/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 <SkColor.h>
#include <SkShader.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 "DeferredDisplayList.h"
#include "DisplayListRenderer.h"
#include "Fence.h"
#include "RenderState.h"
#include "PathTessellator.h"
#include "Properties.h"
#include "ShadowTessellator.h"
#include "SkiaShader.h"
#include "utils/GLUtils.h"
#include "utils/TraceUtils.h"
#include "Vector.h"
#include "VertexBuffer.h"

#if DEBUG_DETAILED_EVENTS
    #define EVENT_LOGD(...) eventMarkDEBUG(__VA_ARGS__)
#else
    #define EVENT_LOGD(...)
#endif

namespace android {
namespace uirenderer {

static GLenum getFilter(const SkPaint* paint) {
    if (!paint || paint->getFilterLevel() != SkPaint::kNone_FilterLevel) {
        return GL_LINEAR;
    }
    return 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::kModulate_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::kModulate_Mode, GL_DST_COLOR,           GL_ZERO },
    { SkXfermode::kScreen_Mode,   GL_ONE_MINUS_DST_COLOR, GL_ONE }
};

///////////////////////////////////////////////////////////////////////////////
// Functions
///////////////////////////////////////////////////////////////////////////////

template<typename T>
static inline T min(T a, T b) {
    return a < b ? a : b;
}

///////////////////////////////////////////////////////////////////////////////
// Constructors/destructor
///////////////////////////////////////////////////////////////////////////////

OpenGLRenderer::OpenGLRenderer(RenderState& renderState)
        : mFrameStarted(false)
        , mCaches(Caches::getInstance())
        , mExtensions(Extensions::getInstance())
        , mRenderState(renderState)
        , mScissorOptimizationDisabled(false)
        , mSuppressTiling(false)
        , mFirstFrameAfterResize(true)
        , mLightCenter((Vector3){FLT_MIN, FLT_MIN, FLT_MIN})
        , mLightRadius(FLT_MIN)
        , mAmbientShadowAlpha(0)
        , mSpotShadowAlpha(0) {
    // *set* draw modifiers to be 0
    memset(&mDrawModifiers, 0, sizeof(mDrawModifiers));
    mDrawModifiers.mOverrideLayerAlpha = 1.0f;

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

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");
    }
}

void OpenGLRenderer::initLight(const Vector3& lightCenter, float lightRadius,
        uint8_t ambientShadowAlpha, uint8_t spotShadowAlpha) {
    mLightCenter = lightCenter;
    mLightRadius = lightRadius;
    mAmbientShadowAlpha = ambientShadowAlpha;
    mSpotShadowAlpha = spotShadowAlpha;
}

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

void OpenGLRenderer::onViewportInitialized() {
    glDisable(GL_DITHER);
    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

    glEnableVertexAttribArray(Program::kBindingPosition);
    mFirstFrameAfterResize = true;
}

void OpenGLRenderer::setupFrameState(float left, float top,
        float right, float bottom, bool opaque) {
    mCaches.clearGarbage();
    initializeSaveStack(left, top, right, bottom, mLightCenter);
    mOpaque = opaque;
    mTilingClip.set(left, top, right, bottom);
}

status_t OpenGLRenderer::startFrame() {
    if (mFrameStarted) return DrawGlInfo::kStatusDone;
    mFrameStarted = true;

    mDirtyClip = true;

    discardFramebuffer(mTilingClip.left, mTilingClip.top, mTilingClip.right, mTilingClip.bottom);

    mRenderState.setViewport(getWidth(), getHeight());

    // 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()
            || mFirstFrameAfterResize;
    mFirstFrameAfterResize = false;

    startTilingCurrentClip(true);

    debugOverdraw(true, true);

    return clear(mTilingClip.left, mTilingClip.top,
            mTilingClip.right, mTilingClip.bottom, mOpaque);
}

status_t OpenGLRenderer::prepareDirty(float left, float top,
        float right, float bottom, bool opaque) {

    setupFrameState(left, top, right, bottom, opaque);

    // Layer renderers will start the frame immediately
    // The framebuffer renderer will first defer the display list
    // for each layer and wait until the first drawing command
    // to start the frame
    if (currentSnapshot()->fbo == 0) {
        syncState();
        updateLayers();
    } else {
        return startFrame();
    }

    return DrawGlInfo::kStatusDone;
}

void OpenGLRenderer::discardFramebuffer(float left, float top, float right, float bottom) {
    // 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 (mExtensions.hasDiscardFramebuffer() &&
            left <= 0.0f && top <= 0.0f && right >= getWidth() && bottom >= getHeight()) {
        const bool isFbo = getTargetFbo() == 0;
        const GLenum attachments[] = {
                isFbo ? (const GLenum) GL_COLOR_EXT : (const GLenum) GL_COLOR_ATTACHMENT0,
                isFbo ? (const GLenum) GL_STENCIL_EXT : (const GLenum) GL_STENCIL_ATTACHMENT };
        glDiscardFramebufferEXT(GL_FRAMEBUFFER, 1, attachments);
    }
}

status_t OpenGLRenderer::clear(float left, float top, float right, float bottom, bool opaque) {
#ifdef QCOM_HARDWARE
    mCaches.enableScissor();
    mCaches.setScissor(left, getViewportHeight() - bottom, right - left, bottom - top);
    glClear(GL_COLOR_BUFFER_BIT);
    if (opaque) {
        mCaches.resetScissor();
        return DrawGlInfo::kStatusDone;
    }
#else
    if (!opaque) {
        mCaches.enableScissor();
        mCaches.setScissor(left, getViewportHeight() - bottom, right - left, bottom - top);
        glClear(GL_COLOR_BUFFER_BIT);
        return DrawGlInfo::kStatusDrew;
    }
#endif
    return DrawGlInfo::kStatusDrew;
}

void OpenGLRenderer::syncState() {
    if (mCaches.blend) {
        glEnable(GL_BLEND);
    } else {
        glDisable(GL_BLEND);
    }
}

void OpenGLRenderer::startTilingCurrentClip(bool opaque, bool expand) {
    if (!mSuppressTiling) {
        const Snapshot* snapshot = currentSnapshot();

        const Rect* clip = &mTilingClip;
        if (snapshot->flags & Snapshot::kFlagFboTarget) {
            clip = &(snapshot->layer->clipRect);
        }

        startTiling(*clip, getViewportHeight(), opaque, expand);
    }
}

void OpenGLRenderer::startTiling(const Rect& clip, int windowHeight, bool opaque, bool expand) {
    if (!mSuppressTiling) {
        if(expand) {
            // Expand the startTiling region by 1
            int leftNotZero = (clip.left > 0) ? 1 : 0;
            int topNotZero = (windowHeight - clip.bottom > 0) ? 1 : 0;

            mCaches.startTiling(
                clip.left - leftNotZero,
                windowHeight - clip.bottom - topNotZero,
                clip.right - clip.left + leftNotZero + 1,
                clip.bottom - clip.top + topNotZero + 1,
                opaque);
        } else {
            mCaches.startTiling(clip.left, windowHeight - clip.bottom,
                clip.right - clip.left, clip.bottom - clip.top, opaque);
        }
    }
}

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

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

    for (size_t i = 0; i < mTempPaths.size(); i++) {
        delete mTempPaths[i];
    }
    mTempPaths.clear();

    // When finish() is invoked on FBO 0 we've reached the end
    // of the current frame
    if (getTargetFbo() == 0) {
        mCaches.pathCache.trim();
        mCaches.tessellationCache.trim();
    }

    if (!suppressErrorChecks()) {
#if DEBUG_OPENGL
        GLUtils::dumpGLErrors();
#endif

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

    mFrameStarted = false;
}

void OpenGLRenderer::resumeAfterLayer() {
    mRenderState.setViewport(getViewportWidth(), getViewportHeight());
    mRenderState.bindFramebuffer(currentSnapshot()->fbo);
    debugOverdraw(true, false);

    mCaches.resetScissor();
    dirtyClip();
}

status_t OpenGLRenderer::callDrawGLFunction(Functor* functor, Rect& dirty) {
    if (currentSnapshot()->isIgnored()) return DrawGlInfo::kStatusDone;

    Rect clip(*currentClipRect());
    clip.snapToPixelBoundaries();

    // Since we don't know what the functor will draw, let's dirty
    // the 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 = getViewportWidth();
    info.height = getViewportHeight();
    currentTransform()->copyTo(&info.transform[0]);

    bool prevDirtyClip = mDirtyClip;
    // setup GL state for functor
    if (mDirtyClip) {
        setStencilFromClip(); // can issue draws, so must precede enableScissor()/interrupt()
    }
    if (mCaches.enableScissor() || prevDirtyClip) {
        setScissorFromClip();
    }

    mRenderState.invokeFunctor(functor, DrawGlInfo::kModeDraw, &info);
    // Scissor may have been modified, reset dirty clip
    dirtyClip();

    return DrawGlInfo::kStatusDrew;
}

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

void OpenGLRenderer::eventMarkDEBUG(const char* fmt, ...) const {
#if DEBUG_DETAILED_EVENTS
    const int BUFFER_SIZE = 256;
    va_list ap;
    char buf[BUFFER_SIZE];

    va_start(ap, fmt);
    vsnprintf(buf, BUFFER_SIZE, fmt, ap);
    va_end(ap);

    eventMark(buf);
#endif
}


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

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

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

void OpenGLRenderer::debugOverdraw(bool enable, bool clear) {
    mRenderState.debugOverdraw(enable, clear);
}

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

        mCaches.enableScissor();
        mCaches.setScissor(clip->left, firstSnapshot()->getViewportHeight() - clip->bottom,
                clip->right - clip->left, clip->bottom - clip->top);

        // 1x overdraw
        mCaches.stencil.enableDebugTest(2);
        drawColor(mCaches.getOverdrawColor(1), SkXfermode::kSrcOver_Mode);

        // 2x overdraw
        mCaches.stencil.enableDebugTest(3);
        drawColor(mCaches.getOverdrawColor(2), SkXfermode::kSrcOver_Mode);

        // 3x overdraw
        mCaches.stencil.enableDebugTest(4);
        drawColor(mCaches.getOverdrawColor(3), SkXfermode::kSrcOver_Mode);

        // 4x overdraw and higher
        mCaches.stencil.enableDebugTest(4, true);
        drawColor(mCaches.getOverdrawColor(4), SkXfermode::kSrcOver_Mode);

        mCaches.stencil.disable();
    }
}

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

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

        if (inFrame) {
            endTiling();
            debugOverdraw(false, false);
        }

        if (CC_UNLIKELY(inFrame || mCaches.drawDeferDisabled)) {
            layer->render(*this);
        } else {
            layer->defer(*this);
        }

        if (inFrame) {
            resumeAfterLayer();
            startTilingCurrentClip();
        }

        layer->debugDrawUpdate = mCaches.debugLayersUpdates;
        layer->hasDrawnSinceUpdate = false;

        return true;
    }

    return false;
}

void OpenGLRenderer::updateLayers() {
    // If draw deferring is enabled this method will simply defer
    // the display list of each individual layer. The layers remain
    // in the layer updates list which will be cleared by flushLayers().
    int count = mLayerUpdates.size();
    if (count > 0) {
        if (CC_UNLIKELY(mCaches.drawDeferDisabled)) {
            startMark("Layer Updates");
        } else {
            startMark("Defer Layer Updates");
        }

        // Note: it is very important to update the layers in order
        for (int i = 0; i < count; i++) {
            Layer* layer = mLayerUpdates.itemAt(i).get();
            updateLayer(layer, false);
        }

        if (CC_UNLIKELY(mCaches.drawDeferDisabled)) {
            mLayerUpdates.clear();
            mRenderState.bindFramebuffer(getTargetFbo());
        }
        endMark();
    }
}

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

        // Note: it is very important to update the layers in order
        for (int i = 0; i < count; i++) {
            mLayerUpdates.itemAt(i)->flush();
        }

        mLayerUpdates.clear();
        mRenderState.bindFramebuffer(getTargetFbo());

        endMark();
    }
}

void OpenGLRenderer::pushLayerUpdate(Layer* layer) {
    if (layer) {
        // Make sure we don't introduce duplicates.
        // SortedVector would do this automatically but we need to respect
        // the insertion order. The linear search is not an issue since
        // this list is usually very short (typically one item, at most a few)
        for (int i = mLayerUpdates.size() - 1; i >= 0; i--) {
            if (mLayerUpdates.itemAt(i) == layer) {
                return;
            }
        }
        mLayerUpdates.push_back(layer);
    }
}

void OpenGLRenderer::cancelLayerUpdate(Layer* layer) {
    if (layer) {
        for (int i = mLayerUpdates.size() - 1; i >= 0; i--) {
            if (mLayerUpdates.itemAt(i) == layer) {
                mLayerUpdates.removeAt(i);
                break;
            }
        }
    }
}

void OpenGLRenderer::flushLayerUpdates() {
    ATRACE_NAME("Update HW Layers");
    syncState();
    updateLayers();
    flushLayers();
    // Wait for all the layer updates to be executed
    AutoFence fence;
}

void OpenGLRenderer::markLayersAsBuildLayers() {
    for (size_t i = 0; i < mLayerUpdates.size(); i++) {
        mLayerUpdates[i]->wasBuildLayered = true;
    }
}

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

void OpenGLRenderer::onSnapshotRestored(const Snapshot& removed, const Snapshot& restored) {
    bool restoreViewport = removed.flags & Snapshot::kFlagIsFboLayer;
    bool restoreClip = removed.flags & Snapshot::kFlagClipSet;
    bool restoreLayer = removed.flags & Snapshot::kFlagIsLayer;

    if (restoreViewport) {
        mRenderState.setViewport(getViewportWidth(), getViewportHeight());
    }

    if (restoreClip) {
        dirtyClip();
    }

    if (restoreLayer) {
        endMark(); // Savelayer
        ATRACE_END(); // SaveLayer
        startMark("ComposeLayer");
        composeLayer(removed, restored);
        endMark();
    }
}

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

int OpenGLRenderer::saveLayer(float left, float top, float right, float bottom,
        const SkPaint* paint, int flags, const SkPath* convexMask) {
    // force matrix/clip isolation for layer
    flags |= SkCanvas::kClip_SaveFlag | SkCanvas::kMatrix_SaveFlag;

    const int count = saveSnapshot(flags);

    if (!currentSnapshot()->isIgnored()) {
        createLayer(left, top, right, bottom, paint, flags, convexMask);
    }

    return count;
}

void OpenGLRenderer::calculateLayerBoundsAndClip(Rect& bounds, Rect& clip, bool fboLayer) {
    const Rect untransformedBounds(bounds);

    currentTransform()->mapRect(bounds);

    // Layers only make sense if they are in the framebuffer's bounds
    if (bounds.intersect(*currentClipRect())) {
        // 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
        const Snapshot& previous = *(currentSnapshot()->previous);
        Rect previousViewport(0, 0, previous.getViewportWidth(), previous.getViewportHeight());
        if (!bounds.intersect(previousViewport)) {
            bounds.setEmpty();
        } else if (fboLayer) {
            clip.set(bounds);
            mat4 inverse;
            inverse.loadInverse(*currentTransform());
            inverse.mapRect(clip);
            clip.snapToPixelBoundaries();
            if (clip.intersect(untransformedBounds)) {
                clip.translate(-untransformedBounds.left, -untransformedBounds.top);
                bounds.set(untransformedBounds);
            } else {
                clip.setEmpty();
            }
        }
    } else {
        bounds.setEmpty();
    }
}

void OpenGLRenderer::updateSnapshotIgnoreForLayer(const Rect& bounds, const Rect& clip,
        bool fboLayer, int alpha) {
    if (bounds.isEmpty() || bounds.getWidth() > mCaches.maxTextureSize ||
            bounds.getHeight() > mCaches.maxTextureSize ||
            (fboLayer && clip.isEmpty())) {
        mSnapshot->empty = fboLayer;
    } else {
        mSnapshot->invisible = mSnapshot->invisible || (alpha <= 0 && fboLayer);
    }
}

int OpenGLRenderer::saveLayerDeferred(float left, float top, float right, float bottom,
        const SkPaint* paint, int flags) {
    const int count = saveSnapshot(flags);

    if (!currentSnapshot()->isIgnored() && (flags & SkCanvas::kClipToLayer_SaveFlag)) {
        // initialize the snapshot as though it almost represents an FBO layer so deferred draw
        // operations will be able to store and restore the current clip and transform info, and
        // quick rejection will be correct (for display lists)

        Rect bounds(left, top, right, bottom);
        Rect clip;
        calculateLayerBoundsAndClip(bounds, clip, true);
        updateSnapshotIgnoreForLayer(bounds, clip, true, getAlphaDirect(paint));

        if (!currentSnapshot()->isIgnored()) {
            mSnapshot->resetTransform(-bounds.left, -bounds.top, 0.0f);
            mSnapshot->resetClip(clip.left, clip.top, clip.right, clip.bottom);
            mSnapshot->initializeViewport(bounds.getWidth(), bounds.getHeight());
            mSnapshot->roundRectClipState = NULL;
        }
    }

    return count;
}

/**
 * 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,
        const SkPaint* paint, int flags, const SkPath* convexMask) {
    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);
    calculateLayerBoundsAndClip(bounds, clip, fboLayer);
    updateSnapshotIgnoreForLayer(bounds, clip, fboLayer, getAlphaDirect(paint));

    // Bail out if we won't draw in this snapshot
    if (currentSnapshot()->isIgnored()) {
        return false;
    }

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

    layer->setPaint(paint);
    layer->layer.set(bounds);
    layer->texCoords.set(0.0f, bounds.getHeight() / float(layer->getHeight()),
            bounds.getWidth() / float(layer->getWidth()), 0.0f);

    layer->setBlend(true);
    layer->setDirty(false);
    layer->setConvexMask(convexMask); // note: the mask must be cleared before returning to the cache

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

    ATRACE_FORMAT_BEGIN("%ssaveLayer %ux%u",
            fboLayer ? "" : "unclipped ",
            layer->getWidth(), layer->getHeight());
    startMark("SaveLayer");
    if (fboLayer) {
        return createFboLayer(layer, bounds, clip);
    } else {
        // Copy the framebuffer into the layer
        layer->bindTexture();
        if (!bounds.isEmpty()) {
            if (layer->isEmpty()) {
                // Workaround for some GL drivers. When reading pixels lying outside
                // of the window we should get undefined values for those pixels.
                // Unfortunately some drivers will turn the entire target texture black
                // when reading outside of the window.
                glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, layer->getWidth(), layer->getHeight(),
                        0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
                layer->setEmpty(false);
            }

            glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0,
                    bounds.left, getViewportHeight() - 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) {
    layer->clipRect.set(clip);
    layer->setFbo(mCaches.fboCache.get());

    mSnapshot->region = &mSnapshot->layer->region;
    mSnapshot->flags |= Snapshot::kFlagFboTarget | 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->initializeViewport(bounds.getWidth(), bounds.getHeight());
    mSnapshot->roundRectClipState = NULL;

    endTiling();
    debugOverdraw(false, false);
    // Bind texture to FBO
    mRenderState.bindFramebuffer(layer->getFbo());
    layer->bindTexture();

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

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

    // Expand the startTiling region by 1
    startTilingCurrentClip(true, true);

    // 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
    mRenderState.setViewport(bounds.getWidth(), bounds.getHeight());
    return true;
}

/**
 * Read the documentation of createLayer() before doing anything in this method.
 */
void OpenGLRenderer::composeLayer(const Snapshot& removed, const Snapshot& restored) {
    if (!removed.layer) {
        ALOGE("Attempting to compose a layer that does not exist");
        return;
    }

    Layer* layer = removed.layer;
    const Rect& rect = layer->layer;
    const bool fboLayer = removed.flags & Snapshot::kFlagIsFboLayer;

    bool clipRequired = false;
    calculateQuickRejectForScissor(rect.left, rect.top, rect.right, rect.bottom,
            &clipRequired, NULL, false); // safely ignore return, should never be rejected
    mCaches.setScissorEnabled(mScissorOptimizationDisabled || clipRequired);

    if (fboLayer) {
        endTiling();

        // Detach the texture from the FBO
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, 0, 0);

        layer->removeFbo(false);

        // Unbind current FBO and restore previous one
        mRenderState.bindFramebuffer(restored.fbo);
        debugOverdraw(true, false);

        startTilingCurrentClip();
    }

    if (!fboLayer && layer->getAlpha() < 255) {
        SkPaint layerPaint;
        layerPaint.setAlpha(layer->getAlpha());
        layerPaint.setXfermodeMode(SkXfermode::kDstIn_Mode);
        layerPaint.setColorFilter(layer->getColorFilter());

        drawColorRect(rect.left, rect.top, rect.right, rect.bottom, &layerPaint, 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, *restored.transform);
        composeLayerRegion(layer, rect);
    } else if (!rect.isEmpty()) {
        dirtyLayer(rect.left, rect.top, rect.right, rect.bottom);

        save(0);
        // the layer contains screen buffer content that shouldn't be alpha modulated
        // (and any necessary alpha modulation was handled drawing into the layer)
        mSnapshot->alpha = 1.0f;
        composeLayerRect(layer, rect, true);
        restore();
    }

    dirtyClip();

    // Failing to add the layer to the cache should happen only if the layer is too large
    layer->setConvexMask(NULL);
    if (!mCaches.layerCache.put(layer)) {
        LAYER_LOGD("Deleting layer");
        layer->decStrong(0);
    }
}

void OpenGLRenderer::drawTextureLayer(Layer* layer, const Rect& rect) {
    float alpha = getLayerAlpha(layer);

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

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

    glDrawArrays(GL_TRIANGLE_STRIP, 0, gMeshCount);
}

void OpenGLRenderer::composeLayerRect(Layer* layer, const Rect& rect, bool swap) {
    if (layer->isTextureLayer()) {
        EVENT_LOGD("composeTextureLayerRect");
        resetDrawTextureTexCoords(0.0f, 1.0f, 1.0f, 0.0f);
        drawTextureLayer(layer, rect);
        resetDrawTextureTexCoords(0.0f, 0.0f, 1.0f, 1.0f);
    } else {
        EVENT_LOGD("composeHardwareLayerRect");
        const Rect& texCoords = layer->texCoords;
        resetDrawTextureTexCoords(texCoords.left, texCoords.top,
                texCoords.right, texCoords.bottom);

        float x = rect.left;
        float y = rect.top;
        bool simpleTransform = currentTransform()->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 + currentTransform()->getTranslateX() + 0.5f);
                y = (int) floorf(rect.top + currentTransform()->getTranslateY() + 0.5f);
            }

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

        SkPaint layerPaint;
        layerPaint.setAlpha(getLayerAlpha(layer) * 255);
        layerPaint.setXfermodeMode(layer->getMode());
        layerPaint.setColorFilter(layer->getColorFilter());

        bool blend = layer->isBlend() || getLayerAlpha(layer) < 1.0f;
        drawTextureMesh(x, y, x + rect.getWidth(), y + rect.getHeight(),
                layer->getTexture(), &layerPaint, blend,
                &mMeshVertices[0].x, &mMeshVertices[0].u,
                GL_TRIANGLE_STRIP, gMeshCount, swap, swap || simpleTransform);

        resetDrawTextureTexCoords(0.0f, 0.0f, 1.0f, 1.0f);
    }
}

/**
 * Issues the command X, and if we're composing a save layer to the fbo or drawing a newly updated
 * hardware layer with overdraw debug on, draws again to the stencil only, so that these draw
 * operations are correctly counted twice for overdraw. NOTE: assumes composeLayerRegion only used
 * by saveLayer's restore
 */
#define DRAW_DOUBLE_STENCIL_IF(COND, DRAW_COMMAND) {                             \
        DRAW_COMMAND;                                                            \
        if (CC_UNLIKELY(mCaches.debugOverdraw && getTargetFbo() == 0 && COND)) { \
            glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);                 \
            DRAW_COMMAND;                                                        \
            glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);                     \
        }                                                                        \
    }

#define DRAW_DOUBLE_STENCIL(DRAW_COMMAND) DRAW_DOUBLE_STENCIL_IF(true, DRAW_COMMAND)

// This class is purely for inspection. It inherits from SkShader, but Skia does not know how to
// use it. The OpenGLRenderer will look at it to find its Layer and whether it is opaque.
class LayerShader : public SkShader {
public:
    LayerShader(Layer* layer, const SkMatrix* localMatrix)
    : INHERITED(localMatrix)
    , mLayer(layer) {
    }

    virtual bool asACustomShader(void** data) const {
        if (data) {
            *data = static_cast<void*>(mLayer);
        }
        return true;
    }

    virtual bool isOpaque() const {
        return !mLayer->isBlend();
    }

protected:
    virtual void shadeSpan(int x, int y, SkPMColor[], int count) {
        LOG_ALWAYS_FATAL("LayerShader should never be drawn with raster backend.");
    }

    virtual void flatten(SkWriteBuffer&) const {
        LOG_ALWAYS_FATAL("LayerShader should never be flattened.");
    }

    virtual Factory getFactory() const {
        LOG_ALWAYS_FATAL("LayerShader should never be created from a stream.");
        return NULL;
    }
private:
    // Unowned.
    Layer* mLayer;
    typedef SkShader INHERITED;
};

void OpenGLRenderer::composeLayerRegion(Layer* layer, const Rect& rect) {
    if (CC_UNLIKELY(layer->region.isEmpty())) return; // nothing to draw

    if (layer->getConvexMask()) {
        save(SkCanvas::kClip_SaveFlag | SkCanvas::kMatrix_SaveFlag);

        // clip to the area of the layer the mask can be larger
        clipRect(rect.left, rect.top, rect.right, rect.bottom, SkRegion::kIntersect_Op);

        SkPaint paint;
        paint.setAntiAlias(true);
        paint.setColor(SkColorSetARGB(int(getLayerAlpha(layer) * 255), 0, 0, 0));

        // create LayerShader to map SaveLayer content into subsequent draw
        SkMatrix shaderMatrix;
        shaderMatrix.setTranslate(rect.left, rect.bottom);
        shaderMatrix.preScale(1, -1);
        LayerShader layerShader(layer, &shaderMatrix);
        paint.setShader(&layerShader);

        // Since the drawing primitive is defined in local drawing space,
        // we don't need to modify the draw matrix
        const SkPath* maskPath = layer->getConvexMask();
        DRAW_DOUBLE_STENCIL(drawConvexPath(*maskPath, &paint));

        paint.setShader(NULL);
        restore();

        return;
    }

    if (layer->region.isRect()) {
        layer->setRegionAsRect();

        DRAW_DOUBLE_STENCIL(composeLayerRect(layer, layer->regionRect));

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

    EVENT_LOGD("composeLayerRegion");
    // standard Region based draw
    size_t count;
    const android::Rect* rects;
    Region safeRegion;
    if (CC_LIKELY(hasRectToRectTransform())) {
        rects = layer->region.getArray(&count);
    } else {
        safeRegion = Region::createTJunctionFreeRegion(layer->region);
        rects = safeRegion.getArray(&count);
    }

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

    setupDraw();

    // We must get (and therefore bind) the region mesh buffer
    // after we setup drawing in case we need to mess with the
    // stencil buffer in setupDraw()
    TextureVertex* mesh = mCaches.getRegionMesh();
    uint32_t numQuads = 0;

    setupDrawWithTexture();
    setupDrawColor(alpha, alpha, alpha, alpha);
    setupDrawColorFilter(layer->getColorFilter());
    setupDrawBlending(layer);
    setupDrawProgram();
    setupDrawDirtyRegionsDisabled();
    setupDrawPureColorUniforms();
    setupDrawColorFilterUniforms(layer->getColorFilter());
    setupDrawTexture(layer->getTexture());
    if (currentTransform()->isPureTranslate()) {
        const float x = (int) floorf(rect.left + currentTransform()->getTranslateX() + 0.5f);
        const float y = (int) floorf(rect.top + currentTransform()->getTranslateY() + 0.5f);

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

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

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

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

    layer->region.clear();
}

#if DEBUG_LAYERS_AS_REGIONS
void OpenGLRenderer::drawRegionRectsDebug(const Region& region) {
    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;
        }

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

void OpenGLRenderer::drawRegionRects(const SkRegion& region, const SkPaint& paint, bool dirty) {
    Vector<float> rects;

    SkRegion::Iterator it(region);
    while (!it.done()) {
        const SkIRect& r = it.rect();
        rects.push(r.fLeft);
        rects.push(r.fTop);
        rects.push(r.fRight);
        rects.push(r.fBottom);
        it.next();
    }

    drawColorRects(rects.array(), rects.size(), &paint, true, dirty, false);
}

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(*currentClipRect())) {
        bounds.snapToPixelBoundaries();
        android::Rect dirty(bounds.left, bounds.top, bounds.right, bounds.bottom);
        if (!dirty.isEmpty()) {
            region->orSelf(dirty);
        }
    }
}

void OpenGLRenderer::issueIndexedQuadDraw(Vertex* mesh, GLsizei quadsCount) {
    GLsizei elementsCount = quadsCount * 6;
    while (elementsCount > 0) {
        GLsizei drawCount = min(elementsCount, (GLsizei) gMaxNumberOfQuads * 6);

        setupDrawIndexedVertices(&mesh[0].x);
        glDrawElements(GL_TRIANGLES, drawCount, GL_UNSIGNED_SHORT, NULL);

        elementsCount -= drawCount;
        // Though there are 4 vertices in a quad, we use 6 indices per
        // quad to draw with GL_TRIANGLES
        mesh += (drawCount / 6) * 4;
    }
}

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

    if (!currentSnapshot()->isIgnored()) {
        EVENT_LOGD("clearLayerRegions");
        // 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 * 4];
        Vertex* vertex = mesh;

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

            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->bottom);

            delete bounds;
        }
        // We must clear the list of dirty rects before we
        // call setupDraw() to prevent stencil setup to do
        // the same thing again
        mLayers.clear();

        SkPaint clearPaint;
        clearPaint.setXfermodeMode(SkXfermode::kClear_Mode);

        setupDraw(false);
        setupDrawColor(0.0f, 0.0f, 0.0f, 1.0f);
        setupDrawBlending(&clearPaint, true);
        setupDrawProgram();
        setupDrawPureColorUniforms();
        setupDrawModelView(kModelViewMode_Translate, false,
                0.0f, 0.0f, 0.0f, 0.0f, true);

        issueIndexedQuadDraw(&mesh[0], count);

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

///////////////////////////////////////////////////////////////////////////////
// State Deferral
///////////////////////////////////////////////////////////////////////////////

bool OpenGLRenderer::storeDisplayState(DeferredDisplayState& state, int stateDeferFlags) {
    const Rect* currentClip = currentClipRect();
    const mat4* currentMatrix = currentTransform();

    if (stateDeferFlags & kStateDeferFlag_Draw) {
        // state has bounds initialized in local coordinates
        if (!state.mBounds.isEmpty()) {
            currentMatrix->mapRect(state.mBounds);
            Rect clippedBounds(state.mBounds);
            // NOTE: if we ever want to use this clipping info to drive whether the scissor
            // is used, it should more closely duplicate the quickReject logic (in how it uses
            // snapToPixelBoundaries)

            if(!clippedBounds.intersect(*currentClip)) {
                // quick rejected
                return true;
            }

            state.mClipSideFlags = kClipSide_None;
            if (!currentClip->contains(state.mBounds)) {
                int& flags = state.mClipSideFlags;
                // op partially clipped, so record which sides are clipped for clip-aware merging
                if (currentClip->left > state.mBounds.left) flags |= kClipSide_Left;
                if (currentClip->top > state.mBounds.top) flags |= kClipSide_Top;
                if (currentClip->right < state.mBounds.right) flags |= kClipSide_Right;
                if (currentClip->bottom < state.mBounds.bottom) flags |= kClipSide_Bottom;
            }
            state.mBounds.set(clippedBounds);
        } else {
            // Empty bounds implies size unknown. Label op as conservatively clipped to disable
            // overdraw avoidance (since we don't know what it overlaps)
            state.mClipSideFlags = kClipSide_ConservativeFull;
            state.mBounds.set(*currentClip);
        }
    }

    state.mClipValid = (stateDeferFlags & kStateDeferFlag_Clip);
    if (state.mClipValid) {
        state.mClip.set(*currentClip);
    }

    // Transform, drawModifiers, and alpha always deferred, since they are used by state operations
    // (Note: saveLayer/restore use colorFilter and alpha, so we just save restore everything)
    state.mMatrix.load(*currentMatrix);
    state.mDrawModifiers = mDrawModifiers;
    state.mAlpha = currentSnapshot()->alpha;

    // always store/restore, since it's just a pointer
    state.mRoundRectClipState = currentSnapshot()->roundRectClipState;
    return false;
}

void OpenGLRenderer::restoreDisplayState(const DeferredDisplayState& state, bool skipClipRestore) {
    setMatrix(state.mMatrix);
    mSnapshot->alpha = state.mAlpha;
    mDrawModifiers = state.mDrawModifiers;
    mSnapshot->roundRectClipState = state.mRoundRectClipState;

    if (state.mClipV