fontchromiumwin.cpp

linux下开源浏览器WebKit的源码,市面上的很多商用浏览器都是移植自WebKit

/*
 * Copyright (C) 2006, 2007 Apple Computer, Inc.
 * Copyright (c) 2006, 2007, 2008, 2009, Google Inc. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * 
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"
#include "Font.h"

#include "ChromiumBridge.h"
#include "FontFallbackList.h"
#include "GlyphBuffer.h"
#include "PlatformContextSkia.h"
#include "SimpleFontData.h"
#include "SkiaFontWin.h"
#include "SkiaUtils.h"
#include "TransparencyWin.h"
#include "UniscribeHelperTextRun.h"

#include "skia/ext/platform_canvas_win.h"
#include "skia/ext/skia_utils_win.h"  // FIXME: remove this dependency.

#include <windows.h>

namespace WebCore {

namespace {

bool canvasHasMultipleLayers(const SkCanvas* canvas)
{
    SkCanvas::LayerIter iter(const_cast<SkCanvas*>(canvas), false);
    iter.next();  // There is always at least one layer.
    return !iter.done();  // There is > 1 layer if the the iterator can stil advance.
}

// Estimates the bounding box of the given text. This is copied from
// FontCGWin.cpp, it is possible, but a lot more work, to get the precide
// bounds.
IntRect estimateTextBounds(const SimpleFontData* font,
                           const GlyphBuffer& glyphBuffer,
                           int from, int numGlyphs,
                           const FloatPoint& point)
{
    int totalWidth = 0;
    for (int i = 0; i < numGlyphs; i++)
        totalWidth += lroundf(glyphBuffer.advanceAt(from + i));

    return IntRect(point.x() - (font->ascent() + font->descent()) / 2,
                   point.y() - font->ascent() - font->lineGap(),
                   totalWidth + font->ascent() + font->descent(),
                   font->lineSpacing()); 
}

class TransparencyAwareFontPainter {
public:
    TransparencyAwareFontPainter(GraphicsContext* context,
                                 const SimpleFontData* font,
                                 const GlyphBuffer& glyphBuffer,
                                 int from, int numGlyphs,
                                 const FloatPoint& point);
    TransparencyAwareFontPainter(GraphicsContext* context,
                                 const SimpleFontData* font);
    ~TransparencyAwareFontPainter();

    // Draws the partial string of glyphs, starting at |startAdvance| to the
    // left of m_point. We express it this way so that if we're using the Skia
    // drawing path we can use floating-point positioning, even though we have
    // to use integer positioning in the GDI path.
    bool drawGlyphs(int numGlyphs, const WORD* glyphs, const int* advances,
                    int startAdvance) const;

private:
    // Call when we're using GDI mode to initialize the TransparencyWin to help
    // us draw GDI text.
    void initializeForGDI(const GlyphBuffer& glyphBuffer, int from, int numGlyphs);

    // Use the context from the transparency helper when drawing with GDI. It
    // may point to a temporary one.
    GraphicsContext* m_graphicsContext;
    PlatformGraphicsContext* m_platformContext;

    const SimpleFontData* m_font;
    FloatPoint m_point;

    // Set when Windows can handle the type of drawing we're doing.
    bool m_useGDI;

    // These members are valid only when m_useGDI is set.
    HDC m_hdc;
    HGDIOBJ m_oldFont;  // For restoring the DC to its original state.
    TransparencyWin m_transparency;
    bool m_createdTransparencyLayer;  // We created a layer to give the font some alpha.
};

TransparencyAwareFontPainter::TransparencyAwareFontPainter(
    GraphicsContext* context,
    const SimpleFontData* font,
    const GlyphBuffer& glyphBuffer,
    int from, int numGlyphs,
    const FloatPoint& point)
    : m_graphicsContext(context)
    , m_platformContext(context->platformContext())
    , m_font(font)
    , m_point(point)
    , m_useGDI(windowsCanHandleTextDrawing(context))
    , m_hdc(0)
    , m_oldFont(0)
    , m_createdTransparencyLayer(false)
{
    if (m_useGDI)
        initializeForGDI(glyphBuffer, from, numGlyphs);
}

void TransparencyAwareFontPainter::initializeForGDI(const GlyphBuffer& glyphBuffer,
                                                    int from, int numGlyphs)
{
    SkColor color = m_platformContext->effectiveFillColor();
    if (SkColorGetA(color) != 0xFF) {
        // When the font has some transparency, apply it by creating a new
        // transparency layer with that opacity applied.
        m_createdTransparencyLayer = true;
        m_graphicsContext->beginTransparencyLayer(SkColorGetA(color) / 255.0f);
        // The color should be opaque now.
        color = SkColorSetRGB(SkColorGetR(color), SkColorGetG(color), SkColorGetB(color));
    }

    TransparencyWin::LayerMode layerMode;
    IntRect layerRect;
    if (m_platformContext->isDrawingToImageBuffer()) {
        // Assume if we're drawing to an image buffer that the background
        // is not opaque and we have to undo ClearType. We may want to
        // enhance this to actually check, since it will often be opaque
        // and we could do ClearType in that case.
        layerMode = TransparencyWin::TextComposite;
        layerRect = estimateTextBounds(m_font, glyphBuffer, from, numGlyphs, m_point);

        // The transparency helper requires that we draw text in black in
        // this mode and it will apply the color.
        m_transparency.setTextCompositeColor(color);
        color = SkColorSetRGB(0, 0, 0);
    } else if (canvasHasMultipleLayers(m_platformContext->canvas())) {
        // When we're drawing a web page, we know the background is opaque,
        // but if we're drawing to a layer, we still need extra work.
        layerMode = TransparencyWin::OpaqueCompositeLayer;
        layerRect = estimateTextBounds(m_font, glyphBuffer, from, numGlyphs, m_point);
    } else {
        // Common case of drawing onto the bottom layer of a web page: we
        // know everything is opaque so don't need to do anything special.
        layerMode = TransparencyWin::NoLayer;
    }
    m_transparency.init(m_graphicsContext, layerMode, TransparencyWin::KeepTransform, layerRect);

    // Set up the DC, using the one from the transparency helper.
    m_hdc = m_transparency.platformContext()->canvas()->beginPlatformPaint();
    m_oldFont = ::SelectObject(m_hdc, m_font->platformData().hfont());
    SetTextColor(m_hdc, skia::SkColorToCOLORREF(color));
    SetBkMode(m_hdc, TRANSPARENT);
}

TransparencyAwareFontPainter::~TransparencyAwareFontPainter()
{
    if (!m_useGDI)
        return;  // Nothing to do.
    if (m_createdTransparencyLayer)
        m_graphicsContext->endTransparencyLayer();

    ::SelectObject(m_hdc, m_oldFont);
    m_platformContext->canvas()->endPlatformPaint();
}

bool TransparencyAwareFontPainter::drawGlyphs(int numGlyphs,
                                              const WORD* glyphs,
                                              const int* advances,
                                              int startAdvance) const
{
    if (!m_useGDI) {
        SkPoint origin = m_point;
        origin.fX += startAdvance;
        return paintSkiaText(m_graphicsContext, m_font->platformData().hfont(),
                             numGlyphs, glyphs, advances, 0, &origin);
    }

    // Windows' origin is the top-left of the bounding box, so we have
    // to subtract off the font ascent to get it.
    int x = lroundf(m_point.x() + startAdvance);
    int y = lroundf(m_point.y() - m_font->ascent());
    return !!ExtTextOut(m_hdc, x, y, ETO_GLYPH_INDEX, 0, reinterpret_cast<const wchar_t*>(&glyphs[0]), numGlyphs, &advances[0]);
}

}  // namespace

void Font::drawGlyphs(GraphicsContext* graphicsContext,
                      const SimpleFontData* font,
                      const GlyphBuffer& glyphBuffer,
                      int from,
                      int numGlyphs,
                      const FloatPoint& point) const
{
    SkColor color = graphicsContext->platformContext()->effectiveFillColor();
    unsigned char alpha = SkColorGetA(color);
    // Skip 100% transparent text; no need to draw anything.
    if (!alpha && graphicsContext->platformContext()->getStrokeStyle() == NoStroke)
        return;

    TransparencyAwareFontPainter painter(graphicsContext, font, glyphBuffer, from, numGlyphs, point);

    // We draw the glyphs in chunks to avoid having to do a heap allocation for
    // the arrays of characters and advances. Since ExtTextOut is the
    // lowest-level text output function on Windows, there should be little
    // penalty for splitting up the text. On the other hand, the buffer cannot
    // be bigger than 4094 or the function will fail.
    const int kMaxBufferLength = 256;
    Vector<WORD, kMaxBufferLength> glyphs;
    Vector<int, kMaxBufferLength> advances;
    int glyphIndex = 0;  // The starting glyph of the current chunk.
    int curAdvance = 0;  // How far from the left the current chunk is.
    while (glyphIndex < numGlyphs) {
        // How many chars will be in this chunk?
        int curLen = std::min(kMaxBufferLength, numGlyphs - glyphIndex);
        glyphs.resize(curLen);
        advances.resize(curLen);

        int curWidth = 0;
        for (int i = 0; i < curLen; ++i, ++glyphIndex) {
            glyphs[i] = glyphBuffer.glyphAt(from + glyphIndex);
            advances[i] = static_cast<int>(glyphBuffer.advanceAt(from + glyphIndex));
            curWidth += advances[i];
        }

        // Actually draw the glyphs (with retry on failure).
        bool success = false;
        for (int executions = 0; executions < 2; ++executions) {
            success = painter.drawGlyphs(curLen, &glyphs[0], &advances[0], curAdvance);
            if (!success && executions == 0) {
                // Ask the browser to load the font for us and retry.
                ChromiumBridge::ensureFontLoaded(font->platformData().hfont());
                continue;
            }
            break;
        }

        ASSERT(success);
        curAdvance += curWidth;
    }
}

FloatRect Font::selectionRectForComplexText(const TextRun& run,
                                            const IntPoint& point,
                                            int h,
                                            int from,
                                            int to) const
{
    UniscribeHelperTextRun state(run, *this);
    float left = static_cast<float>(point.x() + state.characterToX(from));
    float right = static_cast<float>(point.x() + state.characterToX(to));

    // If the text is RTL, left will actually be after right.
    if (left < right)
        return FloatRect(left, static_cast<float>(point.y()),
                       right - left, static_cast<float>(h));

    return FloatRect(right, static_cast<float>(point.y()),
                     left - right, static_cast<float>(h));
}

void Font::drawComplexText(GraphicsContext* graphicsContext,
                           const TextRun& run,
                           const FloatPoint& point,
                           int from,
                           int to) const
{
    PlatformGraphicsContext* context = graphicsContext->platformContext();
    UniscribeHelperTextRun state(run, *this);

    SkColor color = context->effectiveFillColor();
    unsigned char alpha = SkColorGetA(color);
    // Skip 100% transparent text; no need to draw anything.
    if (!alpha)
        return;

    HDC hdc = context->canvas()->beginPlatformPaint();

    // TODO(maruel): http://b/700464 SetTextColor doesn't support transparency.
    // Enforce non-transparent color.
    color = SkColorSetRGB(SkColorGetR(color), SkColorGetG(color), SkColorGetB(color));
    SetTextColor(hdc, skia::SkColorToCOLORREF(color));
    SetBkMode(hdc, TRANSPARENT);

    // Uniscribe counts the coordinates from the upper left, while WebKit uses
    // the baseline, so we have to subtract off the ascent.
    state.draw(graphicsContext, hdc, static_cast<int>(point.x()),
               static_cast<int>(point.y() - ascent()), from, to);

    context->canvas()->endPlatformPaint();
}

float Font::floatWidthForComplexText(const TextRun& run) const
{
    UniscribeHelperTextRun state(run, *this);
    return static_cast<float>(state.width());
}

int Font::offsetForPositionForComplexText(const TextRun& run, int x,
                                          bool includePartialGlyphs) const
{
    // Mac code ignores includePartialGlyphs, and they don't know what it's
    // supposed to do, so we just ignore it as well.
    UniscribeHelperTextRun state(run, *this);
    int charIndex = state.xToCharacter(x);

    // XToCharacter will return -1 if the position is before the first
    // character (we get called like this sometimes).
    if (charIndex < 0)
        charIndex = 0;
    return charIndex;
}

} // namespace WebCore