextureTransform();
    setupDrawColor(alpha, alpha, alpha, alpha);
    setupDrawColorFilter();
    setupDrawBlending(layer->isBlend() || alpha < 1.0f, layer->getMode());
    setupDrawProgram();
    setupDrawPureColorUniforms();
    setupDrawColorFilterUniforms();
    if (layer->getRenderTarget() == GL_TEXTURE_2D) {
        setupDrawTexture(layer->getTexture());
    } else {
        setupDrawExternalTexture(layer->getTexture());
    }
    if (mSnapshot->transform->isPureTranslate() &&
            layer->getWidth() == (uint32_t) rect.getWidth() &&
            layer->getHeight() == (uint32_t) rect.getHeight()) {
        const float x = (int) floorf(rect.left + mSnapshot->transform->getTranslateX() + 0.5f);
        const float y = (int) floorf(rect.top + mSnapshot->transform->getTranslateY() + 0.5f);

        layer->setFilter(GL_NEAREST);
        setupDrawModelView(x, y, x + rect.getWidth(), y + rect.getHeight(), true);
    } else {
        layer->setFilter(GL_LINEAR);
        setupDrawModelView(rect.left, rect.top, rect.right, rect.bottom);
    }
    setupDrawTextureTransformUniforms(layer->getTexTransform());
    setupDrawMesh(&mMeshVertices[0].position[0], &mMeshVertices[0].texture[0]);

    glDrawArrays(GL_TRIANGLE_STRIP, 0, gMeshCount);

    finishDrawTexture();
}

void OpenGLRenderer::composeLayerRect(Layer* layer, const Rect& rect, bool swap) {
    if (!layer->isTextureLayer()) {
        const Rect& texCoords = layer->texCoords;
        resetDrawTextureTexCoords(texCoords.left, texCoords.top,
                texCoords.right, texCoords.bottom);

        float x = rect.left;
        float y = rect.top;
        bool simpleTransform = mSnapshot->transform->isPureTranslate() &&
                layer->getWidth() == (uint32_t) rect.getWidth() &&
                layer->getHeight() == (uint32_t) rect.getHeight();

        if (simpleTransform) {
            // When we're swapping, the layer is already in screen coordinates
            if (!swap) {
                x = (int) floorf(rect.left + mSnapshot->transform->getTranslateX() + 0.5f);
                y = (int) floorf(rect.top + mSnapshot->transform->getTranslateY() + 0.5f);
            }

            layer->setFilter(GL_NEAREST, true);
        } else {
            layer->setFilter(GL_LINEAR, true);
        }

        drawTextureMesh(x, y, x + rect.getWidth(), y + rect.getHeight(),
                layer->getTexture(), layer->getAlpha() / 255.0f,
                layer->getMode(), layer->isBlend(),
                &mMeshVertices[0].position[0], &mMeshVertices[0].texture[0],
                GL_TRIANGLE_STRIP, gMeshCount, swap, swap || simpleTransform);

        resetDrawTextureTexCoords(0.0f, 0.0f, 1.0f, 1.0f);
    } else {
        resetDrawTextureTexCoords(0.0f, 1.0f, 1.0f, 0.0f);
        drawTextureLayer(layer, rect);
        resetDrawTextureTexCoords(0.0f, 0.0f, 1.0f, 1.0f);
    }
}

void OpenGLRenderer::composeLayerRegion(Layer* layer, const Rect& rect) {
    if (layer->region.isRect()) {
        layer->setRegionAsRect();

        composeLayerRect(layer, layer->regionRect);

        layer->region.clear();
        return;
    }

    // TODO: See LayerRenderer.cpp::generateMesh() for important
    //       information about this implementation
    if (CC_LIKELY(!layer->region.isEmpty())) {
        size_t count;
        const android::Rect* rects = layer->region.getArray(&count);

        const float alpha = layer->getAlpha() / 255.0f;
        const float texX = 1.0f / float(layer->getWidth());
        const float texY = 1.0f / float(layer->getHeight());
        const float height = rect.getHeight();

        TextureVertex* mesh = mCaches.getRegionMesh();
        GLsizei numQuads = 0;

        setupDraw();
        setupDrawWithTexture();
        setupDrawColor(alpha, alpha, alpha, alpha);
        setupDrawColorFilter();
        setupDrawBlending(layer->isBlend() || alpha < 1.0f, layer->getMode(), false);
        setupDrawProgram();
        setupDrawDirtyRegionsDisabled();
        setupDrawPureColorUniforms();
        setupDrawColorFilterUniforms();
        setupDrawTexture(layer->getTexture());
        if (mSnapshot->transform->isPureTranslate()) {
            const float x = (int) floorf(rect.left + mSnapshot->transform->getTranslateX() + 0.5f);
            const float y = (int) floorf(rect.top + mSnapshot->transform->getTranslateY() + 0.5f);

            layer->setFilter(GL_NEAREST);
            setupDrawModelViewTranslate(x, y, x + rect.getWidth(), y + rect.getHeight(), true);
        } else {
            layer->setFilter(GL_LINEAR);
            setupDrawModelViewTranslate(rect.left, rect.top, rect.right, rect.bottom);
        }
        setupDrawMeshIndices(&mesh[0].position[0], &mesh[0].texture[0]);

        for (size_t i = 0; i < count; i++) {
            const android::Rect* r = &rects[i];

            const float u1 = r->left * texX;
            const float v1 = (height - r->top) * texY;
            const float u2 = r->right * texX;
            const float v2 = (height - r->bottom) * texY;

            // TODO: Reject quads outside of the clip
            TextureVertex::set(mesh++, r->left, r->top, u1, v1);
            TextureVertex::set(mesh++, r->right, r->top, u2, v1);
            TextureVertex::set(mesh++, r->left, r->bottom, u1, v2);
            TextureVertex::set(mesh++, r->right, r->bottom, u2, v2);

            numQuads++;

            if (numQuads >= REGION_MESH_QUAD_COUNT) {
                glDrawElements(GL_TRIANGLES, numQuads * 6, GL_UNSIGNED_SHORT, NULL);
                numQuads = 0;
                mesh = mCaches.getRegionMesh();
            }
        }

        if (numQuads > 0) {
            glDrawElements(GL_TRIANGLES, numQuads * 6, GL_UNSIGNED_SHORT, NULL);
        }

        finishDrawTexture();

#if DEBUG_LAYERS_AS_REGIONS
        drawRegionRects(layer->region);
#endif

        layer->region.clear();
    }
}

void OpenGLRenderer::drawRegionRects(const Region& region) {
#if DEBUG_LAYERS_AS_REGIONS
    size_t count;
    const android::Rect* rects = region.getArray(&count);

    uint32_t colors[] = {
            0x7fff0000, 0x7f00ff00,
            0x7f0000ff, 0x7fff00ff,
    };

    int offset = 0;
    int32_t top = rects[0].top;

    for (size_t i = 0; i < count; i++) {
        if (top != rects[i].top) {
            offset ^= 0x2;
            top = rects[i].top;
        }

        Rect r(rects[i].left, rects[i].top, rects[i].right, rects[i].bottom);
        drawColorRect(r.left, r.top, r.right, r.bottom, colors[offset + (i & 0x1)],
                SkXfermode::kSrcOver_Mode);
    }
#endif
}

void OpenGLRenderer::dirtyLayer(const float left, const float top,
        const float right, const float bottom, const mat4 transform) {
    if (hasLayer()) {
        Rect bounds(left, top, right, bottom);
        transform.mapRect(bounds);
        dirtyLayerUnchecked(bounds, getRegion());
    }
}

void OpenGLRenderer::dirtyLayer(const float left, const float top,
        const float right, const float bottom) {
    if (hasLayer()) {
        Rect bounds(left, top, right, bottom);
        dirtyLayerUnchecked(bounds, getRegion());
    }
}

void OpenGLRenderer::dirtyLayerUnchecked(Rect& bounds, Region* region) {
    if (bounds.intersect(*mSnapshot->clipRect)) {
        bounds.snapToPixelBoundaries();
        android::Rect dirty(bounds.left, bounds.top, bounds.right, bounds.bottom);
        if (!dirty.isEmpty()) {
            region->orSelf(dirty);
        }
    }
}

void OpenGLRenderer::clearLayerRegions() {
    const size_t count = mLayers.size();
    if (count == 0) return;

    if (!mSnapshot->isIgnored()) {
        // Doing several glScissor/glClear here can negatively impact
        // GPUs with a tiler architecture, instead we draw quads with
        // the Clear blending mode

        // The list contains bounds that have already been clipped
        // against their initial clip rect, and the current clip
        // is likely different so we need to disable clipping here
        bool scissorChanged = mCaches.disableScissor();

        Vertex mesh[count * 6];
        Vertex* vertex = mesh;

        for (uint32_t i = 0; i < count; i++) {
            Rect* bounds = mLayers.itemAt(i);

            Vertex::set(vertex++, bounds->left, bounds->bottom);
            Vertex::set(vertex++, bounds->left, bounds->top);
            Vertex::set(vertex++, bounds->right, bounds->top);
            Vertex::set(vertex++, bounds->left, bounds->bottom);
            Vertex::set(vertex++, bounds->right, bounds->top);
            Vertex::set(vertex++, bounds->right, bounds->bottom);

            delete bounds;
        }

        setupDraw(false);
        setupDrawColor(0.0f, 0.0f, 0.0f, 1.0f);
        setupDrawBlending(true, SkXfermode::kClear_Mode);
        setupDrawProgram();
        setupDrawPureColorUniforms();
        setupDrawModelViewTranslate(0.0f, 0.0f, 0.0f, 0.0f, true);
        setupDrawVertices(&mesh[0].position[0]);

        glDrawArrays(GL_TRIANGLES, 0, count * 6);

        if (scissorChanged) mCaches.enableScissor();
    } else {
        for (uint32_t i = 0; i < count; i++) {
            delete mLayers.itemAt(i);
        }
    }

    mLayers.clear();
}

///////////////////////////////////////////////////////////////////////////////
// Transforms
///////////////////////////////////////////////////////////////////////////////

void OpenGLRenderer::translate(float dx, float dy) {
    mSnapshot->transform->translate(dx, dy, 0.0f);
}

void OpenGLRenderer::rotate(float degrees) {
    mSnapshot->transform->rotate(degrees, 0.0f, 0.0f, 1.0f);
}

void OpenGLRenderer::scale(float sx, float sy) {
    mSnapshot->transform->scale(sx, sy, 1.0f);
}

void OpenGLRenderer::skew(float sx, float sy) {
    mSnapshot->transform->skew(sx, sy);
}

void OpenGLRenderer::setMatrix(SkMatrix* matrix) {
    if (matrix) {
        mSnapshot->transform->load(*matrix);
    } else {
        mSnapshot->transform->loadIdentity();
    }
}

void OpenGLRenderer::getMatrix(SkMatrix* matrix) {
    mSnapshot->transform->copyTo(*matrix);
}

void OpenGLRenderer::concatMatrix(SkMatrix* matrix) {
    SkMatrix transform;
    mSnapshot->transform->copyTo(transform);
    transform.preConcat(*matrix);
    mSnapshot->transform->load(transform);
}

///////////////////////////////////////////////////////////////////////////////
// Clipping
///////////////////////////////////////////////////////////////////////////////

void OpenGLRenderer::setScissorFromClip() {
    Rect clip(*mSnapshot->clipRect);
    clip.snapToPixelBoundaries();

    if (mCaches.setScissor(clip.left, mSnapshot->height - clip.bottom,
            clip.getWidth(), clip.getHeight())) {
        mDirtyClip = false;
    }
}

const Rect& OpenGLRenderer::getClipBounds() {
    return mSnapshot->getLocalClip();
}

bool OpenGLRenderer::quickRejectNoScissor(float left, float top, float right, float bottom) {
    if (mSnapshot->isIgnored()) {
        return true;
    }

    Rect r(left, top, right, bottom);
    mSnapshot->transform->mapRect(r);
    r.snapToPixelBoundaries();

    Rect clipRect(*mSnapshot->clipRect);
    clipRect.snapToPixelBoundaries();

    return !clipRect.intersects(r);
}

bool OpenGLRenderer::quickRejectNoScissor(float left, float top, float right, float bottom,
        Rect& transformed, Rect& clip) {
    if (mSnapshot->isIgnored()) {
        return true;
    }

    transformed.set(left, top, right, bottom);
    mSnapshot->transform->mapRect(transformed);
    transformed.snapToPixelBoundaries();

    clip.set(*mSnapshot->clipRect);
    clip.snapToPixelBoundaries();

    return !clip.intersects(transformed);
}

bool OpenGLRenderer::quickRejectPreStroke(float left, float top, float right, float bottom, SkPaint* paint) {
    if (paint->getStyle() != SkPaint::kFill_Style) {
        float outset = paint->getStrokeWidth() * 0.5f;
        return quickReject(left - outset, top - outset, right + outset, bottom + outset);
    } else {
        return quickReject(left, top, right, bottom);
    }
}

bool OpenGLRenderer::quickReject(float left, float top, float right, float bottom) {
    if (mSnapshot->isIgnored() || bottom <= top || right <= left) {
        return true;
    }

    Rect r(left, top, right, bottom);
    mSnapshot->transform->mapRect(r);
    r.snapToPixelBoundaries();

    Rect clipRect(*mSnapshot->clipRect);
    clipRect.snapToPixelBoundaries();

    bool rejected = !clipRect.intersects(r);
    if (!isDeferred() && !rejected) {
        mCaches.setScissorEnabled(mScissorOptimizationDisabled || !clipRect.contains(r));
    }

    return rejected;
}

bool OpenGLRenderer::clipRect(float left, float top, float right, float bottom, SkRegion::Op op) {
    bool clipped = mSnapshot->clip(left, top, right, bottom, op);
    if (clipped) {
        dirtyClip();
    }
    return !mSnapshot->clipRect->isEmpty();
}

Rect* OpenGLRenderer::getClipRect() {
    return mSnapshot->clipRect;
}

///////////////////////////////////////////////////////////////////////////////
// Drawing commands
///////////////////////////////////////////////////////////////////////////////

void OpenGLRenderer::setupDraw(bool clear) {
    // TODO: It would be best if we could do this before quickReject()
    //       changes the scissor test state
    if (clear) clearLayerRegions();
    if (mDirtyClip) {
        setScissorFromClip();
    }
    mDescription.reset();
    mSetShaderColor = false;
    mColorSet = false;
    mColorA = mColorR = mColorG = mColorB = 0.0f;
    mTextureUnit = 0;
    mTrackDirtyRegions = true;
}

void OpenGLRenderer::setupDrawWithTexture(bool isAlpha8) {
    mDescription.hasTexture = true;
    mDescription.hasAlpha8Texture = isAlpha8;
}

void OpenGLRenderer::setupDrawWithExternalTexture() {
    mDescription.hasExternalTexture = true;
}

void OpenGLRenderer::setupDrawNoTexture() {
    mCaches.disbaleTexCoordsVertexArray();
}

void OpenGLRenderer::setupDrawAA() {
    mDescription.isAA = true;
}

void OpenGLRenderer::setupDrawVertexShape() {
    mDescription.isVertexShape = true;
}

void OpenGLRenderer::setupDrawPoint(float pointSize) {
    mDescription.isPoint = true;
    mDescription.pointSize = pointSize;
}

void OpenGLRenderer::setupDrawColor(int color) {
    setupDrawColor(color, (color >> 24) & 0xFF);
}

void OpenGLRenderer::setupDrawColor(int color, int alpha) {
    mColorA = alpha / 255.0f;
    // Second divide of a by 255 is an optimization, allowing us to simply multiply
    // the rgb values by a instead of also dividing by 255
    const float a = mColorA / 255.0f;
    mColorR = a * ((color >> 16) & 0xFF);
    mColorG = a * ((color >>  8) & 0xFF);
    mColorB = a * ((color      ) & 0xFF);
    mColorSet = true;
    mSetShaderColor = mDescription.setColor(mColorR, mColorG, mColorB, mColorA);
}

void OpenGLRenderer::setupDrawAlpha8Color(int color, int alpha) {
    mColorA = alpha / 255.0f;
    // Double-divide of a by 255 is an optimization, allowing us to simply multiply
    // the rgb values by a instead of also dividing by 255
    const float a = mColorA / 255.0f;
    mColorR = a * ((color >> 16) & 0xFF);
    mColorG = a * ((color >>  8) & 0xFF);
    mColorB = a * ((color      ) & 0xFF);
    mColorSet = true;
    mSetShaderColor = mDescription.setAlpha8Color(mColorR, mColorG, mColorB, mColorA);
}

void OpenGLRenderer::setupDrawTextGamma(const SkPaint* paint) {
    mCaches.fontRenderer->describe(mDescription, paint);
}

void OpenGLRenderer::setupDrawColor(float r, float g, float b, float a) {
    mColorA = a;
    mColorR = r;
    mColorG = g;
    mColorB = b;
    mColorSet = true;
    mSetShaderColor = mDescription.setColor(r, g, b, a);
}

void OpenGLRenderer::setupDrawShader() {
    if (mShader) {
        mShader->describe(mDescription, mCaches.extensions);
    }
}

void OpenGLRenderer::setupDrawColorFilter() {
    if (mColorFilter) {
        mColorFilter->describe(mDescription, mCaches.extensions);
    }
}

void OpenGLRenderer::accountForClear(SkXfermode::Mode mode) {
    if (mColorSet && mode == SkXfermode::kClear_Mode) {
        mColorA = 1.0f;
        mColorR = mColorG = mColorB = 0.0f;
        mSetShaderColor = mDescription.modulate = true;
    }
}

void OpenGLRenderer::setupDrawBlending(SkXfermode::Mode mode, bool swapSrcDst) {
    // When the blending mode is kClear_Mode, we need to use a modulate color
    // argb=1,0,0,0
    accountForClear(mode);
    chooseBlending((mColorSet && mColorA < 1.0f) || (mShader && mShader->blend()), mode,
            mDescription, swapSrcDst);
}

void OpenGLRenderer::setupDrawBlending(bool blend, SkXfermode::Mode mode, bool swapSrcDst) {
    // When the blending mode is kClear_Mode, we need to use a modulate color
    // argb=1,0,0,0
    accountForClear(mode);
    chooseBlending(blend || (mColorSet && mColorA < 1.0f) || (mShader && mShader->blend()) ||
            (mColorFilter && mColorFilter->blend()), mode, mDescription, swapSrcDst);
}

void OpenGLRenderer::setupDrawP