gecko/layout/generic/nsCanvasFrame.h
Robert O'Callahan d0dd680745 Bug 733607. Restructure logic to compute snapped bounds of display items in layer coordinates. Moves responsibility for computing snapped bounds from within the display items to callers of GetBounds/GetOpaqueRegion. r=tnikkel
Previously we snapped the results of nsDisplayItem::GetBounds and
nsDisplayItem::GetOpaqueRegion internally. By tracking which display items were
inside transforms, we disabled snapping quite conservatively whenever an ancestor
had a transform, which is undesirable.

With this patch, we don't snap inside GetBounds or GetOpaqueRegion, but just return
a boolean flag indicating whether the item will draw with snapping or not. This flag
is conservative so that "true" means we will snap (if the graphics context has a transform
that allows snapping), but "false" means we might or might not snap (so it's always safe
to return false).

FrameLayerBuilder takes over responsibility for snapping item bounds. When it converts
display item bounds to layer pixel coordinates, it checks the snap flag returned from
the display item and checks whether the transform when we draw into the layer will be
a known scale (the ContainerParameters scale factors) plus integer translation. If both
are true, we snap the item bounds when converting to layer pixel coordinates. With
this approach, we can snap item bounds even when the items have ancestors with active
transforms.
2012-04-10 23:24:18 +12:00

223 lines
7.8 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* rendering object that goes directly inside the document's scrollbars */
#ifndef nsCanvasFrame_h___
#define nsCanvasFrame_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);
NS_IMETHOD AppendFrames(ChildListID aListID,
nsFrameList& aFrameList);
NS_IMETHOD InsertFrames(ChildListID aListID,
nsIFrame* aPrevFrame,
nsFrameList& aFrameList);
NS_IMETHOD RemoveFrame(ChildListID aListID,
nsIFrame* aOldFrame);
virtual nscoord GetMinWidth(nsRenderingContext *aRenderingContext);
virtual nscoord GetPrefWidth(nsRenderingContext *aRenderingContext);
NS_IMETHOD Reflow(nsPresContext* aPresContext,
nsHTMLReflowMetrics& aDesiredSize,
const nsHTMLReflowState& aReflowState,
nsReflowStatus& aStatus);
virtual bool IsFrameOfType(PRUint32 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);
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;
virtual nsresult StealFrame(nsPresContext* aPresContext,
nsIFrame* aChild,
bool aForceNormal)
{
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;
#endif
NS_IMETHOD GetContentForEvent(nsEvent* aEvent,
nsIContent** aContent);
nsRect CanvasArea() const;
protected:
virtual PRIntn 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 nsDisplayBackground {
public:
nsDisplayCanvasBackground(nsDisplayListBuilder* aBuilder, nsIFrame *aFrame)
: nsDisplayBackground(aBuilder, aFrame)
{
mExtraBackgroundColor = NS_RGBA(0,0,0,0);
}
virtual bool ComputeVisibility(nsDisplayListBuilder* aBuilder,
nsRegion* aVisibleRegion,
const nsRect& aAllowVisibleRegionExpansion)
{
return NS_GET_A(mExtraBackgroundColor) > 0 ||
nsDisplayBackground::ComputeVisibility(aBuilder, aVisibleRegion,
aAllowVisibleRegionExpansion);
}
virtual nsRegion GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
bool* aSnap,
bool* aForceTransparentSurface)
{
if (NS_GET_A(mExtraBackgroundColor) == 255) {
*aForceTransparentSurface = false;
return nsRegion(GetBounds(aBuilder, aSnap));
}
return nsDisplayBackground::GetOpaqueRegion(aBuilder, aSnap,
aForceTransparentSurface);
}
virtual bool IsUniform(nsDisplayListBuilder* aBuilder, nscolor* aColor)
{
nscolor background;
if (!nsDisplayBackground::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)
{
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)
{
// We need to override so we don't consider border-radius.
aOutFrames->AppendElement(mFrame);
}
virtual void Paint(nsDisplayListBuilder* aBuilder,
nsRenderingContext* aCtx);
void SetExtraBackgroundColor(nscolor aColor)
{
mExtraBackgroundColor = aColor;
}
NS_DISPLAY_DECL_NAME("CanvasBackground", TYPE_CANVAS_BACKGROUND)
private:
nscolor mExtraBackgroundColor;
};
#endif /* nsCanvasFrame_h___ */