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/*
* Copyright 2011 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef GrPathRenderer_DEFINED
#define GrPathRenderer_DEFINED
#include "GrTypesPriv.h"
#include "SkTArray.h"
#include "SkRefCnt.h"
class GrCaps;
class GrClip;
class GrContext;
class GrFixedClip;
class GrHardClip;
class GrPaint;
class GrRenderTargetContext;
class GrShape;
class GrStyle;
struct GrUserStencilSettings;
struct SkIRect;
class SkMatrix;
class SkPath;
/**
* Base class for drawing paths into a GrOpList.
*/
class SK_API GrPathRenderer : public SkRefCnt {
public:
GrPathRenderer();
/**
* A caller may wish to use a path renderer to draw a path into the stencil buffer. However,
* the path renderer itself may require use of the stencil buffer. Also a path renderer may
* use a GrProcessor coverage stage that sets coverage to zero to eliminate pixels that are
* covered by bounding geometry but outside the path. These exterior pixels would still be
* rendered into the stencil.
*
* A GrPathRenderer can provide three levels of support for stenciling paths:
* 1) kNoRestriction: This is the most general. The caller passes a GrPaint and calls drawPath().
* The path is rendered exactly as the draw state indicates including support
* for simultaneous color and stenciling with arbitrary stenciling rules.
* Pixels partially covered by AA paths are affected by the stencil settings.
* 2) kStencilOnly: The path renderer cannot apply arbitrary stencil rules nor shade and stencil
* simultaneously. The path renderer does support the stencilPath() function
* which performs no color writes and writes a non-zero stencil value to pixels
* covered by the path.
* 3) kNoSupport: This path renderer cannot be used to stencil the path.
*/
enum StencilSupport {
kNoSupport_StencilSupport,
kStencilOnly_StencilSupport,
kNoRestriction_StencilSupport,
};
/**
* This function is to get the stencil support for a particular path. The path's fill must
* not be an inverse type. The path will always be filled and not stroked.
*
* @param shape the shape that will be drawn. Must be simple fill styled and non-inverse
* filled.
*/
StencilSupport getStencilSupport(const GrShape& shape) const;
enum class CanDrawPath {
kNo,
kAsBackup, // i.e. This renderer is better than SW fallback if no others can draw the path.
kYes
};
struct CanDrawPathArgs {
SkDEBUGCODE(CanDrawPathArgs() { memset(this, 0, sizeof(*this)); }) // For validation.
const GrCaps* fCaps;
const SkIRect* fClipConservativeBounds;
const SkMatrix* fViewMatrix;
const GrShape* fShape;
GrAAType fAAType;
// These next two are only used by GrStencilAndCoverPathRenderer
bool fHasUserStencilSettings;
#ifdef SK_DEBUG
void validate() const {
SkASSERT(fCaps);
SkASSERT(fClipConservativeBounds);
SkASSERT(fViewMatrix);
SkASSERT(fShape);
}
#endif
};
/**
* Returns how well this path renderer is able to render the given path. Returning kNo or
* kAsBackup allows the caller to keep searching for a better path renderer. This function is
* called when searching for the best path renderer to draw a path.
*/
CanDrawPath canDrawPath(const CanDrawPathArgs& args) const {
SkDEBUGCODE(args.validate();)
return this->onCanDrawPath(args);
}
struct DrawPathArgs {
GrContext* fContext;
GrPaint&& fPaint;
const GrUserStencilSettings* fUserStencilSettings;
GrRenderTargetContext* fRenderTargetContext;
const GrClip* fClip;
const SkIRect* fClipConservativeBounds;
const SkMatrix* fViewMatrix;
const GrShape* fShape;
GrAAType fAAType;
bool fGammaCorrect;
#ifdef SK_DEBUG
void validate() const {
SkASSERT(fContext);
SkASSERT(fUserStencilSettings);
SkASSERT(fRenderTargetContext);
SkASSERT(fClip);
SkASSERT(fClipConservativeBounds);
SkASSERT(fViewMatrix);
SkASSERT(fShape);
}
#endif
};
/**
* Draws the path into the draw target. If getStencilSupport() would return kNoRestriction then
* the subclass must respect the stencil settings.
*/
bool drawPath(const DrawPathArgs& args);
/**
* Args to stencilPath(). fAAType cannot be kCoverage.
*/
struct StencilPathArgs {
SkDEBUGCODE(StencilPathArgs() { memset(this, 0, sizeof(*this)); }) // For validation.
GrContext* fContext;
GrRenderTargetContext* fRenderTargetContext;
const GrHardClip* fClip;
const SkIRect* fClipConservativeBounds;
const SkMatrix* fViewMatrix;
GrAAType fAAType;
const GrShape* fShape;
SkDEBUGCODE(void validate() const);
};
/**
* Draws the path to the stencil buffer. Assume the writable stencil bits are already
* initialized to zero. The pixels inside the path will have non-zero stencil values afterwards.
*/
void stencilPath(const StencilPathArgs& args) {
SkDEBUGCODE(args.validate();)
SkASSERT(kNoSupport_StencilSupport != this->getStencilSupport(*args.fShape));
this->onStencilPath(args);
}
// Helper for determining if we can treat a thin stroke as a hairline w/ coverage.
// If we can, we draw lots faster (raster device does this same test).
static bool IsStrokeHairlineOrEquivalent(const GrStyle&, const SkMatrix&,
SkScalar* outCoverage);
protected:
// Helper for getting the device bounds of a path. Inverse filled paths will have bounds set
// by devSize. Non-inverse path bounds will not necessarily be clipped to devSize.
static void GetPathDevBounds(const SkPath& path,
int devW,
int devH,
const SkMatrix& matrix,
SkRect* bounds);
private:
/**
* Subclass overrides if it has any limitations of stenciling support.
*/
virtual StencilSupport onGetStencilSupport(const GrShape&) const {
return kNoRestriction_StencilSupport;
}
/**
* Subclass implementation of drawPath()
*/
virtual bool onDrawPath(const DrawPathArgs& args) = 0;
/**
* Subclass implementation of canDrawPath()
*/
virtual CanDrawPath onCanDrawPath(const CanDrawPathArgs& args) const = 0;
/**
* Subclass implementation of stencilPath(). Subclass must override iff it ever returns
* kStencilOnly in onGetStencilSupport().
*/
virtual void onStencilPath(const StencilPathArgs&);
typedef SkRefCnt INHERITED;
};
#endif
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