libs/hwui/FontRenderer.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 <SkGlyph.h>
#include <SkUtils.h>

#include <cutils/properties.h>

#include <utils/Log.h>

#ifdef ANDROID_ENABLE_RENDERSCRIPT
#include <RenderScript.h>
#endif

#include "utils/Blur.h"
#include "utils/Timing.h"

#include "Caches.h"
#include "Debug.h"
#include "Extensions.h"
#include "FontRenderer.h"
#include "OpenGLRenderer.h"
#include "PixelBuffer.h"
#include "Rect.h"

namespace android {
namespace uirenderer {

// blur inputs smaller than this constant will bypass renderscript
#define RS_MIN_INPUT_CUTOFF 10000

///////////////////////////////////////////////////////////////////////////////
// TextSetupFunctor
///////////////////////////////////////////////////////////////////////////////
status_t TextSetupFunctor::operator ()(int what, void* data) {
    Data* typedData = reinterpret_cast<Data*>(data);
    GLenum glyphFormat = typedData ? typedData->glyphFormat : GL_ALPHA;

    renderer->setupDraw();
    renderer->setupDrawTextGamma(paint);
    renderer->setupDrawDirtyRegionsDisabled();
    renderer->setupDrawWithTexture(glyphFormat == GL_ALPHA);
    switch (glyphFormat) {
        case GL_ALPHA: {
            renderer->setupDrawAlpha8Color(paint->getColor(), alpha);
            break;
        }
        case GL_RGBA: {
            float floatAlpha = alpha / 255.0f;
            renderer->setupDrawColor(floatAlpha, floatAlpha, floatAlpha, floatAlpha);
            break;
        }
        default: {
#if DEBUG_FONT_RENDERER
            ALOGD("TextSetupFunctor: called with unknown glyph format %x", glyphFormat);
#endif
            break;
        }
    }
    renderer->setupDrawColorFilter();
    renderer->setupDrawShader();
    renderer->setupDrawBlending(true, mode);
    renderer->setupDrawProgram();
    renderer->setupDrawModelView(x, y, x, y, pureTranslate, true);
    // Calling setupDrawTexture with the name 0 will enable the
    // uv attributes and increase the texture unit count
    // texture binding will be performed by the font renderer as
    // needed
    renderer->setupDrawTexture(0);
    renderer->setupDrawPureColorUniforms();
    renderer->setupDrawColorFilterUniforms();
    renderer->setupDrawShaderUniforms(pureTranslate);
    renderer->setupDrawTextGammaUniforms();

    return NO_ERROR;
}

///////////////////////////////////////////////////////////////////////////////
// FontRenderer
///////////////////////////////////////////////////////////////////////////////

static bool sLogFontRendererCreate = true;

FontRenderer::FontRenderer() :
        mActiveFonts(LruCache<Font::FontDescription, Font*>::kUnlimitedCapacity) {

    if (sLogFontRendererCreate) {
        INIT_LOGD("Creating FontRenderer");
    }

    mGammaTable = NULL;
    mInitialized = false;

    mCurrentCacheTexture = NULL;

    mLinearFiltering = false;

    mSmallCacheWidth = DEFAULT_TEXT_SMALL_CACHE_WIDTH;
    mSmallCacheHeight = DEFAULT_TEXT_SMALL_CACHE_HEIGHT;
    mLargeCacheWidth = DEFAULT_TEXT_LARGE_CACHE_WIDTH;
    mLargeCacheHeight = DEFAULT_TEXT_LARGE_CACHE_HEIGHT;

    char property[PROPERTY_VALUE_MAX];
    if (property_get(PROPERTY_TEXT_SMALL_CACHE_WIDTH, property, NULL) > 0) {
        mSmallCacheWidth = atoi(property);
    }

    if (property_get(PROPERTY_TEXT_SMALL_CACHE_HEIGHT, property, NULL) > 0) {
        mSmallCacheHeight = atoi(property);
    }

    if (property_get(PROPERTY_TEXT_LARGE_CACHE_WIDTH, property, NULL) > 0) {
        mLargeCacheWidth = atoi(property);
    }

    if (property_get(PROPERTY_TEXT_LARGE_CACHE_HEIGHT, property, NULL) > 0) {
        mLargeCacheHeight = atoi(property);
    }

    uint32_t maxTextureSize = (uint32_t) Caches::getInstance().maxTextureSize;
    mSmallCacheWidth = mSmallCacheWidth > maxTextureSize ? maxTextureSize : mSmallCacheWidth;
    mSmallCacheHeight = mSmallCacheHeight > maxTextureSize ? maxTextureSize : mSmallCacheHeight;
    mLargeCacheWidth = mLargeCacheWidth > maxTextureSize ? maxTextureSize : mLargeCacheWidth;
    mLargeCacheHeight = mLargeCacheHeight > maxTextureSize ? maxTextureSize : mLargeCacheHeight;

    if (sLogFontRendererCreate) {
        INIT_LOGD("  Text cache sizes, in pixels: %i x %i, %i x %i, %i x %i, %i x %i",
                mSmallCacheWidth, mSmallCacheHeight,
                mLargeCacheWidth, mLargeCacheHeight >> 1,
                mLargeCacheWidth, mLargeCacheHeight >> 1,
                mLargeCacheWidth, mLargeCacheHeight);
    }

    sLogFontRendererCreate = false;
}

void clearCacheTextures(Vector<CacheTexture*>& cacheTextures) {
    for (uint32_t i = 0; i < cacheTextures.size(); i++) {
        delete cacheTextures[i];
    }
    cacheTextures.clear();
}

FontRenderer::~FontRenderer() {
    clearCacheTextures(mACacheTextures);
    clearCacheTextures(mRGBACacheTextures);

    LruCache<Font::FontDescription, Font*>::Iterator it(mActiveFonts);
    while (it.next()) {
        delete it.value();
    }
    mActiveFonts.clear();
}

void FontRenderer::flushAllAndInvalidate() {
    issueDrawCommand();

    LruCache<Font::FontDescription, Font*>::Iterator it(mActiveFonts);
    while (it.next()) {
        it.value()->invalidateTextureCache();
    }

    for (uint32_t i = 0; i < mACacheTextures.size(); i++) {
        mACacheTextures[i]->init();
    }

    for (uint32_t i = 0; i < mRGBACacheTextures.size(); i++) {
        mRGBACacheTextures[i]->init();
    }
}

void FontRenderer::flushLargeCaches(Vector<CacheTexture*>& cacheTextures) {
    // Start from 1; don't deallocate smallest/default texture
    for (uint32_t i = 1; i < cacheTextures.size(); i++) {
        CacheTexture* cacheTexture = cacheTextures[i];
        if (cacheTexture->getPixelBuffer()) {
            cacheTexture->init();
            LruCache<Font::FontDescription, Font*>::Iterator it(mActiveFonts);
            while (it.next()) {
                it.value()->invalidateTextureCache(cacheTexture);
            }
            cacheTexture->releaseTexture();
        }
    }
}

void FontRenderer::flushLargeCaches() {
    flushLargeCaches(mACacheTextures);
    flushLargeCaches(mRGBACacheTextures);
}

CacheTexture* FontRenderer::cacheBitmapInTexture(Vector<CacheTexture*>& cacheTextures,
        const SkGlyph& glyph, uint32_t* startX, uint32_t* startY) {
    for (uint32_t i = 0; i < cacheTextures.size(); i++) {
        if (cacheTextures[i]->fitBitmap(glyph, startX, startY)) {
            return cacheTextures[i];
        }
    }
    // Could not fit glyph into current cache textures
    return NULL;
}

void FontRenderer::cacheBitmap(const SkGlyph& glyph, CachedGlyphInfo* cachedGlyph,
        uint32_t* retOriginX, uint32_t* retOriginY, bool precaching) {
    checkInit();

    // If the glyph bitmap is empty let's assum the glyph is valid
    // so we can avoid doing extra work later on
    if (glyph.fWidth == 0 || glyph.fHeight == 0) {
        cachedGlyph->mIsValid = true;
        cachedGlyph->mCacheTexture = NULL;
        return;
    }

    cachedGlyph->mIsValid = false;

    // choose an appropriate cache texture list for this glyph format
    SkMask::Format format = static_cast<SkMask::Format>(glyph.fMaskFormat);
    Vector<CacheTexture*>* cacheTextures = NULL;
    switch (format) {
        case SkMask::kA8_Format:
        case SkMask::kBW_Format:
            cacheTextures = &mACacheTextures;
            break;
        case SkMask::kARGB32_Format:
            cacheTextures = &mRGBACacheTextures;
            break;
        default:
#if DEBUG_FONT_RENDERER
            ALOGD("getCacheTexturesForFormat: unknown SkMask format %x", format);
#endif
        return;
    }

    // If the glyph is too tall, don't cache it
    if (glyph.fHeight + TEXTURE_BORDER_SIZE * 2 >
                (*cacheTextures)[cacheTextures->size() - 1]->getHeight()) {
        ALOGE("Font size too large to fit in cache. width, height = %i, %i",
                (int) glyph.fWidth, (int) glyph.fHeight);
        return;
    }

    // Now copy the bitmap into the cache texture
    uint32_t startX = 0;
    uint32_t startY = 0;

    CacheTexture* cacheTexture = cacheBitmapInTexture(*cacheTextures, glyph, &startX, &startY);

    if (!cacheTexture) {
        if (!precaching) {
            // If the new glyph didn't fit and we are not just trying to precache it,
            // clear out the cache and try again
            flushAllAndInvalidate();
            cacheTexture = cacheBitmapInTexture(*cacheTextures, glyph, &startX, &startY);
        }

        if (!cacheTexture) {
            // either the glyph didn't fit or we're precaching and will cache it when we draw
            return;
        }
    }

    cachedGlyph->mCacheTexture = cacheTexture;

    *retOriginX = startX;
    *retOriginY = startY;

    uint32_t endX = startX + glyph.fWidth;
    uint32_t endY = startY + glyph.fHeight;

    uint32_t cacheWidth = cacheTexture->getWidth();

    if (!cacheTexture->getPixelBuffer()) {
        Caches::getInstance().activeTexture(0);
        // Large-glyph texture memory is allocated only as needed
        cacheTexture->allocateTexture();
    }
    if (!cacheTexture->mesh()) {
        cacheTexture->allocateMesh();
    }

    uint8_t* cacheBuffer = cacheTexture->getPixelBuffer()->map();
    uint8_t* bitmapBuffer = (uint8_t*) glyph.fImage;
    int srcStride = glyph.rowBytes();

    // Copy the glyph image, taking the mask format into account
    switch (format) {
        case SkMask::kA8_Format: {
            uint32_t cacheX = 0, bX = 0, cacheY = 0, bY = 0;
            uint32_t row = (startY - TEXTURE_BORDER_SIZE) * cacheWidth + startX
                    - TEXTURE_BORDER_SIZE;
            // write leading border line
            memset(&cacheBuffer[row], 0, glyph.fWidth + 2 * TEXTURE_BORDER_SIZE);
            // write glyph data
            if (mGammaTable) {
                for (cacheY = startY, bY = 0; cacheY < endY; cacheY++, bY += srcStride) {
                    row = cacheY * cacheWidth;
                    cacheBuffer[row + startX - TEXTURE_BORDER_SIZE] = 0;
                    for (cacheX = startX, bX = 0; cacheX < endX; cacheX++, bX++) {
                        uint8_t tempCol = bitmapBuffer[bY + bX];
                        cacheBuffer[row + cacheX] = mGammaTable[tempCol];
                    }
                    cacheBuffer[row + endX + TEXTURE_BORDER_SIZE - 1] = 0;
                }
            } else {
                for (cacheY = startY, bY = 0; cacheY < endY; cacheY++, bY += srcStride) {
                    row = cacheY * cacheWidth;
                    memcpy(&cacheBuffer[row + startX], &bitmapBuffer[bY], glyph.fWidth);
                    cacheBuffer[row + startX - TEXTURE_BORDER_SIZE] = 0;
                    cacheBuffer[row + endX + TEXTURE_BORDER_SIZE - 1] = 0;
                }
            }
            // write trailing border line
            row = (endY + TEXTURE_BORDER_SIZE - 1) * cacheWidth + startX - TEXTURE_BORDER_SIZE;
            memset(&cacheBuffer[row], 0, glyph.fWidth + 2 * TEXTURE_BORDER_SIZE);
            break;
        }
        case SkMask::kARGB32_Format: {
            // prep data lengths
            const size_t formatSize = PixelBuffer::formatSize(GL_RGBA);
            const size_t borderSize = formatSize * TEXTURE_BORDER_SIZE;
            size_t rowSize = formatSize * glyph.fWidth;
            // prep advances
            size_t dstStride = formatSize * cacheWidth;
            // prep indices
            // - we actually start one row early, and then increment before first copy
            uint8_t* src = &bitmapBuffer[0 - srcStride];
            uint8_t* dst = &cacheBuffer[cacheTexture->getOffset(startX, startY - 1)];
            uint8_t* dstEnd = &cacheBuffer[cacheTexture->getOffset(startX, endY - 1)];
            uint8_t* dstL = dst - borderSize;
            uint8_t* dstR = dst + rowSize;
            // write leading border line
            memset(dstL, 0, rowSize + 2 * borderSize);
            // write glyph data
            while (dst < dstEnd) {
                memset(dstL += dstStride, 0, borderSize); // leading border column
                memcpy(dst += dstStride, src += srcStride, rowSize); // glyph data
                memset(dstR += dstStride, 0, borderSize); // trailing border column
            }
            // write trailing border line
            memset(dstL += dstStride, 0, rowSize + 2 * borderSize);
            break;
        }
        case SkMask::kBW_Format: {
            uint32_t cacheX = 0, bX = 0, cacheY = 0, bY = 0;
            uint32_t row = (startY - TEXTURE_BORDER_SIZE) * cacheWidth + startX
                    - TEXTURE_BORDER_SIZE;
            static const uint8_t COLORS[2] = { 0, 255 };
            // write leading border line
            memset(&cacheBuffer[row], 0, glyph.fWidth + 2 * TEXTURE_BORDER_SIZE);
            // write glyph data
            for (cacheY = startY; cacheY < endY; cacheY++) {
                cacheX = startX;
                int rowBytes = srcStride;
                uint8_t* buffer = bitmapBuffer;

                row = cacheY * cacheWidth;
                cacheBuffer[row + startX - TEXTURE_BORDER_SIZE] = 0;
                while (--rowBytes >= 0) {
                    uint8_t b = *buffer++;
                    for (int8_t mask = 7; mask >= 0 && cacheX < endX; mask--) {
                        cacheBuffer[cacheY * cacheWidth + cacheX++] = COLORS[(b >> mask) & 0x1];
                    }
                }
                cacheBuffer[row + endX + TEXTURE_BORDER_SIZE - 1] = 0;

                bitmapBuffer += srcStride;
            }
            // write trailing border line
            row = (endY + TEXTURE_BORDER_SIZE - 1) * cacheWidth + startX - TEXTURE_BORDER_SIZE;
            memset(&cacheBuffer[row], 0, glyph.fWidth + 2 * TEXTURE_BORDER_SIZE);
            break;
        }
        default:
            ALOGW("Unknown glyph format: 0x%x", format);
            break;
    }

    cachedGlyph->mIsValid = true;
}

CacheTexture* FontRenderer::createCacheTexture(int width, int height, GLenum format,
        bool allocate) {
    CacheTexture* cacheTexture = new CacheTexture(width, height, format, gMaxNumberOfQuads);

    if (allocate) {
        Caches::getInstance().activeTexture(0);
        cacheTexture->allocateTexture();
        cacheTexture->allocateMesh();
    }

    return cacheTexture;
}

void FontRenderer::initTextTexture() {
    clearCacheTextures(mACacheTextures);
    clearCacheTextures(mRGBACacheTextures);

    mUploadTexture = false;
    mACacheTextures.push(createCacheTexture(mSmallCacheWidth, mSmallCacheHeight,
            GL_ALPHA, true));
    mACacheTextures.push(createCacheTexture(mLargeCacheWidth, mLargeCacheHeight >> 1,
            GL_ALPHA, false));
    mACacheTextures.push(createCacheTexture(mLargeCacheWidth, mLargeCacheHeight >> 1,
            GL_ALPHA, false));
    mACacheTextures.push(createCacheTexture(mLargeCacheWidth, mLargeCacheHeight,
            GL_ALPHA, false));
    mRGBACacheTextures.push(createCacheTexture(mSmallCacheWidth, mSmallCacheHeight,
            GL_RGBA, false));
    mRGBACacheTextures.push(createCacheTexture(mLargeCacheWidth, mLargeCacheHeight >> 1,
            GL_RGBA, false));
    mCurrentCacheTexture = mACacheTextures[0];
}

// We don't want to allocate anything unless we actually draw text
void FontRenderer::checkInit() {
    if (mInitialized) {
        return;
    }

    initTextTexture();

    mInitialized = true;
}

void checkTextureUpdateForCache(Caches& caches, Vector<CacheTexture*>& cacheTextures,
        bool& resetPixelStore, GLuint& lastTextureId) {
    for (uint32_t i = 0; i < cacheTextures.size(); i++) {
        CacheTexture* cacheTexture = cacheTextures[i];
        if (cacheTexture->isDirty() && cacheTexture->getPixelBuffer()) {
            if (cacheTexture->getTextureId() != lastTextureId) {
                lastTextureId = cacheTexture->getTextureId();
                caches.activeTexture(0);
                caches.bindTexture(lastTextureId);
            }

            if (cacheTexture->upload()) {
                resetPixelStore = true;
            }
        }
    }
}

void FontRenderer::checkTextureUpdate() {
    if (!mUploadTexture) {
        return;
    }

    Caches& caches = Caches::getInstance();
    GLuint lastTextureId = 0;

    bool resetPixelStore = false;
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

    // Iterate over all the cache textures and see which ones need to be updated
    checkTextureUpdateForCache(caches, mACacheTextures, resetPixelStore, lastTextureId);
    checkTextureUpdateForCache(caches, mRGBACacheTextures, resetPixelStore, lastTextureId);

    // Unbind any PBO we might have used to update textures
    caches.unbindPixelBuffer();

    // Reset to default unpack row length to avoid affecting texture
    // uploads in other parts of the renderer
    if (resetPixelStore) {
        glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
    }

    mUploadTexture = false;
}

void FontRenderer::issueDrawCommand(Vector<CacheTexture*>& cacheTextures) {
    Caches& caches = Caches::getInstance();
    bool first = true;
    bool force = false;
    for (uint32_t i = 0; i < cacheTextures.size(); i++) {
        CacheTexture* texture = cacheTextures[i];
        if (texture->canDraw()) {
            if (first) {
                if (mFunctor) {
                    TextSetupFunctor::Data functorData(texture->getFormat());
                    (*mFunctor)(0, &functorData);
                }

                checkTextureUpdate();
                caches.bindIndicesBuffer();

                if (!mDrawn) {
                    // If returns true, a VBO was bound and we must
                    // rebind our vertex attrib pointers even if
                    // they have the same values as the current pointers
                    force = caches.unbindMeshBuffer();
                }

                caches.activeTexture(0);
                first = false;
            }

            caches.bindTexture(texture->getTextureId());
            texture->setLinearFiltering(mLinearFiltering, false);

            TextureVertex* mesh = texture->mesh();
            caches.bindPositionVertexPointer(force, &mesh[0].position[0]);
            caches.bindTexCoordsVertexPointer(force, &mesh[0].texture[0]);
            force = false;

            glDrawElements(GL_TRIANGLES, texture->meshElementCount(),
                    GL_UNSIGNED_SHORT, texture->indices());

            texture->resetMesh();
        }
    }
}

void FontRenderer::issueDrawCommand() {
    issueDrawCommand(mACacheTextures);
    issueDrawCommand(mRGBACacheTextures);

    mDrawn = true;
}

void FontRenderer::appendMeshQuadNoClip(float x1, float y1, float u1, float v1,
        float x2, float y2, float u2, float v2, float x3, float y3, float u3, float v3,
        float x4, float y4, float u4, float v4, CacheTexture* texture) {
    if (texture != mCurrentCacheTexture) {
        // Now use the new texture id
        mCurrentCacheTexture = texture;
    }

    mCurrentCacheTexture->addQuad(x1, y1, u1, v1, x2, y2, u2, v2,
            x3, y3, u3, v3, x4, y4, u4, v4);
}

void FontRenderer::appendMeshQuad(float x1, float y1, float u1, float v1,
        float x2, float y2, float u2, float v2, float x3, float y3, float u3, float v3,
        float x4, float y4, float u4, float v4, CacheTexture* texture) {

    if (mClip &&
            (x1 > mClip->right || y1 < mClip->top || x2 < mClip->left || y4 > mClip->bottom)) {
        return;
    }

    appendMeshQuadNoClip(x1, y1, u1, v1, x2, y2, u2, v2, x3, y3, u3, v3, x4, y4, u4, v4, texture);

    if (mBounds) {
        mBounds->left = fmin(mBounds->left, x1);
        mBounds->top = fmin(mBounds->top, y3);
        mBounds->right = fmax(mBounds->right, x3);
        mBounds->bottom = fmax(mBounds->bottom, y1);
    }

    if (mCurrentCacheTexture->endOfMesh()) {
        issueDrawCommand();
    }
}

void FontRenderer::appendRotatedMeshQuad(float x1, float y1, float u1, float v1,
        float x2, float y2, float u2, float v2, float x3, float y3, float u3, float v3,
        float x4, float y4, float u4, float v4, CacheTexture* texture) {

    appendMeshQuadNoClip(x1, y1, u1, v1, x2, y2, u2, v2, x3, y3, u3, v3, x4, y4, u4, v4, texture);

    if (mBounds) {
        mBounds->left = fmin(mBounds->left, fmin(x1, fmin(x2, fmin(x3, x4))));
        mBounds->top = fmin(mBounds->top, fmin(y1, fmin(y2, fmin(y3, y4))));
        mBounds->right = fmax(mBounds->right, fmax(x1, fmax(x2, fmax(x3, x4))));
        mBounds->bottom = fmax(mBounds->bottom, fmax(y1, fmax(y2, fmax(y3, y4))));
    }

    if (mCurrentCacheTexture->endOfMesh()) {
        issueDrawCommand();
    }
}

void FontRenderer::setFont(SkPaint* paint, const mat4& matrix) {
    mCurrentFont = Font::create(this, paint, matrix);
}

FontRenderer::DropShadow FontRenderer::renderDropShadow(SkPaint* paint, const char *text,
        uint32_t startIndex, uint32_t len, int numGlyphs, uint32_t radius, const float* positions) {
    checkInit();

    DropShadow image;
    image.width = 0;
    image.height = 0;
    image.image = NULL;
    image.penX = 0;
    image.penY = 0;

    if (!mCurrentFont) {
        return image;
    }

    mDrawn = false;
    mClip = NULL;
    mBounds = NULL;

    Rect bounds;
    mCurrentFont->measure(paint, text, startIndex, len, numGlyphs, &bounds, positions);

    uint32_t paddedWidth = (uint32_t) (bounds.right - bounds.left) + 2 * radius;
    uint32_t paddedHeight = (uint32_t) (bounds.top - bounds.bottom) + 2 * radius;

    uint32_t maxSize = Caches::getInstance().maxTextureSize;
    if (paddedWidth > maxSize || paddedHeight > maxSize) {
        return image;
    }

#ifdef ANDROID_ENABLE_RENDERSCRIPT
    // Align buffers for renderscript usage
    if (paddedWidth & (RS_CPU_ALLOCATION_ALIGNMENT - 1)) {
        paddedWidth += RS_CPU_ALLOCATION_ALIGNMENT - paddedWidth % RS_CPU_ALLOCATION_ALIGNMENT;
    }
    int size = paddedWidth * paddedHeight;
    uint8_t* dataBuffer = (uint8_t*) memalign(RS_CPU_ALLOCATION_ALIGNMENT, size);
#else
    int size = paddedWidth * paddedHeight;
    uint8_t* dataBuffer = (uint8_t*) malloc(size);
#endif

    memset(dataBuffer, 0, size);

    int penX = radius - bounds.left;
    int penY = radius - bounds.bottom;

    if ((bounds.right > bounds.left) && (bounds.top > bounds.bottom)) {
        // text has non-whitespace, so draw and blur to create the shadow
        // NOTE: bounds.isEmpty() can't be used here, since vertical coordinates are inverted
        // TODO: don't draw pure whitespace in the first place, and avoid needing this check
        mCurrentFont->render(paint, text, startIndex, len, numGlyphs, penX, penY,
                Font::BITMAP, dataBuffer, paddedWidth, paddedHeight, NULL, positions);

        // Unbind any PBO we might have used
        Caches::getInstance().unbindPixelBuffer();

        blurImage(&dataBuffer, paddedWidth, paddedHeight, radius);
    }

    image.width = paddedWidth;
    image.height = paddedHeight;
    image.image = dataBuffer;
    image.penX = penX;
    image.penY = penY;

    return image;
}

void FontRenderer::initRender(const Rect* clip, Rect* bounds, Functor* functor) {
    checkInit();

    mDrawn = false;
    mBounds = bounds;
    mFunctor = functor;
    mClip = clip;
}

void FontRenderer::finishRender() {
    mBounds = NULL;
    mClip = NULL;

    issueDrawCommand();
}

void FontRenderer::precache(SkPaint* paint, const char* text, int numGlyphs, const mat4& matrix) {
    Font* font = Font::create(this, paint, matrix);
    font->precache(paint, text, numGlyphs);
}

void FontRenderer::endPrecaching() {
    checkTextureUpdate();
}

bool FontRenderer::renderPosText(SkPaint* paint, const Rect* clip, const char *text,
        uint32_t startIndex, uint32_t len, int numGlyphs, int x, int y,
        const float* positions, Rect* bounds, Functor* functor, bool forceFinish) {
    if (!mCurrentFont) {
        ALOGE("No font set");
        return false;
    }

    initRender(clip, bounds, functor);
    mCurrentFont->render(paint, text, startIndex, len, numGlyphs, x, y, positions);

    if (forceFinish) {
        finishRender();
    }

    return mDrawn;
}

bool FontRenderer::renderTextOnPath(SkPaint* paint, const Rect* clip, const char *text,
        uint32_t startIndex, uint32_t len, int numGlyphs, SkPath* path,
        float hOffset, float vOffset, Rect* bounds, Functor* functor) {
    if (!mCurrentFont) {
        ALOGE("No font set");
        return false;
    }

    initRender(clip, bounds, functor);
    mCurrentFont->render(paint, text, startIndex, len, numGlyphs, path, hOffset, vOffset);
    finishRender();

    return mDrawn;
}

void FontRenderer::removeFont(const Font* font) {
    mActiveFonts.remove(font->getDescription());

    if (mCurrentFont == font) {
        mCurrentFont = NULL;
    }
}

void FontRenderer::blurImage(uint8_t** image, int32_t width, int32_t height, int32_t radius) {
#ifdef ANDROID_ENABLE_RENDERSCRIPT
    if (width * height * radius >= RS_MIN_INPUT_CUTOFF) {
        uint8_t* outImage = (uint8_t*) memalign(RS_CPU_ALLOCATION_ALIGNMENT, width * height);

        if (mRs == 0) {
            mRs = new RSC::RS();
            // a null path is OK because there are no custom kernels used
            // hence nothing gets cached by RS
            if (!mRs->init("", RSC::RS_INIT_LOW_LATENCY | RSC::RS_INIT_SYNCHRONOUS)) {
                ALOGE("blur RS failed to init");
            }

            mRsElement = RSC::Element::A_8(mRs);
            mRsScript = RSC::ScriptIntrinsicBlur::create(mRs, mRsElement);
        }

        RSC::sp<const RSC::Type> t = RSC::Type::create(mRs, mRsElement, width, height, 0);
        RSC::sp<RSC::Allocation> ain = RSC::Allocation::createTyped(mRs, t,
                RS_ALLOCATION_MIPMAP_NONE, RS_ALLOCATION_USAGE_SCRIPT | RS_ALLOCATION_USAGE_SHARED,
                *image);
        RSC::sp<RSC::Allocation> aout = RSC::Allocation::createTyped(mRs, t,
                RS_ALLOCATION_MIPMAP_NONE, RS_ALLOCATION_USAGE_SCRIPT | RS_ALLOCATION_USAGE_SHARED,
                outImage);

        mRsScript->setRadius(radius);
        mRsScript->setInput(ain);
        mRsScript->forEach(aout);

        // replace the original image's pointer, avoiding a copy back to the original buffer
        free(*image);
        *image = outImage;

        return;
    }
#endif

    float *gaussian = new float[2 * radius + 1];
    Blur::generateGaussianWeights(gaussian, radius);

    uint8_t* scratch = new uint8_t[width * height];
    Blur::horizontal(gaussian, radius, *image, scratch, width, height);
    Blur::vertical(gaussian, radius, scratch, *image, width, height);

    delete[] gaussian;
    delete[] scratch;
}

static uint32_t calculateCacheSize(const Vector<CacheTexture*>& cacheTextures) {
    uint32_t size = 0;
    for (uint32_t i = 0; i < cacheTextures.size(); i++) {
        CacheTexture* cacheTexture = cacheTextures[i];
        if (cacheTexture && cacheTexture->getPixelBuffer()) {
            size += cacheTexture->getPixelBuffer()->getSize();
        }
    }
    return size;
}

uint32_t FontRenderer::getCacheSize(GLenum format) const {
    switch (format) {
        case GL_ALPHA: {
            return calculateCacheSize(mACacheTextures);
        }
        case GL_RGBA: {
            return calculateCacheSize(mRGBACacheTextures);
        }
        default: {
            return 0;
        }
    }
}

}; // namespace uirenderer
}; // namespace android