The Tor Browser: comparison gfx/layers/RotatedBuffer.h

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+/* -*- 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 ROTATEDBUFFER_H_
+#define ROTATEDBUFFER_H_
+#include "gfxTypes.h"
+#include <stdint.h>                     // for uint32_t
+#include "mozilla/Assertions.h"         // for MOZ_ASSERT, etc
+#include "mozilla/RefPtr.h"             // for RefPtr, TemporaryRef
+#include "mozilla/gfx/2D.h"             // for DrawTarget, etc
+#include "mozilla/mozalloc.h"           // for operator delete
+#include "nsAutoPtr.h"                  // for nsRefPtr
+#include "nsCOMPtr.h"                   // for already_AddRefed
+#include "nsDebug.h"                    // for NS_RUNTIMEABORT
+#include "nsISupportsImpl.h"            // for MOZ_COUNT_CTOR, etc
+#include "nsPoint.h"                    // for nsIntPoint
+#include "nsRect.h"                     // for nsIntRect
+#include "nsRegion.h"                   // for nsIntRegion
+#include "LayersTypes.h"
+struct nsIntSize;
+namespace mozilla {
+namespace gfx {
+class Matrix;
+}
+namespace layers {
+class TextureClient;
+class ThebesLayer;
+/**
+* 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 RotatedBuffer {
+public:
+typedef gfxContentType ContentType;
+RotatedBuffer(gfx::DrawTarget* aDTBuffer, gfx::DrawTarget* aDTBufferOnWhite,
+const nsIntRect& aBufferRect,
+const nsIntPoint& aBufferRotation)
+: mDTBuffer(aDTBuffer)
+, mDTBufferOnWhite(aDTBufferOnWhite)
+, mBufferRect(aBufferRect)
+, mBufferRotation(aBufferRotation)
+, mDidSelfCopy(false)
+{ }
+RotatedBuffer()
+: mDidSelfCopy(false)
+{ }
+/*
+* Which buffer should be drawn to/read from.
+*/
+enum ContextSource {
+BUFFER_BLACK, // The normal buffer, or buffer with black background when using component alpha.
+BUFFER_WHITE, // The buffer with white background, only valid with component alpha.
+BUFFER_BOTH // The combined black/white buffers, only valid for writing operations, not reading.
+};
+// It is the callers repsonsibility to ensure aTarget is flushed after calling
+// this method.
+void DrawBufferWithRotation(gfx::DrawTarget* aTarget, ContextSource aSource,
+float aOpacity = 1.0,
+gfx::CompositionOp aOperator = gfx::CompositionOp::OP_OVER,
+gfx::SourceSurface* aMask = nullptr,
+const gfx::Matrix* aMaskTransform = nullptr) const;
+/**
+* |BufferRect()| is the rect of device pixels that this
+* RotatedBuffer covers.  That is what DrawBufferWithRotation()
+* will paint when it's called.
+*/
+const nsIntRect& BufferRect() const { return mBufferRect; }
+const nsIntPoint& BufferRotation() const { return mBufferRotation; }
+virtual bool HaveBuffer() const { return mDTBuffer; }
+virtual bool HaveBufferOnWhite() const { return mDTBufferOnWhite; }
+protected:
+enum XSide {
+LEFT, RIGHT
+};
+enum YSide {
+TOP, BOTTOM
+};
+nsIntRect GetQuadrantRectangle(XSide aXSide, YSide aYSide) const;
+gfx::Rect GetSourceRectangle(XSide aXSide, YSide aYSide) const;
+/*
+* 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(gfx::DrawTarget* aTarget, XSide aXSide, YSide aYSide,
+ContextSource aSource,
+float aOpacity,
+gfx::CompositionOp aOperator,
+gfx::SourceSurface* aMask,
+const gfx::Matrix* aMaskTransform) const;
+RefPtr<gfx::DrawTarget> mDTBuffer;
+RefPtr<gfx::DrawTarget> mDTBufferOnWhite;
+/** 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;
+// When this is true it means that all pixels have moved inside the buffer.
+// It's not possible to sync with another buffer without a full copy.
+bool                  mDidSelfCopy;
+};
+// Mixin class for classes which need logic for loaning out a draw target.
+// See comments on BorrowDrawTargetForQuadrantUpdate.
+class BorrowDrawTarget
+{
+protected:
+void ReturnDrawTarget(gfx::DrawTarget*& aReturned);
+// The draw target loaned by BorrowDrawTargetForQuadrantUpdate. It should not
+// be used, we just keep a reference to ensure it is kept alive and so we can
+// correctly restore state when it is returned.
+RefPtr<gfx::DrawTarget> mLoanedDrawTarget;
+gfx::Matrix mLoanedTransform;
+};
+/**
+* This class encapsulates the buffer used to retain ThebesLayer contents,
+* i.e., the contents of the layer's GetVisibleRegion().
+*/
+class RotatedContentBuffer : public RotatedBuffer
+, public BorrowDrawTarget
+{
+public:
+typedef 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
+};
+RotatedContentBuffer(BufferSizePolicy aBufferSizePolicy)
+: mBufferProvider(nullptr)
+, mBufferProviderOnWhite(nullptr)
+, mBufferSizePolicy(aBufferSizePolicy)
+{
+MOZ_COUNT_CTOR(RotatedContentBuffer);
+}
+virtual ~RotatedContentBuffer()
+{
+MOZ_COUNT_DTOR(RotatedContentBuffer);
+}
+/**
+* Wipe out all retained contents. Call this when the entire
+* buffer becomes invalid.
+*/
+void Clear()
+{
+mDTBuffer = nullptr;
+mDTBufferOnWhite = nullptr;
+mBufferProvider = nullptr;
+mBufferProviderOnWhite = nullptr;
+mBufferRect.SetEmpty();
+}
+/**
+* This is returned by BeginPaint. The caller should draw into mTarget.
+* mRegionToDraw must be drawn. mRegionToInvalidate has been invalidated
+* by RotatedContentBuffer 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()
+: mMode(SurfaceMode::SURFACE_NONE)
+, mContentType(gfxContentType::SENTINEL)
+, mDidSelfCopy(false)
+{}
+nsIntRegion mRegionToDraw;
+nsIntRegion mRegionToInvalidate;
+SurfaceMode mMode;
+DrawRegionClip mClip;
+ContentType mContentType;
+bool mDidSelfCopy;
+};
+enum {
+PAINT_WILL_RESAMPLE = 0x01,
+PAINT_NO_ROTATION = 0x02,
+PAINT_CAN_DRAW_ROTATED = 0x04
+};
+/**
+* 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 mTarget 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).
+* PAINT_CAN_DRAW_ROTATED can be passed if the caller supports drawing
+* rotated content that crosses the physical buffer boundary. The caller
+* will need to call BorrowDrawTargetForPainting multiple times to achieve
+* this.
+*/
+PaintState BeginPaint(ThebesLayer* aLayer,
+uint32_t aFlags);
+struct DrawIterator {
+friend class RotatedContentBuffer;
+friend class ContentClientIncremental;
+DrawIterator()
+: mCount(0)
+{}
+nsIntRegion mDrawRegion;
+private:
+uint32_t mCount;
+};
+/**
+* Fetch a DrawTarget for rendering. The DrawTarget remains owned by
+* this. See notes on BorrowDrawTargetForQuadrantUpdate.
+* May return null. If the return value is non-null, it must be
+* 'un-borrowed' using ReturnDrawTarget.
+*
+* If PAINT_CAN_DRAW_ROTATED was specified for BeginPaint, then the caller
+* must call this function repeatedly (with an iterator) until it returns
+* nullptr. The caller should draw the mDrawRegion of the iterator instead
+* of mRegionToDraw in the PaintState.
+*
+* @param aPaintState Paint state data returned by a call to BeginPaint
+* @param aIter Paint state iterator. Only required if PAINT_CAN_DRAW_ROTATED
+* was specified to BeginPaint.
+*/
+gfx::DrawTarget* BorrowDrawTargetForPainting(const PaintState& aPaintState,
+DrawIterator* aIter = nullptr);
+enum {
+ALLOW_REPEAT = 0x01,
+BUFFER_COMPONENT_ALPHA = 0x02 // Dual buffers should be created for drawing with
+// component alpha.
+};
+/**
+* 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
+* If the created buffer supports azure content, then the result(s) will
+* be returned in aBlackDT/aWhiteDT, otherwise aBlackSurface/aWhiteSurface
+* will be used.
+*/
+virtual void
+CreateBuffer(ContentType aType, const nsIntRect& aRect, uint32_t aFlags,
+RefPtr<gfx::DrawTarget>* aBlackDT, RefPtr<gfx::DrawTarget>* aWhiteDT) = 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!
+*/
+gfx::DrawTarget* GetDTBuffer() { return mDTBuffer; }
+gfx::DrawTarget* GetDTBufferOnWhite() { return mDTBufferOnWhite; }
+/**
+* Complete the drawing operation. The region to draw must have been
+* drawn before this is called. The contents of the buffer are drawn
+* to aTarget.
+*/
+void DrawTo(ThebesLayer* aLayer,
+gfx::DrawTarget* aTarget,
+float aOpacity,
+gfx::CompositionOp aOp,
+gfx::SourceSurface* aMask,
+const gfx::Matrix* aMaskTransform);
+protected:
+// new texture client versions
+void SetBufferProvider(TextureClient* aClient)
+{
+// Only this buffer provider can give us a buffer.  If we
+// already have one, something has gone wrong.
+MOZ_ASSERT(!aClient || !mDTBuffer);
+mBufferProvider = aClient;
+if (!mBufferProvider) {
+mDTBuffer = nullptr;
+}
+}
+void SetBufferProviderOnWhite(TextureClient* aClient)
+{
+// Only this buffer provider can give us a buffer.  If we
+// already have one, something has gone wrong.
+MOZ_ASSERT(!aClient || !mDTBufferOnWhite);
+mBufferProviderOnWhite = aClient;
+if (!mBufferProviderOnWhite) {
+mDTBufferOnWhite = nullptr;
+}
+}
+/**
+* Get a draw target at the specified resolution for updating |aBounds|,
+* which must be contained within a single quadrant.
+*
+* The result should only be held temporarily by the caller (it will be kept
+* alive by this). Once used it should be returned using ReturnDrawTarget.
+* BorrowDrawTargetForQuadrantUpdate may not be called more than once without
+* first calling ReturnDrawTarget.
+*
+* ReturnDrawTarget will restore the transform on the draw target. But it is
+* the callers responsibility to restore the clip. The caller should flush the
+* draw target, if necessary.
+*/
+gfx::DrawTarget*
+BorrowDrawTargetForQuadrantUpdate(const nsIntRect& aBounds,
+ContextSource aSource,
+DrawIterator* aIter);
+static bool IsClippingCheap(gfx::DrawTarget* aTarget, const nsIntRegion& aRegion);
+protected:
+/**
+* Return the buffer's content type.  Requires a valid buffer or
+* buffer provider.
+*/
+gfxContentType BufferContentType();
+bool BufferSizeOkFor(const nsIntSize& aSize);
+/**
+* If the buffer hasn't been mapped, map it.
+*/
+bool EnsureBuffer();
+bool EnsureBufferOnWhite();
+// Flush our buffers if they are mapped.
+void FlushBuffers();
+/**
+* True if we have a buffer where we can get it (but not necessarily
+* mapped currently).
+*/
+virtual bool HaveBuffer() const;
+virtual bool HaveBufferOnWhite() const;
+/**
+* Any actions that should be performed at the last moment before we begin
+* rendering the next frame. I.e., after we calculate what we will draw,
+* but before we rotate the buffer and possibly create new buffers.
+* aRegionToDraw is the region which is guaranteed to be overwritten when
+* drawing the next frame.
+*/
+virtual void FinalizeFrame(const nsIntRegion& aRegionToDraw) {}
+/**
+* These members are only set transiently.  They're used to map mDTBuffer
+* when we're using surfaces that require explicit map/unmap. Only one
+* may be used at a time.
+*/
+TextureClient* mBufferProvider;
+TextureClient* mBufferProviderOnWhite;
+BufferSizePolicy      mBufferSizePolicy;
+};
+}
+}
+#endif /* ROTATEDBUFFER_H_ */

The Tor Browser / file comparison

comparison: gfx/layers/RotatedBuffer.h

gfx/layers/RotatedBuffer.h