graphicscontextcg.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) 2003, 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.
 * Copyright (C) 2008 Eric Seidel <[e-mail]>
 *
 * 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. 
 */

#define _USE_MATH_DEFINES 1
#include "config.h"
#include "GraphicsContext.h"

#include "TransformationMatrix.h"
#include "FloatConversion.h"
#include "GraphicsContextPrivate.h"
#include "GraphicsContextPlatformPrivateCG.h"
#include "ImageBuffer.h"
#include "KURL.h"
#include "Path.h"
#include "Pattern.h"
#include <CoreGraphics/CGBitmapContext.h>
#include <CoreGraphics/CGPDFContext.h>
#include <wtf/MathExtras.h>
#include <wtf/OwnArrayPtr.h>
#include <wtf/RetainPtr.h>

#if PLATFORM(MAC) && !defined(BUILDING_ON_TIGER) && !defined(BUILDING_ON_LEOPARD)
#define HAVE_CG_INTERPOLATION_MEDIUM 1
#endif

using namespace std;

namespace WebCore {

static void setCGFillColor(CGContextRef context, const Color& color)
{
    CGFloat red, green, blue, alpha;
    color.getRGBA(red, green, blue, alpha);
    CGContextSetRGBFillColor(context, red, green, blue, alpha);
}

static void setCGStrokeColor(CGContextRef context, const Color& color)
{
    CGFloat red, green, blue, alpha;
    color.getRGBA(red, green, blue, alpha);
    CGContextSetRGBStrokeColor(context, red, green, blue, alpha);
}

GraphicsContext::GraphicsContext(CGContextRef cgContext)
    : m_common(createGraphicsContextPrivate())
    , m_data(new GraphicsContextPlatformPrivate(cgContext))
{
    setPaintingDisabled(!cgContext);
    if (cgContext) {
        // Make sure the context starts in sync with our state.
        setPlatformFillColor(fillColor());
        setPlatformStrokeColor(strokeColor());
    }
}

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

CGContextRef GraphicsContext::platformContext() const
{
    ASSERT(!paintingDisabled());
    ASSERT(m_data->m_cgContext);
    return m_data->m_cgContext;
}

void GraphicsContext::savePlatformState()
{
    // Note: Do not use this function within this class implementation, since we want to avoid the extra
    // save of the secondary context (in GraphicsContextPlatformPrivateCG.h).
    CGContextSaveGState(platformContext());
    m_data->save();
}

void GraphicsContext::restorePlatformState()
{
    // Note: Do not use this function within this class implementation, since we want to avoid the extra
    // restore of the secondary context (in GraphicsContextPlatformPrivateCG.h).
    CGContextRestoreGState(platformContext());
    m_data->restore();
    m_data->m_userToDeviceTransformKnownToBeIdentity = false;
}

// Draws a filled rectangle with a stroked border.
void GraphicsContext::drawRect(const IntRect& rect)
{
    // FIXME: this function does not handle patterns and gradients
    // like drawPath does, it probably should.
    if (paintingDisabled())
        return;

    CGContextRef context = platformContext();

    if (fillColor().alpha())
        CGContextFillRect(context, rect);

    if (strokeStyle() != NoStroke && strokeColor().alpha()) {
        // We do a fill of four rects to simulate the stroke of a border.
        Color oldFillColor = fillColor();
        if (oldFillColor != strokeColor())
            setCGFillColor(context, strokeColor());
        CGRect rects[4] = {
            FloatRect(rect.x(), rect.y(), rect.width(), 1),
            FloatRect(rect.x(), rect.bottom() - 1, rect.width(), 1),
            FloatRect(rect.x(), rect.y() + 1, 1, rect.height() - 2),
            FloatRect(rect.right() - 1, rect.y() + 1, 1, rect.height() - 2)
        };
        CGContextFillRects(context, rects, 4);
        if (oldFillColor != strokeColor())
            setCGFillColor(context, oldFillColor);
    }
}

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

    if (strokeStyle() == NoStroke || !strokeColor().alpha())
        return;

    float width = strokeThickness();

    FloatPoint p1 = point1;
    FloatPoint p2 = point2;
    bool isVerticalLine = (p1.x() == p2.x());
    
    // 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 (strokeStyle() == DottedStroke || strokeStyle() == DashedStroke) {
        if (isVerticalLine) {
            p1.move(0, width);
            p2.move(0, -width);
        } else {
            p1.move(width, 0);
            p2.move(-width, 0);
        }
    }
    
    if (((int)width) % 2) {
        if (isVerticalLine) {
            // We're a vertical line.  Adjust our x.
            p1.move(0.5f, 0.0f);
            p2.move(0.5f, 0.0f);
        } else {
            // We're a horizontal line. Adjust our y.
            p1.move(0.0f, 0.5f);
            p2.move(0.0f, 0.5f);
        }
    }
    
    int patWidth = 0;
    switch (strokeStyle()) {
        case NoStroke:
        case SolidStroke:
            break;
        case DottedStroke:
            patWidth = (int)width;
            break;
        case DashedStroke:
            patWidth = 3 * (int)width;
            break;
    }

    CGContextRef context = platformContext();
    
    if (shouldAntialias())
        CGContextSetShouldAntialias(context, false);

    if (patWidth) {
        CGContextSaveGState(context);

        // 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.
        setCGFillColor(context, strokeColor());  // The save/restore make it safe to mutate the fill color here without setting it back to the old color.
        if (isVerticalLine) {
            CGContextFillRect(context, FloatRect(p1.x() - width / 2, p1.y() - width, width, width));
            CGContextFillRect(context, FloatRect(p2.x() - width / 2, p2.y(), width, width));
        } else {
            CGContextFillRect(context, FloatRect(p1.x() - width, p1.y() - width / 2, width, width));
            CGContextFillRect(context, FloatRect(p2.x(), p2.y() - width / 2, width, width));
        }

        // 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*(int)width;
        int remainder = distance % patWidth;
        int coverage = distance - remainder;
        int numSegments = coverage / patWidth;

        float patternOffset = 0.0f;
        // Special case 1px dotted borders for speed.
        if (patWidth == 1)
            patternOffset = 1.0f;
        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 (remainder)
                    patternOffset = (patWidth - remainder)/2;
            }
        }
        
        const CGFloat dottedLine[2] = { patWidth, patWidth };
        CGContextSetLineDash(context, patternOffset, dottedLine, 2);
    }

    CGContextBeginPath(context);
    CGContextMoveToPoint(context, p1.x(), p1.y());
    CGContextAddLineToPoint(context, p2.x(), p2.y());

    CGContextStrokePath(context);

    if (patWidth)
        CGContextRestoreGState(context);
        
    if (shouldAntialias())
        CGContextSetShouldAntialias(context, true);
}

// This method is only used to draw the little circles used in lists.
void GraphicsContext::drawEllipse(const IntRect& rect)
{
    // FIXME: CG added CGContextAddEllipseinRect in Tiger, so we should be able to quite easily draw an ellipse.
    // This code can only handle circles, not ellipses. But khtml only
    // uses it for circles.
    ASSERT(rect.width() == rect.height());

    if (paintingDisabled())
        return;
        
    CGContextRef context = platformContext();
    CGContextBeginPath(context);
    float r = (float)rect.width() / 2;
    CGContextAddArc(context, rect.x() + r, rect.y() + r, r, 0.0f, 2.0f * piFloat, 0);
    CGContextClosePath(context);

    drawPath();
}


void GraphicsContext::strokeArc(const IntRect& rect, int startAngle, int angleSpan)
{ 
    if (paintingDisabled() || strokeStyle() == NoStroke || strokeThickness() <= 0.0f || !strokeColor().alpha())
        return;
    
    CGContextRef context = platformContext();
    CGContextSaveGState(context);
    CGContextBeginPath(context);
    CGContextSetShouldAntialias(context, false);
    
    int x = rect.x();
    int y = rect.y();
    float w = (float)rect.width();
    float h = (float)rect.height();
    float scaleFactor = h / w;
    float reverseScaleFactor = w / h;
    
    if (w != h)
        scale(FloatSize(1, scaleFactor));
    
    float hRadius = w / 2;
    float vRadius = h / 2;
    float fa = startAngle;
    float falen =  fa + angleSpan;
    float start = -fa * piFloat / 180.0f;
    float end = -falen * piFloat / 180.0f;
    CGContextAddArc(context, x + hRadius, (y + vRadius) * reverseScaleFactor, hRadius, start, end, true);

    if (w != h)
        scale(FloatSize(1, reverseScaleFactor));
    
    
    float width = strokeThickness();
    int patWidth = 0;
    
    switch (strokeStyle()) {
        case DottedStroke:
            patWidth = (int)(width / 2);
            break;
        case DashedStroke:
            patWidth = 3 * (int)(width / 2);
            break;
        default:
            break;
    }
    
    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>((piFloat * hRadius) / 2.0f);
        else // We are elliptical and will have to estimate the distance
            distance = static_cast<int>((piFloat * sqrtf((hRadius * hRadius + vRadius * vRadius) / 2.0f)) / 2.0f);
        
        int remainder = distance % patWidth;
        int coverage = distance - remainder;
        int numSegments = coverage / patWidth;

        float patternOffset = 0.0f;
        // Special case 1px dotted borders for speed.
        if (patWidth == 1)
            patternOffset = 1.0f;
        else {
            bool evenNumberOfSegments = numSegments % 2 == 0;
            if (remainder)
                evenNumberOfSegments = !evenNumberOfSegments;
            if (evenNumberOfSegments) {
                if (remainder) {
                    patternOffset += patWidth - remainder;
                    patternOffset += remainder / 2.0f;
                } else
                    patternOffset = patWidth / 2.0f;
            } else {
                if (remainder)
                    patternOffset = (patWidth - remainder) / 2.0f;
            }
        }
    
        const CGFloat dottedLine[2] = { patWidth, patWidth };
        CGContextSetLineDash(context, patternOffset, dottedLine, 2);
    }

    CGContextStrokePath(context);
    
    CGContextRestoreGState(context);
}

void GraphicsContext::drawConvexPolygon(size_t npoints, const FloatPoint* points, bool antialiased)
{
    if (paintingDisabled() || !fillColor().alpha() && (strokeThickness() <= 0 || strokeStyle() == NoStroke))
        return;

    if (npoints <= 1)
        return;

    CGContextRef context = platformContext();

    if (antialiased != shouldAntialias())
        CGContextSetShouldAntialias(context, antialiased);
    
    CGContextBeginPath(context);
    CGContextMoveToPoint(context, points[0].x(), points[0].y());
    for (size_t i = 1; i < npoints; i++)
        CGContextAddLineToPoint(context, points[i].x(), points[i].y());
    CGContextClosePath(context);

    drawPath();
    
    if (antialiased != shouldAntialias())
        CGContextSetShouldAntialias(context, shouldAntialias());
}

void GraphicsContext::applyStrokePattern()
{
    CGContextRef cgContext = platformContext();
    
    CGPatternRef platformPattern = m_common->state.strokePattern.get()->createPlatformPattern(getCTM());
    if (!platformPattern)
        return;

    CGColorSpaceRef patternSpace = CGColorSpaceCreatePattern(0);
    CGContextSetStrokeColorSpace(cgContext, patternSpace);