path: root/gpu/src/GrStencil.cpp

/*
    Copyright 2011 Google Inc.

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

         http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
 */

#include "GrStencil.h"

const GrStencilSettings GrStencilSettings::gDisabled = {};
GR_STATIC_ASSERT(0 == kKeep_StencilOp);
GR_STATIC_ASSERT(0 == kAlways_StencilFunc);

////////////////////////////////////////////////////////////////////////////////
// Stencil Rules for Merging user stencil space into clip

// We can't include the clip bit in the ref or mask values because the division
// between user and clip bits in the stencil depends on the number of stencil
// bits in the runtime. Comments below indicate what the code should do to
// incorporate the clip bit into these settings.

///////
// Replace

// set the ref to be the clip bit, but mask it out for the test
static const GrStencilSettings gUserToClipReplace = {
    kReplace_StencilOp,  kReplace_StencilOp,
    kZero_StencilOp,     kZero_StencilOp,
    kLess_StencilFunc,   kLess_StencilFunc,
    0xffffffff,          0xffffffff,    // unset clip bit
    0x0,                 0x0,           // set clip bit
    0xffffffff,          0xffffffff
};
static const GrStencilSettings gInvUserToClipReplace = {
    kReplace_StencilOp,  kReplace_StencilOp,
    kZero_StencilOp,     kZero_StencilOp,
    kEqual_StencilFunc,  kEqual_StencilFunc,
    0xffffffff,          0xffffffff,    // unset clip bit
    0x0,                 0x0,           // set clip bit
    0xffffffff,          0xffffffff
};

///////
// Intersect
static const GrStencilSettings gUserToClipIsect = {
    kReplace_StencilOp,  kReplace_StencilOp,
    kZero_StencilOp,     kZero_StencilOp,
    kLess_StencilFunc,   kLess_StencilFunc,
    0xffffffff,          0xffffffff,
    0x0,                 0x0,           // set clip bit
    0xffffffff,          0xffffffff
};
static const GrStencilSettings gInvUserToClipIsect = {
    kReplace_StencilOp,  kReplace_StencilOp,
    kZero_StencilOp,     kZero_StencilOp,
    kEqual_StencilFunc,  kEqual_StencilFunc,
    0xffffffff,          0xffffffff,
    0x0,                 0x0,           // set clip bit
    0xffffffff,          0xffffffff
};

///////
// Difference
static const GrStencilSettings gUserToClipDiff = {
    kReplace_StencilOp,  kReplace_StencilOp,
    kZero_StencilOp,     kZero_StencilOp,
    kEqual_StencilFunc,  kEqual_StencilFunc,
    0xffffffff,          0xffffffff,
    0x0,                 0x0,           // set clip bit
    0xffffffff,          0xffffffff
};
static const GrStencilSettings gInvUserToClipDiff = {
    kReplace_StencilOp,  kReplace_StencilOp,
    kZero_StencilOp,     kZero_StencilOp,
    kLess_StencilFunc,   kLess_StencilFunc,
    0xffffffff,          0xffffffff,
    0x0,                 0x0,           // set clip bit
    0xffffffff,          0xffffffff
};

///////
// Union

// first pass makes all the passing cases >= just clip bit set.
static const GrStencilSettings gUserToClipUnionPass0 = {
    kReplace_StencilOp,  kReplace_StencilOp,
    kKeep_StencilOp,     kKeep_StencilOp,
    kLEqual_StencilFunc, kLEqual_StencilFunc,
    0xffffffff,          0xffffffff,    // unset clip bit
    0x00000001,          0x00000001,    // set clip bit
    0xffffffff,          0xffffffff
};

// second pass allows anything greater than just clip bit set to pass
static const GrStencilSettings gUserToClipUnionPass1 = {
    kReplace_StencilOp,  kReplace_StencilOp,
    kZero_StencilOp,     kZero_StencilOp,
    kLEqual_StencilFunc, kLEqual_StencilFunc,
    0xffffffff,          0xffffffff,
    0x00000000,          0x00000000,    // set clip bit
    0xffffffff,          0xffffffff
};

// for inverse first pass finds non-zerp user with clip bit set
// and converts it to just clip bit set
static const GrStencilSettings gInvUserToClipUnionPass0 = {
    kReplace_StencilOp,  kReplace_StencilOp,
    kKeep_StencilOp,     kKeep_StencilOp,
    kLess_StencilFunc,   kLess_StencilFunc,
    0xffffffff,          0xffffffff,
    0x00000000,          0x00000000,    // set clip bit
    0xffffffff,          0xffffffff
};

// second pass lets anything through with a nonzero user portion
// and writes a ref value with just the clip bit set to it.
static const GrStencilSettings gInvUserToClipUnionPass1 = {
    kReplace_StencilOp,  kReplace_StencilOp,
    kZero_StencilOp,     kZero_StencilOp,
    kLess_StencilFunc,   kLess_StencilFunc,
    0xffffffff,          0xffffffff,    // unset clip bit
    0x00000000,          0x00000000,    // set clip bit
    0xffffffff,          0xffffffff
};

///////
// Xor
static const GrStencilSettings gUserToClipXorPass0 = {
    kInvert_StencilOp,   kInvert_StencilOp,
    kKeep_StencilOp,     kKeep_StencilOp,
    kEqual_StencilFunc,  kEqual_StencilFunc,
    0xffffffff,          0xffffffff,    // unset clip bit
    0x00000000,          0x00000000,
    0xffffffff,          0xffffffff
};

static const GrStencilSettings gUserToClipXorPass1 = {
    kReplace_StencilOp,   kReplace_StencilOp,
    kZero_StencilOp,      kZero_StencilOp,
    kGreater_StencilFunc, kGreater_StencilFunc,
    0xffffffff,           0xffffffff,
    0x00000000,           0x00000000,   // set clip bit
    0xffffffff,           0xffffffff
};

static const GrStencilSettings gInvUserToClipXorPass0 = {
    kInvert_StencilOp,   kInvert_StencilOp,
    kKeep_StencilOp,     kKeep_StencilOp,
    kEqual_StencilFunc,  kEqual_StencilFunc,
    0xffffffff,          0xffffffff,    // unset clip bit
    0x00000000,          0x00000000,
    0xffffffff,          0xffffffff
};

static const GrStencilSettings gInvUserToClipXorPass1 = {
    kReplace_StencilOp,   kReplace_StencilOp,
    kZero_StencilOp,      kZero_StencilOp,
    kLess_StencilFunc,    kLess_StencilFunc,
    0xffffffff,           0xffffffff,
    0x00000000,           0x00000000,   // set clip bit
    0xffffffff,           0xffffffff
};

///////
// Reverse Diff
static const GrStencilSettings gUserToClipRDiffPass0 = {
    kInvert_StencilOp,   kInvert_StencilOp,
    kZero_StencilOp,     kZero_StencilOp,
    kLess_StencilFunc,   kLess_StencilFunc,
    0xffffffff,          0xffffffff,  // unset clip bit
    0x00000000,          0x00000000,  // set clip bit
    0xffffffff,          0xffffffff
};

static const GrStencilSettings gUserToClipRDiffPass1 = {
    kReplace_StencilOp,   kReplace_StencilOp,
    kZero_StencilOp,      kZero_StencilOp,
    kEqual_StencilFunc,   kEqual_StencilFunc,
    0x00000000,           0x00000000,   // set clip bit
    0x00000000,           0x00000000,   // set clip bit
    0xffffffff,           0xffffffff
};

static const GrStencilSettings gInvUserToClipRDiff = {
    kInvert_StencilOp,    kInvert_StencilOp,
    kZero_StencilOp,      kZero_StencilOp,
    kEqual_StencilFunc,   kEqual_StencilFunc,
    0xffffffff,           0xffffffff,
    0x00000000,           0x00000000, 
    0x00000000,           0x00000000    // set clip bit
};
///////
// Direct to Stencil

// We can render a clip element directly without first writing to the client
// portion of the clip when the fill is not inverse and the set operation will
// only modify the in/out status of samples covered by the clip element.

// this one only works if used right after stencil clip was cleared.
// Our GrClip doesn't allow midstream replace ops.
static const GrStencilSettings gReplaceClip = {
    kReplace_StencilOp,  kReplace_StencilOp,
    kReplace_StencilOp,  kReplace_StencilOp,
    kAlways_StencilFunc, kAlways_StencilFunc,
    0xffffffff,          0xffffffff,
    0x00000000,          0x00000000,    // set clip bit
    0x00000000,          0x00000000     // set clipBit
};

static const GrStencilSettings gUnionClip = {
    kReplace_StencilOp,  kReplace_StencilOp,
    kReplace_StencilOp,  kReplace_StencilOp,
    kAlways_StencilFunc, kAlways_StencilFunc,
    0xffffffff,          0xffffffff,
    0x00000000,          0x00000000,    // set clip bit
    0x00000000,          0x00000000     // set clip bit
};

static const GrStencilSettings gXorClip = {
    kInvert_StencilOp,   kInvert_StencilOp,
    kInvert_StencilOp,   kInvert_StencilOp,
    kAlways_StencilFunc, kAlways_StencilFunc,
    0xffffffff,          0xffffffff,
    0x00000000,          0x00000000,
    0x00000000,          0x00000000     // set clip bit
};

static const GrStencilSettings gDiffClip = {
    kZero_StencilOp,     kZero_StencilOp,
    kZero_StencilOp,     kZero_StencilOp,
    kAlways_StencilFunc, kAlways_StencilFunc,
    0xffffffff,          0xffffffff,
    0x00000000,          0x00000000,
    0x00000000,          0x00000000     // set clip bit
};

bool GrStencilSettings::GetClipPasses(GrSetOp op, 
                                      bool canBeDirect,
                                      unsigned int stencilClipMask,
                                      bool invertedFill,
                                      int* numPasses,
                                      GrStencilSettings settings[kMaxStencilClipPasses]) {
    if (canBeDirect) {
        *numPasses = 0;
        switch (op) {
            case kReplace_SetOp:
                *numPasses = 1;
                settings[0] = gReplaceClip;
                break;
            case kUnion_SetOp:
                *numPasses = 1;
                settings[0] = gUnionClip;
                break;
            case kXor_SetOp:
                *numPasses = 1;
                settings[0] = gXorClip;
                break;
            case kDifference_SetOp:
                *numPasses = 1;
                settings[0] = gDiffClip;
                break;
            default: // suppress warning
                break;
        }
        if (1 == *numPasses) {
            settings[0].fFrontFuncRef |= stencilClipMask;
            settings[0].fFrontWriteMask |= stencilClipMask;
            settings[0].fBackFuncRef = settings[0].fFrontFuncRef;
            settings[0].fBackWriteMask = settings[0].fFrontWriteMask;
            return true;
        }
    }
    switch (op) {
        // if we make the path renderer go to stencil we always give it a
        // non-inverted fill and we use the stencil rules on the client->clipbit
        // pass to select either the zeros or nonzeros.
        case kReplace_SetOp:
            *numPasses= 1;
            settings[0] = invertedFill ? gInvUserToClipReplace : gUserToClipReplace;
            settings[0].fFrontFuncMask &= ~stencilClipMask;
            settings[0].fFrontFuncRef |= stencilClipMask;
            settings[0].fBackFuncMask = settings[0].fFrontFuncMask;
            settings[0].fBackFuncRef = settings[0].fFrontFuncRef;
            break;
        case kIntersect_SetOp:
            *numPasses = 1;
            settings[0] = invertedFill ? gInvUserToClipIsect : gUserToClipIsect;
            settings[0].fFrontFuncRef = stencilClipMask;
            settings[0].fBackFuncRef = settings[0].fFrontFuncRef;
            break;
        case kUnion_SetOp:
            *numPasses = 2;
            if (invertedFill) {
                settings[0] = gInvUserToClipUnionPass0;
                settings[0].fFrontFuncRef |= stencilClipMask;
                settings[0].fBackFuncRef = settings[0].fFrontFuncMask;

                settings[1] = gInvUserToClipUnionPass1;
                settings[1].fFrontFuncMask &= ~stencilClipMask;
                settings[1].fFrontFuncRef |= stencilClipMask;
                settings[1].fBackFuncMask = settings[1].fFrontFuncMask;
                settings[1].fBackFuncRef = settings[1].fFrontFuncRef;

            } else {
                settings[0] = gUserToClipUnionPass0;
                settings[0].fFrontFuncMask &= ~stencilClipMask;
                settings[0].fFrontFuncRef |= stencilClipMask;
                settings[0].fBackFuncMask = settings[0].fFrontFuncMask;
                settings[0].fBackFuncRef = settings[0].fFrontFuncRef;

                settings[1] = gUserToClipUnionPass1;
                settings[1].fFrontFuncRef |= stencilClipMask;
                settings[1].fBackFuncRef = settings[1].fFrontFuncRef;
            }
            break;
        case kXor_SetOp:
            *numPasses = 2;
            if (invertedFill) {
                settings[0] = gInvUserToClipXorPass0;
                settings[0].fFrontFuncMask &= ~stencilClipMask;
                settings[0].fBackFuncMask = settings[0].fFrontFuncMask;

                settings[1] = gInvUserToClipXorPass1;
                settings[1].fFrontFuncRef |= stencilClipMask;
                settings[1].fBackFuncRef = settings[1].fFrontFuncRef;
            } else {
                settings[0] = gUserToClipXorPass0;
                settings[0].fFrontFuncMask &= ~stencilClipMask;
                settings[0].fBackFuncMask = settings[0].fFrontFuncMask;

                settings[1] = gUserToClipXorPass1;
                settings[1].fFrontFuncRef |= stencilClipMask;
                settings[1].fBackFuncRef = settings[1].fFrontFuncRef;
            }
            break;
        case kDifference_SetOp:
            *numPasses = 1;
            settings[0] = invertedFill ? gInvUserToClipDiff : gUserToClipDiff;
            settings[0].fFrontFuncRef |= stencilClipMask;
            settings[0].fBackFuncRef = settings[0].fFrontFuncRef;
            break;
        case kReverseDifference_SetOp:
            if (invertedFill) {
                *numPasses = 1;
                settings[0] = gInvUserToClipRDiff;
                settings[0].fFrontWriteMask |= stencilClipMask;
                settings[0].fBackWriteMask = settings[0].fFrontWriteMask;
            } else {
                *numPasses = 2;
                settings[0] = gUserToClipRDiffPass0;
                settings[0].fFrontFuncMask &= ~stencilClipMask;
                settings[0].fBackFuncMask = settings[0].fFrontFuncMask;
                settings[0].fFrontFuncRef |= stencilClipMask;
                settings[0].fBackFuncRef = settings[0].fFrontFuncRef;

                settings[1] = gUserToClipRDiffPass1;
                settings[1].fFrontFuncMask |= stencilClipMask;
                settings[1].fFrontFuncRef |= stencilClipMask;
                settings[1].fBackFuncMask = settings[1].fFrontFuncMask;
                settings[1].fBackFuncRef = settings[1].fFrontFuncRef;
            }
            break;
        default:
            GrCrash("Unknown set op");
    }
    return false;
}