GrStencilAndCoverPathRenderer.cpp revision 58190644c30e1c4aa8e527f3503c58f841e0fcf3 
1
2/*
3 * Copyright 2012 Google Inc.
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8
9
10#include "GrStencilAndCoverPathRenderer.h"
11#include "GrContext.h"
12#include "GrDrawTargetCaps.h"
13#include "GrGpu.h"
14#include "GrPath.h"
15#include "SkStrokeRec.h"
16
17GrPathRenderer* GrStencilAndCoverPathRenderer::Create(GrContext* context) {
18    GrAssert(NULL != context);
19    GrAssert(NULL != context->getGpu());
20    if (context->getGpu()->caps()->pathStencilingSupport()) {
21        return SkNEW_ARGS(GrStencilAndCoverPathRenderer, (context->getGpu()));
22    } else {
23        return NULL;
24    }
25}
26
27GrStencilAndCoverPathRenderer::GrStencilAndCoverPathRenderer(GrGpu* gpu) {
28    GrAssert(gpu->caps()->pathStencilingSupport());
29    fGpu = gpu;
30    gpu->ref();
31}
32
33GrStencilAndCoverPathRenderer::~GrStencilAndCoverPathRenderer() {
34    fGpu->unref();
35}
36
37bool GrStencilAndCoverPathRenderer::canDrawPath(const SkPath& path,
38                                                const SkStrokeRec& stroke,
39                                                const GrDrawTarget* target,
40                                                bool antiAlias) const {
41    return stroke.isFillStyle() &&
42           !antiAlias && // doesn't do per-path AA, relies on the target having MSAA
43           target->getDrawState().getStencil().isDisabled();
44}
45
46GrPathRenderer::StencilSupport GrStencilAndCoverPathRenderer::onGetStencilSupport(
47                                                        const SkPath&,
48                                                        const SkStrokeRec& ,
49                                                        const GrDrawTarget*) const {
50    return GrPathRenderer::kStencilOnly_StencilSupport;
51}
52
53void GrStencilAndCoverPathRenderer::onStencilPath(const SkPath& path,
54                                                  const SkStrokeRec& stroke,
55                                                  GrDrawTarget* target) {
56    GrAssert(!path.isInverseFillType());
57    SkAutoTUnref<GrPath> p(fGpu->createPath(path));
58    target->stencilPath(p, stroke, path.getFillType());
59}
60
61bool GrStencilAndCoverPathRenderer::onDrawPath(const SkPath& path,
62                                               const SkStrokeRec& stroke,
63                                               GrDrawTarget* target,
64                                               bool antiAlias) {
65    GrAssert(!antiAlias);
66    GrAssert(!stroke.isHairlineStyle());
67
68    GrDrawState* drawState = target->drawState();
69    GrAssert(drawState->getStencil().isDisabled());
70
71    SkAutoTUnref<GrPath> p(fGpu->createPath(path));
72
73    SkPath::FillType nonInvertedFill = SkPath::ConvertToNonInverseFillType(path.getFillType());
74    target->stencilPath(p, stroke, nonInvertedFill);
75
76    // TODO: Use built in cover operation rather than a rect draw. This will require making our
77    // fragment shaders be able to eat varyings generated by a matrix.
78
79    // fill the path, zero out the stencil
80    SkRect bounds = p->getBounds();
81    SkScalar bloat = drawState->getViewMatrix().getMaxStretch() * SK_ScalarHalf;
82    GrDrawState::AutoViewMatrixRestore avmr;
83
84    if (nonInvertedFill == path.getFillType()) {
85        GR_STATIC_CONST_SAME_STENCIL(kStencilPass,
86            kZero_StencilOp,
87            kZero_StencilOp,
88            kNotEqual_StencilFunc,
89            0xffff,
90            0x0000,
91            0xffff);
92        *drawState->stencil() = kStencilPass;
93    } else {
94        GR_STATIC_CONST_SAME_STENCIL(kInvertedStencilPass,
95            kZero_StencilOp,
96            kZero_StencilOp,
97            // We know our rect will hit pixels outside the clip and the user bits will be 0
98            // outside the clip. So we can't just fill where the user bits are 0. We also need to
99            // check that the clip bit is set.
100            kEqualIfInClip_StencilFunc,
101            0xffff,
102            0x0000,
103            0xffff);
104        SkMatrix vmi;
105        bounds.setLTRB(0, 0,
106                       SkIntToScalar(drawState->getRenderTarget()->width()),
107                       SkIntToScalar(drawState->getRenderTarget()->height()));
108        // mapRect through persp matrix may not be correct
109        if (!drawState->getViewMatrix().hasPerspective() && drawState->getViewInverse(&vmi)) {
110            vmi.mapRect(&bounds);
111            // theoretically could set bloat = 0, instead leave it because of matrix inversion
112            // precision.
113        } else {
114            avmr.setIdentity(drawState);
115            bloat = 0;
116        }
117        *drawState->stencil() = kInvertedStencilPass;
118    }
119    bounds.outset(bloat, bloat);
120    target->drawSimpleRect(bounds, NULL);
121    target->drawState()->stencil()->setDisabled();
122    return true;
123}
124