third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp

/*
 * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 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, 2013 Intel Corporation. All rights reserved.
 * Copyright (C) 2013 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 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 "modules/canvas2d/CanvasRenderingContext2D.h"

#include "bindings/core/v8/ExceptionMessages.h"
#include "bindings/core/v8/ExceptionState.h"
#include "bindings/modules/v8/RenderingContext.h"
#include "core/CSSPropertyNames.h"
#include "core/css/StylePropertySet.h"
#include "core/css/resolver/StyleResolver.h"
#include "core/dom/AXObjectCache.h"
#include "core/dom/StyleEngine.h"
#include "core/dom/TaskRunnerHelper.h"
#include "core/events/Event.h"
#include "core/events/MouseEvent.h"
#include "core/frame/Settings.h"
#include "core/html/TextMetrics.h"
#include "core/html/canvas/CanvasFontCache.h"
#include "core/layout/HitTestCanvasResult.h"
#include "core/layout/LayoutBox.h"
#include "core/layout/LayoutTheme.h"
#include "modules/canvas2d/CanvasStyle.h"
#include "modules/canvas2d/HitRegion.h"
#include "modules/canvas2d/Path2D.h"
#include "platform/fonts/FontCache.h"
#include "platform/graphics/CanvasHeuristicParameters.h"
#include "platform/graphics/DrawLooperBuilder.h"
#include "platform/graphics/ImageBuffer.h"
#include "platform/graphics/StrokeData.h"
#include "platform/graphics/paint/PaintCanvas.h"
#include "platform/graphics/paint/PaintFlags.h"
#include "platform/graphics/skia/SkiaUtils.h"
#include "platform/text/BidiTextRun.h"
#include "platform/wtf/MathExtras.h"
#include "platform/wtf/text/StringBuilder.h"
#include "platform/wtf/typed_arrays/ArrayBufferContents.h"
#include "public/platform/Platform.h"
#include "third_party/skia/include/core/SkImageFilter.h"

namespace blink {

static const char kDefaultFont[] = "10px sans-serif";
static const char kInheritDirectionString[] = "inherit";
static const char kRtlDirectionString[] = "rtl";
static const char kLtrDirectionString[] = "ltr";
static const double kTryRestoreContextInterval = 0.5;
static const unsigned kMaxTryRestoreContextAttempts = 4;
static const double kCDeviceScaleFactor = 1.0;  // Canvas is device independent

static bool ContextLostRestoredEventsEnabled() {
  return RuntimeEnabledFeatures::experimentalCanvasFeaturesEnabled();
}

// Drawing methods need to use this instead of SkAutoCanvasRestore in case
// overdraw detection substitutes the recording canvas (to discard overdrawn
// draw calls).
class CanvasRenderingContext2DAutoRestoreSkCanvas {
  STACK_ALLOCATED();

 public:
  explicit CanvasRenderingContext2DAutoRestoreSkCanvas(
      CanvasRenderingContext2D* context)
      : context_(context), save_count_(0) {
    DCHECK(context_);
    PaintCanvas* c = context_->DrawingCanvas();
    if (c) {
      save_count_ = c->getSaveCount();
    }
  }

  ~CanvasRenderingContext2DAutoRestoreSkCanvas() {
    PaintCanvas* c = context_->DrawingCanvas();
    if (c)
      c->restoreToCount(save_count_);
    context_->ValidateStateStack();
  }

 private:
  Member<CanvasRenderingContext2D> context_;
  int save_count_;
};

CanvasRenderingContext2D::CanvasRenderingContext2D(
    HTMLCanvasElement* canvas,
    const CanvasContextCreationAttributes& attrs)
    : CanvasRenderingContext(canvas, attrs),
      context_lost_mode_(kNotLostContext),
      context_restorable_(true),
      try_restore_context_attempt_count_(0),
      dispatch_context_lost_event_timer_(
          TaskRunnerHelper::Get(TaskType::kMiscPlatformAPI,
                                canvas->GetDocument().GetFrame()),
          this,
          &CanvasRenderingContext2D::DispatchContextLostEvent),
      dispatch_context_restored_event_timer_(
          TaskRunnerHelper::Get(TaskType::kMiscPlatformAPI,
                                canvas->GetDocument().GetFrame()),
          this,
          &CanvasRenderingContext2D::DispatchContextRestoredEvent),
      try_restore_context_event_timer_(
          TaskRunnerHelper::Get(TaskType::kMiscPlatformAPI,
                                canvas->GetDocument().GetFrame()),
          this,
          &CanvasRenderingContext2D::TryRestoreContextEvent),
      should_prune_local_font_cache_(false) {
  if (canvas->GetDocument().GetSettings() &&
      canvas->GetDocument().GetSettings()->GetAntialiasedClips2dCanvasEnabled())
    clip_antialiasing_ = kAntiAliased;
  SetShouldAntialias(true);
  ValidateStateStack();
}

void CanvasRenderingContext2D::SetCanvasGetContextResult(
    RenderingContext& result) {
  result.setCanvasRenderingContext2D(this);
}

CanvasRenderingContext2D::~CanvasRenderingContext2D() {}

void CanvasRenderingContext2D::ValidateStateStack() const {
#if DCHECK_IS_ON()
  if (PaintCanvas* sk_canvas = canvas()->ExistingDrawingCanvas()) {
    // The canvas should always have an initial save frame, to support
    // resetting the top level matrix and clip.
    DCHECK_GT(sk_canvas->getSaveCount(), 1);

    if (context_lost_mode_ == kNotLostContext) {
      DCHECK_EQ(static_cast<size_t>(sk_canvas->getSaveCount()),
                state_stack_.size() + 1);
    }
  }
#endif
  CHECK(state_stack_.front()
            .Get());  // Temporary for investigating crbug.com/648510
}

bool CanvasRenderingContext2D::IsAccelerated() const {
  if (!HasImageBuffer())
    return false;
  return GetImageBuffer()->IsAccelerated();
}

bool CanvasRenderingContext2D::IsComposited() const {
  return IsAccelerated();
}

void CanvasRenderingContext2D::Stop() {
  if (!isContextLost()) {
    // Never attempt to restore the context because the page is being torn down.
    LoseContext(kSyntheticLostContext);
  }
}

bool CanvasRenderingContext2D::isContextLost() const {
  return context_lost_mode_ != kNotLostContext;
}

void CanvasRenderingContext2D::LoseContext(LostContextMode lost_mode) {
  if (context_lost_mode_ != kNotLostContext)
    return;
  context_lost_mode_ = lost_mode;
  if (context_lost_mode_ == kSyntheticLostContext && canvas()) {
    host()->DiscardImageBuffer();
  }
  dispatch_context_lost_event_timer_.StartOneShot(0, BLINK_FROM_HERE);
}

void CanvasRenderingContext2D::DidSetSurfaceSize() {
  if (!context_restorable_)
    return;
  // This code path is for restoring from an eviction
  // Restoring from surface failure is handled internally
  DCHECK(context_lost_mode_ != kNotLostContext && !HasImageBuffer());

  if (GetImageBuffer()) {
    if (ContextLostRestoredEventsEnabled()) {
      dispatch_context_restored_event_timer_.StartOneShot(0, BLINK_FROM_HERE);
    } else {
      // legacy synchronous context restoration.
      Reset();
      context_lost_mode_ = kNotLostContext;
    }
  }
}

DEFINE_TRACE(CanvasRenderingContext2D) {
  visitor->Trace(hit_region_manager_);
  visitor->Trace(filter_operations_);
  CanvasRenderingContext::Trace(visitor);
  BaseRenderingContext2D::Trace(visitor);
  SVGResourceClient::Trace(visitor);
}

void CanvasRenderingContext2D::DispatchContextLostEvent(TimerBase*) {
  if (canvas() && ContextLostRestoredEventsEnabled()) {
    Event* event = Event::CreateCancelable(EventTypeNames::contextlost);
    canvas()->DispatchEvent(event);
    if (event->defaultPrevented()) {
      context_restorable_ = false;
    }
  }

  // If RealLostContext, it means the context was not lost due to surface
  // failure but rather due to a an eviction, which means image buffer exists.
  if (context_restorable_ && context_lost_mode_ == kRealLostContext) {
    try_restore_context_attempt_count_ = 0;
    try_restore_context_event_timer_.StartRepeating(kTryRestoreContextInterval,
                                                    BLINK_FROM_HERE);
  }
}

void CanvasRenderingContext2D::TryRestoreContextEvent(TimerBase* timer) {
  if (context_lost_mode_ == kNotLostContext) {
    // Canvas was already restored (possibly thanks to a resize), so stop
    // trying.
    try_restore_context_event_timer_.Stop();
    return;
  }

  DCHECK(context_lost_mode_ == kRealLostContext);
  if (HasImageBuffer() && GetImageBuffer()->RestoreSurface()) {
    try_restore_context_event_timer_.Stop();
    DispatchContextRestoredEvent(nullptr);
  }

  if (++try_restore_context_attempt_count_ > kMaxTryRestoreContextAttempts) {
    // final attempt: allocate a brand new image buffer instead of restoring
    host()->DiscardImageBuffer();
    try_restore_context_event_timer_.Stop();
    if (GetImageBuffer())
      DispatchContextRestoredEvent(nullptr);
  }
}

void CanvasRenderingContext2D::DispatchContextRestoredEvent(TimerBase*) {
  if (context_lost_mode_ == kNotLostContext)
    return;
  Reset();
  context_lost_mode_ = kNotLostContext;
  if (ContextLostRestoredEventsEnabled()) {
    Event* event(Event::Create(EventTypeNames::contextrestored));
    canvas()->DispatchEvent(event);
  }
}

void CanvasRenderingContext2D::WillDrawImage(CanvasImageSource* source) const {
  canvas()->WillDrawImageTo2DContext(source);
}

CanvasColorSpace CanvasRenderingContext2D::ColorSpace() const {
  return color_params().color_space();
}

String CanvasRenderingContext2D::ColorSpaceAsString() const {
  return CanvasRenderingContext::ColorSpaceAsString();
}

CanvasPixelFormat CanvasRenderingContext2D::PixelFormat() const {
  return color_params().pixel_format();
}

void CanvasRenderingContext2D::Reset() {
  // This is a multiple inherritance bootstrap
  BaseRenderingContext2D::Reset();
}

void CanvasRenderingContext2D::RestoreCanvasMatrixClipStack(
    PaintCanvas* c) const {
  RestoreMatrixClipStack(c);
}

bool CanvasRenderingContext2D::ShouldAntialias() const {
  return GetState().ShouldAntialias();
}

void CanvasRenderingContext2D::SetShouldAntialias(bool do_aa) {
  ModifiableState().SetShouldAntialias(do_aa);
}

void CanvasRenderingContext2D::scrollPathIntoView() {
  ScrollPathIntoViewInternal(path_);
}

void CanvasRenderingContext2D::scrollPathIntoView(Path2D* path2d) {
  ScrollPathIntoViewInternal(path2d->GetPath());
}

void CanvasRenderingContext2D::ScrollPathIntoViewInternal(const Path& path) {
  if (!GetState().IsTransformInvertible() || path.IsEmpty())
    return;

  canvas()->GetDocument().UpdateStyleAndLayoutIgnorePendingStylesheets();

  LayoutObject* renderer = canvas()->GetLayoutObject();
  LayoutBox* layout_box = canvas()->GetLayoutBox();
  if (!renderer || !layout_box)
    return;

  // Apply transformation and get the bounding rect
  Path transformed_path = path;
  transformed_path.Transform(GetState().Transform());
  FloatRect bounding_rect = transformed_path.BoundingRect();

  // Offset by the canvas rect
  LayoutRect path_rect(bounding_rect);
  IntRect canvas_rect = layout_box->AbsoluteContentBox();
  path_rect.MoveBy(canvas_rect.Location());

  renderer->ScrollRectToVisible(path_rect, ScrollAlignment::kAlignCenterAlways,
                                ScrollAlignment::kAlignTopAlways);

  // TODO: should implement "inform the user" that the caret and/or
  // selection the specified rectangle of the canvas. See
  // http://crbug.com/357987
}

void CanvasRenderingContext2D::clearRect(double x,
                                         double y,
                                         double width,
                                         double height) {
  BaseRenderingContext2D::clearRect(x, y, width, height);

  if (hit_region_manager_) {
    FloatRect rect(x, y, width, height);
    hit_region_manager_->RemoveHitRegionsInRect(rect, GetState().Transform());
  }
}

void CanvasRenderingContext2D::DidDraw(const SkIRect& dirty_rect) {
  if (dirty_rect.isEmpty())
    return;

  if (CanvasHeuristicParameters::kBlurredShadowsAreExpensive &&
      GetState().ShouldDrawShadows() && GetState().ShadowBlur() > 0) {
    ImageBuffer* buffer = GetImageBuffer();
    if (buffer)
      buffer->SetHasExpensiveOp();
  }

  CanvasRenderingContext::DidDraw(dirty_rect);
}

bool CanvasRenderingContext2D::StateHasFilter() {
  return GetState().HasFilter(canvas(), canvas()->Size(), this);
}

sk_sp<SkImageFilter> CanvasRenderingContext2D::StateGetFilter() {
  return GetState().GetFilter(canvas(), canvas()->Size(), this);
}

void CanvasRenderingContext2D::SnapshotStateForFilter() {
  // The style resolution required for fonts is not available in frame-less
  // documents.
  if (!canvas()->GetDocument().GetFrame())
    return;

  ModifiableState().SetFontForFilter(AccessFont());
}

PaintCanvas* CanvasRenderingContext2D::DrawingCanvas() const {
  if (isContextLost())
    return nullptr;
  return canvas()->DrawingCanvas();
}

PaintCanvas* CanvasRenderingContext2D::ExistingDrawingCanvas() const {
  return canvas()->ExistingDrawingCanvas();
}

void CanvasRenderingContext2D::DisableDeferral(DisableDeferralReason reason) {
  canvas()->DisableDeferral(reason);
}

AffineTransform CanvasRenderingContext2D::BaseTransform() const {
  return canvas()->BaseTransform();
}

String CanvasRenderingContext2D::font() const {
  if (!GetState().HasRealizedFont())
    return kDefaultFont;

  canvas()->GetDocument().GetCanvasFontCache()->WillUseCurrentFont();
  StringBuilder serialized_font;
  const FontDescription& font_description =
      GetState().GetFont().GetFontDescription();

  if (font_description.Style() == kFontStyleItalic)
    serialized_font.Append("italic ");
  if (font_description.Weight() == kFontWeightBold)
    serialized_font.Append("bold ");
  if (font_description.VariantCaps() == FontDescription::kSmallCaps)
    serialized_font.Append("small-caps ");

  serialized_font.AppendNumber(font_description.ComputedPixelSize());
  serialized_font.Append("px");

  const FontFamily& first_font_family = font_description.Family();
  for (const FontFamily* font_family = &first_font_family; font_family;
       font_family = font_family->Next()) {
    if (font_family != &first_font_family)
      serialized_font.Append(',');

    // FIXME: We should append family directly to serializedFont rather than
    // building a temporary string.
    String family = font_family->Family();
    if (family.StartsWith("-webkit-"))
      family = family.Substring(8);
    if (family.Contains(' '))
      family = "\"" + family + "\"";

    serialized_font.Append(' ');
    serialized_font.Append(family);
  }

  return serialized_font.ToString();
}

void CanvasRenderingContext2D::setFont(const String& new_font) {
  // The style resolution required for fonts is not available in frame-less
  // documents.
  if (!canvas()->GetDocument().GetFrame())
    return;

  canvas()->GetDocument().UpdateStyleAndLayoutTreeForNode(canvas());

  // The following early exit is dependent on the cache not being empty
  // because an empty cache may indicate that a style change has occured
  // which would require that the font be re-resolved. This check has to
  // come after the layout tree update to flush pending style changes.
  if (new_font == GetState().UnparsedFont() && GetState().HasRealizedFont() &&
      fonts_resolved_using_current_style_.size() > 0)
    return;

  CanvasFontCache* canvas_font_cache =
      canvas()->GetDocument().GetCanvasFontCache();

  // Map the <canvas> font into the text style. If the font uses keywords like
  // larger/smaller, these will work relative to the canvas.
  RefPtr<ComputedStyle> font_style;
  const ComputedStyle* computed_style = canvas()->EnsureComputedStyle();
  if (computed_style) {
    HashMap<String, Font>::iterator i =
        fonts_resolved_using_current_style_.find(new_font);
    if (i != fonts_resolved_using_current_style_.end()) {
      DCHECK(font_lru_list_.Contains(new_font));
      font_lru_list_.erase(new_font);
      font_lru_list_.insert(new_font);
      ModifiableState().SetFont(
          i->value, canvas()->GetDocument().GetStyleEngine().FontSelector());
    } else {
      MutableStylePropertySet* parsed_style =
          canvas_font_cache->ParseFont(new_font);
      if (!parsed_style)
        return;
      font_style = ComputedStyle::Create();
      FontDescription element_font_description(
          computed_style->GetFontDescription());
      // Reset the computed size to avoid inheriting the zoom factor from the
      // <canvas> element.
      element_font_description.SetComputedSize(
          element_font_description.SpecifiedSize());
      font_style->SetFontDescription(element_font_description);
      font_style->GetFont().Update(font_style->GetFont().GetFontSelector());
      canvas()->GetDocument().EnsureStyleResolver().ComputeFont(
          font_style.Get(), *parsed_style);
      fonts_resolved_using_current_style_.insert(new_font,
                                                 font_style->GetFont());
      DCHECK(!font_lru_list_.Contains(new_font));
      font_lru_list_.insert(new_font);
      PruneLocalFontCache(canvas_font_cache->HardMaxFonts());  // hard limit
      should_prune_local_font_cache_ = true;  // apply soft limit
      ModifiableState().SetFont(
          font_style->GetFont(),
          canvas()->GetDocument().GetStyleEngine().FontSelector());
    }
  } else {
    Font resolved_font;
    if (!canvas_font_cache->GetFontUsingDefaultStyle(new_font, resolved_font))
      return;
    ModifiableState().SetFont(
        resolved_font, canvas()->GetDocument().GetStyleEngine().FontSelector());
  }

  // The parse succeeded.
  String new_font_safe_copy(
      new_font);  // Create a string copy since newFont can be
                  // deleted inside realizeSaves.
  ModifiableState().SetUnparsedFont(new_font_safe_copy);
}

void CanvasRenderingContext2D::DidProcessTask() {
  CanvasRenderingContext::DidProcessTask();
  // This should be the only place where canvas() needs to be checked for
  // nullness because the circular refence with HTMLCanvasElement means the
  // canvas and the context keep each other alive. As long as the pair is
  // referenced, the task observer is the only persistent refernce to this
  // object
  // that is not traced, so didProcessTask() may be called at a time when the
  // canvas has been garbage collected but not the context.
  if (should_prune_local_font_cache_ && canvas()) {
    should_prune_local_font_cache_ = false;
    PruneLocalFontCache(
        canvas()->GetDocument().GetCanvasFontCache()->MaxFonts());
  }
}

void CanvasRenderingContext2D::PruneLocalFontCache(size_t target_size) {
  if (target_size == 0) {
    // Short cut: LRU does not matter when evicting everything
    font_lru_list_.clear();
    fonts_resolved_using_current_style_.clear();
    return;
  }
  while (font_lru_list_.size() > target_size) {
    fonts_resolved_using_current_style_.erase(font_lru_list_.front());
    font_lru_list_.RemoveFirst();
  }
}

void CanvasRenderingContext2D::StyleDidChange(const ComputedStyle* old_style,
                                              const ComputedStyle& new_style) {
  if (old_style && old_style->GetFont() == new_style.GetFont())
    return;
  PruneLocalFontCache(0);
}

TreeScope* CanvasRenderingContext2D::GetTreeScope() {
  return &canvas()->GetTreeScope();
}

void CanvasRenderingContext2D::ClearFilterReferences() {
  filter_operations_.RemoveClient(this);
  filter_operations_.clear();
}

void CanvasRenderingContext2D::UpdateFilterReferences(
    const FilterOperations& filters) {
  ClearFilterReferences();
  filters.AddClient(this);
  filter_operations_ = filters;
}

void CanvasRenderingContext2D::ResourceContentChanged() {
  ResourceElementChanged();
}

void CanvasRenderingContext2D::ResourceElementChanged() {
  ClearFilterReferences();
  GetState().ClearResolvedFilter();
}

bool CanvasRenderingContext2D::OriginClean() const {
  return host()->OriginClean();
}

void CanvasRenderingContext2D::SetOriginTainted() {
  return host()->SetOriginTainted();
}

int CanvasRenderingContext2D::Width() const {
  return host()->Size().Width();
}

int CanvasRenderingContext2D::Height() const {
  return host()->Size().Height();
}

bool CanvasRenderingContext2D::HasImageBuffer() const {
  return host()->GetImageBuffer();
}

ImageBuffer* CanvasRenderingContext2D::GetImageBuffer() const {
  return const_cast<CanvasRenderingContextHost*>(host())
      ->GetOrCreateImageBuffer();
}

PassRefPtr<Image> blink::CanvasRenderingContext2D::GetImage(
    AccelerationHint hint,
    SnapshotReason reason) const {
  if (!HasImageBuffer())
    return nullptr;
  return GetImageBuffer()->NewImageSnapshot(hint, reason);
}

bool CanvasRenderingContext2D::ParseColorOrCurrentColor(
    Color& color,
    const String& color_string) const {
  return ::blink::ParseColorOrCurrentColor(color, color_string, canvas());
}

HitTestCanvasResult* CanvasRenderingContext2D::GetControlAndIdIfHitRegionExists(
    const LayoutPoint& location) {
  if (HitRegionsCount() <= 0)
    return HitTestCanvasResult::Create(String(), nullptr);

  LayoutBox* box = canvas()->GetLayoutBox();
  FloatPoint local_pos =
      box->AbsoluteToLocal(FloatPoint(location), kUseTransforms);
  if (box->HasBorderOrPadding())
    local_pos.Move(-box->ContentBoxOffset());
  local_pos.Scale(canvas()->width() / box->ContentWidth(),
                  canvas()->height() / box->ContentHeight());

  HitRegion* hit_region = HitRegionAtPoint(local_pos);
  if (hit_region) {
    Element* control = hit_region->Control();
    if (control && canvas()->IsSupportedInteractiveCanvasFallback(*control))
      return HitTestCanvasResult::Create(hit_region->Id(),
                                         hit_region->Control());
    return HitTestCanvasResult::Create(hit_region->Id(), nullptr);
  }
  return HitTestCanvasResult::Create(String(), nullptr);
}

String CanvasRenderingContext2D::GetIdFromControl(const Element* element) {
  if (HitRegionsCount() <= 0)
    return String();

  if (HitRegion* hit_region =
          hit_region_manager_->GetHitRegionByControl(element))
    return hit_region->Id();
  return String();
}

String CanvasRenderingContext2D::textAlign() const {
  return TextAlignName(GetState().GetTextAlign());
}

void CanvasRenderingContext2D::setTextAlign(const String& s) {
  TextAlign align;
  if (!ParseTextAlign(s, align))
    return;
  if (GetState().GetTextAlign() == align)
    return;
  ModifiableState().SetTextAlign(align);
}

String CanvasRenderingContext2D::textBaseline() const {
  return TextBaselineName(GetState().GetTextBaseline());
}

void CanvasRenderingContext2D::setTextBaseline(const String& s) {
  TextBaseline baseline;
  if (!ParseTextBaseline(s, baseline))
    return;
  if (GetState().GetTextBaseline() == baseline)
    return;
  ModifiableState().SetTextBaseline(baseline);
}

static inline TextDirection ToTextDirection(
    CanvasRenderingContext2DState::Direction direction,
    HTMLCanvasElement* canvas,
    const ComputedStyle** computed_style = 0) {
  const ComputedStyle* style =
      (computed_style ||
       direction == CanvasRenderingContext2DState::kDirectionInherit)
          ? canvas->EnsureComputedStyle()
          : nullptr;
  if (computed_style)
    *computed_style = style;
  switch (direction) {
    case CanvasRenderingContext2DState::kDirectionInherit:
      return style ? style->Direction() : TextDirection::kLtr;
    case CanvasRenderingContext2DState::kDirectionRTL:
      return TextDirection::kRtl;
    case CanvasRenderingContext2DState::kDirectionLTR:
      return TextDirection::kLtr;
  }
  NOTREACHED();
  return TextDirection::kLtr;
}

String CanvasRenderingContext2D::direction() const {
  if (GetState().GetDirection() ==
      CanvasRenderingContext2DState::kDirectionInherit)
    canvas()->GetDocument().UpdateStyleAndLayoutTreeForNode(canvas());
  return ToTextDirection(GetState().GetDirection(), canvas()) ==
                 TextDirection::kRtl
             ? kRtlDirectionString
             : kLtrDirectionString;
}

void CanvasRenderingContext2D::setDirection(const String& direction_string) {
  CanvasRenderingContext2DState::Direction direction;
  if (direction_string == kInheritDirectionString)
    direction = CanvasRenderingContext2DState::kDirectionInherit;
  else if (direction_string == kRtlDirectionString)
    direction = CanvasRenderingContext2DState::kDirectionRTL;
  else if (direction_string == kLtrDirectionString)
    direction = CanvasRenderingContext2DState::kDirectionLTR;
  else
    return;

  if (GetState().GetDirection() == direction)
    return;

  ModifiableState().SetDirection(direction);
}

void CanvasRenderingContext2D::fillText(const String& text,
                                        double x,
                                        double y) {
  DrawTextInternal(text, x, y, CanvasRenderingContext2DState::kFillPaintType);
}

void CanvasRenderingContext2D::fillText(const String& text,
                                        double x,
                                        double y,
                                        double max_width) {
  DrawTextInternal(text, x, y, CanvasRenderingContext2DState::kFillPaintType,
                   &max_width);
}

void CanvasRenderingContext2D::strokeText(const String& text,
                                          double x,
                                          double y) {
  DrawTextInternal(text, x, y, CanvasRenderingContext2DState::kStrokePaintType);
}

void CanvasRenderingContext2D::strokeText(const String& text,
                                          double x,
                                          double y,
                                          double max_width) {
  DrawTextInternal(text, x, y, CanvasRenderingContext2DState::kStrokePaintType,
                   &max_width);
}

TextMetrics* CanvasRenderingContext2D::measureText(const String& text) {
  TextMetrics* metrics = TextMetrics::Create();

  // The style resolution required for fonts is not available in frame-less
  // documents.
  if (!canvas()->GetDocument().GetFrame())
    return metrics;

  canvas()->GetDocument().UpdateStyleAndLayoutTreeForNode(canvas());
  const Font& font = AccessFont();
  const SimpleFontData* font_data = font.PrimaryFont();
  DCHECK(font_data);
  if (!font_data)
    return metrics;

  TextDirection direction;
  if (GetState().GetDirection() ==
      CanvasRenderingContext2DState::kDirectionInherit)
    direction = DetermineDirectionality(text);
  else
    direction = ToTextDirection(GetState().GetDirection(), canvas());
  TextRun text_run(
      text, 0, 0,
      TextRun::kAllowTrailingExpansion | TextRun::kForbidLeadingExpansion,
      direction, false);
  text_run.SetNormalizeSpace(true);
  FloatRect text_bounds = font.SelectionRectForText(
      text_run, FloatPoint(), font.GetFontDescription().ComputedSize(), 0, -1,
      true);

  // x direction
  metrics->SetWidth(font.Width(text_run));
  metrics->SetActualBoundingBoxLeft(-text_bounds.X());
  metrics->SetActualBoundingBoxRight(text_bounds.MaxX());

  // y direction
  const FontMetrics& font_metrics = font_data->GetFontMetrics();
  const float ascent = font_metrics.FloatAscent();
  const float descent = font_metrics.FloatDescent();
  const float baseline_y = GetFontBaseline(font_metrics);

  metrics->SetFontBoundingBoxAscent(ascent - baseline_y);
  metrics->SetFontBoundingBoxDescent(descent + baseline_y);
  metrics->SetActualBoundingBoxAscent(-text_bounds.Y() - baseline_y);
  metrics->SetActualBoundingBoxDescent(text_bounds.MaxY() + baseline_y);

  // Note : top/bottom and ascend/descend are currently the same, so there's no
  // difference between the EM box's top and bottom and the font's ascend and
  // descend
  metrics->SetEmHeightAscent(0);
  metrics->SetEmHeightDescent(0);

  metrics->SetHangingBaseline(0.8f * ascent - baseline_y);
  metrics->SetAlphabeticBaseline(-baseline_y);
  metrics->SetIdeographicBaseline(-descent - baseline_y);
  return metrics;
}

void CanvasRenderingContext2D::DrawTextInternal(
    const String& text,
    double x,
    double y,
    CanvasRenderingContext2DState::PaintType paint_type,
    double* max_width) {
  // The style resolution required for fonts is not available in frame-less
  // documents.
  if (!canvas()->GetDocument().GetFrame())
    return;

  // accessFont needs the style to be up to date, but updating style can cause
  // script to run, (e.g. due to autofocus) which can free the canvas (set size
  // to 0, for example), so update style before grabbing the drawingCanvas.
  canvas()->GetDocument().UpdateStyleAndLayoutTreeForNode(canvas());

  PaintCanvas* c = DrawingCanvas();
  if (!c)
    return;

  if (!std::isfinite(x) || !std::isfinite(y))
    return;
  if (max_width && (!std::isfinite(*max_width) || *max_width <= 0))
    return;

  // Currently, SkPictureImageFilter does not support subpixel text
  // anti-aliasing, which is expected when !creationAttributes().alpha(), so we
  // need to fall out of display list mode when drawing text to an opaque
  // canvas. crbug.com/583809
  if (!IsComposited()) {
    canvas()->DisableDeferral(
        kDisableDeferralReasonSubPixelTextAntiAliasingSupport);
  }

  const Font& font = AccessFont();
  font.GetFontDescription().SetSubpixelAscentDescent(true);
  const SimpleFontData* font_data = font.PrimaryFont();
  DCHECK(font_data);
  if (!font_data)
    return;
  const FontMetrics& font_metrics = font_data->GetFontMetrics();

  // FIXME: Need to turn off font smoothing.

  const ComputedStyle* computed_style = 0;
  TextDirection direction =
      ToTextDirection(GetState().GetDirection(), canvas(), &computed_style);
  bool is_rtl = direction == TextDirection::kRtl;
  bool override =
      computed_style ? IsOverride(computed_style->GetUnicodeBidi()) : false;

  TextRun text_run(text, 0, 0, TextRun::kAllowTrailingExpansion, direction,
                   override);
  text_run.SetNormalizeSpace(true);
  // Draw the item text at the correct point.
  FloatPoint location(x, y + GetFontBaseline(font_metrics));
  double font_width = font.Width(text_run);

  bool use_max_width = (max_width && *max_width < font_width);
  double width = use_max_width ? *max_width : font_width;

  TextAlign align = GetState().GetTextAlign();
  if (align == kStartTextAlign)
    align = is_rtl ? kRightTextAlign : kLeftTextAlign;
  else if (align == kEndTextAlign)
    align = is_rtl ? kLeftTextAlign : kRightTextAlign;

  switch (align) {
    case kCenterTextAlign:
      location.SetX(location.X() - width / 2);
      break;
    case kRightTextAlign:
      location.SetX(location.X() - width);
      break;
    default:
      break;
  }

  // The slop built in to this mask rect matches the heuristic used in
  // FontCGWin.cpp for GDI text.
  TextRunPaintInfo text_run_paint_info(text_run);
  text_run_paint_info.bounds =
      FloatRect(location.X() - font_metrics.Height() / 2,
                location.Y() - font_metrics.Ascent() - font_metrics.LineGap(),
                width + font_metrics.Height(), font_metrics.LineSpacing());
  if (paint_type == CanvasRenderingContext2DState::kStrokePaintType)
    InflateStrokeRect(text_run_paint_info.bounds);

  CanvasRenderingContext2DAutoRestoreSkCanvas state_restorer(this);
  if (use_max_width) {
    DrawingCanvas()->save();
    DrawingCanvas()->translate(location.X(), location.Y());
    // We draw when fontWidth is 0 so compositing operations (eg, a "copy" op)
    // still work.
    DrawingCanvas()->scale((font_width > 0 ? (width / font_width) : 0), 1);
    location = FloatPoint();
  }

  Draw(
      [&font, &text_run_paint_info, &location](
          PaintCanvas* c, const PaintFlags* flags)  // draw lambda
      {
        font.DrawBidiText(c, text_run_paint_info, location,
                          Font::kUseFallbackIfFontNotReady, kCDeviceScaleFactor,
                          *flags);
      },
      [](const SkIRect& rect)  // overdraw test lambda
      { return false; },
      text_run_paint_info.bounds, paint_type);
}

const Font& CanvasRenderingContext2D::AccessFont() {
  if (!GetState().HasRealizedFont())
    setFont(GetState().UnparsedFont());
  canvas()->GetDocument().GetCanvasFontCache()->WillUseCurrentFont();
  return GetState().GetFont();
}

float CanvasRenderingContext2D::GetFontBaseline(
    const FontMetrics& font_metrics) const {
  // If the font is so tiny that the lroundf operations result in two
  // different types of text baselines to return the same baseline, use
  // floating point metrics (crbug.com/338908).
  // If you changed the heuristic here, for consistency please also change it
  // in SimpleFontData::platformInit().
  bool use_float_ascent_descent =
      font_metrics.Ascent() < 3 || font_metrics.Height() < 2;
  switch (GetState().GetTextBaseline()) {
    case kTopTextBaseline:
      return use_float_ascent_descent ? font_metrics.FloatAscent()
                                      : font_metrics.Ascent();
    case kHangingTextBaseline:
      // According to
      // http://wiki.apache.org/xmlgraphics-fop/LineLayout/AlignmentHandling
      // "FOP (Formatting Objects Processor) puts the hanging baseline at 80% of
      // the ascender height"
      return use_float_ascent_descent ? (font_metrics.FloatAscent() * 4.0) / 5.0
                                      : (font_metrics.Ascent() * 4) / 5;
    case kBottomTextBaseline:
    case kIdeographicTextBaseline:
      return use_float_ascent_descent ? -font_metrics.FloatDescent()
                                      : -font_metrics.Descent();
    case kMiddleTextBaseline:
      return use_float_ascent_descent
                 ? -font_metrics.FloatDescent() +
                       font_metrics.FloatHeight() / 2.0
                 : -font_metrics.Descent() + font_metrics.Height() / 2;
    case kAlphabeticTextBaseline:
    default:
      // Do nothing.
      break;
  }
  return 0;
}

void CanvasRenderingContext2D::SetIsHidden(bool hidden) {
  if (HasImageBuffer())
    GetImageBuffer()->SetIsHidden(hidden);
  if (hidden) {
    PruneLocalFontCache(0);
  }
}

bool CanvasRenderingContext2D::IsTransformInvertible() const {
  return GetState().IsTransformInvertible();
}

WebLayer* CanvasRenderingContext2D::PlatformLayer() const {
  return GetImageBuffer() ? GetImageBuffer()->PlatformLayer() : 0;
}

void CanvasRenderingContext2D::getContextAttributes(
    CanvasRenderingContext2DSettings& settings) const {
  settings.setAlpha(CreationAttributes().alpha());
  settings.setColorSpace(ColorSpaceAsString());
  settings.setPixelFormat(PixelFormatAsString());
  settings.setLinearPixelMath(color_params().LinearPixelMath());
}

void CanvasRenderingContext2D::drawFocusIfNeeded(Element* element) {
  DrawFocusIfNeededInternal(path_, element);
}

void CanvasRenderingContext2D::drawFocusIfNeeded(Path2D* path2d,
                                                 Element* element) {
  DrawFocusIfNeededInternal(path2d->GetPath(), element);
}

void CanvasRenderingContext2D::DrawFocusIfNeededInternal(const Path& path,
                                                         Element* element) {
  if (!FocusRingCallIsValid(path, element))
    return;

  // Note: we need to check document->focusedElement() rather than just calling
  // element->focused(), because element->focused() isn't updated until after
  // focus events fire.
  if (element->GetDocument().FocusedElement() == element) {
    ScrollPathIntoViewInternal(path);
    DrawFocusRing(path);
  }

  // Update its accessible bounds whether it's focused or not.
  UpdateElementAccessibility(path, element);
}

bool CanvasRenderingContext2D::FocusRingCallIsValid(const Path& path,
                                                    Element* element) {
  DCHECK(element);
  if (!GetState().IsTransformInvertible())
    return false;
  if (path.IsEmpty())
    return false;
  if (!element->IsDescendantOf(canvas()))
    return false;

  return true;
}

void CanvasRenderingContext2D::DrawFocusRing(const Path& path) {
  usage_counters_.num_draw_focus_calls++;
  if (!DrawingCanvas())
    return;

  SkColor color = LayoutTheme::GetTheme().FocusRingColor().Rgb();
  const int kFocusRingWidth = 5;

  DrawPlatformFocusRing(path.GetSkPath(), DrawingCanvas(), color,
                        kFocusRingWidth);

  // We need to add focusRingWidth to dirtyRect.
  StrokeData stroke_data;
  stroke_data.SetThickness(kFocusRingWidth);

  SkIRect dirty_rect;
  if (!ComputeDirtyRect(path.StrokeBoundingRect(stroke_data), &dirty_rect))
    return;

  DidDraw(dirty_rect);
}

void CanvasRenderingContext2D::UpdateElementAccessibility(const Path& path,
                                                          Element* element) {
  element->GetDocument().UpdateStyleAndLayoutIgnorePendingStylesheets();
  AXObjectCache* ax_object_cache =
      element->GetDocument().ExistingAXObjectCache();
  LayoutBoxModelObject* lbmo = canvas()->GetLayoutBoxModelObject();
  LayoutObject* renderer = canvas()->GetLayoutObject();
  if (!ax_object_cache || !lbmo || !renderer)
    return;

  // Get the transformed path.
  Path transformed_path = path;
  transformed_path.Transform(GetState().Transform());

  // Add border and padding to the bounding rect.
  LayoutRect element_rect =
      EnclosingLayoutRect(transformed_path.BoundingRect());
  element_rect.Move(lbmo->BorderLeft() + lbmo->PaddingLeft(),
                    lbmo->BorderTop() + lbmo->PaddingTop());

  // Update the accessible object.
  ax_object_cache->SetCanvasObjectBounds(canvas(), element, element_rect);
}

void CanvasRenderingContext2D::addHitRegion(const HitRegionOptions& options,
                                            ExceptionState& exception_state) {
  if (options.id().IsEmpty() && !options.control()) {
    exception_state.ThrowDOMException(kNotSupportedError,
                                      "Both id and control are null.");
    return;
  }

  if (options.control() &&
      !canvas()->IsSupportedInteractiveCanvasFallback(*options.control())) {
    exception_state.ThrowDOMException(kNotSupportedError,
                                      "The control is neither null nor a "
                                      "supported interactive canvas fallback "
                                      "element.");
    return;
  }

  Path hit_region_path = options.hasPath() ? options.path()->GetPath() : path_;

  PaintCanvas* c = DrawingCanvas();

  if (hit_region_path.IsEmpty() || !c || !GetState().IsTransformInvertible() ||
      c->isClipEmpty()) {
    exception_state.ThrowDOMException(kNotSupportedError,
                                      "The specified path has no pixels.");
    return;
  }

  hit_region_path.Transform(GetState().Transform());

  if (GetState().HasClip()) {
    hit_region_path.IntersectPath(GetState().GetCurrentClipPath());
    if (hit_region_path.IsEmpty()) {
      exception_state.ThrowDOMException(kNotSupportedError,
                                        "The specified path has no pixels.");
    }
  }

  if (!hit_region_manager_)
    hit_region_manager_ = HitRegionManager::Create();

  // Remove previous region (with id or control)
  hit_region_manager_->RemoveHitRegionById(options.id());
  hit_region_manager_->RemoveHitRegionByControl(options.control());

  HitRegion* hit_region = HitRegion::Create(hit_region_path, options);
  Element* element = hit_region->Control();
  if (element && element->IsDescendantOf(canvas()))
    UpdateElementAccessibility(hit_region->GetPath(), hit_region->Control());
  hit_region_manager_->AddHitRegion(hit_region);
}

void CanvasRenderingContext2D::removeHitRegion(const String& id) {
  if (hit_region_manager_)
    hit_region_manager_->RemoveHitRegionById(id);
}

void CanvasRenderingContext2D::clearHitRegions() {
  if (hit_region_manager_)
    hit_region_manager_->RemoveAllHitRegions();
}

HitRegion* CanvasRenderingContext2D::HitRegionAtPoint(const FloatPoint& point) {
  if (hit_region_manager_)
    return hit_region_manager_->GetHitRegionAtPoint(point);

  return nullptr;
}

unsigned CanvasRenderingContext2D::HitRegionsCount() const {
  if (hit_region_manager_)
    return hit_region_manager_->GetHitRegionsCount();

  return 0;
}

}  // namespace blink