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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 "GrContext.h"
#include "GrDrawState.h"
#include "GrNoncopyable.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 "GrClipMaskCache.h"
class GrGpu;
class GrPathRenderer;
class GrPathRendererChain;
class SkPath;
class GrTexture;
* 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 : public GrNoncopyable {
: fGpu(NULL)
, fCurrClipMaskType(kNone_ClipMaskType) {
* 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.
bool setupClipping(const GrClipData* clipDataIn, GrDrawState::AutoRestoreEffects*);
void releaseResources();
bool isClipInStencil() const {
return kStencil_ClipMaskType == fCurrClipMaskType;
bool isClipInAlpha() const {
return kAlpha_ClipMaskType == fCurrClipMaskType;
void invalidateStencilMask() {
if (kStencil_ClipMaskType == fCurrClipMaskType) {
fCurrClipMaskType = kNone_ClipMaskType;
GrContext* getContext() {
return fAACache.getContext();
void setGpu(GrGpu* gpu);
* 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.
GrGpu* fGpu;
* 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
// Draws the clip into the stencil buffer
bool createStencilClipMask(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 clipStackGenID,
GrReducedClip::InitialState initialState,
const GrReducedClip::ElementList& elements,
const SkIRect& clipSpaceIBounds);
// Similar to createAlphaClipMask but it rasterizes in SW and uploads to the result texture.
GrTexture* createSoftwareClipMask(int32_t clipStackGenID,
GrReducedClip::InitialState initialState,
const GrReducedClip::ElementList& elements,
const SkIRect& clipSpaceIBounds);
// Gets a texture to use for the clip mask. If true is returned then a cached mask was found
// that already contains the rasterization of the clip stack, otherwise an uninitialized texture
// is returned.
bool getMaskTexture(int32_t clipStackGenID,
const SkIRect& clipSpaceIBounds,
GrTexture** result);
bool useSWOnlyPath(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(GrTexture* target, const SkClipStack::Element*, GrPathRenderer* = 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(GrTexture* target, const SkClipStack::Element*, GrPathRenderer**);
void mergeMask(GrTexture* dstMask,
GrTexture* srcMask,
SkRegion::Op op,
const SkIRect& dstBound,
const SkIRect& srcBound);
void getTemp(int width, int height, GrAutoScratchTexture* temp);
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 setGpuStencil();
* Adjusts the stencil settings to account for interaction with stencil
* clipping.
void adjustStencilParams(GrStencilSettings* settings,
StencilClipMode mode,
int stencilBitCnt);
typedef GrNoncopyable INHERITED;
#endif // GrClipMaskManager_DEFINED