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1 /*
2  * Copyright 2016 Google Inc.
3  *
4  * Use of this source code is governed by a BSD-style license that can be
5  * found in the LICENSE file.
6  */
7 
8 
9 #ifndef GrStencilSettings_DEFINED
10 #define GrStencilSettings_DEFINED
11 
12 #include "GrUserStencilSettings.h"
13 #include "SkRegion.h"
14 
15 class GrProcessorKeyBuilder;
16 
17 enum class GrStencilTest : uint16_t {
18     kAlways,
19     kNever,
20     kGreater,
21     kGEqual,
22     kLess,
23     kLEqual,
24     kEqual,
25     kNotEqual
26 };
27 static constexpr int kGrStencilTestCount = 1 + (int)GrStencilTest::kNotEqual;
28 
29 enum class GrStencilOp : uint8_t {
30     kKeep,
31     kZero,
32     kReplace, // Replace stencil value with fRef (only the bits enabled in fWriteMask).
33     kInvert,
34     kIncWrap,
35     kDecWrap,
36     // NOTE: clamping occurs before the write mask. So if the MSB is zero and masked out, stencil
37     // values will still wrap when using clamping ops.
38     kIncClamp,
39     kDecClamp
40 };
41 static constexpr int kGrStencilOpCount = 1 + (int)GrStencilOp::kDecClamp;
42 
43 /**
44  * This class defines concrete stencil settings that map directly to the underlying hardware. It
45  * is deduced from user stencil settings, stencil clip status, and the number of bits in the
46  * target stencil buffer.
47  */
48 class GrStencilSettings {
49 public:
GrStencilSettings()50     GrStencilSettings() { this->setDisabled(); }
GrStencilSettings(const GrUserStencilSettings & user,bool hasStencilClip,int numStencilBits)51     GrStencilSettings(const GrUserStencilSettings& user, bool hasStencilClip, int numStencilBits) {
52         this->reset(user, hasStencilClip, numStencilBits);
53     }
GrStencilSettings(const GrStencilSettings & that)54     GrStencilSettings(const GrStencilSettings& that) { this->reset(that); }
55     GrStencilSettings& operator=(const GrStencilSettings& that) { this->reset(that); return *this; }
56 
invalidate()57     void invalidate() { fFlags |= kInvalid_PrivateFlag; }
setDisabled()58     void setDisabled() { fFlags = kAll_StencilFlags; }
59     void reset(const GrUserStencilSettings&, bool hasStencilClip, int numStencilBits);
60     void reset(const GrStencilSettings&);
61 
isValid()62     bool isValid() const { return !(fFlags & kInvalid_PrivateFlag); }
isDisabled()63     bool isDisabled() const { SkASSERT(this->isValid()); return fFlags & kDisabled_StencilFlag; }
doesWrite()64     bool doesWrite() const { SkASSERT(this->isValid());
65                              return !(fFlags & kNoModifyStencil_StencilFlag); }
isTwoSided()66     bool isTwoSided() const { SkASSERT(this->isValid());
67                               return !(fFlags & kSingleSided_StencilFlag); }
usesWrapOp()68     bool usesWrapOp() const { SkASSERT(this->isValid());
69                               return !(fFlags & kNoWrapOps_StencilFlag); }
70 
71     void genKey(GrProcessorKeyBuilder* b) const;
72 
73     bool operator!=(const GrStencilSettings& that) const { return !(*this == that); }
74     bool operator==(const GrStencilSettings&) const;
75 
76     struct Face : public GrTStencilFaceSettings<GrStencilTest, GrStencilOp> {
77         void reset(const GrUserStencilSettings::Face&, bool useStencilClip, int numStencilBits);
78         void setDisabled();
79     };
80 
front()81     const Face& front() const { SkASSERT(!this->isDisabled()); return fFront; }
back()82     const Face& back() const { SkASSERT(this->isTwoSided()); return fBack; }
83 
84     /**
85      * Given a thing to draw into the stencil clip, a fill type, and a set op
86      * this function determines:
87      *      1. Whether the thing can be draw directly to the stencil clip or
88      *      needs to be drawn to the client portion of the stencil first.
89      *      2. How many passes are needed.
90      *      3. What those passes are.
91      *
92      * @param op                the set op to combine this element with the existing clip
93      * @param canBeDirect       can the caller draw this element directly (without using stencil)?
94      * @param invertedFill      is this path inverted
95      * @param drawDirectToClip  out: true if caller should draw the element directly, false if it
96      *                          should draw it into the user stencil bits first.
97      *
98      * @return a null-terminated array of settings for stencil passes.
99      *
100      *         If drawDirectToClip is false, the caller must first draw the element into the user
101      *         stencil bits, and then cover the clip area with multiple passes using the returned
102      *         stencil settings.
103      *
104      *         If drawDirectToClip is true, the returned array will only have one pass and the
105      *         caller should use those stencil settings while drawing the element directly.
106      */
107     static GrUserStencilSettings const* const* GetClipPasses(SkRegion::Op op,
108                                                              bool canBeDirect,
109                                                              bool invertedFill,
110                                                              bool* drawDirectToClip);
111 
112     /** Gets the user stencil settings to directly set the clip bit. */
113     static const GrUserStencilSettings* SetClipBitSettings(bool setToInside);
114 
115 private:
116     // Internal flag for backends to optionally mark their tracked stencil state as invalid.
117     enum { kInvalid_PrivateFlag = (kLast_StencilFlag << 1) };
118 
119     uint32_t   fFlags;
120     Face       fFront;
121     Face       fBack;
122 };
123 
124 #endif
125