gecko-dev/layout/generic/nsCanvasFrame.h

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/* rendering object that goes directly inside the document's scrollbars */

#ifndef nsCanvasFrame_h___
#define nsCanvasFrame_h___

#include "mozilla/Attributes.h"
#include "nsContainerFrame.h"
#include "nsIScrollPositionListener.h"
#include "nsDisplayList.h"
#include "nsGkAtoms.h"

class nsPresContext;
class nsRenderingContext;
class nsEvent;

/**
 * Root frame class.
 *
 * The root frame is the parent frame for the document element's frame.
 * It only supports having a single child frame which must be an area
 * frame
 */
class nsCanvasFrame : public nsContainerFrame,
                      public nsIScrollPositionListener
{
public:
  nsCanvasFrame(nsStyleContext* aContext)
  : nsContainerFrame(aContext),
    mDoPaintFocus(false),
    mAddedScrollPositionListener(false) {}

  NS_DECL_QUERYFRAME_TARGET(nsCanvasFrame)
  NS_DECL_QUERYFRAME
  NS_DECL_FRAMEARENA_HELPERS


  virtual void DestroyFrom(nsIFrame* aDestructRoot);

  NS_IMETHOD SetInitialChildList(ChildListID     aListID,
                                 nsFrameList&    aChildList) MOZ_OVERRIDE;
  NS_IMETHOD AppendFrames(ChildListID     aListID,
                          nsFrameList&    aFrameList) MOZ_OVERRIDE;
  NS_IMETHOD InsertFrames(ChildListID     aListID,
                          nsIFrame*       aPrevFrame,
                          nsFrameList&    aFrameList) MOZ_OVERRIDE;
  NS_IMETHOD RemoveFrame(ChildListID     aListID,
                         nsIFrame*       aOldFrame) MOZ_OVERRIDE;

  virtual nscoord GetMinWidth(nsRenderingContext *aRenderingContext) MOZ_OVERRIDE;
  virtual nscoord GetPrefWidth(nsRenderingContext *aRenderingContext) MOZ_OVERRIDE;
  NS_IMETHOD Reflow(nsPresContext*          aPresContext,
                    nsHTMLReflowMetrics&     aDesiredSize,
                    const nsHTMLReflowState& aReflowState,
                    nsReflowStatus&          aStatus) MOZ_OVERRIDE;
  virtual bool IsFrameOfType(uint32_t aFlags) const
  {
    return nsContainerFrame::IsFrameOfType(aFlags &
             ~(nsIFrame::eCanContainOverflowContainers));
  }

  /** SetHasFocus tells the CanvasFrame to draw with focus ring
   *  @param aHasFocus true to show focus ring, false to hide it
   */
  NS_IMETHOD SetHasFocus(bool aHasFocus);

  NS_IMETHOD BuildDisplayList(nsDisplayListBuilder*   aBuilder,
                              const nsRect&           aDirtyRect,
                              const nsDisplayListSet& aLists) MOZ_OVERRIDE;

  void PaintFocus(nsRenderingContext& aRenderingContext, nsPoint aPt);

  // nsIScrollPositionListener
  virtual void ScrollPositionWillChange(nscoord aX, nscoord aY);
  virtual void ScrollPositionDidChange(nscoord aX, nscoord aY) {}

  /**
   * Get the "type" of the frame
   *
   * @see nsGkAtoms::canvasFrame
   */
  virtual nsIAtom* GetType() const MOZ_OVERRIDE;

  virtual nsresult StealFrame(nsPresContext* aPresContext,
                              nsIFrame*      aChild,
                              bool           aForceNormal) MOZ_OVERRIDE
  {
    NS_ASSERTION(!aForceNormal, "No-one should be passing this in here");

    // nsCanvasFrame keeps overflow container continuations of its child
    // frame in main child list
    nsresult rv = nsContainerFrame::StealFrame(aPresContext, aChild, true);
    if (NS_FAILED(rv)) {
      rv = nsContainerFrame::StealFrame(aPresContext, aChild);
    }
    return rv;
  }

#ifdef DEBUG
  NS_IMETHOD GetFrameName(nsAString& aResult) const MOZ_OVERRIDE;
#endif
  NS_IMETHOD GetContentForEvent(nsEvent* aEvent,
                                nsIContent** aContent) MOZ_OVERRIDE;

  nsRect CanvasArea() const;

protected:
  virtual int GetSkipSides() const;

  // Data members
  bool                      mDoPaintFocus;
  bool                      mAddedScrollPositionListener;
};

/**
 * Override nsDisplayBackground methods so that we pass aBGClipRect to
 * PaintBackground, covering the whole overflow area.
 * We can also paint an "extra background color" behind the normal
 * background.
 */
class nsDisplayCanvasBackground : public nsDisplayBackgroundImage {
public:
  nsDisplayCanvasBackground(nsDisplayListBuilder* aBuilder, nsIFrame *aFrame,
                            uint32_t aLayer, bool aIsThemed,
                            const nsStyleBackground* aBackgroundStyle)
    : nsDisplayBackgroundImage(aBuilder, aFrame, aLayer, aIsThemed, aBackgroundStyle),
      mExtraBackgroundColor(NS_RGBA(0,0,0,0))
  {
  }

  virtual bool ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                 nsRegion* aVisibleRegion,
                                 const nsRect& aAllowVisibleRegionExpansion) MOZ_OVERRIDE
  {
    return NS_GET_A(mExtraBackgroundColor) > 0 ||
      nsDisplayBackgroundImage::ComputeVisibility(aBuilder, aVisibleRegion,
                                             aAllowVisibleRegionExpansion);
  }
  virtual nsRegion GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
                                   bool* aSnap) MOZ_OVERRIDE
  {
    if (NS_GET_A(mExtraBackgroundColor) == 255) {
      return nsRegion(GetBounds(aBuilder, aSnap));
    }
    return nsDisplayBackgroundImage::GetOpaqueRegion(aBuilder, aSnap);
  }
  virtual bool IsUniform(nsDisplayListBuilder* aBuilder, nscolor* aColor) MOZ_OVERRIDE
  {
    nscolor background;
    if (!nsDisplayBackgroundImage::IsUniform(aBuilder, &background))
      return false;
    NS_ASSERTION(background == NS_RGBA(0,0,0,0),
                 "The nsDisplayBackground for a canvas frame doesn't paint "
                 "its background color normally");
    *aColor = mExtraBackgroundColor;
    return true;
  }
  virtual nsRect GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) MOZ_OVERRIDE
  {
    nsCanvasFrame* frame = static_cast<nsCanvasFrame*>(mFrame);
    *aSnap = true;
    return frame->CanvasArea() + ToReferenceFrame();
  }
  virtual void HitTest(nsDisplayListBuilder* aBuilder, const nsRect& aRect,
                       HitTestState* aState, nsTArray<nsIFrame*> *aOutFrames) MOZ_OVERRIDE
  {
    // We need to override so we don't consider border-radius.
    aOutFrames->AppendElement(mFrame);
  }
  virtual bool ShouldFixToViewport(nsDisplayListBuilder* aBuilder) MOZ_OVERRIDE
  {
    // Put background-attachment:fixed canvas background images in their own
    // compositing layer. Since we know their background painting area can't
    // change (unless the viewport size itself changes), async scrolling
    // will work well.
    return mBackgroundStyle &&
      mBackgroundStyle->mLayers[mLayer].mAttachment == NS_STYLE_BG_ATTACHMENT_FIXED &&
      !mBackgroundStyle->mLayers[mLayer].mImage.IsEmpty();
  }
  virtual void NotifyRenderingChanged() MOZ_OVERRIDE
  {
    mFrame->Properties().Delete(nsIFrame::CachedBackgroundImage());
  }

  virtual void Paint(nsDisplayListBuilder* aBuilder,
                     nsRenderingContext* aCtx) MOZ_OVERRIDE;
 
  // We still need to paint a background color as well as an image for this item, 
  // so we can't support this yet.
  virtual bool SupportsOptimizingToImage() { return false; }

  void SetExtraBackgroundColor(nscolor aColor)
  {
    mExtraBackgroundColor = aColor;
  }

  NS_DISPLAY_DECL_NAME("CanvasBackground", TYPE_CANVAS_BACKGROUND)

private:
  nscolor mExtraBackgroundColor;
};

#endif /* nsCanvasFrame_h___ */