graphicscontextskia.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, 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.
 *     * 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.
 *     * 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
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER 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"

#include "GraphicsContextPlatformPrivate.h"
#include "GraphicsContextPrivate.h"
#include "Color.h"
#include "FloatRect.h"
#include "Gradient.h"
#include "ImageBuffer.h"
#include "IntRect.h"
#include "NativeImageSkia.h"
#include "NotImplemented.h"
#include "PlatformContextSkia.h"
#include "TransformationMatrix.h"

#include "SkBitmap.h"
#include "SkBlurDrawLooper.h"
#include "SkCornerPathEffect.h"
#include "skia/ext/platform_canvas.h"
#include "SkiaUtils.h"
#include "SkShader.h"

#include <math.h>
#include <wtf/Assertions.h>
#include <wtf/MathExtras.h>

using namespace std;

namespace WebCore {

namespace {

// "Seatbelt" functions ------------------------------------------------------
//
// These functions check certain graphics primitives for being "safe".
// Skia has historically crashed when sent crazy data. These functions do
// additional checking to prevent crashes.
//
// Ideally, all of these would be fixed in the graphics layer and we would not
// have to do any checking. You can uncomment the ENSURE_VALUE_SAFETY_FOR_SKIA
// flag to check the graphics layer.
#define ENSURE_VALUE_SAFETY_FOR_SKIA

static bool isCoordinateSkiaSafe(float coord)
{
#ifdef ENSURE_VALUE_SAFETY_FOR_SKIA
    // First check for valid floats.
#if defined(_MSC_VER)
    if (!_finite(coord))
#else
    if (!finite(coord))
#endif
        return false;

    // Skia uses 16.16 fixed point and 26.6 fixed point in various places. If
    // the transformed point exceeds 15 bits, we just declare that it's
    // unreasonable to catch both of these cases.
    static const int maxPointMagnitude = 32767;
    if (coord > maxPointMagnitude || coord < -maxPointMagnitude)
        return false;

    return true;
#else
    return true;
#endif
}

static bool isPointSkiaSafe(const SkMatrix& transform, const SkPoint& pt)
{
#ifdef ENSURE_VALUE_SAFETY_FOR_SKIA
    // Now check for points that will overflow. We check the *transformed*
    // points since this is what will be rasterized.
    SkPoint xPt;
    transform.mapPoints(&xPt, &pt, 1);
    return isCoordinateSkiaSafe(xPt.fX) && isCoordinateSkiaSafe(xPt.fY);
#else
    return true;
#endif
}

static bool isRectSkiaSafe(const SkMatrix& transform, const SkRect& rc)
{
#ifdef ENSURE_VALUE_SAFETY_FOR_SKIA
    SkPoint topleft = {rc.fLeft, rc.fTop};
    SkPoint bottomright = {rc.fRight, rc.fBottom};
    return isPointSkiaSafe(transform, topleft) && isPointSkiaSafe(transform, bottomright);
#else
    return true;
#endif
}

bool isPathSkiaSafe(const SkMatrix& transform, const SkPath& path)
{
#ifdef ENSURE_VALUE_SAFETY_FOR_SKIA
    SkPoint current_points[4];
    SkPath::Iter iter(path, false);
    for (SkPath::Verb verb = iter.next(current_points);
         verb != SkPath::kDone_Verb;
         verb = iter.next(current_points)) {
        switch (verb) {
        case SkPath::kMove_Verb:
            // This move will be duplicated in the next verb, so we can ignore.
            break;
        case SkPath::kLine_Verb:
            // iter.next returns 2 points.
            if (!isPointSkiaSafe(transform, current_points[0])
                || !isPointSkiaSafe(transform, current_points[1]))
                return false;
            break;
        case SkPath::kQuad_Verb:
            // iter.next returns 3 points.
            if (!isPointSkiaSafe(transform, current_points[0])
                || !isPointSkiaSafe(transform, current_points[1])
                || !isPointSkiaSafe(transform, current_points[2]))
                return false;
            break;
        case SkPath::kCubic_Verb:
            // iter.next returns 4 points.
            if (!isPointSkiaSafe(transform, current_points[0])
                || !isPointSkiaSafe(transform, current_points[1])
                || !isPointSkiaSafe(transform, current_points[2])
                || !isPointSkiaSafe(transform, current_points[3]))
                return false;
            break;
        case SkPath::kClose_Verb:
        case SkPath::kDone_Verb:
        default:
            break;
        }
    }
    return true;
#else
    return true;
#endif
}

// Local helper functions ------------------------------------------------------

void addCornerArc(SkPath* path, const SkRect& rect, const IntSize& size, int startAngle)
{
    SkIRect ir;
    int rx = SkMin32(SkScalarRound(rect.width()), size.width());
    int ry = SkMin32(SkScalarRound(rect.height()), size.height());

    ir.set(-rx, -ry, rx, ry);
    switch (startAngle) {
    case 0:
        ir.offset(rect.fRight - ir.fRight, rect.fBottom - ir.fBottom);
        break;
    case 90:
        ir.offset(rect.fLeft - ir.fLeft, rect.fBottom - ir.fBottom);
        break;
    case 180:
        ir.offset(rect.fLeft - ir.fLeft, rect.fTop - ir.fTop);
        break;
    case 270:
        ir.offset(rect.fRight - ir.fRight, rect.fTop - ir.fTop);
        break;
    default:
        ASSERT(0);
    }

    SkRect r;
    r.set(ir);
    path->arcTo(r, SkIntToScalar(startAngle), SkIntToScalar(90), false);
}

inline int fastMod(int value, int max)
{
    int sign = SkExtractSign(value);

    value = SkApplySign(value, sign);
    if (value >= max)
        value %= max;
    return SkApplySign(value, sign);
}

inline float square(float n)
{
    return n * n;
}

}  // namespace

// -----------------------------------------------------------------------------

// This may be called with a NULL pointer to create a graphics context that has
// no painting.
GraphicsContext::GraphicsContext(PlatformGraphicsContext* gc)
    : m_common(createGraphicsContextPrivate())
    , m_data(new GraphicsContextPlatformPrivate(gc))
{
    setPaintingDisabled(!gc || !platformContext()->canvas());
}

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

PlatformGraphicsContext* GraphicsContext::platformContext() const
{
    ASSERT(!paintingDisabled());
    return m_data->context();
}

// State saving ----------------------------------------------------------------

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

    // Save our private State.
    platformContext()->save();
}

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

    // Restore our private State.
    platformContext()->restore();
}

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

    // We need the "alpha" layer flag here because the base layer is opaque
    // (the surface of the page) but layers on top may have transparent parts.
    // Without explicitly setting the alpha flag, the layer will inherit the
    // opaque setting of the base and some things won't work properly.
    platformContext()->canvas()->saveLayerAlpha(
        0,
        static_cast<unsigned char>(opacity * 255),
        static_cast<SkCanvas::SaveFlags>(SkCanvas::kHasAlphaLayer_SaveFlag |
                                         SkCanvas::kFullColorLayer_SaveFlag));
}

void GraphicsContext::endTransparencyLayer()
{
    if (paintingDisabled())
        return;
    platformContext()->canvas()->restore();
}

// Graphics primitives ---------------------------------------------------------

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

    SkRect r(rect);
    if (!isRectSkiaSafe(getCTM(), r))
        return;

    SkPath path;
    path.addOval(r, SkPath::kCW_Direction);
    // only perform the inset if we won't invert r
    if (2 * thickness < rect.width() && 2 * thickness < rect.height()) {
        r.inset(SkIntToScalar(thickness) ,SkIntToScalar(thickness));
        path.addOval(r, SkPath::kCCW_Direction);
    }
    platformContext()->canvas()->clipPath(path);
}

void GraphicsContext::addPath(const Path& path)
{
    if (paintingDisabled())
        return;
    platformContext()->addPath(*path.platformPath());
}

void GraphicsContext::beginPath()
{
    if (paintingDisabled())
        return;
    platformContext()->beginPath();
}

void GraphicsContext::clearPlatformShadow()
{
    if (paintingDisabled())
        return;
    platformContext()->setDrawLooper(0);
}

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

    SkRect r = rect;
    if (!isRectSkiaSafe(getCTM(), r))
        ClipRectToCanvas(*platformContext()->canvas(), r, &r);

    SkPaint paint;
    platformContext()->setupPaintForFilling(&paint);
    paint.setPorterDuffXfermode(SkPorterDuff::kClear_Mode);
    platformContext()->canvas()->drawRect(r, paint);
}

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

    SkRect r(rect);
    if (!isRectSkiaSafe(getCTM(), r))
        return;

    platformContext()->canvas()->clipRect(r);
}

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

    const SkPath& p = *path.platformPath();
    if (!isPathSkiaSafe(getCTM(), p))
        return;

    platformContext()->canvas()->clipPath(p);
}

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

    SkRect r(rect);
    if (!isRectSkiaSafe(getCTM(), r))
        return;

    platformContext()->canvas()->clipRect(r, SkRegion::kDifference_Op);
}

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

    const SkPath& path = *p.platformPath();
    if (!isPathSkiaSafe(getCTM(), path))