mirror of https://github.com/axmolengine/axmol.git
211 lines
8.3 KiB
C
211 lines
8.3 KiB
C
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/*
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Copyright 2011 Google Inc.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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#ifndef GrStencil_DEFINED
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#define GrStencil_DEFINED
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#include "GrTypes.h"
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/**
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* Gr uses the stencil buffer to implement complex clipping inside the
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* GrDrawTarget class. The GrDrawTarget makes a subset of the stencil buffer
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* bits available for other uses by external code (clients). Client code can
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* modify these bits. GrDrawTarget will ignore ref, mask, and writemask bits
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* provided by clients that overlap the bits used to implement clipping. The
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* client can use the getUsableStencilBits() function to find out how many
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* client accessible stencil bits are available.
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*
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* When code outside the GrDrawTarget class uses the stencil buffer the contract
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* is as follows:
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*
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* > Normal stencil funcs allow the GrGpu client to modify the client bits of
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* the stencil buffer outside of the clip.
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* > Special functions allow a test against the clip. These are more limited
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* than the general stencil functions.
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* > Client can assume all client bits are zero initially.
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* > Client must ensure that after all its passes are finished it has only
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* written to the color buffer in the region inside the clip. Furthermore, it
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* must zero all client bits that were modifed (both inside and outside the
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* clip).
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*/
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/**
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* Determines which pixels pass / fail the stencil test.
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* Stencil test passes if (ref & mask) FUNC (stencil & mask) is true
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*/
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enum GrStencilFunc {
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kAlways_StencilFunc = 0,
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kNever_StencilFunc,
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kGreater_StencilFunc,
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kGEqual_StencilFunc,
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kLess_StencilFunc,
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kLEqual_StencilFunc,
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kEqual_StencilFunc,
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kNotEqual_StencilFunc,
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// Gr stores the current clip in the
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// stencil buffer in the high bits that
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// are not directly accessible modifiable
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// via the GrDrawTarget interface. The below
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// stencil funcs test against the current
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// clip in addition to the GrDrawTarget
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// client's stencil bits.
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// pass if inside the clip
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kAlwaysIfInClip_StencilFunc,
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kEqualIfInClip_StencilFunc,
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kLessIfInClip_StencilFunc,
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kLEqualIfInClip_StencilFunc,
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kNonZeroIfInClip_StencilFunc, // this one forces the ref to be 0
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// counts
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kStencilFuncCount,
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kClipStencilFuncCount = kNonZeroIfInClip_StencilFunc -
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kAlwaysIfInClip_StencilFunc + 1,
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kBasicStencilFuncCount = kStencilFuncCount - kClipStencilFuncCount
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};
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/**
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* Operations to perform based on whether stencil test passed failed.
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*/
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enum GrStencilOp {
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kKeep_StencilOp = 0, // preserve existing stencil value
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kReplace_StencilOp, // replace with reference value from stencl test
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kIncWrap_StencilOp, // increment and wrap at max
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kIncClamp_StencilOp, // increment and clamp at max
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kDecWrap_StencilOp, // decrement and wrap at 0
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kDecClamp_StencilOp, // decrement and clamp at 0
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kZero_StencilOp, // zero stencil bits
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kInvert_StencilOp, // invert stencil bits
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kStencilOpCount
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};
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/**
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* Struct representing stencil state.
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*/
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struct GrStencilSettings {
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GrStencilOp fFrontPassOp; // op to perform when front faces pass
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GrStencilOp fBackPassOp; // op to perform when back faces pass
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GrStencilOp fFrontFailOp; // op to perform when front faces fail
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GrStencilOp fBackFailOp; // op to perform when back faces fail
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GrStencilFunc fFrontFunc; // test function for front faces
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GrStencilFunc fBackFunc; // test function for back faces
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unsigned int fFrontFuncMask; // mask for front face test
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unsigned int fBackFuncMask; // mask for back face test
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unsigned int fFrontFuncRef; // reference value for front face test
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unsigned int fBackFuncRef; // reference value for back face test
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unsigned int fFrontWriteMask; // stencil write mask for front faces
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unsigned int fBackWriteMask; // stencil write mask for back faces
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bool operator == (const GrStencilSettings& s) const {
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// make sure this is tightly packed.
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GR_STATIC_ASSERT(0 == sizeof(GrStencilOp)%4);
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GR_STATIC_ASSERT(0 == sizeof(GrStencilFunc)%4);
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GR_STATIC_ASSERT(sizeof(GrStencilSettings) ==
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4*sizeof(GrStencilOp) +
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2*sizeof(GrStencilFunc) +
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6*sizeof(unsigned int));
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return 0 == memcmp(this, &s, sizeof(GrStencilSettings));
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}
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bool operator != (const GrStencilSettings& s) const {
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return !(*this == s);
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}
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GrStencilSettings& operator =(const GrStencilSettings& s) {
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memcpy(this, &s, sizeof(GrStencilSettings));
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return *this;
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}
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void setSame(GrStencilOp passOp,
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GrStencilOp failOp,
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GrStencilFunc func,
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unsigned int funcMask,
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unsigned int funcRef,
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unsigned int writeMask) {
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fFrontPassOp = passOp;
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fBackPassOp = passOp;
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fFrontFailOp = failOp;
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fBackFailOp = failOp;
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fFrontFunc = func;
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fBackFunc = func;
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fFrontFuncMask = funcMask;
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fBackFuncMask = funcMask;
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fFrontFuncRef = funcRef;
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fBackFuncRef = funcRef;
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fFrontWriteMask = writeMask;
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fBackWriteMask = writeMask;
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}
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// canonical value for disabled stenciling
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static const GrStencilSettings gDisabled;
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void setDisabled() {
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*this = gDisabled;
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}
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bool isDisabled() const {
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return kKeep_StencilOp == fFrontPassOp &&
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kKeep_StencilOp == fBackPassOp &&
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kKeep_StencilOp == fFrontFailOp &&
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kKeep_StencilOp == fBackFailOp &&
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kAlways_StencilFunc == fFrontFunc &&
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kAlways_StencilFunc == fBackFunc;
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}
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void invalidate() {
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// just write an illegal value to the first member
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fFrontPassOp = (GrStencilOp)-1;
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}
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private:
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friend class GrGpu;
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enum {
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kMaxStencilClipPasses = 2 // maximum number of passes to add a clip
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// element to the stencil buffer.
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};
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/**
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* Given a thing to draw into the stencil clip, a fill type, and a set op
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* this function determines:
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* 1. Whether the thing can be draw directly to the stencil clip or
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* needs to be drawn to the client portion of the stencil first.
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* 2. How many passes are needed.
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* 3. What those passes are.
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* 4. The fill rule that should actually be used to render (will
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* always be non-inverted).
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*
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* @param op the set op to combine this element with the
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* existing clip
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* @param stencilClipMask mask with just the stencil bit used for clipping
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* enabled.
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* @param invertedFill is this path inverted
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* @param numPasses out: the number of passes needed to add the
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* element to the clip.
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* @param settings out: the stencil settings to use for each pass
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*
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* @return true if the clip element's geometry can be drawn directly to the
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* stencil clip bit. Will only be true if canBeDirect is true.
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* numPasses will be 1 if return value is true.
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*/
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static bool GetClipPasses(GrSetOp op,
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bool canBeDirect,
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unsigned int stencilClipMask,
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bool invertedFill,
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int* numPasses,
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GrStencilSettings settings[kMaxStencilClipPasses]);
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};
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#endif
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