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* Copyright 2012 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef GrClipMaskManager_DEFINED
#define GrClipMaskManager_DEFINED
#include "GrClipMaskCache.h"
#include "GrContext.h"
#include "GrPipelineBuilder.h"
#include "GrReducedClip.h"
#include "GrStencil.h"
#include "GrTexture.h"
#include "SkClipStack.h"
#include "SkDeque.h"
#include "SkPath.h"
#include "SkRefCnt.h"
#include "SkTLList.h"
#include "SkTypes.h"
class GrClipTarget;
class GrPathRenderer;
class GrPathRendererChain;
class GrTexture;
class SkPath;
* The clip mask creator handles the generation of the clip mask. If anti
* aliasing is requested it will (in the future) generate a single channel
* (8bit) mask. If no anti aliasing is requested it will generate a 1-bit
* mask in the stencil buffer. In the non anti-aliasing case, if the clip
* mask can be represented as a rectangle then scissoring is used. In all
* cases scissoring is used to bound the range of the clip mask.
class GrClipMaskManager : SkNoncopyable {
: fCurrClipMaskType(kNone_ClipMaskType)
, fClipTarget(NULL)
, fClipMode(kIgnoreClip_StencilClipMode) {
* Creates a clip mask if necessary as a stencil buffer or alpha texture
* and sets the GrGpu's scissor and stencil state. If the return is false
* then the draw can be skipped. The AutoRestoreEffects is initialized by
* the manager when it must install additional effects to implement the
* clip. devBounds is optional but can help optimize clipping.
bool setupClipping(GrPipelineBuilder*,
const GrClipData* clipDataIn,
const SkRect* devBounds);
* Purge resources to free up memory. TODO: This class shouldn't hold any long lived refs
* which will allow ResourceCache2 to automatically purge anything this class has created.
void purgeResources();
bool isClipInStencil() const {
return kStencil_ClipMaskType == fCurrClipMaskType;
bool isClipInAlpha() const {
return kAlpha_ClipMaskType == fCurrClipMaskType;
GrContext* getContext() {
return fAACache.getContext();
void setClipTarget(GrClipTarget*);
void adjustPathStencilParams(const GrStencilBuffer*, GrStencilSettings*);
* Informs the helper function adjustStencilParams() about how the stencil
* buffer clip is being used.
enum StencilClipMode {
// Draw to the clip bit of the stencil buffer
// Clip against the existing representation of the clip in the high bit
// of the stencil buffer.
// Neither writing to nor clipping against the clip bit.
// Attempts to install a series of coverage effects to implement the clip. Return indicates
// whether the element list was successfully converted to effects.
bool installClipEffects(GrPipelineBuilder*,
const GrReducedClip::ElementList&,
const SkVector& clipOffset,
const SkRect* devBounds);
// Draws the clip into the stencil buffer
bool createStencilClipMask(GrRenderTarget*,
int32_t elementsGenID,
GrReducedClip::InitialState initialState,
const GrReducedClip::ElementList& elements,
const SkIRect& clipSpaceIBounds,
const SkIPoint& clipSpaceToStencilOffset);
// Creates an alpha mask of the clip. The mask is a rasterization of elements through the
// rect specified by clipSpaceIBounds.
GrTexture* createAlphaClipMask(int32_t elementsGenID,
GrReducedClip::InitialState initialState,
const GrReducedClip::ElementList& elements,
const SkVector& clipToMaskOffset,
const SkIRect& clipSpaceIBounds);
// Similar to createAlphaClipMask but it rasterizes in SW and uploads to the result texture.
GrTexture* createSoftwareClipMask(int32_t elementsGenID,
GrReducedClip::InitialState initialState,
const GrReducedClip::ElementList& elements,
const SkVector& clipToMaskOffset,
const SkIRect& clipSpaceIBounds);
// Returns the cached mask texture if it matches the elementsGenID and the clipSpaceIBounds.
// Returns NULL if not found.
GrTexture* getCachedMaskTexture(int32_t elementsGenID, const SkIRect& clipSpaceIBounds);
// Handles allocation (if needed) of a clip alpha-mask texture for both the sw-upload
// or gpu-rendered cases.
GrTexture* allocMaskTexture(int32_t elementsGenID,
const SkIRect& clipSpaceIBounds,
bool willUpload);
bool useSWOnlyPath(const GrPipelineBuilder*,
const SkVector& clipToMaskOffset,
const GrReducedClip::ElementList& elements);
// Draws a clip element into the target alpha mask. The caller should have already setup the
// desired blend operation. Optionally if the caller already selected a path renderer it can
// be passed. Otherwise the function will select one if the element is a path.
bool drawElement(GrPipelineBuilder*,
const SkMatrix& viewMatrix,
GrTexture* target,
const SkClipStack::Element*,
GrPathRenderer* pr = NULL);
// Determines whether it is possible to draw the element to both the stencil buffer and the
// alpha mask simultaneously. If so and the element is a path a compatible path renderer is
// also returned.
bool canStencilAndDrawElement(GrPipelineBuilder*,
GrTexture* target,
const SkClipStack::Element*);
void mergeMask(GrPipelineBuilder*,
GrTexture* dstMask,
GrTexture* srcMask,
SkRegion::Op op,
const SkIRect& dstBound,
const SkIRect& srcBound);
GrTexture* createTempMask(int width, int height);
void setupCache(const SkClipStack& clip,
const SkIRect& bounds);
* Called prior to return control back the GrGpu in setupClipping. It
* updates the GrGpu with stencil settings that account stencil-based
* clipping.
void setPipelineBuilderStencil(GrPipelineBuilder*, GrPipelineBuilder::AutoRestoreStencil*);
* Adjusts the stencil settings to account for interaction with stencil
* clipping.
void adjustStencilParams(GrStencilSettings* settings,
StencilClipMode mode,
int stencilBitCnt);
* We may represent the clip as a mask in the stencil buffer or as an alpha
* texture. It may be neither because the scissor rect suffices or we
* haven't yet examined the clip.
enum ClipMaskType {
} fCurrClipMaskType;
GrClipMaskCache fAACache; // cache for the AA path
GrClipTarget* fClipTarget;
StencilClipMode fClipMode;
typedef SkNoncopyable INHERITED;
#endif // GrClipMaskManager_DEFINED