WebCore/html/HTMLCanvasElement.cpp

/*
 * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
 * Copyright (C) 2007 Alp Toker <alp@atoker.com>
 * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. 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 "HTMLCanvasElement.h"

#include "Attribute.h"
#include "CanvasContextAttributes.h"
#include "CanvasGradient.h"
#include "CanvasPattern.h"
#include "CanvasRenderingContext2D.h"
#include "CanvasStyle.h"
#include "Chrome.h"
#include "Document.h"
#include "ExceptionCode.h"
#include "Frame.h"
#include "GraphicsContext.h"
#include "HTMLNames.h"
#include "ImageBuffer.h"
#include "MIMETypeRegistry.h"
#include "Page.h"
#include "RenderHTMLCanvas.h"
#include "Settings.h"
#include <math.h>
#include <stdio.h>

#if ENABLE(3D_CANVAS)    
#include "WebGLContextAttributes.h"
#include "WebGLRenderingContext.h"
#endif

namespace WebCore {

using namespace HTMLNames;

// These values come from the WhatWG spec.
static const int DefaultWidth = 300;
static const int DefaultHeight = 150;

// Firefox limits width/height to 32767 pixels, but slows down dramatically before it
// reaches that limit. We limit by area instead, giving us larger maximum dimensions,
// in exchange for a smaller maximum canvas size.
static const float MaxCanvasArea = 32768 * 8192; // Maximum canvas area in CSS pixels

//In Skia, we will also limit width/height to 32767.
static const float MaxSkiaDim = 32767.0F; // Maximum width/height in CSS pixels.

HTMLCanvasElement::HTMLCanvasElement(const QualifiedName& tagName, Document* document)
    : HTMLElement(tagName, document)
    , m_observer(0)
    , m_size(DefaultWidth, DefaultHeight)
    , m_ignoreReset(false)
    , m_pageScaleFactor(document->frame() ? document->frame()->page()->chrome()->scaleFactor() : 1)
    , m_originClean(true)
    , m_hasCreatedImageBuffer(false)
{
    ASSERT(hasTagName(canvasTag));
}

PassRefPtr<HTMLCanvasElement> HTMLCanvasElement::create(Document* document)
{
    return adoptRef(new HTMLCanvasElement(canvasTag, document));
}

PassRefPtr<HTMLCanvasElement> HTMLCanvasElement::create(const QualifiedName& tagName, Document* document)
{
    return adoptRef(new HTMLCanvasElement(tagName, document));
}

HTMLCanvasElement::~HTMLCanvasElement()
{
    if (m_observer)
        m_observer->canvasDestroyed(this);
}

void HTMLCanvasElement::parseMappedAttribute(Attribute* attr)
{
    const QualifiedName& attrName = attr->name();
    if (attrName == widthAttr || attrName == heightAttr)
        reset();
    HTMLElement::parseMappedAttribute(attr);
}

RenderObject* HTMLCanvasElement::createRenderer(RenderArena* arena, RenderStyle* style)
{
    Frame* frame = document()->frame();
    if (frame && frame->script()->canExecuteScripts(NotAboutToExecuteScript)) {
        m_rendererIsCanvas = true;
        return new (arena) RenderHTMLCanvas(this);
    }

    m_rendererIsCanvas = false;
    return HTMLElement::createRenderer(arena, style);
}

void HTMLCanvasElement::setHeight(int value)
{
    setAttribute(heightAttr, String::number(value));
}

void HTMLCanvasElement::setWidth(int value)
{
    setAttribute(widthAttr, String::number(value));
}

CanvasRenderingContext* HTMLCanvasElement::getContext(const String& type, CanvasContextAttributes* attrs)
{
    // A Canvas can either be "2D" or "webgl" but never both. If you request a 2D canvas and the existing
    // context is already 2D, just return that. If the existing context is WebGL, then destroy it
    // before creating a new 2D context. Vice versa when requesting a WebGL canvas. Requesting a
    // context with any other type string will destroy any existing context.
    
    // FIXME - The code depends on the context not going away once created, to prevent JS from
    // seeing a dangling pointer. So for now we will disallow the context from being changed
    // once it is created.
    if (type == "2d") {
        if (m_context && !m_context->is2d())
            return 0;
        if (!m_context) {
            bool usesDashbardCompatibilityMode = false;
#if ENABLE(DASHBOARD_SUPPORT)
            if (Settings* settings = document()->settings())
                usesDashbardCompatibilityMode = settings->usesDashboardBackwardCompatibilityMode();
#endif
            m_context = adoptPtr(new CanvasRenderingContext2D(this, document()->inQuirksMode(), usesDashbardCompatibilityMode));
#if ENABLE(ACCELERATED_2D_CANVAS) && USE(ACCELERATED_COMPOSITING)
            if (m_context) {
                // Need to make sure a RenderLayer and compositing layer get created for the Canvas
                setNeedsStyleRecalc(SyntheticStyleChange);
            }
#endif
        }
        return m_context.get();
    }
#if ENABLE(3D_CANVAS)    
    Settings* settings = document()->settings();
    if (settings && settings->webGLEnabled()
#if !PLATFORM(CHROMIUM) && !PLATFORM(QT)
        && settings->acceleratedCompositingEnabled()
#endif
        ) {
        // Accept the legacy "webkit-3d" name as well as the provisional "experimental-webgl" name.
        // Once ratified, we will also accept "webgl" as the context name.
        if ((type == "webkit-3d") ||
            (type == "experimental-webgl")) {
            if (m_context && !m_context->is3d())
                return 0;
            if (!m_context) {
                m_context = WebGLRenderingContext::create(this, static_cast<WebGLContextAttributes*>(attrs));
                if (m_context) {
                    // Need to make sure a RenderLayer and compositing layer get created for the Canvas
                    setNeedsStyleRecalc(SyntheticStyleChange);
                }
            }
            return m_context.get();
        }
    }
#else
    UNUSED_PARAM(attrs);
#endif
    return 0;
}

void HTMLCanvasElement::didDraw(const FloatRect& rect)
{
    m_copiedImage.clear(); // Clear our image snapshot if we have one.

    if (RenderBox* ro = renderBox()) {
        FloatRect destRect = ro->contentBoxRect();
        FloatRect r = mapRect(rect, FloatRect(0, 0, size().width(), size().height()), destRect);
        r.intersect(destRect);
        if (m_dirtyRect.contains(r))
            return;

        m_dirtyRect.unite(r);
        ro->repaintRectangle(enclosingIntRect(m_dirtyRect));
    }

    if (m_observer)
        m_observer->canvasChanged(this, rect);
}

void HTMLCanvasElement::reset()
{
    if (m_ignoreReset)
        return;

    bool ok;
    bool hadImageBuffer = hasCreatedImageBuffer();
    int w = getAttribute(widthAttr).toInt(&ok);
    if (!ok || w < 0)
        w = DefaultWidth;
    int h = getAttribute(heightAttr).toInt(&ok);
    if (!ok || h < 0)
        h = DefaultHeight;

    IntSize oldSize = size();
    setSurfaceSize(IntSize(w, h)); // The image buffer gets cleared here.

#if ENABLE(3D_CANVAS)
    if (m_context && m_context->is3d() && oldSize != size())
        static_cast<WebGLRenderingContext*>(m_context.get())->reshape(width(), height());
#endif

    if (m_context && m_context->is2d())
        static_cast<CanvasRenderingContext2D*>(m_context.get())->reset();

    if (RenderObject* renderer = this->renderer()) {
        if (m_rendererIsCanvas) {
            if (oldSize != size())
                toRenderHTMLCanvas(renderer)->canvasSizeChanged();
            if (hadImageBuffer)
                renderer->repaint();
        }
    }

    if (m_observer)
        m_observer->canvasResized(this);
}

void HTMLCanvasElement::paint(GraphicsContext* context, const IntRect& r)
{
    // Clear the dirty rect
    m_dirtyRect = FloatRect();

    if (context->paintingDisabled())
        return;
    
    if (m_context) {
        if (!m_context->paintsIntoCanvasBuffer())
            return;
        m_context->paintRenderingResultsToCanvas();
    }

    if (hasCreatedImageBuffer()) {
        ImageBuffer* imageBuffer = buffer();
        if (imageBuffer) {
            if (imageBuffer->drawsUsingCopy())
                context->drawImage(copiedImage(), DeviceColorSpace, r);
            else
                context->drawImageBuffer(imageBuffer, DeviceColorSpace, r);
        }
    }
}

#if ENABLE(3D_CANVAS)    
bool HTMLCanvasElement::is3D() const
{
    return m_context && m_context->is3d();
}
#endif

void HTMLCanvasElement::makeRenderingResultsAvailable()
{
    if (m_context)
        m_context->paintRenderingResultsToCanvas();
}

void HTMLCanvasElement::recalcStyle(StyleChange change)
{
    HTMLElement::recalcStyle(change);

    // Update font if needed.
    if (change == Force && m_context && m_context->is2d()) {
        CanvasRenderingContext2D* ctx = static_cast<CanvasRenderingContext2D*>(m_context.get());
        ctx->updateFont();
    }
}

void HTMLCanvasElement::setSurfaceSize(const IntSize& size)
{
    m_size = size;
    m_hasCreatedImageBuffer = false;
    m_imageBuffer.clear();
    m_copiedImage.clear();
}

String HTMLCanvasElement::toDataURL(const String& mimeType, const double* quality, ExceptionCode& ec)
{
    if (!m_originClean) {
        ec = SECURITY_ERR;
        return String();
    }

    if (m_size.isEmpty() || !buffer())
        return String("data:,");

    String lowercaseMimeType = mimeType.lower();

    makeRenderingResultsAvailable();

    // FIXME: Make isSupportedImageMIMETypeForEncoding threadsafe (to allow this method to be used on a worker thread).
    if (mimeType.isNull() || !MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(lowercaseMimeType))
        return buffer()->toDataURL("image/png");

    return buffer()->toDataURL(lowercaseMimeType, quality);
}

IntRect HTMLCanvasElement::convertLogicalToDevice(const FloatRect& logicalRect) const
{
    return IntRect(convertLogicalToDevice(logicalRect.location()), convertLogicalToDevice(logicalRect.size()));
}

IntSize HTMLCanvasElement::convertLogicalToDevice(const FloatSize& logicalSize) const
{
    float wf = ceilf(logicalSize.width() * m_pageScaleFactor);
    float hf = ceilf(logicalSize.height() * m_pageScaleFactor);

    if (!(wf >= 1 && hf >= 1 && wf * hf <= MaxCanvasArea))
        return IntSize();

#if PLATFORM(SKIA)
    if (wf > MaxSkiaDim || hf > MaxSkiaDim)
        return IntSize();
#endif

    return IntSize(static_cast<unsigned>(wf), static_cast<unsigned>(hf));
}

IntPoint HTMLCanvasElement::convertLogicalToDevice(const FloatPoint& logicalPos) const
{
    float xf = logicalPos.x() * m_pageScaleFactor;
    float yf = logicalPos.y() * m_pageScaleFactor;

    return IntPoint(static_cast<unsigned>(xf), static_cast<unsigned>(yf));
}

const SecurityOrigin& HTMLCanvasElement::securityOrigin() const
{
    return *document()->securityOrigin();
}

CSSStyleSelector* HTMLCanvasElement::styleSelector()
{
    return document()->styleSelector();
}

void HTMLCanvasElement::createImageBuffer() const
{
    ASSERT(!m_imageBuffer);

    m_hasCreatedImageBuffer = true;

    FloatSize unscaledSize(width(), height());
    IntSize size = convertLogicalToDevice(unscaledSize);
    if (!size.width() || !size.height())
        return;

    m_imageBuffer = ImageBuffer::create(size);
    // The convertLogicalToDevice MaxCanvasArea check should prevent common cases
    // where ImageBuffer::create() returns 0, however we could still be low on memory.
    if (!m_imageBuffer)
        return;
    m_imageBuffer->context()->scale(FloatSize(size.width() / unscaledSize.width(), size.height() / unscaledSize.height()));
    m_imageBuffer->context()->setShadowsIgnoreTransforms(true);
    m_imageBuffer->context()->setImageInterpolationQuality(CanvasInterpolationQuality);
}

GraphicsContext* HTMLCanvasElement::drawingContext() const
{
    return buffer() ? m_imageBuffer->context() : 0;
}

ImageBuffer* HTMLCanvasElement::buffer() const
{
    if (!m_hasCreatedImageBuffer)
        createImageBuffer();
    return m_imageBuffer.get();
}

Image* HTMLCanvasElement::copiedImage() const
{
    if (!m_copiedImage && buffer()) {
        if (m_context) {
            // If we're not rendering to the ImageBuffer, copy the rendering results to it.
            if (!m_context->paintsIntoCanvasBuffer())
                m_context->paintRenderingResultsToCanvas();
        }
        m_copiedImage = buffer()->copyImage();
    }
    return m_copiedImage.get();
}

void HTMLCanvasElement::clearCopiedImage()
{
    m_copiedImage.clear();
}

AffineTransform HTMLCanvasElement::baseTransform() const
{
    ASSERT(m_hasCreatedImageBuffer);
    FloatSize unscaledSize(width(), height());
    IntSize size = convertLogicalToDevice(unscaledSize);
    AffineTransform transform;
    if (size.width() && size.height())
        transform.scaleNonUniform(size.width() / unscaledSize.width(), size.height() / unscaledSize.height());
    transform.multiply(m_imageBuffer->baseTransform());
    return transform;
}

}