src/gpu/GrTextContext.cpp

/*
 * Copyright 2010 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "GrTextContext.h"
#include "GrContext.h"

#include "SkAutoKern.h"
#include "SkGlyphCache.h"
#include "GrFontScaler.h"

GrTextContext::GrTextContext(GrContext* context, const SkDeviceProperties& properties) :
                            fFallbackTextContext(NULL),
                            fContext(context), fDeviceProperties(properties), fDrawTarget(NULL) {
}

GrTextContext::~GrTextContext() {
    SkDELETE(fFallbackTextContext);
}

void GrTextContext::init(const GrPaint& grPaint, const SkPaint& skPaint) {
    const GrClipData* clipData = fContext->getClip();

    SkRect devConservativeBound;
    clipData->fClipStack->getConservativeBounds(
                                     -clipData->fOrigin.fX,
                                     -clipData->fOrigin.fY,
                                     fContext->getRenderTarget()->width(),
                                     fContext->getRenderTarget()->height(),
                                     &devConservativeBound);

    devConservativeBound.roundOut(&fClipRect);

    fDrawTarget = fContext->getTextTarget();

    fPaint = grPaint;
    fSkPaint = skPaint;
}

bool GrTextContext::drawText(const GrPaint& paint, const SkPaint& skPaint,
                             const char text[], size_t byteLength,
                             SkScalar x, SkScalar y) {

    SkASSERT(byteLength == 0 || text != NULL);

    // nothing to draw
    if (text == NULL || byteLength == 0) {
        return true;
    }

    SkDrawCacheProc          glyphCacheProc = skPaint.getDrawCacheProc();
    SkAutoGlyphCache         autoCache(skPaint, &fDeviceProperties, NULL);
    SkGlyphCache*            cache = autoCache.getCache();

    SkTArray<SkScalar> positions;

    const char* textPtr = text;
    SkFixed stopX = 0;
    SkFixed stopY = 0;
    SkFixed origin;
    switch (skPaint.getTextAlign()) {
        case SkPaint::kRight_Align: origin = SK_Fixed1; break;
        case SkPaint::kCenter_Align: origin = SK_FixedHalf; break;
        case SkPaint::kLeft_Align: origin = 0; break;
        default: SkFAIL("Invalid paint origin"); return false;
    }

    SkAutoKern autokern;
    const char* stop = text + byteLength;
    while (textPtr < stop) {
        // don't need x, y here, since all subpixel variants will have the
        // same advance
        const SkGlyph& glyph = glyphCacheProc(cache, &textPtr, 0, 0);

        SkFixed width = glyph.fAdvanceX + autokern.adjust(glyph);
        positions.push_back(SkFixedToScalar(stopX + SkFixedMul_portable(origin, width)));

        SkFixed height = glyph.fAdvanceY;
        positions.push_back(SkFixedToScalar(stopY + SkFixedMul_portable(origin, height)));

        stopX += width;
        stopY += height;
    }
    SkASSERT(textPtr == stop);

    // now adjust starting point depending on alignment
    SkScalar alignX = SkFixedToScalar(stopX);
    SkScalar alignY = SkFixedToScalar(stopY);
    if (skPaint.getTextAlign() == SkPaint::kCenter_Align) {
        alignX = SkScalarHalf(alignX);
        alignY = SkScalarHalf(alignY);
    } else if (skPaint.getTextAlign() == SkPaint::kLeft_Align) {
        alignX = 0;
        alignY = 0;
    }
    x -= alignX;
    y -= alignY;
    SkPoint offset = SkPoint::Make(x, y);

    return this->drawPosText(paint, skPaint, text, byteLength, positions.begin(), 2, offset);
}

bool GrTextContext::drawPosText(const GrPaint& paint, const SkPaint& skPaint,
                                const char text[], size_t byteLength,
                                const SkScalar pos[], int scalarsPerPosition,
                                const SkPoint& offset) {

    GrTextContext* textContext = this;
    do {
        if (textContext->canDraw(skPaint)) {
            textContext->onDrawPosText(paint, skPaint, text, byteLength, pos, scalarsPerPosition,
                                     offset);
            return true;
        }
        textContext = textContext->fFallbackTextContext;
    } while (textContext);

    return false;
}


//*** change to output positions?
void GrTextContext::MeasureText(SkGlyphCache* cache, SkDrawCacheProc glyphCacheProc,
                                const char text[], size_t byteLength, SkVector* stopVector) {
    SkFixed     x = 0, y = 0;
    const char* stop = text + byteLength;

    SkAutoKern  autokern;

    while (text < stop) {
        // don't need x, y here, since all subpixel variants will have the
        // same advance
        const SkGlyph& glyph = glyphCacheProc(cache, &text, 0, 0);

        x += autokern.adjust(glyph) + glyph.fAdvanceX;
        y += glyph.fAdvanceY;
    }
    stopVector->set(SkFixedToScalar(x), SkFixedToScalar(y));

    SkASSERT(text == stop);
}

static void GlyphCacheAuxProc(void* data) {
    GrFontScaler* scaler = (GrFontScaler*)data;
    SkSafeUnref(scaler);
}

GrFontScaler* GrTextContext::GetGrFontScaler(SkGlyphCache* cache) {
    void* auxData;
    GrFontScaler* scaler = NULL;

    if (cache->getAuxProcData(GlyphCacheAuxProc, &auxData)) {
        scaler = (GrFontScaler*)auxData;
    }
    if (NULL == scaler) {
        scaler = SkNEW_ARGS(GrFontScaler, (cache));
        cache->setAuxProc(GlyphCacheAuxProc, scaler);
    }

    return scaler;
}