Source/WebCore/html/canvas/CanvasRenderingContext2D.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2004-2017 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008 Dirk Schulze <krit@webkit.org>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  * Copyright (C) 2012 Intel Corporation. All rights reserved.
  * Copyright (C) 2013, 2014 Adobe Systems Incorporated. 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 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 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 "CanvasRenderingContext2D.h"

 #include "CSSFontSelector.h"
 #include "CSSParser.h"
 #include "CSSPropertyNames.h"
 #include "ImageBuffer.h"
 #include "ImageData.h"
 #include "InspectorInstrumentation.h"
 #include "Path2D.h"
 #include "RenderTheme.h"
 #include "ResourceLoadObserver.h"
 #include "RuntimeEnabledFeatures.h"
 #include "StyleProperties.h"
 #include "StyleResolver.h"
 #include "TextMetrics.h"
 #include "TextRun.h"
 #include <wtf/CheckedArithmetic.h>
 #include <wtf/IsoMallocInlines.h>
 #include <wtf/MathExtras.h>
 #include <wtf/text/StringBuilder.h>

 namespace WebCore {

 using namespace HTMLNames;

 WTF_MAKE_ISO_ALLOCATED_IMPL(CanvasRenderingContext2D);

 std::unique_ptr<CanvasRenderingContext2D> CanvasRenderingContext2D::create(CanvasBase& canvas, bool usesCSSCompatibilityParseMode)
 {
     auto renderingContext = std::unique_ptr<CanvasRenderingContext2D>(new CanvasRenderingContext2D(canvas, usesCSSCompatibilityParseMode));

     InspectorInstrumentation::didCreateCanvasRenderingContext(*renderingContext);

     return renderingContext;
 }

 CanvasRenderingContext2D::CanvasRenderingContext2D(CanvasBase& canvas, bool usesCSSCompatibilityParseMode)
     : CanvasRenderingContext2DBase(canvas, usesCSSCompatibilityParseMode)
 {
 }

 CanvasRenderingContext2D::~CanvasRenderingContext2D() = default;

 void CanvasRenderingContext2D::drawFocusIfNeeded(Element& element)
 {
     drawFocusIfNeededInternal(m_path, element);
 }

 void CanvasRenderingContext2D::drawFocusIfNeeded(Path2D& path, Element& element)
 {
     drawFocusIfNeededInternal(path.path(), element);
 }

 void CanvasRenderingContext2D::drawFocusIfNeededInternal(const Path& path, Element& element)
 {
     auto* context = drawingContext();
     if (!element.focused() || !state().hasInvertibleTransform || path.isEmpty() || !element.isDescendantOf(canvas()) || !context)
         return;
     context->drawFocusRing(path, 1, 1, RenderTheme::singleton().focusRingColor(element.document().styleColorOptions(canvas().computedStyle())));
 }

 String CanvasRenderingContext2D::font() const
 {
     if (!state().font.realized())
         return DefaultFont;

     StringBuilder serializedFont;
     const auto& fontDescription = state().font.fontDescription();

     if (fontDescription.italic())
         serializedFont.appendLiteral("italic ");
     if (fontDescription.variantCaps() == FontVariantCaps::Small)
         serializedFont.appendLiteral("small-caps ");

     serializedFont.appendNumber(fontDescription.computedPixelSize());
     serializedFont.appendLiteral("px");

     for (unsigned i = 0; i < fontDescription.familyCount(); ++i) {
         if (i)
             serializedFont.append(',');

         // FIXME: We should append family directly to serializedFont rather than building a temporary string.
         String family = fontDescription.familyAt(i);
         if (family.startsWith("-webkit-"))
             family = family.substring(8);
         if (family.contains(' '))
             family = makeString('"', family, '"');

         serializedFont.append(' ', family);
     }

     return serializedFont.toString();
 }

 void CanvasRenderingContext2D::setFont(const String& newFont)
 {
     if (newFont.isEmpty())
         return;

     if (newFont == state().unparsedFont && state().font.realized())
         return;

     auto parsedStyle = MutableStyleProperties::create();
     CSSParser::parseValue(parsedStyle, CSSPropertyFont, newFont, true, strictToCSSParserMode(!m_usesCSSCompatibilityParseMode));
     if (parsedStyle->isEmpty())
         return;

     String fontValue = parsedStyle->getPropertyValue(CSSPropertyFont);

     // According to http://lists.w3.org/Archives/Public/public-html/2009Jul/0947.html,
     // the "inherit" and "initial" values must be ignored.
     if (fontValue == "inherit" || fontValue == "initial")
         return;

     // The parse succeeded.
     String newFontSafeCopy(newFont); // Create a string copy since newFont can be deleted inside realizeSaves.
     realizeSaves();
     modifiableState().unparsedFont = newFontSafeCopy;

     // Map the <canvas> font into the text style. If the font uses keywords like larger/smaller, these will work
     // relative to the canvas.
     auto newStyle = RenderStyle::createPtr();

     Document& document = canvas().document();
     document.updateStyleIfNeeded();

     if (auto* computedStyle = canvas().computedStyle())
         newStyle->setFontDescription(FontCascadeDescription { computedStyle->fontDescription() });
     else {
         FontCascadeDescription defaultFontDescription;
         defaultFontDescription.setOneFamily(DefaultFontFamily);
         defaultFontDescription.setSpecifiedSize(DefaultFontSize);
         defaultFontDescription.setComputedSize(DefaultFontSize);

         newStyle->setFontDescription(WTFMove(defaultFontDescription));
     }

     newStyle->fontCascade().update(&document.fontSelector());

     // Now map the font property longhands into the style.
     StyleResolver& styleResolver = canvas().styleResolver();
     styleResolver.applyPropertyToStyle(CSSPropertyFontFamily, parsedStyle->getPropertyCSSValue(CSSPropertyFontFamily).get(), WTFMove(newStyle));
     styleResolver.applyPropertyToCurrentStyle(CSSPropertyFontStyle, parsedStyle->getPropertyCSSValue(CSSPropertyFontStyle).get());
     styleResolver.applyPropertyToCurrentStyle(CSSPropertyFontVariantCaps, parsedStyle->getPropertyCSSValue(CSSPropertyFontVariantCaps).get());
     styleResolver.applyPropertyToCurrentStyle(CSSPropertyFontWeight, parsedStyle->getPropertyCSSValue(CSSPropertyFontWeight).get());

     // As described in BUG66291, setting font-size and line-height on a font may entail a CSSPrimitiveValue::computeLengthDouble call,
     // which assumes the fontMetrics are available for the affected font, otherwise a crash occurs (see http://trac.webkit.org/changeset/96122).
     // The updateFont() calls below update the fontMetrics and ensure the proper setting of font-size and line-height.
     styleResolver.updateFont();
     styleResolver.applyPropertyToCurrentStyle(CSSPropertyFontSize, parsedStyle->getPropertyCSSValue(CSSPropertyFontSize).get());
     styleResolver.updateFont();
     styleResolver.applyPropertyToCurrentStyle(CSSPropertyLineHeight, parsedStyle->getPropertyCSSValue(CSSPropertyLineHeight).get());

     modifiableState().font.initialize(document.fontSelector(), *styleResolver.style());
 }

 static CanvasTextAlign toCanvasTextAlign(TextAlign textAlign)
 {
     switch (textAlign) {
     case StartTextAlign:
         return CanvasTextAlign::Start;
     case EndTextAlign:
         return CanvasTextAlign::End;
     case LeftTextAlign:
         return CanvasTextAlign::Left;
     case RightTextAlign:
         return CanvasTextAlign::Right;
     case CenterTextAlign:
         return CanvasTextAlign::Center;
     }

     ASSERT_NOT_REACHED();
     return CanvasTextAlign::Start;
 }

 static TextAlign fromCanvasTextAlign(CanvasTextAlign canvasTextAlign)
 {
     switch (canvasTextAlign) {
     case CanvasTextAlign::Start:
         return StartTextAlign;
     case CanvasTextAlign::End:
         return EndTextAlign;
     case CanvasTextAlign::Left:
         return LeftTextAlign;
     case CanvasTextAlign::Right:
         return RightTextAlign;
     case CanvasTextAlign::Center:
         return CenterTextAlign;
     }

     ASSERT_NOT_REACHED();
     return StartTextAlign;
 }

 CanvasTextAlign CanvasRenderingContext2D::textAlign() const
 {
     return toCanvasTextAlign(state().textAlign);
 }

 void CanvasRenderingContext2D::setTextAlign(CanvasTextAlign canvasTextAlign)
 {
     auto textAlign = fromCanvasTextAlign(canvasTextAlign);
     if (state().textAlign == textAlign)
         return;
     realizeSaves();
     modifiableState().textAlign = textAlign;
 }

 static CanvasTextBaseline toCanvasTextBaseline(TextBaseline textBaseline)
 {
     switch (textBaseline) {
     case TopTextBaseline:
         return CanvasTextBaseline::Top;
     case HangingTextBaseline:
         return CanvasTextBaseline::Hanging;
     case MiddleTextBaseline:
         return CanvasTextBaseline::Middle;
     case AlphabeticTextBaseline:
         return CanvasTextBaseline::Alphabetic;
     case IdeographicTextBaseline:
         return CanvasTextBaseline::Ideographic;
     case BottomTextBaseline:
         return CanvasTextBaseline::Bottom;
     }

     ASSERT_NOT_REACHED();
     return CanvasTextBaseline::Top;
 }

 static TextBaseline fromCanvasTextBaseline(CanvasTextBaseline canvasTextBaseline)
 {
     switch (canvasTextBaseline) {
     case CanvasTextBaseline::Top:
         return TopTextBaseline;
     case CanvasTextBaseline::Hanging:
         return HangingTextBaseline;
     case CanvasTextBaseline::Middle:
         return MiddleTextBaseline;
     case CanvasTextBaseline::Alphabetic:
         return AlphabeticTextBaseline;
     case CanvasTextBaseline::Ideographic:
         return IdeographicTextBaseline;
     case CanvasTextBaseline::Bottom:
         return BottomTextBaseline;
     }

     ASSERT_NOT_REACHED();
     return TopTextBaseline;
 }

 CanvasTextBaseline CanvasRenderingContext2D::textBaseline() const
 {
     return toCanvasTextBaseline(state().textBaseline);
 }

 void CanvasRenderingContext2D::setTextBaseline(CanvasTextBaseline canvasTextBaseline)
 {
     auto textBaseline = fromCanvasTextBaseline(canvasTextBaseline);
     if (state().textBaseline == textBaseline)
         return;
     realizeSaves();
     modifiableState().textBaseline = textBaseline;
 }

 inline TextDirection CanvasRenderingContext2D::toTextDirection(Direction direction, const RenderStyle** computedStyle) const
 {
     auto* style = (computedStyle || direction == Direction::Inherit) ? canvas().computedStyle() : nullptr;
     if (computedStyle)
         *computedStyle = style;
     switch (direction) {
     case Direction::Inherit:
         return style ? style->direction() : TextDirection::LTR;
     case Direction::Rtl:
         return TextDirection::RTL;
     case Direction::Ltr:
         return TextDirection::LTR;
     }
     ASSERT_NOT_REACHED();
     return TextDirection::LTR;
 }

 CanvasDirection CanvasRenderingContext2D::direction() const
 {
     if (state().direction == Direction::Inherit)
         canvas().document().updateStyleIfNeeded();
     return toTextDirection(state().direction) == TextDirection::RTL ? CanvasDirection::Rtl : CanvasDirection::Ltr;
 }

 void CanvasRenderingContext2D::setDirection(CanvasDirection direction)
 {
     if (state().direction == direction)
         return;

     realizeSaves();
     modifiableState().direction = direction;
 }

 void CanvasRenderingContext2D::fillText(const String& text, float x, float y, Optional<float> maxWidth)
 {
     drawTextInternal(text, x, y, true, maxWidth);
 }

 void CanvasRenderingContext2D::strokeText(const String& text, float x, float y, Optional<float> maxWidth)
 {
     drawTextInternal(text, x, y, false, maxWidth);
 }

 static inline bool isSpaceThatNeedsReplacing(UChar c)
 {
     // According to specification all space characters should be replaced with 0x0020 space character.
     // http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#text-preparation-algorithm
     // The space characters according to specification are : U+0020, U+0009, U+000A, U+000C, and U+000D.
     // http://www.whatwg.org/specs/web-apps/current-work/multipage/common-microsyntaxes.html#space-character
     // This function returns true for 0x000B also, so that this is backward compatible.
     // Otherwise, the test LayoutTests/canvas/philip/tests/2d.text.draw.space.collapse.space.html will fail
     return c == 0x0009 || c == 0x000A || c == 0x000B || c == 0x000C || c == 0x000D;
 }

 static void normalizeSpaces(String& text)
 {
     size_t i = text.find(isSpaceThatNeedsReplacing);
     if (i == notFound)
         return;

     unsigned textLength = text.length();
     Vector<UChar> charVector(textLength);
     StringView(text).getCharactersWithUpconvert(charVector.data());

     charVector[i++] = ' ';

     for (; i < textLength; ++i) {
         if (isSpaceThatNeedsReplacing(charVector[i]))
             charVector[i] = ' ';
     }
     text = String::adopt(WTFMove(charVector));
 }

 Ref<TextMetrics> CanvasRenderingContext2D::measureText(const String& text)
 {
     if (RuntimeEnabledFeatures::sharedFeatures().webAPIStatisticsEnabled()) {
         auto& canvas = this->canvas();
         ResourceLoadObserver::shared().logCanvasWriteOrMeasure(canvas.document(), text);
         ResourceLoadObserver::shared().logCanvasRead(canvas.document());
     }

     Ref<TextMetrics> metrics = TextMetrics::create();

     String normalizedText = text;
     normalizeSpaces(normalizedText);

     const RenderStyle* computedStyle;
     auto direction = toTextDirection(state().direction, &computedStyle);
     bool override = computedStyle ? isOverride(computedStyle->unicodeBidi()) : false;

     TextRun textRun(normalizedText, 0, 0, AllowTrailingExpansion, direction, override, true);
     auto& font = fontProxy();
     auto& fontMetrics = font.fontMetrics();

     GlyphOverflow glyphOverflow;
     glyphOverflow.computeBounds = true;
     float fontWidth = font.width(textRun, &glyphOverflow);
     metrics->setWidth(fontWidth);

     FloatPoint offset = textOffset(fontWidth, direction);

     metrics->setActualBoundingBoxAscent(glyphOverflow.top - offset.y());
     metrics->setActualBoundingBoxDescent(glyphOverflow.bottom + offset.y());
     metrics->setFontBoundingBoxAscent(fontMetrics.ascent() - offset.y());
     metrics->setFontBoundingBoxDescent(fontMetrics.descent() + offset.y());
     metrics->setEmHeightAscent(fontMetrics.ascent() - offset.y());
     metrics->setEmHeightDescent(fontMetrics.descent() + offset.y());
     metrics->setHangingBaseline(fontMetrics.ascent() - offset.y());
     metrics->setAlphabeticBaseline(-offset.y());
     metrics->setIdeographicBaseline(-fontMetrics.descent() - offset.y());

     metrics->setActualBoundingBoxLeft(glyphOverflow.left - offset.x());
     metrics->setActualBoundingBoxRight(fontWidth + glyphOverflow.right + offset.x());

     return metrics;
 }

 auto CanvasRenderingContext2D::fontProxy() -> const FontProxy& {
     auto& canvas = downcast<HTMLCanvasElement>(canvasBase());
     canvas.document().updateStyleIfNeeded();
     if (!state().font.realized())
         setFont(state().unparsedFont);
     return state().font;
 }

 FloatPoint CanvasRenderingContext2D::textOffset(float width, TextDirection direction)
 {
     auto& fontMetrics = fontProxy().fontMetrics();
     FloatPoint offset;

     switch (state().textBaseline) {
     case TopTextBaseline:
     case HangingTextBaseline:
         offset.setY(fontMetrics.ascent());
         break;
     case BottomTextBaseline:
     case IdeographicTextBaseline:
         offset.setY(-fontMetrics.descent());
         break;
     case MiddleTextBaseline:
         offset.setY(fontMetrics.height() / 2 - fontMetrics.descent());
         break;
     case AlphabeticTextBaseline:
     default:
         break;
     }

     bool isRTL = direction == TextDirection::RTL;
     auto align = state().textAlign;
     if (align == StartTextAlign)
         align = isRTL ? RightTextAlign : LeftTextAlign;
     else if (align == EndTextAlign)
         align = isRTL ? LeftTextAlign : RightTextAlign;

     switch (align) {
     case CenterTextAlign:
         offset.setX(-width / 2);
         break;
     case RightTextAlign:
         offset.setX(-width);
         break;
     default:
         break;
     }
     return offset;
 }

 void CanvasRenderingContext2D::drawTextInternal(const String& text, float x, float y, bool fill, Optional<float> maxWidth)
 {
     if (RuntimeEnabledFeatures::sharedFeatures().webAPIStatisticsEnabled())
         ResourceLoadObserver::shared().logCanvasWriteOrMeasure(this->canvas().document(), text);

     auto& fontProxy = this->fontProxy();
     const auto& fontMetrics = fontProxy.fontMetrics();

     auto* c = drawingContext();
     if (!c)
         return;
     if (!state().hasInvertibleTransform)
         return;
     if (!std::isfinite(x) | !std::isfinite(y))
         return;
     if (maxWidth && (!std::isfinite(maxWidth.value()) || maxWidth.value() <= 0))
         return;

     // If gradient size is zero, then paint nothing.
     auto gradient = c->strokeGradient();
     if (!fill && gradient && gradient->isZeroSize())
         return;

     gradient = c->fillGradient();
     if (fill && gradient && gradient->isZeroSize())
         return;

     String normalizedText = text;
     normalizeSpaces(normalizedText);

     // FIXME: Need to turn off font smoothing.

     const RenderStyle* computedStyle;
     auto direction = toTextDirection(state().direction, &computedStyle);
     bool override = computedStyle ? isOverride(computedStyle->unicodeBidi()) : false;

     TextRun textRun(normalizedText, 0, 0, AllowTrailingExpansion, direction, override, true);
     float fontWidth = fontProxy.width(textRun);
     bool useMaxWidth = maxWidth && maxWidth.value() < fontWidth;
     float width = useMaxWidth ? maxWidth.value() : fontWidth;
     FloatPoint location(x, y);
     location += textOffset(width, direction);

     // The slop built in to this mask rect matches the heuristic used in FontCGWin.cpp for GDI text.
     FloatRect textRect = FloatRect(location.x() - fontMetrics.height() / 2, location.y() - fontMetrics.ascent() - fontMetrics.lineGap(),
         width + fontMetrics.height(), fontMetrics.lineSpacing());
     if (!fill)
         inflateStrokeRect(textRect);

 #if USE(CG)
     const CanvasStyle& drawStyle = fill ? state().fillStyle : state().strokeStyle;
     if (drawStyle.canvasGradient() || drawStyle.canvasPattern()) {
         IntRect maskRect = enclosingIntRect(textRect);

         // If we have a shadow, we need to draw it before the mask operation.
         // Follow a procedure similar to paintTextWithShadows in TextPainter.

         if (shouldDrawShadows()) {
             GraphicsContextStateSaver stateSaver(*c);

             FloatSize offset(0, 2 * maskRect.height());

             FloatSize shadowOffset;
             float shadowRadius;
             Color shadowColor;
             c->getShadow(shadowOffset, shadowRadius, shadowColor);

             FloatRect shadowRect(maskRect);
             shadowRect.inflate(shadowRadius * 1.4);
             shadowRect.move(shadowOffset * -1);
             c->clip(shadowRect);

             shadowOffset += offset;

             c->setLegacyShadow(shadowOffset, shadowRadius, shadowColor);

             if (fill)
                 c->setFillColor(Color::black);
             else
                 c->setStrokeColor(Color::black);

             fontProxy.drawBidiText(*c, textRun, location + offset, FontCascade::UseFallbackIfFontNotReady);
         }

         auto maskImage = ImageBuffer::createCompatibleBuffer(maskRect.size(), ColorSpaceSRGB, *c);
         if (!maskImage)
             return;

         auto& maskImageContext = maskImage->context();

         if (fill)
             maskImageContext.setFillColor(Color::black);
         else {
             maskImageContext.setStrokeColor(Color::black);
             maskImageContext.setStrokeThickness(c->strokeThickness());
         }

         maskImageContext.setTextDrawingMode(fill ? TextModeFill : TextModeStroke);

         if (useMaxWidth) {
             maskImageContext.translate(location - maskRect.location());
             // We draw when fontWidth is 0 so compositing operations (eg, a "copy" op) still work.
             maskImageContext.scale(FloatSize((fontWidth > 0 ? (width / fontWidth) : 0), 1));
             fontProxy.drawBidiText(maskImageContext, textRun, FloatPoint(0, 0), FontCascade::UseFallbackIfFontNotReady);
         } else {
             maskImageContext.translate(-maskRect.location());
             fontProxy.drawBidiText(maskImageContext, textRun, location, FontCascade::UseFallbackIfFontNotReady);
         }

         GraphicsContextStateSaver stateSaver(*c);
         c->clipToImageBuffer(*maskImage, maskRect);
         drawStyle.applyFillColor(*c);
         c->fillRect(maskRect);
         return;
     }
 #endif

     c->setTextDrawingMode(fill ? TextModeFill : TextModeStroke);

     GraphicsContextStateSaver stateSaver(*c);
     if (useMaxWidth) {
         c->translate(location);
         // We draw when fontWidth is 0 so compositing operations (eg, a "copy" op) still work.
         c->scale(FloatSize((fontWidth > 0 ? (width / fontWidth) : 0), 1));
         location = FloatPoint();
     }

     if (isFullCanvasCompositeMode(state().globalComposite)) {
         beginCompositeLayer();
         fontProxy.drawBidiText(*c, textRun, location, FontCascade::UseFallbackIfFontNotReady);
         endCompositeLayer();
         didDrawEntireCanvas();
     } else if (state().globalComposite == CompositeCopy) {
         clearCanvas();
         fontProxy.drawBidiText(*c, textRun, location, FontCascade::UseFallbackIfFontNotReady);
         didDrawEntireCanvas();
     } else {
         fontProxy.drawBidiText(*c, textRun, location, FontCascade::UseFallbackIfFontNotReady);
         didDraw(textRect);
     }
 }

 } // namespace WebCore
	/*
	* Copyright (C) 2004-2017 Apple Inc. All rights reserved.
	* Copyright (C) 2008, 2010 Nokia Corporation and/or its subsidiary(-ies)
	* Copyright (C) 2007 Alp Toker <alp@atoker.com>
	* Copyright (C) 2008 Eric Seidel <eric@webkit.org>
	* Copyright (C) 2008 Dirk Schulze <krit@webkit.org>
	* Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
	* Copyright (C) 2012 Intel Corporation. All rights reserved.
	* Copyright (C) 2013, 2014 Adobe Systems Incorporated. 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 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 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 "CanvasRenderingContext2D.h"

	#include "CSSFontSelector.h"
	#include "CSSParser.h"
	#include "CSSPropertyNames.h"
	#include "ImageBuffer.h"
	#include "ImageData.h"
	#include "InspectorInstrumentation.h"
	#include "Path2D.h"
	#include "RenderTheme.h"
	#include "ResourceLoadObserver.h"
	#include "RuntimeEnabledFeatures.h"
	#include "StyleProperties.h"
	#include "StyleResolver.h"
	#include "TextMetrics.h"
	#include "TextRun.h"
	#include <wtf/CheckedArithmetic.h>
	#include <wtf/IsoMallocInlines.h>
	#include <wtf/MathExtras.h>
	#include <wtf/text/StringBuilder.h>

	namespace WebCore {

	using namespace HTMLNames;

	WTF_MAKE_ISO_ALLOCATED_IMPL(CanvasRenderingContext2D);

	std::unique_ptr<CanvasRenderingContext2D> CanvasRenderingContext2D::create(CanvasBase& canvas, bool usesCSSCompatibilityParseMode)
	{
	auto renderingContext = std::unique_ptr<CanvasRenderingContext2D>(new CanvasRenderingContext2D(canvas, usesCSSCompatibilityParseMode));

	InspectorInstrumentation::didCreateCanvasRenderingContext(*renderingContext);

	return renderingContext;
	}

	CanvasRenderingContext2D::CanvasRenderingContext2D(CanvasBase& canvas, bool usesCSSCompatibilityParseMode)
	: CanvasRenderingContext2DBase(canvas, usesCSSCompatibilityParseMode)
	{
	}

	CanvasRenderingContext2D::~CanvasRenderingContext2D() = default;

	void CanvasRenderingContext2D::drawFocusIfNeeded(Element& element)
	{
	drawFocusIfNeededInternal(m_path, element);
	}

	void CanvasRenderingContext2D::drawFocusIfNeeded(Path2D& path, Element& element)
	{
	drawFocusIfNeededInternal(path.path(), element);
	}

	void CanvasRenderingContext2D::drawFocusIfNeededInternal(const Path& path, Element& element)
	{
	auto* context = drawingContext();
	if (!element.focused() \|\| !state().hasInvertibleTransform \|\| path.isEmpty() \|\| !element.isDescendantOf(canvas()) \|\| !context)
	return;
	context->drawFocusRing(path, 1, 1, RenderTheme::singleton().focusRingColor(element.document().styleColorOptions(canvas().computedStyle())));
	}

	String CanvasRenderingContext2D::font() const
	{
	if (!state().font.realized())
	return DefaultFont;

	StringBuilder serializedFont;
	const auto& fontDescription = state().font.fontDescription();

	if (fontDescription.italic())
	serializedFont.appendLiteral("italic ");
	if (fontDescription.variantCaps() == FontVariantCaps::Small)
	serializedFont.appendLiteral("small-caps ");

	serializedFont.appendNumber(fontDescription.computedPixelSize());
	serializedFont.appendLiteral("px");

	for (unsigned i = 0; i < fontDescription.familyCount(); ++i) {
	if (i)
	serializedFont.append(',');

	// FIXME: We should append family directly to serializedFont rather than building a temporary string.
	String family = fontDescription.familyAt(i);
	if (family.startsWith("-webkit-"))
	family = family.substring(8);
	if (family.contains(' '))
	family = makeString('"', family, '"');

	serializedFont.append(' ', family);
	}

	return serializedFont.toString();
	}

	void CanvasRenderingContext2D::setFont(const String& newFont)
	{
	if (newFont.isEmpty())
	return;

	if (newFont == state().unparsedFont && state().font.realized())
	return;

	auto parsedStyle = MutableStyleProperties::create();
	CSSParser::parseValue(parsedStyle, CSSPropertyFont, newFont, true, strictToCSSParserMode(!m_usesCSSCompatibilityParseMode));
	if (parsedStyle->isEmpty())
	return;

	String fontValue = parsedStyle->getPropertyValue(CSSPropertyFont);

	// According to http://lists.w3.org/Archives/Public/public-html/2009Jul/0947.html,
	// the "inherit" and "initial" values must be ignored.
	if (fontValue == "inherit" \|\| fontValue == "initial")
	return;

	// The parse succeeded.
	String newFontSafeCopy(newFont); // Create a string copy since newFont can be deleted inside realizeSaves.
	realizeSaves();
	modifiableState().unparsedFont = newFontSafeCopy;

	// Map the <canvas> font into the text style. If the font uses keywords like larger/smaller, these will work
	// relative to the canvas.
	auto newStyle = RenderStyle::createPtr();

	Document& document = canvas().document();
	document.updateStyleIfNeeded();

	if (auto* computedStyle = canvas().computedStyle())
	newStyle->setFontDescription(FontCascadeDescription { computedStyle->fontDescription() });
	else {
	FontCascadeDescription defaultFontDescription;
	defaultFontDescription.setOneFamily(DefaultFontFamily);
	defaultFontDescription.setSpecifiedSize(DefaultFontSize);
	defaultFontDescription.setComputedSize(DefaultFontSize);

	newStyle->setFontDescription(WTFMove(defaultFontDescription));
	}

	newStyle->fontCascade().update(&document.fontSelector());

	// Now map the font property longhands into the style.
	StyleResolver& styleResolver = canvas().styleResolver();
	styleResolver.applyPropertyToStyle(CSSPropertyFontFamily, parsedStyle->getPropertyCSSValue(CSSPropertyFontFamily).get(), WTFMove(newStyle));
	styleResolver.applyPropertyToCurrentStyle(CSSPropertyFontStyle, parsedStyle->getPropertyCSSValue(CSSPropertyFontStyle).get());
	styleResolver.applyPropertyToCurrentStyle(CSSPropertyFontVariantCaps, parsedStyle->getPropertyCSSValue(CSSPropertyFontVariantCaps).get());
	styleResolver.applyPropertyToCurrentStyle(CSSPropertyFontWeight, parsedStyle->getPropertyCSSValue(CSSPropertyFontWeight).get());

	// As described in BUG66291, setting font-size and line-height on a font may entail a CSSPrimitiveValue::computeLengthDouble call,
	// which assumes the fontMetrics are available for the affected font, otherwise a crash occurs (see http://trac.webkit.org/changeset/96122).
	// The updateFont() calls below update the fontMetrics and ensure the proper setting of font-size and line-height.
	styleResolver.updateFont();
	styleResolver.applyPropertyToCurrentStyle(CSSPropertyFontSize, parsedStyle->getPropertyCSSValue(CSSPropertyFontSize).get());
	styleResolver.updateFont();
	styleResolver.applyPropertyToCurrentStyle(CSSPropertyLineHeight, parsedStyle->getPropertyCSSValue(CSSPropertyLineHeight).get());

	modifiableState().font.initialize(document.fontSelector(), *styleResolver.style());
	}

	static CanvasTextAlign toCanvasTextAlign(TextAlign textAlign)
	{
	switch (textAlign) {
	case StartTextAlign:
	return CanvasTextAlign::Start;
	case EndTextAlign:
	return CanvasTextAlign::End;
	case LeftTextAlign:
	return CanvasTextAlign::Left;
	case RightTextAlign:
	return CanvasTextAlign::Right;
	case CenterTextAlign:
	return CanvasTextAlign::Center;
	}

	ASSERT_NOT_REACHED();
	return CanvasTextAlign::Start;
	}

	static TextAlign fromCanvasTextAlign(CanvasTextAlign canvasTextAlign)
	{
	switch (canvasTextAlign) {
	case CanvasTextAlign::Start:
	return StartTextAlign;
	case CanvasTextAlign::End:
	return EndTextAlign;
	case CanvasTextAlign::Left:
	return LeftTextAlign;
	case CanvasTextAlign::Right:
	return RightTextAlign;
	case CanvasTextAlign::Center:
	return CenterTextAlign;
	}

	ASSERT_NOT_REACHED();
	return StartTextAlign;
	}

	CanvasTextAlign CanvasRenderingContext2D::textAlign() const
	{
	return toCanvasTextAlign(state().textAlign);
	}

	void CanvasRenderingContext2D::setTextAlign(CanvasTextAlign canvasTextAlign)
	{
	auto textAlign = fromCanvasTextAlign(canvasTextAlign);
	if (state().textAlign == textAlign)
	return;
	realizeSaves();
	modifiableState().textAlign = textAlign;
	}

	static CanvasTextBaseline toCanvasTextBaseline(TextBaseline textBaseline)
	{
	switch (textBaseline) {
	case TopTextBaseline:
	return CanvasTextBaseline::Top;
	case HangingTextBaseline:
	return CanvasTextBaseline::Hanging;
	case MiddleTextBaseline:
	return CanvasTextBaseline::Middle;
	case AlphabeticTextBaseline:
	return CanvasTextBaseline::Alphabetic;
	case IdeographicTextBaseline:
	return CanvasTextBaseline::Ideographic;
	case BottomTextBaseline:
	return CanvasTextBaseline::Bottom;
	}

	ASSERT_NOT_REACHED();
	return CanvasTextBaseline::Top;
	}

	static TextBaseline fromCanvasTextBaseline(CanvasTextBaseline canvasTextBaseline)
	{
	switch (canvasTextBaseline) {
	case CanvasTextBaseline::Top:
	return TopTextBaseline;
	case CanvasTextBaseline::Hanging:
	return HangingTextBaseline;
	case CanvasTextBaseline::Middle:
	return MiddleTextBaseline;
	case CanvasTextBaseline::Alphabetic:
	return AlphabeticTextBaseline;
	case CanvasTextBaseline::Ideographic:
	return IdeographicTextBaseline;
	case CanvasTextBaseline::Bottom:
	return BottomTextBaseline;
	}

	ASSERT_NOT_REACHED();
	return TopTextBaseline;
	}

	CanvasTextBaseline CanvasRenderingContext2D::textBaseline() const
	{
	return toCanvasTextBaseline(state().textBaseline);
	}

	void CanvasRenderingContext2D::setTextBaseline(CanvasTextBaseline canvasTextBaseline)
	{
	auto textBaseline = fromCanvasTextBaseline(canvasTextBaseline);
	if (state().textBaseline == textBaseline)
	return;
	realizeSaves();
	modifiableState().textBaseline = textBaseline;
	}

	inline TextDirection CanvasRenderingContext2D::toTextDirection(Direction direction, const RenderStyle** computedStyle) const
	{
	auto* style = (computedStyle \|\| direction == Direction::Inherit) ? canvas().computedStyle() : nullptr;
	if (computedStyle)
	*computedStyle = style;
	switch (direction) {
	case Direction::Inherit:
	return style ? style->direction() : TextDirection::LTR;
	case Direction::Rtl:
	return TextDirection::RTL;
	case Direction::Ltr:
	return TextDirection::LTR;
	}
	ASSERT_NOT_REACHED();
	return TextDirection::LTR;
	}

	CanvasDirection CanvasRenderingContext2D::direction() const
	{
	if (state().direction == Direction::Inherit)
	canvas().document().updateStyleIfNeeded();
	return toTextDirection(state().direction) == TextDirection::RTL ? CanvasDirection::Rtl : CanvasDirection::Ltr;
	}

	void CanvasRenderingContext2D::setDirection(CanvasDirection direction)
	{
	if (state().direction == direction)
	return;

	realizeSaves();
	modifiableState().direction = direction;
	}

	void CanvasRenderingContext2D::fillText(const String& text, float x, float y, Optional<float> maxWidth)
	{
	drawTextInternal(text, x, y, true, maxWidth);
	}

	void CanvasRenderingContext2D::strokeText(const String& text, float x, float y, Optional<float> maxWidth)
	{
	drawTextInternal(text, x, y, false, maxWidth);
	}

	static inline bool isSpaceThatNeedsReplacing(UChar c)
	{
	// According to specification all space characters should be replaced with 0x0020 space character.
	// http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#text-preparation-algorithm
	// The space characters according to specification are : U+0020, U+0009, U+000A, U+000C, and U+000D.
	// http://www.whatwg.org/specs/web-apps/current-work/multipage/common-microsyntaxes.html#space-character
	// This function returns true for 0x000B also, so that this is backward compatible.
	// Otherwise, the test LayoutTests/canvas/philip/tests/2d.text.draw.space.collapse.space.html will fail
	return c == 0x0009 \|\| c == 0x000A \|\| c == 0x000B \|\| c == 0x000C \|\| c == 0x000D;
	}

	static void normalizeSpaces(String& text)
	{
	size_t i = text.find(isSpaceThatNeedsReplacing);
	if (i == notFound)
	return;

	unsigned textLength = text.length();
	Vector<UChar> charVector(textLength);
	StringView(text).getCharactersWithUpconvert(charVector.data());

	charVector[i++] = ' ';

	for (; i < textLength; ++i) {
	if (isSpaceThatNeedsReplacing(charVector[i]))
	charVector[i] = ' ';
	}
	text = String::adopt(WTFMove(charVector));
	}

	Ref<TextMetrics> CanvasRenderingContext2D::measureText(const String& text)
	{
	if (RuntimeEnabledFeatures::sharedFeatures().webAPIStatisticsEnabled()) {
	auto& canvas = this->canvas();
	ResourceLoadObserver::shared().logCanvasWriteOrMeasure(canvas.document(), text);
	ResourceLoadObserver::shared().logCanvasRead(canvas.document());
	}

	Ref<TextMetrics> metrics = TextMetrics::create();

	String normalizedText = text;
	normalizeSpaces(normalizedText);

	const RenderStyle* computedStyle;
	auto direction = toTextDirection(state().direction, &computedStyle);
	bool override = computedStyle ? isOverride(computedStyle->unicodeBidi()) : false;

	TextRun textRun(normalizedText, 0, 0, AllowTrailingExpansion, direction, override, true);
	auto& font = fontProxy();
	auto& fontMetrics = font.fontMetrics();

	GlyphOverflow glyphOverflow;
	glyphOverflow.computeBounds = true;
	float fontWidth = font.width(textRun, &glyphOverflow);
	metrics->setWidth(fontWidth);

	FloatPoint offset = textOffset(fontWidth, direction);

	metrics->setActualBoundingBoxAscent(glyphOverflow.top - offset.y());
	metrics->setActualBoundingBoxDescent(glyphOverflow.bottom + offset.y());
	metrics->setFontBoundingBoxAscent(fontMetrics.ascent() - offset.y());
	metrics->setFontBoundingBoxDescent(fontMetrics.descent() + offset.y());
	metrics->setEmHeightAscent(fontMetrics.ascent() - offset.y());
	metrics->setEmHeightDescent(fontMetrics.descent() + offset.y());
	metrics->setHangingBaseline(fontMetrics.ascent() - offset.y());
	metrics->setAlphabeticBaseline(-offset.y());
	metrics->setIdeographicBaseline(-fontMetrics.descent() - offset.y());

	metrics->setActualBoundingBoxLeft(glyphOverflow.left - offset.x());
	metrics->setActualBoundingBoxRight(fontWidth + glyphOverflow.right + offset.x());

	return metrics;
	}

	auto CanvasRenderingContext2D::fontProxy() -> const FontProxy& {
	auto& canvas = downcast<HTMLCanvasElement>(canvasBase());
	canvas.document().updateStyleIfNeeded();
	if (!state().font.realized())
	setFont(state().unparsedFont);
	return state().font;
	}

	FloatPoint CanvasRenderingContext2D::textOffset(float width, TextDirection direction)
	{
	auto& fontMetrics = fontProxy().fontMetrics();
	FloatPoint offset;

	switch (state().textBaseline) {
	case TopTextBaseline:
	case HangingTextBaseline:
	offset.setY(fontMetrics.ascent());
	break;
	case BottomTextBaseline:
	case IdeographicTextBaseline:
	offset.setY(-fontMetrics.descent());
	break;
	case MiddleTextBaseline:
	offset.setY(fontMetrics.height() / 2 - fontMetrics.descent());
	break;
	case AlphabeticTextBaseline:
	default:
	break;
	}

	bool isRTL = direction == TextDirection::RTL;
	auto align = state().textAlign;
	if (align == StartTextAlign)
	align = isRTL ? RightTextAlign : LeftTextAlign;
	else if (align == EndTextAlign)
	align = isRTL ? LeftTextAlign : RightTextAlign;

	switch (align) {
	case CenterTextAlign:
	offset.setX(-width / 2);
	break;
	case RightTextAlign:
	offset.setX(-width);
	break;
	default:
	break;
	}
	return offset;
	}

	void CanvasRenderingContext2D::drawTextInternal(const String& text, float x, float y, bool fill, Optional<float> maxWidth)
	{
	if (RuntimeEnabledFeatures::sharedFeatures().webAPIStatisticsEnabled())
	ResourceLoadObserver::shared().logCanvasWriteOrMeasure(this->canvas().document(), text);

	auto& fontProxy = this->fontProxy();
	const auto& fontMetrics = fontProxy.fontMetrics();

	auto* c = drawingContext();
	if (!c)
	return;
	if (!state().hasInvertibleTransform)
	return;
	if (!std::isfinite(x) \| !std::isfinite(y))
	return;
	if (maxWidth && (!std::isfinite(maxWidth.value()) \|\| maxWidth.value() <= 0))
	return;

	// If gradient size is zero, then paint nothing.
	auto gradient = c->strokeGradient();
	if (!fill && gradient && gradient->isZeroSize())
	return;

	gradient = c->fillGradient();
	if (fill && gradient && gradient->isZeroSize())
	return;

	String normalizedText = text;
	normalizeSpaces(normalizedText);

	// FIXME: Need to turn off font smoothing.

	const RenderStyle* computedStyle;
	auto direction = toTextDirection(state().direction, &computedStyle);
	bool override = computedStyle ? isOverride(computedStyle->unicodeBidi()) : false;

	TextRun textRun(normalizedText, 0, 0, AllowTrailingExpansion, direction, override, true);
	float fontWidth = fontProxy.width(textRun);
	bool useMaxWidth = maxWidth && maxWidth.value() < fontWidth;
	float width = useMaxWidth ? maxWidth.value() : fontWidth;
	FloatPoint location(x, y);
	location += textOffset(width, direction);

	// The slop built in to this mask rect matches the heuristic used in FontCGWin.cpp for GDI text.
	FloatRect textRect = FloatRect(location.x() - fontMetrics.height() / 2, location.y() - fontMetrics.ascent() - fontMetrics.lineGap(),
	width + fontMetrics.height(), fontMetrics.lineSpacing());
	if (!fill)
	inflateStrokeRect(textRect);

	#if USE(CG)
	const CanvasStyle& drawStyle = fill ? state().fillStyle : state().strokeStyle;
	if (drawStyle.canvasGradient() \|\| drawStyle.canvasPattern()) {
	IntRect maskRect = enclosingIntRect(textRect);

	// If we have a shadow, we need to draw it before the mask operation.
	// Follow a procedure similar to paintTextWithShadows in TextPainter.

	if (shouldDrawShadows()) {
	GraphicsContextStateSaver stateSaver(*c);

	FloatSize offset(0, 2 * maskRect.height());

	FloatSize shadowOffset;
	float shadowRadius;
	Color shadowColor;
	c->getShadow(shadowOffset, shadowRadius, shadowColor);

	FloatRect shadowRect(maskRect);
	shadowRect.inflate(shadowRadius * 1.4);
	shadowRect.move(shadowOffset * -1);
	c->clip(shadowRect);

	shadowOffset += offset;

	c->setLegacyShadow(shadowOffset, shadowRadius, shadowColor);

	if (fill)
	c->setFillColor(Color::black);
	else
	c->setStrokeColor(Color::black);

	fontProxy.drawBidiText(*c, textRun, location + offset, FontCascade::UseFallbackIfFontNotReady);
	}

	auto maskImage = ImageBuffer::createCompatibleBuffer(maskRect.size(), ColorSpaceSRGB, *c);
	if (!maskImage)
	return;

	auto& maskImageContext = maskImage->context();

	if (fill)
	maskImageContext.setFillColor(Color::black);
	else {
	maskImageContext.setStrokeColor(Color::black);
	maskImageContext.setStrokeThickness(c->strokeThickness());
	}

	maskImageContext.setTextDrawingMode(fill ? TextModeFill : TextModeStroke);

	if (useMaxWidth) {
	maskImageContext.translate(location - maskRect.location());
	// We draw when fontWidth is 0 so compositing operations (eg, a "copy" op) still work.
	maskImageContext.scale(FloatSize((fontWidth > 0 ? (width / fontWidth) : 0), 1));
	fontProxy.drawBidiText(maskImageContext, textRun, FloatPoint(0, 0), FontCascade::UseFallbackIfFontNotReady);
	} else {
	maskImageContext.translate(-maskRect.location());
	fontProxy.drawBidiText(maskImageContext, textRun, location, FontCascade::UseFallbackIfFontNotReady);
	}

	GraphicsContextStateSaver stateSaver(*c);
	c->clipToImageBuffer(*maskImage, maskRect);
	drawStyle.applyFillColor(*c);
	c->fillRect(maskRect);
	return;
	}
	#endif

	c->setTextDrawingMode(fill ? TextModeFill : TextModeStroke);

	GraphicsContextStateSaver stateSaver(*c);
	if (useMaxWidth) {
	c->translate(location);
	// We draw when fontWidth is 0 so compositing operations (eg, a "copy" op) still work.
	c->scale(FloatSize((fontWidth > 0 ? (width / fontWidth) : 0), 1));
	location = FloatPoint();
	}

	if (isFullCanvasCompositeMode(state().globalComposite)) {
	beginCompositeLayer();
	fontProxy.drawBidiText(*c, textRun, location, FontCascade::UseFallbackIfFontNotReady);
	endCompositeLayer();
	didDrawEntireCanvas();
	} else if (state().globalComposite == CompositeCopy) {
	clearCanvas();
	fontProxy.drawBidiText(*c, textRun, location, FontCascade::UseFallbackIfFontNotReady);
	didDrawEntireCanvas();
	} else {
	fontProxy.drawBidiText(*c, textRun, location, FontCascade::UseFallbackIfFontNotReady);
	didDraw(textRect);
	}
	}

	} // namespace WebCore