/*
* 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 "GrDrawTarget.h"
#include "GrStencil.h"
#include "GrStrokeInfo.h"
#include "SkDrawProcs.h"
#include "SkTArray.h"
class SkPath;
struct GrPoint;
/**
* Base class for drawing paths into a GrDrawTarget.
*
* Derived classes can use stages GrPaint::kTotalStages through GrPipelineBuilder::kNumStages-1.
* The stages before GrPaint::kTotalStages are reserved for setting up the draw (i.e., textures and
* filter masks).
*/
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 sets up the GrPipelineBuilder on the target
* 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.
*
* @param path the path that will be drawn
* @param stroke the stroke information (width, join, cap).
*/
StencilSupport getStencilSupport(const SkPath& path, const GrStrokeInfo& stroke) const {
SkASSERT(!path.isInverseFillType());
return this->onGetStencilSupport(path, stroke);
}
/** Args to canDrawPath()
*
* fShaderCaps The shader caps
* fPipelineBuilder The pipelineBuilder
* fViewMatrix The viewMatrix
* fPath The path to draw
* fStroke The stroke information (width, join, cap)
* fAntiAlias True if anti-aliasing is required.
*/
struct CanDrawPathArgs {
const GrShaderCaps* fShaderCaps;
const SkMatrix* fViewMatrix;
const SkPath* fPath;
const GrStrokeInfo* fStroke;
bool fAntiAlias;
// These next two are only used by GrStencilAndCoverPathRenderer
bool fIsStencilDisabled;
bool fIsStencilBufferMSAA;
void validate() const {
SkASSERT(fShaderCaps);
SkASSERT(fViewMatrix);
SkASSERT(fPath);
SkASSERT(fStroke);
SkASSERT(!fPath->isEmpty());
}
};
/**
* Returns true if this path renderer is able to render the path. Returning false allows the
* caller to fallback to another path renderer This function is called when searching for a path
* renderer capable of rendering a path.
*
* @return true if the path can be drawn by this object, false otherwise.
*/
bool canDrawPath(const CanDrawPathArgs& args) const {
SkDEBUGCODE(args.validate();)
return this->onCanDrawPath(args);
}
/**
* Args to drawPath()
*
* fTarget The target that the path will be rendered to
* fResourceProvider The resource provider for creating gpu resources to render the path
* fPipelineBuilder The pipelineBuilder
* fColor Color to render with
* fViewMatrix The viewMatrix
* fPath the path to draw.
* fStroke the stroke information (width, join, cap)
* fAntiAlias true if anti-aliasing is required.
*/
struct DrawPathArgs {
GrDrawTarget* fTarget;
GrResourceProvider* fResourceProvider;
GrPipelineBuilder* fPipelineBuilder;
GrColor fColor;
const SkMatrix* fViewMatrix;
const SkPath* fPath;
const GrStrokeInfo* fStroke;
bool fAntiAlias;
void validate() const {
SkASSERT(fTarget);
SkASSERT(fResourceProvider);
SkASSERT(fPipelineBuilder);
SkASSERT(fViewMatrix);
SkASSERT(fPath);
SkASSERT(fStroke);
SkASSERT(!fPath->isEmpty());
}
};
/**
* Draws the path into the draw target. If getStencilSupport() would return kNoRestriction then
* the subclass must respect the stencil settings of the GrPipelineBuilder.
*/
bool drawPath(const DrawPathArgs& args) {
SkDEBUGCODE(args.validate();)
#ifdef SK_DEBUG
CanDrawPathArgs canArgs;
canArgs.fShaderCaps = args.fTarget->caps()->shaderCaps();
canArgs.fViewMatrix = args.fViewMatrix;
canArgs.fPath = args.fPath;
canArgs.fStroke = args.fStroke;
canArgs.fAntiAlias = args.fAntiAlias;
canArgs.fIsStencilDisabled = args.fPipelineBuilder->getStencil().isDisabled();
canArgs.fIsStencilBufferMSAA =
args.fPipelineBuilder->getRenderTarget()->isStencilBufferMultisampled();
SkASSERT(this->canDrawPath(canArgs));
SkASSERT(args.fPipelineBuilder->getStencil().isDisabled() ||
kNoRestriction_StencilSupport == this->getStencilSupport(*args.fPath,
*args.fStroke));
#endif
return this->onDrawPath(args);
}
/* Args to stencilPath().
*
* fTarget The target that the path will be rendered to.
* fResourceProvider The resource provider for creating gpu resources to render the path
* fPipelineBuilder The pipeline builder.
* fViewMatrix Matrix applied to the path.
* fPath The path to draw.
* fStroke The stroke information (width, join, cap)
*/
struct StencilPathArgs {
GrDrawTarget* fTarget;
GrResourceProvider* fResourceProvider;
GrPipelineBuilder* fPipelineBuilder;
const SkMatrix* fViewMatrix;
const SkPath* fPath;
const GrStrokeInfo* fStroke;
void validate() const {
SkASSERT(fTarget);
SkASSERT(fResourceProvider);
SkASSERT(fPipelineBuilder);
SkASSERT(fViewMatrix);
SkASSERT(fPath);
SkASSERT(fStroke);
SkASSERT(!fPath->isEmpty());
}
};
/**
* 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.fPath, *args.fStroke));
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 GrStrokeInfo& stroke, const SkMatrix& matrix,
SkScalar* outCoverage) {
if (stroke.isDashed()) {
return false;
}
if (stroke.isHairlineStyle()) {
if (outCoverage) {
*outCoverage = SK_Scalar1;
}
return true;
}
return stroke.getStyle() == SkStrokeRec::kStroke_Style &&
SkDrawTreatAAStrokeAsHairline(stroke.getWidth(), matrix, 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);
// Helper version that gets the dev width and height from a GrSurface.
static void GetPathDevBounds(const SkPath& path,
const GrSurface* device,
const SkMatrix& matrix,
SkRect* bounds) {
GetPathDevBounds(path, device->width(), device->height(), matrix, bounds);
}
private:
/**
* Subclass overrides if it has any limitations of stenciling support.
*/
virtual StencilSupport onGetStencilSupport(const SkPath&, const GrStrokeInfo&) const {
return kNoRestriction_StencilSupport;
}
/**
* Subclass implementation of drawPath()
*/
virtual bool onDrawPath(const DrawPathArgs& args) = 0;
/**
* Subclass implementation of canDrawPath()
*/
virtual bool 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& args) {
GR_STATIC_CONST_SAME_STENCIL(kIncrementStencil,
kReplace_StencilOp,
kReplace_StencilOp,
kAlways_StencilFunc,
0xffff,
0xffff,
0xffff);
args.fPipelineBuilder->setStencil(kIncrementStencil);
args.fPipelineBuilder->setDisableColorXPFactory();
DrawPathArgs drawArgs;
drawArgs.fTarget = args.fTarget;
drawArgs.fResourceProvider = args.fResourceProvider;
drawArgs.fPipelineBuilder = args.fPipelineBuilder;
drawArgs.fColor = 0xFFFFFFFF;
drawArgs.fViewMatrix = args.fViewMatrix;
drawArgs.fPath = args.fPath;
drawArgs.fStroke = args.fStroke;
drawArgs.fAntiAlias = false;
this->drawPath(drawArgs);
}
typedef SkRefCnt INHERITED;
};
#endif