GraphicsContextCairo.cpp   [plain text]

/*
 * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
 * Copyright (C) 2007 Alp Toker <alp@atoker.com>
 * Copyright (C) 2008, 2009 Dirk Schulze <krit@webkit.org>
 * Copyright (C) 2008 Nuanti Ltd.
 * Copyright (C) 2009 Brent Fulgham <bfulgham@webkit.org>
 * Copyright (C) 2010, 2011 Igalia S.L.
 * Copyright (C) Research In Motion Limited 2010. All rights reserved.
 *
 * 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 USE(CAIRO)

#include "AffineTransform.h"
#include "CairoUtilities.h"
#include "FloatConversion.h"
#include "FloatRect.h"
#include "Font.h"
#include "GraphicsContextPlatformPrivateCairo.h"
#include "OwnPtrCairo.h"
#include "IntRect.h"
#include "NotImplemented.h"
#include "Path.h"
#include "Pattern.h"
#include "PlatformContextCairo.h"
#include "PlatformPathCairo.h"
#include "RefPtrCairo.h"
#include "ShadowBlur.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

using namespace std;

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

namespace WebCore {

// A helper which quickly fills a rectangle with a simple color fill.
static inline void fillRectWithColor(cairo_t* cr, const FloatRect& rect, const Color& color)
{
    if (!color.alpha())
        return;
    setSourceRGBAFromColor(cr, color);
    cairo_rectangle(cr, rect.x(), rect.y(), rect.width(), rect.height());
    cairo_fill(cr);
}

static void addConvexPolygonToContext(cairo_t* context, size_t numPoints, const FloatPoint* points)
{
    cairo_move_to(context, points[0].x(), points[0].y());
    for (size_t i = 1; i < numPoints; i++)
        cairo_line_to(context, points[i].x(), points[i].y());
    cairo_close_path(context);
}

enum PathDrawingStyle { 
    Fill = 1,
    Stroke = 2,
    FillAndStroke = Fill + Stroke
};

static inline void drawPathShadow(GraphicsContext* context, PathDrawingStyle drawingStyle)
{
    ShadowBlur& shadow = context->platformContext()->shadowBlur();
    if (shadow.type() == ShadowBlur::NoShadow)
        return;

    // Calculate the extents of the rendered solid paths.
    cairo_t* cairoContext = context->platformContext()->cr();
    OwnPtr<cairo_path_t> path = adoptPtr(cairo_copy_path(cairoContext));

    FloatRect solidFigureExtents;
    double x0 = 0;
    double x1 = 0;
    double y0 = 0;
    double y1 = 0;
    if (drawingStyle & Stroke) {
        cairo_stroke_extents(cairoContext, &x0, &y0, &x1, &y1);
        solidFigureExtents = FloatRect(x0, y0, x1 - x0, y1 - y0);
    }
    if (drawingStyle & Fill) {
        cairo_fill_extents(cairoContext, &x0, &y0, &x1, &y1);
        FloatRect fillExtents(x0, y0, x1 - x0, y1 - y0);
        solidFigureExtents.unite(fillExtents);
    }

    GraphicsContext* shadowContext = shadow.beginShadowLayer(context, solidFigureExtents);
    if (!shadowContext)
        return;

    cairo_t* cairoShadowContext = shadowContext->platformContext()->cr();

    // It's important to copy the context properties to the new shadow
    // context to preserve things such as the fill rule and stroke width.
    copyContextProperties(cairoContext, cairoShadowContext);

    if (drawingStyle & Fill) {
        cairo_save(cairoShadowContext);
        cairo_append_path(cairoShadowContext, path.get());
        shadowContext->platformContext()->prepareForFilling(context->state(), PlatformContextCairo::NoAdjustment);
        cairo_fill(cairoShadowContext);
        cairo_restore(cairoShadowContext);
    }

    if (drawingStyle & Stroke) {
        cairo_append_path(cairoShadowContext, path.get());
        shadowContext->platformContext()->prepareForStroking(context->state(), PlatformContextCairo::DoNotPreserveAlpha);
        cairo_stroke(cairoShadowContext);
    }

    shadow.endShadowLayer(context);

    // ShadowBlur::endShadowLayer destroys the current path on the Cairo context. We restore it here.
    cairo_new_path(cairoContext);
    cairo_append_path(cairoContext, path.get());
}

static inline void shadowAndFillCurrentCairoPath(GraphicsContext* context)
{
    cairo_t* cr = context->platformContext()->cr();
    cairo_save(cr);

    drawPathShadow(context, Fill);

    context->platformContext()->prepareForFilling(context->state(), PlatformContextCairo::AdjustPatternForGlobalAlpha);
    cairo_fill(cr);

    cairo_restore(cr);
}

static inline void shadowAndStrokeCurrentCairoPath(GraphicsContext* context)
{
    drawPathShadow(context, Stroke);
    context->platformContext()->prepareForStroking(context->state());
    cairo_stroke(context->platformContext()->cr());
}

GraphicsContext::GraphicsContext(cairo_t* cr)
    : m_updatingControlTints(false),
      m_transparencyCount(0)
{
    m_data = new GraphicsContextPlatformPrivateToplevel(new PlatformContextCairo(cr));
}

void GraphicsContext::platformInit(PlatformContextCairo* platformContext)
{
    m_data = new GraphicsContextPlatformPrivate(platformContext);
    if (platformContext)
        m_data->syncContext(platformContext->cr());
    else
        setPaintingDisabled(true);
}

void GraphicsContext::platformDestroy()
{
    delete m_data;
}

AffineTransform GraphicsContext::getCTM(IncludeDeviceScale) const
{
    if (paintingDisabled())
        return AffineTransform();

    cairo_t* cr = platformContext()->cr();
    cairo_matrix_t m;
    cairo_get_matrix(cr, &m);
    return AffineTransform(m.xx, m.yx, m.xy, m.yy, m.x0, m.y0);
}

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

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

void GraphicsContext::restorePlatformState()
{
    platformContext()->restore();
    m_data->restore();

    platformContext()->shadowBlur().setShadowValues(FloatSize(m_state.shadowBlur, m_state.shadowBlur),
                                                    m_state.shadowOffset,
                                                    m_state.shadowColor,
                                                    m_state.shadowColorSpace,
                                                    m_state.shadowsIgnoreTransforms);
}

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

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

    fillRectWithColor(cr, rect, fillColor());

    if (strokeStyle() != NoStroke) {
        setSourceRGBAFromColor(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);
}

static double calculateStrokePatternOffset(int distance, int patternWidth)
{
    // 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 remainder = distance % patternWidth;
    int numSegments = (distance - remainder) / patternWidth;

    // Special case 1px dotted borders for speed.
    if (patternWidth == 1)
        return 1;

    bool evenNumberOfSegments = !(numSegments % 2);
    if (remainder)
        evenNumberOfSegments = !evenNumberOfSegments;

    if (evenNumberOfSegments) {
        if (remainder)
            return (patternWidth - remainder) + (remainder / 2);
        return patternWidth / 2;
    }

    // Odd number of segments.
    if (remainder)
        return (patternWidth - remainder) / 2.f;
    return 0;
}

static void drawLineOnCairoContext(GraphicsContext* graphicsContext, cairo_t* context, const FloatPoint& point1, const FloatPoint& point2)
{
    StrokeStyle style = graphicsContext->strokeStyle();
    if (style == NoStroke)
        return;

    const Color& strokeColor = graphicsContext->strokeColor();
    int strokeThickness = floorf(graphicsContext->strokeThickness());
    if (graphicsContext->strokeThickness() < 1)
        strokeThickness = 1;

    int patternWidth = 0;
    if (style == DottedStroke)
        patternWidth = strokeThickness;
    else if (style == DashedStroke)
        patternWidth = 3 * strokeThickness;

    bool isVerticalLine = point1.x() == point2.x();
    FloatPoint point1OnPixelBoundaries = point1;
    FloatPoint point2OnPixelBoundaries = point2;
    GraphicsContext::adjustLineToPixelBoundaries(point1OnPixelBoundaries, point2OnPixelBoundaries, strokeThickness, style);

    cairo_set_antialias(context, CAIRO_ANTIALIAS_NONE);
    if (patternWidth) {
        // 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.
        FloatRect firstRect(point1OnPixelBoundaries, FloatSize(strokeThickness, strokeThickness));
        FloatRect secondRect(point2OnPixelBoundaries, FloatSize(strokeThickness, strokeThickness));
        if (isVerticalLine) {
            firstRect.move(-strokeThickness / 2, -strokeThickness);
            secondRect.move(-strokeThickness / 2, 0);
        } else {
            firstRect.move(-strokeThickness, -strokeThickness / 2);
            secondRect.move(0, -strokeThickness / 2);
        }
        fillRectWithColor(context, firstRect, strokeColor);
        fillRectWithColor(context, secondRect, strokeColor);

        int distance = (isVerticalLine ? (point2.y() - point1.y()) : (point2.x() - point1.x())) - 2 * strokeThickness;
        double patternOffset = calculateStrokePatternOffset(distance, patternWidth);
        double patternWidthAsDouble = patternWidth;
        cairo_set_dash(context, &patternWidthAsDouble, 1, patternOffset);
    }

    setSourceRGBAFromColor(context, strokeColor);
    cairo_set_line_width(context, strokeThickness);
    cairo_move_to(context, point1OnPixelBoundaries.x(), point1OnPixelBoundaries.y());
    cairo_line_to(context, point2OnPixelBoundaries.x(), point2OnPixelBoundaries.y());
    cairo_stroke(context);
}

// This is only used to draw borders, so we should not draw shadows.
void GraphicsContext::drawLine(const IntPoint& point1, const IntPoint& point2)
{
    if (paintingDisabled())
        return;

    cairo_t* cairoContext = platformContext()->cr();
    cairo_save(cairoContext);
    drawLineOnCairoContext(this, cairoContext, point1, point2);
    cairo_restore(cairoContext);
}

// 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 = platformContext()->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()) {
        setSourceRGBAFromColor(cr, fillColor());
        cairo_fill_preserve(cr);
    }

    if (strokeStyle() != NoStroke) {
        setSourceRGBAFromColor(cr, strokeColor());
        cairo_set_line_width(cr, strokeThickness());
        cairo_stroke(cr);
    } else
        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 = platformContext()->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);

    int patternWidth = 0;
    switch (strokeStyle()) {
    case DottedStroke:
        patternWidth = floorf(strokeThickness() / 2.f);
        break;
    case DashedStroke:
        patternWidth = 3 * floorf(strokeThickness() / 2.f);
        break;
    default:
        break;
    }

    setSourceRGBAFromColor(cr, strokeColor());

    if (patternWidth) {
        float distance = 0;
        if (hRadius == vRadius)
            distance = (piFloat * hRadius) / 2.f;
        else // We are elliptical and will have to estimate the distance
            distance = (piFloat * sqrtf((hRadius * hRadius + vRadius * vRadius) / 2.f)) / 2.f;
        double patternOffset = calculateStrokePatternOffset(floorf(distance), patternWidth);
        double patternWidthAsDouble = patternWidth;
        cairo_set_dash(cr, &patternWidthAsDouble, 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 = platformContext()->cr();

    cairo_save(cr);
    cairo_set_antialias(cr, shouldAntialias ? CAIRO_ANTIALIAS_DEFAULT : CAIRO_ANTIALIAS_NONE);
    addConvexPolygonToContext(cr, npoints, points);

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

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

    cairo_restore(cr);
}

void GraphicsContext::clipConvexPolygon(size_t numPoints, const FloatPoint* points, bool antialiased)
{
    if (paintingDisabled())
        return;

    if (numPoints <= 1)
        return;

    cairo_t* cr = platformContext()->cr();

    cairo_new_path(cr);
    cairo_fill_rule_t savedFillRule = cairo_get_fill_rule(cr);
    cairo_antialias_t savedAntialiasRule = cairo_get_antialias(cr);

    cairo_set_antialias(cr, antialiased ? CAIRO_ANTIALIAS_DEFAULT : CAIRO_ANTIALIAS_NONE);
    cairo_set_fill_rule(cr, CAIRO_FILL_RULE_WINDING);
    addConvexPolygonToContext(cr, numPoints, points);
    cairo_clip(cr);

    cairo_set_antialias(cr, savedAntialiasRule);
    cairo_set_fill_rule(cr, savedFillRule);
}

void GraphicsContext::fillPath(const Path& path)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = platformContext()->cr();
    setPathOnCairoContext(cr, path.platformPath()->context());
    shadowAndFillCurrentCairoPath(this);
}

void GraphicsContext::strokePath(const Path& path)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = platformContext()->cr();
    setPathOnCairoContext(cr, path.platformPath()->context());
    shadowAndStrokeCurrentCairoPath(this);
}

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

    cairo_t* cr = platformContext()->cr();
    cairo_rectangle(cr, rect.x(), rect.y(), rect.width(), rect.height());
    shadowAndFillCurrentCairoPath(this);
}

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

    if (hasShadow())
        platformContext()->shadowBlur().drawRectShadow(this, rect, RoundedRect::Radii());

    fillRectWithColor(platformContext()->cr(), rect, color);
}

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

    cairo_t* cr = platformContext()->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(const Path& path, WindRule clipRule)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = platformContext()->cr();
    setPathOnCairoContext(cr, path.platformPath()->context());
    cairo_set_fill_rule(cr, clipRule == RULE_EVENODD ? CAIRO_FILL_RULE_EVEN_ODD : CAIRO_FILL_RULE_WINDING);
    cairo_clip(cr);
}

IntRect GraphicsContext::clipBounds() const
{
    double x1, x2, y1, y2;
    cairo_clip_extents(platformContext()->cr(), &x1, &y1, &x2, &y2);
    return enclosingIntRect(FloatRect(x1, y1, x2 - x1, y2 - y1));
}

static inline void adjustFocusRingColor(Color& color)
{
#if !PLATFORM(GTK)
    // Force the alpha to 50%.  This matches what the Mac does with outline rings.
    color.setRGB(makeRGBA(color.red(), color.green(), color.blue(), 127));
#endif
}

static inline void adjustFocusRingLineWidth(int& width)
{
#if PLATFORM(GTK)
    width = 2;
#endif
}

static inline StrokeStyle focusRingStrokeStyle()
{
#if PLATFORM(GTK)
    return DottedStroke;
#else
    return SolidStroke;
#endif
}

void GraphicsContext::drawFocusRing(const Path& path, int width, int /* offset */, const Color& color)
{
    // FIXME: We should draw paths that describe a rectangle with rounded corners
    // so as to be consistent with how we draw rectangular focus rings.
    Color ringColor = color;
    adjustFocusRingColor(ringColor);
    adjustFocusRingLineWidth(width);

    cairo_t* cr = platformContext()->cr();
    cairo_save(cr);
    appendWebCorePathToCairoContext(cr, path);
    setSourceRGBAFromColor(cr, ringColor);
    cairo_set_line_width(cr, width);
    setPlatformStrokeStyle(focusRingStrokeStyle());
    cairo_stroke(cr);
    cairo_restore(cr);
}

void GraphicsContext::drawFocusRing(const Vector<IntRect>& rects, int width, int /* offset */, const Color& color)
{
    if (paintingDisabled())
        return;

    unsigned rectCount = rects.size();

    cairo_t* cr = platformContext()->cr();
    cairo_save(cr);
    cairo_push_group(cr);
    cairo_new_path(cr);

#if PLATFORM(GTK)
#ifdef GTK_API_VERSION_2
    GdkRegion* reg = gdk_region_new();
#else
    cairo_region_t* reg = cairo_region_create();
#endif

    for (unsigned i = 0; i < rectCount; i++) {
#ifdef GTK_API_VERSION_2
        GdkRectangle rect = rects[i];
        gdk_region_union_with_rect(reg, &rect);
#else
        cairo_rectangle_int_t rect = rects[i];
        cairo_region_union_rectangle(reg, &rect);
#endif
    }
    gdk_cairo_region(cr, reg);
#ifdef GTK_API_VERSION_2
    gdk_region_destroy(reg);
#else
    cairo_region_destroy(reg);
#endif
#else
    int radius = (width - 1) / 2;
    Path path;
    for (unsigned i = 0; i < rectCount; ++i) {
        if (i > 0)
            path.clear();
        path.addRoundedRect(rects[i], FloatSize(radius, radius));
        appendWebCorePathToCairoContext(cr, path);
    }
#endif
    Color ringColor = color;
    adjustFocusRingColor(ringColor);
    adjustFocusRingLineWidth(width);
    setSourceRGBAFromColor(cr, ringColor);
    cairo_set_line_width(cr, width);
    setPlatformStrokeStyle(focusRingStrokeStyle());

    cairo_set_operator(cr, CAIRO_OPERATOR_OVER);
    cairo_stroke_preserve(cr);

    cairo_set_operator(cr, CAIRO_OPERATOR_CLEAR);
    cairo_set_fill_rule(cr, CAIRO_FILL_RULE_WINDING);
    cairo_fill(cr);

    cairo_pop_group_to_source(cr);
    cairo_set_operator(cr, CAIRO_OPERATOR_OVER);
    cairo_paint(cr);
    cairo_restore(cr);
}

void GraphicsContext::drawLineForText(const FloatPoint& origin, float width, bool printing)
{
    if (paintingDisabled())
        return;

    cairo_t* cairoContext = platformContext()->cr();
    cairo_save(cairoContext);

    // This bumping of <1 stroke thicknesses matches the one in drawLineOnCairoContext.
    FloatPoint endPoint(origin + IntSize(width, 0));
    FloatRect lineExtents(origin, FloatSize(width, strokeThickness()));

    ShadowBlur& shadow = platformContext()->shadowBlur();
    if (GraphicsContext* shadowContext = shadow.beginShadowLayer(this, lineExtents)) {
        drawLineOnCairoContext(this, shadowContext->platformContext()->cr(), origin, endPoint);
        shadow.endShadowLayer(this);
    }

    drawLineOnCairoContext(this, cairoContext, origin, endPoint);
    cairo_restore(cairoContext);
}

#if !PLATFORM(GTK)
#include "DrawErrorUnderline.h"
#endif

void GraphicsContext::drawLineForDocumentMarker(const FloatPoint& origin, float width, DocumentMarkerLineStyle style)
{
    if (paintingDisabled())
        return;

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

    switch (style) {
    case DocumentMarkerSpellingLineStyle:
        cairo_set_source_rgb(cr, 1, 0, 0);
        break;
    case DocumentMarkerGrammarLineStyle:
        cairo_set_source_rgb(cr, 0, 1, 0);
        break;
    default:
        cairo_restore(cr);
        return;
    }

#if PLATFORM(GTK)
    // We ignore most of the provided constants in favour of the platform style
    pango_cairo_show_error_underline(cr, origin.x(), origin.y(), width, cMisspellingLineThickness);
#else
    drawErrorUnderline(cr, origin.x(), origin.y(), width, cMisspellingLineThickness);
#endif

    cairo_restore(cr);
}

FloatRect GraphicsContext::roundToDevicePixels(const FloatRect& frect, RoundingMode)
{
    FloatRect result;
    double x = frect.x();
    double y = frect.y();
    cairo_t* cr = platformContext()->cr();
    cairo_user_to_device(cr, &x, &y);
    x = round(x);
    y = round(y);
    cairo_device_to_user(cr, &x, &y);
    result.setX(narrowPrecisionToFloat(x));
    result.setY(narrowPrecisionToFloat(y));

    // We must ensure width and height are at least 1 (or -1) when
    // we're given float values in the range between 0 and 1 (or -1 and 0).
    double width = frect.width();
    double height = frect.height();
    cairo_user_to_device_distance(cr, &width, &height);
    if (width > -1 && width < 0)
        width = -1;
    else if (width > 0 && width < 1)
        width = 1;
    else
        width = round(width);
    if (height > -1 && width < 0)
        height = -1;
    else if (height > 0 && height < 1)
        height = 1;
    else
        height = round(height);
    cairo_device_to_user_distance(cr, &width, &height);
    result.setWidth(narrowPrecisionToFloat(width));
    result.setHeight(narrowPrecisionToFloat(height));

    return result;
}

void GraphicsContext::translate(float x, float y)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = platformContext()->cr();
    cairo_translate(cr, x, y);
    m_data->translate(x, y);
}

void GraphicsContext::setPlatformFillColor(const Color& col, ColorSpace colorSpace)
{
    // Cairo contexts can't hold separate fill and stroke colors
    // so we set them just before we actually fill or stroke
}

void GraphicsContext::setPlatformStrokeColor(const Color& col, ColorSpace colorSpace)
{
    // Cairo contexts can't hold separate fill and stroke colors
    // so we set them just before we actually fill or stroke
}

void GraphicsContext::setPlatformStrokeThickness(float strokeThickness)
{
    if (paintingDisabled())
        return;

    cairo_set_line_width(platformContext()->cr(), strokeThickness);
}

void GraphicsContext::setPlatformStrokeStyle(StrokeStyle strokeStyle)
{
    static double dashPattern[] = {5.0, 5.0};
    static double dotPattern[] = {1.0, 1.0};

    if (paintingDisabled())
        return;

    switch (strokeStyle) {
    case NoStroke:
        // FIXME: is it the right way to emulate NoStroke?
        cairo_set_line_width(platformContext()->cr(), 0);
        break;
    case SolidStroke:
        cairo_set_dash(platformContext()->cr(), 0, 0, 0);
        break;
    case DottedStroke:
        cairo_set_dash(platformContext()->cr(), dotPattern, 2, 0);
        break;
    case DashedStroke:
        cairo_set_dash(platformContext()->cr(), dashPattern, 2, 0);
        break;
    }
}

void GraphicsContext::setURLForRect(const KURL& link, const IntRect& destRect)
{
    notImplemented();
}

void GraphicsContext::concatCTM(const AffineTransform& transform)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = platformContext()->cr();
    const cairo_matrix_t matrix = cairo_matrix_t(transform);
    cairo_transform(cr, &matrix);
    m_data->concatCTM(transform);
}

void GraphicsContext::setCTM(const AffineTransform& transform)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = platformContext()->cr();
    const cairo_matrix_t matrix = cairo_matrix_t(transform);
    cairo_set_matrix(cr, &matrix);
    m_data->setCTM(transform);
}

void GraphicsContext::addInnerRoundedRectClip(const IntRect& rect, int thickness)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = platformContext()->cr();
    clip(rect);

    Path p;
    FloatRect r(rect);
    // Add outer ellipse
    p.addEllipse(r);
    // Add inner ellipse
    r.inflate(-thickness);
    p.addEllipse(r);
    appendWebCorePathToCairoContext(cr, p);

    cairo_fill_rule_t savedFillRule = cairo_get_fill_rule(cr);
    cairo_set_fill_rule(cr, CAIRO_FILL_RULE_EVEN_ODD);
    cairo_clip(cr);
    cairo_set_fill_rule(cr, savedFillRule);
}

void GraphicsContext::setPlatformShadow(FloatSize const& size, float blur, Color const& color, ColorSpace)
{
    if (paintingDisabled())
        return;

    if (m_state.shadowsIgnoreTransforms) {
        // Meaning that this graphics context is associated with a CanvasRenderingContext
        // We flip the height since CG and HTML5 Canvas have opposite Y axis
        m_state.shadowOffset = FloatSize(size.width(), -size.height());
    }

    // Cairo doesn't support shadows natively, they are drawn manually in the draw* functions using ShadowBlur.
    platformContext()->shadowBlur().setShadowValues(FloatSize(m_state.shadowBlur, m_state.shadowBlur),
                                                    m_state.shadowOffset,
                                                    m_state.shadowColor,
                                                    m_state.shadowColorSpace,
                                                    m_state.shadowsIgnoreTransforms);
}

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

    platformContext()->shadowBlur().clear();
}

void GraphicsContext::beginPlatformTransparencyLayer(float opacity)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = platformContext()->cr();
    cairo_push_group(cr);
    m_data->layers.append(opacity);
}

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

    cairo_t* cr = platformContext()->cr();

    cairo_pop_group_to_source(cr);
    cairo_paint_with_alpha(cr, m_data->layers.last());
    m_data->layers.removeLast();
}

bool GraphicsContext::supportsTransparencyLayers()
{
    return true;
}

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

    cairo_t* cr = platformContext()->cr();

    cairo_save(cr);
    cairo_rectangle(cr, rect.x(), rect.y(), rect.width(), rect.height());
    cairo_set_operator(cr, CAIRO_OPERATOR_CLEAR);
    cairo_fill(cr);
    cairo_restore(cr);
}

void GraphicsContext::strokeRect(const FloatRect& rect, float width)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = platformContext()->cr();
    cairo_save(cr);
    cairo_rectangle(cr, rect.x(), rect.y(), rect.width(), rect.height());
    cairo_set_line_width(cr, width);
    shadowAndStrokeCurrentCairoPath(this);
    cairo_restore(cr);
}

void GraphicsContext::setLineCap(LineCap lineCap)
{
    if (paintingDisabled())
        return;

    cairo_line_cap_t cairoCap = CAIRO_LINE_CAP_BUTT;
    switch (lineCap) {
    case ButtCap:
        // no-op
        break;
    case RoundCap:
        cairoCap = CAIRO_LINE_CAP_ROUND;
        break;
    case SquareCap:
        cairoCap = CAIRO_LINE_CAP_SQUARE;
        break;
    }
    cairo_set_line_cap(platformContext()->cr(), cairoCap);
}

void GraphicsContext::setLineDash(const DashArray& dashes, float dashOffset)
{
    cairo_set_dash(platformContext()->cr(), dashes.data(), dashes.size(), dashOffset);
}

void GraphicsContext::setLineJoin(LineJoin lineJoin)
{
    if (paintingDisabled())
        return;

    cairo_line_join_t cairoJoin = CAIRO_LINE_JOIN_MITER;
    switch (lineJoin) {
    case MiterJoin:
        // no-op
        break;
    case RoundJoin:
        cairoJoin = CAIRO_LINE_JOIN_ROUND;
        break;
    case BevelJoin:
        cairoJoin = CAIRO_LINE_JOIN_BEVEL;
        break;
    }
    cairo_set_line_join(platformContext()->cr(), cairoJoin);
}

void GraphicsContext::setMiterLimit(float miter)
{
    if (paintingDisabled())
        return;

    cairo_set_miter_limit(platformContext()->cr(), miter);
}

void GraphicsContext::setAlpha(float alpha)
{
    platformContext()->setGlobalAlpha(alpha);
}

void GraphicsContext::setPlatformCompositeOperation(CompositeOperator op)
{
    if (paintingDisabled())
        return;

    cairo_set_operator(platformContext()->cr(), toCairoOperator(op));
}

void GraphicsContext::clip(const Path& path)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = platformContext()->cr();
    OwnPtr<cairo_path_t> pathCopy = adoptPtr(cairo_copy_path(path.platformPath()->context()));
    cairo_append_path(cr, pathCopy.get());
    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(path);
}

void GraphicsContext::canvasClip(const Path& path)
{
    clip(path);
}

void GraphicsContext::clipOut(const Path& path)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = platformContext()->cr();
    double x1, y1, x2, y2;
    cairo_clip_extents(cr, &x1, &y1, &x2, &y2);
    cairo_rectangle(cr, x1, y1, x2 - x1, y2 - y1);
    appendWebCorePathToCairoContext(cr, path);

    cairo_fill_rule_t savedFillRule = cairo_get_fill_rule(cr);
    cairo_set_fill_rule(cr, CAIRO_FILL_RULE_EVEN_ODD);
    cairo_clip(cr);
    cairo_set_fill_rule(cr, savedFillRule);
}

void GraphicsContext::rotate(float radians)
{
    if (paintingDisabled())
        return;

    cairo_rotate(platformContext()->cr(), radians);
    m_data->rotate(radians);
}

void GraphicsContext::scale(const FloatSize& size)
{
    if (paintingDisabled())
        return;

    cairo_scale(platformContext()->cr(), size.width(), size.height());
    m_data->scale(size);
}

void GraphicsContext::clipOut(const IntRect& r)
{
    if (paintingDisabled())
        return;

    cairo_t* cr = platformContext()->cr();
    double x1, y1, x2, y2;
    cairo_clip_extents(cr, &x1, &y1, &x2, &y2);
    cairo_rectangle(cr, x1, y1, x2 - x1, y2 - y1);
    cairo_rectangle(cr, r.x(), r.y(), r.width(), r.height());
    cairo_fill_rule_t savedFillRule = cairo_get_fill_rule(cr);
    cairo_set_fill_rule(cr, CAIRO_FILL_RULE_EVEN_ODD);
    cairo_clip(cr);
    cairo_set_fill_rule(cr, savedFillRule);
}

static inline FloatPoint getPhase(const FloatRect& dest, const FloatRect& tile)
{
    FloatPoint phase = dest.location();
    phase.move(-tile.x(), -tile.y());

    return phase;
}

void GraphicsContext::fillRoundedRect(const IntRect& r, const IntSize& topLeft, const IntSize& topRight, const IntSize& bottomLeft, const IntSize& bottomRight, const Color& color, ColorSpace colorSpace)
{
    if (paintingDisabled())
        return;

    if (hasShadow())
        platformContext()->shadowBlur().drawRectShadow(this, r, RoundedRect::Radii(topLeft, topRight, bottomLeft, bottomRight));

    cairo_t* cr = platformContext()->cr();
    cairo_save(cr);
    Path path;
    path.addRoundedRect(r, topLeft, topRight, bottomLeft, bottomRight);
    appendWebCorePathToCairoContext(cr, path);
    setSourceRGBAFromColor(cr, color);
    cairo_fill(cr);
    cairo_restore(cr);
}

#if PLATFORM(GTK)
void GraphicsContext::setGdkExposeEvent(GdkEventExpose* expose)
{
    m_data->expose = expose;
}

GdkEventExpose* GraphicsContext::gdkExposeEvent() const
{
    return m_data->expose;
}

GdkWindow* GraphicsContext::gdkWindow() const
{
    if (!m_data->expose)
        return 0;

    return m_data->expose->window;
}
#endif

void GraphicsContext::setPlatformShouldAntialias(bool enable)
{
    if (paintingDisabled())
        return;

    // When true, use the default Cairo backend antialias mode (usually this
    // enables standard 'grayscale' antialiasing); false to explicitly disable
    // antialiasing. This is the same strategy as used in drawConvexPolygon().
    cairo_set_antialias(platformContext()->cr(), enable ? CAIRO_ANTIALIAS_DEFAULT : CAIRO_ANTIALIAS_NONE);
}

void GraphicsContext::setImageInterpolationQuality(InterpolationQuality quality)
{
    platformContext()->setImageInterpolationQuality(quality);
}

InterpolationQuality GraphicsContext::imageInterpolationQuality() const
{
    return platformContext()->imageInterpolationQuality();
}

#if ENABLE(3D_RENDERING) && USE(TEXTURE_MAPPER)
TransformationMatrix GraphicsContext::get3DTransform() const
{
    notImplemented();
    return TransformationMatrix();
}

void GraphicsContext::concat3DTransform(const TransformationMatrix& transform)
{
    notImplemented();
}

void GraphicsContext::set3DTransform(const TransformationMatrix& transform)
{
    notImplemented();
}
#endif

} // namespace WebCore

#endif // USE(CAIRO)