gecko-dev/gfx/layers/ThebesLayerBuffer.h

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/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla Corporation code.
*
* The Initial Developer of the Original Code is Mozilla Foundation.
* Portions created by the Initial Developer are Copyright (C) 2010
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Robert O'Callahan <robert@ocallahan.org>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#ifndef THEBESLAYERBUFFER_H_
#define THEBESLAYERBUFFER_H_
#include "gfxContext.h"
#include "gfxASurface.h"
#include "nsRegion.h"
namespace mozilla {
namespace layers {
class ThebesLayer;
/**
* This class encapsulates the buffer used to retain ThebesLayer contents,
* i.e., the contents of the layer's GetVisibleRegion().
*
* This is a cairo/Thebes surface, but with a literal twist. Scrolling
* causes the layer's visible region to move. We want to keep
* reusing the same surface if the region size hasn't changed, but we don't
* want to keep moving the contents of the surface around in memory. So
* we use a trick.
* Consider just the vertical case, and suppose the buffer is H pixels
* high and we're scrolling down by N pixels. Instead of copying the
* buffer contents up by N pixels, we leave the buffer contents in place,
* and paint content rows H to H+N-1 into rows 0 to N-1 of the buffer.
* Then we can refresh the screen by painting rows N to H-1 of the buffer
* at row 0 on the screen, and then painting rows 0 to N-1 of the buffer
* at row H-N on the screen.
* mBufferRotation.y would be N in this example.
*/
class ThebesLayerBuffer {
public:
typedef gfxASurface::gfxContentType ContentType;
/**
* Controls the size of the backing buffer of this.
* - SizedToVisibleBounds: the backing buffer is exactly the same
* size as the bounds of ThebesLayer's visible region
* - ContainsVisibleBounds: the backing buffer is large enough to
* fit visible bounds. May be larger.
*/
enum BufferSizePolicy {
SizedToVisibleBounds,
ContainsVisibleBounds
};
ThebesLayerBuffer(BufferSizePolicy aBufferSizePolicy)
: mBufferRotation(0,0)
, mBufferSizePolicy(aBufferSizePolicy)
{
MOZ_COUNT_CTOR(ThebesLayerBuffer);
}
virtual ~ThebesLayerBuffer()
{
MOZ_COUNT_DTOR(ThebesLayerBuffer);
}
/**
* Wipe out all retained contents. Call this when the entire
* buffer becomes invalid.
*/
void Clear()
{
mBuffer = nsnull;
mBufferRect.SetEmpty();
}
/**
* This is returned by BeginPaint. The caller should draw into mContext.
* mRegionToDraw must be drawn. mRegionToInvalidate has been invalidated
* by ThebesLayerBuffer and must be redrawn on the screen.
* mRegionToInvalidate is set when the buffer has changed from
* opaque to transparent or vice versa, since the details of rendering can
* depend on the buffer type. mDidSelfCopy is true if we kept our buffer
* but used MovePixels() to shift its content.
*/
struct PaintState {
PaintState()
: mDidSelfCopy(PR_FALSE)
{}
nsRefPtr<gfxContext> mContext;
nsIntRegion mRegionToDraw;
nsIntRegion mRegionToInvalidate;
bool mDidSelfCopy;
};
enum {
PAINT_WILL_RESAMPLE = 0x01
};
/**
* Start a drawing operation. This returns a PaintState describing what
* needs to be drawn to bring the buffer up to date in the visible region.
* This queries aLayer to get the currently valid and visible regions.
* The returned mContext may be null if mRegionToDraw is empty.
* Otherwise it must not be null.
* mRegionToInvalidate will contain mRegionToDraw.
* @param aFlags when PAINT_WILL_RESAMPLE is passed, this indicates that
* buffer will be resampled when rendering (i.e the effective transform
* combined with the scale for the resolution is not just an integer
* translation). This will disable buffer rotation (since we don't want
* to resample across the rotation boundary) and will ensure that we
* make the entire buffer contents valid (since we don't want to sample
* invalid pixels outside the visible region, if the visible region doesn't
* fill the buffer bounds).
*/
PaintState BeginPaint(ThebesLayer* aLayer, ContentType aContentType,
PRUint32 aFlags);
enum {
ALLOW_REPEAT = 0x01
};
/**
* Return a new surface of |aSize| and |aType|.
* @param aFlags if ALLOW_REPEAT is set, then the buffer should be configured
* to allow repeat-mode, otherwise it should be in pad (clamp) mode
*/
virtual already_AddRefed<gfxASurface>
CreateBuffer(ContentType aType, const nsIntSize& aSize, PRUint32 aFlags) = 0;
/**
* Get the underlying buffer, if any. This is useful because we can pass
* in the buffer as the default "reference surface" if there is one.
* Don't use it for anything else!
*/
gfxASurface* GetBuffer() { return mBuffer; }
protected:
enum XSide {
LEFT, RIGHT
};
enum YSide {
TOP, BOTTOM
};
nsIntRect GetQuadrantRectangle(XSide aXSide, YSide aYSide);
void DrawBufferQuadrant(gfxContext* aTarget, XSide aXSide, YSide aYSide,
float aOpacity);
void DrawBufferWithRotation(gfxContext* aTarget, float aOpacity);
/**
* |BufferRect()| is the rect of device pixels that this
* ThebesLayerBuffer covers. That is what DrawBufferWithRotation()
* will paint when it's called.
*/
const nsIntRect& BufferRect() const { return mBufferRect; }
const nsIntPoint& BufferRotation() const { return mBufferRotation; }
already_AddRefed<gfxASurface>
SetBuffer(gfxASurface* aBuffer,
const nsIntRect& aBufferRect, const nsIntPoint& aBufferRotation)
{
nsRefPtr<gfxASurface> tmp = mBuffer.forget();
mBuffer = aBuffer;
mBufferRect = aBufferRect;
mBufferRotation = aBufferRotation;
return tmp.forget();
}
/**
* Get a context at the specified resolution for updating |aBounds|,
* which must be contained within a single quadrant.
*/
already_AddRefed<gfxContext>
GetContextForQuadrantUpdate(const nsIntRect& aBounds);
private:
bool BufferSizeOkFor(const nsIntSize& aSize)
{
return (aSize == mBufferRect.Size() ||
(SizedToVisibleBounds != mBufferSizePolicy &&
aSize < mBufferRect.Size()));
}
nsRefPtr<gfxASurface> mBuffer;
/** The area of the ThebesLayer that is covered by the buffer as a whole */
nsIntRect mBufferRect;
/**
* The x and y rotation of the buffer. Conceptually the buffer
* has its origin translated to mBufferRect.TopLeft() - mBufferRotation,
* is tiled to fill the plane, and the result is clipped to mBufferRect.
* So the pixel at mBufferRotation within the buffer is what gets painted at
* mBufferRect.TopLeft().
* This is "rotation" in the sense of rotating items in a linear buffer,
* where items falling off the end of the buffer are returned to the
* buffer at the other end, not 2D rotation!
*/
nsIntPoint mBufferRotation;
BufferSizePolicy mBufferSizePolicy;
};
}
}
#endif /* THEBESLAYERBUFFER_H_ */