Use stencil ops that don't issue writes whenever possible

src/gpu/gl/GrGLGpu.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "GrGLGpu.h"
 #include "GrGLGLSL.h"
@@ skipping 2100 matching lines @@
 
     GrGLint ref = settings.funcRef(grFace);
     GrGLint mask = settings.funcMask(grFace);
     GrGLint writeMask = settings.writeMask(grFace);
 
     if (GR_GL_FRONT_AND_BACK == glFace) {
         // we call the combined func just in case separate stencil is not
         // supported.
         GR_GL_CALL(gl, StencilFunc(glFunc, ref, mask));
         GR_GL_CALL(gl, StencilMask(writeMask));
-        GR_GL_CALL(gl, StencilOp(glFailOp, glPassOp, glPassOp));
+        GR_GL_CALL(gl, StencilOp(glFailOp, GR_GL_KEEP, glPassOp));

[Chris Dalton, 2015/08/18 19:33:11]

I'm not sure it seems correct to modify this part.

Shouldn't we just use the ops supplied in the stencil settings? And if we want
something to be "keep", then the code above this level is responsible to set it
accordingly?

[vbuzinov, 2015/08/21 12:16:57]

Chris, stencil settings don't contain a separate value for depth test fail case,
since skia never uses the depth test.  Effectively we are not changing the
existing behavior here in any way, other than hinting the driver.

     } else {
         GR_GL_CALL(gl, StencilFuncSeparate(glFace, glFunc, ref, mask));
         GR_GL_CALL(gl, StencilMaskSeparate(glFace, writeMask));
-        GR_GL_CALL(gl, StencilOpSeparate(glFace, glFailOp, glPassOp, glPassOp));
+        GR_GL_CALL(gl, StencilOpSeparate(glFace, glFailOp, GR_GL_KEEP, glPassOp));
     }
 }
 }
 
 void GrGLGpu::flushStencil(const GrStencilSettings& stencilSettings) {
     if (fHWStencilSettings != stencilSettings) {
         if (stencilSettings.isDisabled()) {
             if (kNo_TriState != fHWStencilTestEnabled) {
                 GL_CALL(Disable(GR_GL_STENCIL_TEST));
                 fHWStencilTestEnabled = kNo_TriState;
@@ skipping 1060 matching lines @@
             this->setVertexArrayID(gpu, 0);
         }
         int attrCount = gpu->glCaps().maxVertexAttributes();
         if (fDefaultVertexArrayAttribState.count() != attrCount) {
             fDefaultVertexArrayAttribState.resize(attrCount);
         }
         attribState = &fDefaultVertexArrayAttribState;
     }
     return attribState;
 }