graphicscontextcairo.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 Apple Computer, Inc.  All rights reserved.
 * Copyright (C) 2007 Alp Toker <[e-mail]>
 * Copyright (C) 2008 Dirk Schulze <[e-mail]>
 * Copyright (C) 2008 Nuanti Ltd.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"
#include "GraphicsContext.h"

#if PLATFORM(CAIRO)

#include "TransformationMatrix.h"
#include "CairoPath.h"
#include "FloatRect.h"
#include "Font.h"
#include "ImageBuffer.h"
#include "IntRect.h"
#include "NotImplemented.h"
#include "Path.h"
#include "Pattern.h"
#include "SimpleFontData.h"

#include <cairo.h>
#include <math.h>
#include <stdio.h>
#include <wtf/MathExtras.h>

#if PLATFORM(GTK)
#include <gdk/gdk.h>
#include <pango/pango.h>
#elif PLATFORM(WIN)
#include <cairo-win32.h>
#endif
#include "GraphicsContextPrivate.h"
#include "GraphicsContextPlatformPrivateCairo.h"

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

namespace WebCore {

static const unsigned aquaFocusRingColor = 0xFF7DADD9;

Color focusRingColor()
{
    static Color focusRingColor = aquaFocusRingColor;

    return focusRingColor;
}

static inline void setColor(cairo_t* cr, const Color& col)
{
    float red, green, blue, alpha;
    col.getRGBA(red, green, blue, alpha);
    cairo_set_source_rgba(cr, red, green, blue, alpha);
}

// A fillRect helper
static inline void fillRectSourceOver(cairo_t* cr, const FloatRect& rect, const Color& col)
{
    setColor(cr, col);
    cairo_rectangle(cr, rect.x(), rect.y(), rect.width(), rect.height());
    cairo_set_operator(cr, CAIRO_OPERATOR_OVER);
    cairo_fill(cr);
}

GraphicsContext::GraphicsContext(PlatformGraphicsContext* cr)
    : m_common(createGraphicsContextPrivate())
    , m_data(new GraphicsContextPlatformPrivate)
{
    m_data->cr = cairo_reference(cr);
    setPaintingDisabled(!cr);
}

GraphicsContext::~GraphicsContext()
{
    destroyGraphicsContextPrivate(m_common);
    delete m_data;
}

TransformationMatrix GraphicsContext::getCTM() const
{
    cairo_t* cr = platformContext();
    cairo_matrix_t m;
    cairo_get_matrix(cr, &m);
    return TransformationMatrix(m.xx, m.yx, m.xy, m.yy, m.x0, m.y0);
}

cairo_t* GraphicsContext::platformContext() const
{
    return m_data->cr;
}

void GraphicsContext::savePlatformState()
{
    cairo_save(m_data->cr);
    m_data->save();
}

void GraphicsContext::restorePlatformState()
{
    cairo_restore(m_data->cr);
    m_data->restore();
}

// Draws a filled rectangle with a stroked border.
void GraphicsContext::drawRect(const IntRect& rect)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = m_data->cr;
    cairo_save(cr);

    if (fillColor().alpha())
        fillRectSourceOver(cr, rect, fillColor());

    if (strokeStyle() != NoStroke) {
        setColor(cr, strokeColor());
        FloatRect r(rect);
        r.inflate(-.5f);
        cairo_rectangle(cr, r.x(), r.y(), r.width(), r.height());
        cairo_set_line_width(cr, 1.0);
        cairo_stroke(cr);
    }

    cairo_restore(cr);
}

// FIXME: Now that this is refactored, it should be shared by all contexts.
static void adjustLineToPixelBoundaries(FloatPoint& p1, FloatPoint& p2, float strokeWidth, StrokeStyle style)
{
    // For odd widths, we add in 0.5 to the appropriate x/y so that the float arithmetic
    // works out.  For example, with a border width of 3, KHTML will pass us (y1+y2)/2, e.g.,
    // (50+53)/2 = 103/2 = 51 when we want 51.5.  It is always true that an even width gave
    // us a perfect position, but an odd width gave us a position that is off by exactly 0.5.
    if (style == DottedStroke || style == DashedStroke) {
        if (p1.x() == p2.x()) {
            p1.setY(p1.y() + strokeWidth);
            p2.setY(p2.y() - strokeWidth);
        }
        else {
            p1.setX(p1.x() + strokeWidth);
            p2.setX(p2.x() - strokeWidth);
        }
    }

    if (static_cast<int>(strokeWidth) % 2) {
        if (p1.x() == p2.x()) {
            // We're a vertical line.  Adjust our x.
            p1.setX(p1.x() + 0.5);
            p2.setX(p2.x() + 0.5);
        }
        else {
            // We're a horizontal line. Adjust our y.
            p1.setY(p1.y() + 0.5);
            p2.setY(p2.y() + 0.5);
        }
    }
}

// This is only used to draw borders.
void GraphicsContext::drawLine(const IntPoint& point1, const IntPoint& point2)
{
    if (paintingDisabled())
        return;

    StrokeStyle style = strokeStyle();
    if (style == NoStroke)
        return;

    cairo_t* cr = m_data->cr;
    cairo_save(cr);

    float width = strokeThickness();
    if (width < 1)
        width = 1;

    FloatPoint p1 = point1;
    FloatPoint p2 = point2;
    bool isVerticalLine = (p1.x() == p2.x());

    adjustLineToPixelBoundaries(p1, p2, width, style);
    cairo_set_line_width(cr, width);

    int patWidth = 0;
    switch (style) {
    case NoStroke:
    case SolidStroke:
        break;
    case DottedStroke:
        patWidth = static_cast<int>(width);
        break;
    case DashedStroke:
        patWidth = 3*static_cast<int>(width);
        break;
    }

    setColor(cr, strokeColor());

    cairo_set_antialias(cr, CAIRO_ANTIALIAS_NONE);

    if (patWidth) {
        // Do a rect fill of our endpoints.  This ensures we always have the
        // appearance of being a border.  We then draw the actual dotted/dashed line.
        if (isVerticalLine) {
            fillRectSourceOver(cr, FloatRect(p1.x() - width/2, p1.y() - width, width, width), strokeColor());
            fillRectSourceOver(cr, FloatRect(p2.x() - width/2, p2.y(), width, width), strokeColor());
        } else {
            fillRectSourceOver(cr, FloatRect(p1.x() - width, p1.y() - width/2, width, width), strokeColor());
            fillRectSourceOver(cr, FloatRect(p2.x(), p2.y() - width/2, width, width), strokeColor());
        }

        // Example: 80 pixels with a width of 30 pixels.
        // Remainder is 20.  The maximum pixels of line we could paint
        // will be 50 pixels.
        int distance = (isVerticalLine ? (point2.y() - point1.y()) : (point2.x() - point1.x())) - 2*static_cast<int>(width);
        int remainder = distance%patWidth;
        int coverage = distance-remainder;
        int numSegments = coverage/patWidth;

        float patternOffset = 0;
        // Special case 1px dotted borders for speed.
        if (patWidth == 1)
            patternOffset = 1.0;
        else {
            bool evenNumberOfSegments = numSegments%2 == 0;
            if (remainder)
                evenNumberOfSegments = !evenNumberOfSegments;
            if (evenNumberOfSegments) {
                if (remainder) {
                    patternOffset += patWidth - remainder;
                    patternOffset += remainder/2;
                }
                else
                    patternOffset = patWidth/2;
            }
            else if (!evenNumberOfSegments) {
                if (remainder)
                    patternOffset = (patWidth - remainder)/2;
            }
        }

        double dash = patWidth;
        cairo_set_dash(cr, &dash, 1, patternOffset);
    }

    cairo_move_to(cr, p1.x(), p1.y());
    cairo_line_to(cr, p2.x(), p2.y());

    cairo_stroke(cr);
    cairo_restore(cr);
}

// This method is only used to draw the little circles used in lists.
void GraphicsContext::drawEllipse(const IntRect& rect)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = m_data->cr;
    cairo_save(cr);
    float yRadius = .5 * rect.height();
    float xRadius = .5 * rect.width();
    cairo_translate(cr, rect.x() + xRadius, rect.y() + yRadius);
    cairo_scale(cr, xRadius, yRadius);
    cairo_arc(cr, 0., 0., 1., 0., 2 * M_PI);
    cairo_restore(cr);

    if (fillColor().alpha()) {
        setColor(cr, fillColor());
        cairo_fill_preserve(cr);
    }

    if (strokeStyle() != NoStroke) {
        setColor(cr, strokeColor());
        cairo_set_line_width(cr, strokeThickness());
        cairo_stroke(cr);
    }

    cairo_new_path(cr);
}

void GraphicsContext::strokeArc(const IntRect& rect, int startAngle, int angleSpan)
{
    if (paintingDisabled() || strokeStyle() == NoStroke)
        return;

    int x = rect.x();
    int y = rect.y();
    float w = rect.width();
    float h = rect.height();
    float scaleFactor = h / w;
    float reverseScaleFactor = w / h;

    float hRadius = w / 2;
    float vRadius = h / 2;
    float fa = startAngle;
    float falen =  fa + angleSpan;

    cairo_t* cr = m_data->cr;
    cairo_save(cr);

    if (w != h)
        cairo_scale(cr, 1., scaleFactor);
    
    cairo_arc_negative(cr, x + hRadius, (y + vRadius) * reverseScaleFactor, hRadius, -fa * M_PI/180, -falen * M_PI/180);

    if (w != h)
        cairo_scale(cr, 1., reverseScaleFactor);

    float width = strokeThickness();
    int patWidth = 0;
    
    switch (strokeStyle()) {
        case DottedStroke:
            patWidth = static_cast<int>(width / 2);
            break;
        case DashedStroke:
            patWidth = 3 * static_cast<int>(width / 2);
            break;
        default:
            break;
    }

    setColor(cr, strokeColor());

    if (patWidth) {
        // Example: 80 pixels with a width of 30 pixels.
        // Remainder is 20.  The maximum pixels of line we could paint
        // will be 50 pixels.
        int distance;
        if (hRadius == vRadius)
            distance = static_cast<int>((M_PI * hRadius) / 2.0);
        else // We are elliptical and will have to estimate the distance
            distance = static_cast<int>((M_PI * sqrtf((hRadius * hRadius + vRadius * vRadius) / 2.0)) / 2.0);
        
        int remainder = distance % patWidth;
        int coverage = distance - remainder;
        int numSegments = coverage / patWidth;

        float patternOffset = 0.0;
        // Special case 1px dotted borders for speed.
        if (patWidth == 1)
            patternOffset = 1.0;
        else {
            bool evenNumberOfSegments = numSegments % 2 == 0;
            if (remainder)
                evenNumberOfSegments = !evenNumberOfSegments;
            if (evenNumberOfSegments) {
                if (remainder) {
                    patternOffset += patWidth - remainder;
                    patternOffset += remainder / 2.0;
                } else
                    patternOffset = patWidth / 2.0;
            } else {
                if (remainder)
                    patternOffset = (patWidth - remainder) / 2.0;
            }
        }

        double dash = patWidth;
        cairo_set_dash(cr, &dash, 1, patternOffset);
    }

    cairo_stroke(cr);
    cairo_restore(cr);
}

void GraphicsContext::drawConvexPolygon(size_t npoints, const FloatPoint* points, bool shouldAntialias)
{
    if (paintingDisabled())
        return;

    if (npoints <= 1)
        return;

    cairo_t* cr = m_data->cr;

    cairo_save(cr);
    cairo_set_antialias(cr, shouldAntialias ? CAIRO_ANTIALIAS_DEFAULT : CAIRO_ANTIALIAS_NONE);
    cairo_move_to(cr, points[0].x(), points[0].y());
    for (size_t i = 1; i < npoints; i++)
        cairo_line_to(cr, points[i].x(), points[i].y());
    cairo_close_path(cr);

    if (fillColor().alpha()) {
        setColor(cr, fillColor());
        cairo_set_fill_rule(cr, CAIRO_FILL_RULE_EVEN_ODD);
        cairo_fill_preserve(cr);
    }

    if (strokeStyle() != NoStroke) {
        setColor(cr, strokeColor());
        cairo_set_line_width(cr, strokeThickness());
        cairo_stroke(cr);
    }

    cairo_new_path(cr);
    cairo_restore(cr);
}

void GraphicsContext::fillPath()
{
    if (paintingDisabled())
        return;

    cairo_t* cr = m_data->cr;
    cairo_save(cr);

    cairo_set_fill_rule(cr, fillRule() == RULE_EVENODD ? CAIRO_FILL_RULE_EVEN_ODD : CAIRO_FILL_RULE_WINDING);
    switch (m_common->state.fillColorSpace) {
    case SolidColorSpace:
        setColor(cr, fillColor());
        cairo_clip(cr);
        cairo_paint_with_alpha(cr, m_common->state.globalAlpha);
        break;
    case PatternColorSpace: {
        TransformationMatrix affine;
        cairo_set_source(cr, m_common->state.fillPattern->createPlatformPattern(affine));
        cairo_clip(cr);
        cairo_paint_with_alpha(cr, m_common->state.globalAlpha);
        break;
    }
    case GradientColorSpace:
        cairo_pattern_t* pattern = m_common->state.fillGradient->platformGradient();
        cairo_set_source(cr, pattern);
        cairo_clip(cr);
        cairo_paint_with_alpha(cr, m_common->state.globalAlpha);
        break;
    }
    cairo_restore(cr);
}

void GraphicsContext::strokePath()
{
    if (paintingDisabled())
        return;

    cairo_t* cr = m_data->cr;
    cairo_save(cr);
    switch (m_common->state.strokeColorSpace) {
    case SolidColorSpace:
        float red, green, blue, alpha;
        strokeColor().getRGBA(red, green, blue, alpha);
        if (m_common->state.globalAlpha < 1.0f)
            alpha *= m_common->state.globalAlpha;
        cairo_set_source_rgba(cr, red, green, blue, alpha);
        cairo_stroke(cr);
        break;
    case PatternColorSpace: {
        TransformationMatrix affine;
        cairo_set_source(cr, m_common->state.strokePattern->createPlatformPattern(affine));
        if (m_common->state.globalAlpha < 1.0f) {
            cairo_push_group(cr);
            cairo_paint_with_alpha(cr, m_common->state.globalAlpha);
            cairo_pop_group_to_source(cr);
        }
        cairo_stroke(cr);
        break;
    }
    case GradientColorSpace:
        cairo_pattern_t* pattern = m_common->state.strokeGradient->platformGradient();
        cairo_set_source(cr, pattern);
        if (m_common->state.globalAlpha < 1.0f) {
            cairo_push_group(cr);
            cairo_paint_with_alpha(cr, m_common->state.globalAlpha);
            cairo_pop_group_to_source(cr);
        }
        cairo_stroke(cr);
        break;
    }
    cairo_restore(cr);
}

void GraphicsContext::drawPath()
{
    fillPath();
    strokePath();
}

void GraphicsContext::fillRect(const FloatRect& rect)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = m_data->cr;
    cairo_rectangle(cr, rect.x(), rect.y(), rect.width(), rect.height());
    fillPath();
}

void GraphicsContext::fillRect(const FloatRect& rect, const Color& color)
{
    if (paintingDisabled())
        return;

    if (color.alpha())
        fillRectSourceOver(m_data->cr, rect, color);
}

void GraphicsContext::clip(const FloatRect& rect)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = m_data->cr;
    cairo_rectangle(cr, rect.x(), rect.y(), rect.width(), rect.height());
    cairo_fill_rule_t savedFillRule = cairo_get_fill_rule(cr);
    cairo_set_fill_rule(cr, CAIRO_FILL_RULE_WINDING);
    cairo_clip(cr);
    cairo_set_fill_rule(cr, savedFillRule);
    m_data->clip(rect);
}

void GraphicsContext::clipPath(WindRule clipRule)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = m_data->cr;
    cairo_set_fill_rule(cr, clipRule == RULE_EVENODD ? CAIRO_FILL_RULE_EVEN_ODD : CAIRO_FILL_RULE_WINDING);
    cairo_clip(cr);
}

void GraphicsContext::drawFocusRing(const Color& color)
{
    if (paintingDisabled())
        return;