Implement support for mixed sampled render targets

src/gpu/gl/GrGLGpu.cpp

Index: src/gpu/gl/GrGLGpu.cpp
diff --git a/src/gpu/gl/GrGLGpu.cpp b/src/gpu/gl/GrGLGpu.cpp
index aff40ccc85a4627071927037b3bd48e053987f74..ea54d1e64dc8a2997dbb4e94bb04ece6c5a56bf3 100644
--- a/src/gpu/gl/GrGLGpu.cpp
+++ b/src/gpu/gl/GrGLGpu.cpp
@@ -301,6 +301,7 @@ void GrGLGpu::onResetContext(uint32_t resetBits) {
 
     if (resetBits & kMSAAEnable_GrGLBackendState) {
         fMSAAEnabled = kUnknown_TriState;
+        fCoverageModulationEnabled = kUnknown_TriState;
     }
 
     fHWActiveTextureUnitIdx = -1; // invalid
@@ -435,6 +436,8 @@ GrRenderTarget* GrGLGpu::onWrapBackendRenderTarget(const GrBackendRenderTargetDe
     idDesc.fRTFBOID = static_cast<GrGLuint>(wrapDesc.fRenderTargetHandle);
     idDesc.fMSColorRenderbufferID = 0;
     idDesc.fTexFBOID = GrGLRenderTarget::kUnresolvableFBOID;
+    idDesc.fSampleConfig = (wrapDesc.fFlags & kStencilMSAAOnly_GrBackendRenderTargetFlags) ?
+                           GrRenderTarget::kStencil_SampleConfig : GrRenderTarget::kUnified_SampleConfig;

[Chris Dalton, 2015/04/07 23:48:23]

Looks like we broke 100 columns...

[vbuzinov, 2015/04/08 12:05:30]

Done.

     idDesc.fLifeCycle = GrGpuResource::kWrapped_LifeCycle;
 
     GrSurfaceDesc desc;
@@ -782,6 +785,7 @@ static bool renderbuffer_storage_msaa(GrGLContext& ctx,
     switch (ctx.caps()->msFBOType()) {
         case GrGLCaps::kDesktop_ARB_MSFBOType:
         case GrGLCaps::kDesktop_EXT_MSFBOType:
+        case GrGLCaps::kMixedSamples_MSFBOType:
         case GrGLCaps::kES_3_0_MSFBOType:
             GL_ALLOC_CALL(ctx.interface(),
                             RenderbufferStorageMultisample(GR_GL_RENDERBUFFER,
@@ -818,6 +822,9 @@ bool GrGLGpu::createRenderTargetObjects(const GrSurfaceDesc& desc, bool budgeted
     idDesc->fTexFBOID = 0;
     idDesc->fLifeCycle = budgeted ? GrGpuResource::kCached_LifeCycle :
                                     GrGpuResource::kUncached_LifeCycle;
+    idDesc->fSampleConfig = GrGLCaps::kMixedSamples_MSFBOType ==
+                            this->glCaps().msFBOType() ? GrRenderTarget::kStencil_SampleConfig :
+                                                         GrRenderTarget::kUnified_SampleConfig;
 
     GrGLenum status;
 
@@ -1139,7 +1146,7 @@ bool GrGLGpu::createStencilBufferForRenderTarget(GrRenderTarget* rt, int width,
     SkASSERT(width >= rt->width());
     SkASSERT(height >= rt->height());
 
-    int samples = rt->numSamples();
+    int samples = rt->numSamples(GrRenderTarget::BufferBits::kStencil_BufferBit);
     GrGLStencilBuffer::IDDesc sbDesc;
 
     int stencilFmtCnt = this->glCaps().stencilFormats().count();
@@ -2096,9 +2103,10 @@ void GrGLGpu::flushStencil(const GrStencilSettings& stencilSettings) {
 }
 
 void GrGLGpu::flushHWAAState(GrRenderTarget* rt, bool useHWAA) {
-    SkASSERT(!useHWAA || rt->isMultisampled());
+    SkASSERT(!useHWAA || rt->isMultisampled(GrRenderTarget::BufferBits::kAny_BufferBits));
 
-    if (kGL_GrGLStandard == this->glStandard()) {
+    if (kGL_GrGLStandard == this->glStandard() ||
+        this->glCaps().fbMixedSamplesSupport()) {
         if (useHWAA) {
             if (kYes_TriState != fMSAAEnabled) {
                 GL_CALL(Enable(GR_GL_MULTISAMPLE));

[Mark Kilgard, 2015/04/08 03:20:09]

warning: enabling/disabling GL_MULTISAMPLE is not officially supported in OpenGL
ES 2.x/3.x

NVIDIA has an accidental allowance (technically a bug) where the Tegra K1 & X1
ES drivers (and desktop ES contexts too) allow GL_MULTISAMPLE to be
enabled/disabled.

We are working to standardize an extension to be called
EXT_multisample_compatibility that will, when advertised, allow GL_MULTISAMPLE
(and GL_SAMPLE_ALPHA_TO_ONE) to be enabled/disabled.

Intel is a likely partner for the EXT.  I should send the specification to
Google's Skia team for their consideration too.  Any OpenGL 1.3 capable hardware
(though not ES-only hardware) should be able to support
EXT_multisample_compatibility.  It has many advantages for ensuring aliased
behavior and is useful with NV_framebuffer_mixed_samples in particular in
certain cases.

If the proposed EXT_multisample_compatibility extension is not advertised and
some NV-only extension such as NV_blend_equation_advanced (K1 or X1) or
NV_framebuffer_mixed_samples (K1 only) is supported, you can try to call
glEnable(GL_MULTISAMPLE).  If there is no GL_INVALID_ENUM error, assume
EXT_multisample_compatibility is de facto supported.

Note: the default GL_MULTISAMPLE state is enabled (and ES acts that way, just
with no way to do the disable).  

[vbuzinov, 2015/04/08 12:05:30]

Doesn't look like there was an explicit check for whether the context is GLES
here before our modification.  Of course, only with Nvfms multisampling will
actually be toggled.  We can add the ES and a caps check here when this
extension is available, but right now we actually depend on this "bug" to render
things properly...

@@ -2111,6 +2119,19 @@ void GrGLGpu::flushHWAAState(GrRenderTarget* rt, bool useHWAA) {
             }
         }
     }
+    if (this->glCaps().fbMixedSamplesSupport()) {
+        if (useHWAA && GrRenderTarget::kStencil_SampleConfig == rt->sampleConfig()) {
+            if (kYes_TriState != fCoverageModulationEnabled) {

[Mark Kilgard, 2015/04/08 03:20:09]

...technically this mode isn't an enable though Skia may use it that way

+                GL_CALL(CoverageModulation(GR_GL_RGBA));
+                fCoverageModulationEnabled = kYes_TriState;
+            }
+        } else {
+            if (kNo_TriState != fCoverageModulationEnabled) {
+                GL_CALL(CoverageModulation(GR_GL_NONE));
+                fCoverageModulationEnabled = kNo_TriState;
+            }
+        }
+    }
 }
 
 void GrGLGpu::flushBlend(const GrXferProcessor::BlendInfo& blendInfo) {