gecko/gfx/layers/ThebesLayerBuffer.h

253 lines
8.6 KiB
C++

/* -*- Mode: C++; tab-width: 20; 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/. */
#ifndef THEBESLAYERBUFFER_H_
#define THEBESLAYERBUFFER_H_
#include "gfxContext.h"
#include "gfxASurface.h"
#include "nsRegion.h"
namespace mozilla {
namespace layers {
class AutoOpenSurface;
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)
: mBufferProvider(nullptr)
, 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 = nullptr;
mBufferProvider = nullptr;
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(false)
{}
nsRefPtr<gfxContext> mContext;
nsIntRegion mRegionToDraw;
nsIntRegion mRegionToInvalidate;
bool mDidSelfCopy;
};
enum {
PAINT_WILL_RESAMPLE = 0x01,
PAINT_NO_ROTATION = 0x02
};
/**
* 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,
uint32_t 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, uint32_t 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);
/*
* If aMask is non-null, then it is used as an alpha mask for rendering this
* buffer. aMaskTransform must be non-null if aMask is non-null, and is used
* to adjust the coordinate space of the mask.
*/
void DrawBufferQuadrant(gfxContext* aTarget, XSide aXSide, YSide aYSide,
float aOpacity,
gfxASurface* aMask,
const gfxMatrix* aMaskTransform);
void DrawBufferWithRotation(gfxContext* aTarget, float aOpacity,
gfxASurface* aMask = nullptr,
const gfxMatrix* aMaskTransform = nullptr);
/**
* |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();
}
/**
* Set the buffer provider only. This is used with surfaces that
* require explicit map/unmap, which |aProvider| is used to do on
* demand in this code.
*
* It's the caller's responsibility to ensure |aProvider| is valid
* for the duration of operations it requests of this
* ThebesLayerBuffer. It's also the caller's responsibility to
* unset the provider when inactive, by calling
* SetBufferProvider(nullptr).
*/
void SetBufferProvider(AutoOpenSurface* aProvider)
{
mBufferProvider = aProvider;
if (!mBufferProvider) {
mBuffer = nullptr;
} else {
// Only this buffer provider can give us a buffer. If we
// already have one, something has gone wrong.
MOZ_ASSERT(!mBuffer);
}
}
/**
* 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:
// Buffer helpers. Don't use mBuffer directly; instead use one of
// these helpers.
/**
* Return the buffer's content type. Requires a valid buffer or
* buffer provider.
*/
gfxASurface::gfxContentType BufferContentType();
bool BufferSizeOkFor(const nsIntSize& aSize);
/**
* If the buffer hasn't been mapped, map it and return it.
*/
gfxASurface* EnsureBuffer();
/**
* True if we have a buffer where we can get it (but not necessarily
* mapped currently).
*/
bool HaveBuffer();
nsRefPtr<gfxASurface> mBuffer;
/**
* This member is only set transiently. It's used to map mBuffer
* when we're using surfaces that require explicit map/unmap.
*/
AutoOpenSurface* mBufferProvider;
/** 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_ */