Revert of Remove gpu support for willUseHWAALines. (https://codereview.chromium.org/423943003/)

Reason for revert:
Breaking windows 7 compare gm's

Original issue's description:
> Remove gpu support for willUseHWAALines.
>
> By removing willUseHWAALines, we also no long reference the blend opt flag kDisableBlend so it has been removed
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/e6dfba868c19b00562f8c733b9bf37dd4ec9e68c

R=bsalomon@google.com
TBR=bsalomon@google.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Author: egdaniel@google.com

Review URL: https://codereview.chromium.org/430493003

include/gpu/GrTypes.h

@@ -667,7 +667,7 @@ enum GrGLBackendState {
     // View state stands for scissor and viewport
     kView_GrGLBackendState             = 1 << 2,
     kBlend_GrGLBackendState            = 1 << 3,
-    kMSAAEnable_GrGLBackendState       = 1 << 4,
+    kAA_GrGLBackendState               = 1 << 4,
     kVertex_GrGLBackendState           = 1 << 5,
     kStencil_GrGLBackendState          = 1 << 6,
     kPixelStore_GrGLBackendState       = 1 << 7,

src/gpu/GrContext.cpp

@@ -751,6 +751,10 @@ static bool apply_aa_to_rect(GrDrawTarget* target,
         return false;
     }
 
+    if (0 == strokeWidth && target->willUseHWAALines()) {
+        return false;
+    }
+
 #if defined(SHADER_AA_FILL_RECT) || !defined(IGNORE_ROT_AA_RECT_OPT)
     if (strokeWidth >= 0) {
 #endif

src/gpu/GrDrawState.cpp

@@ -339,7 +339,8 @@ GrDrawState::BlendOptFlags GrDrawState::calcBlendOpts(bool forceCoverage,
     // (0,1). The same applies when coverage is known to be 0.
     if ((kZero_GrBlendCoeff == *srcCoeff && dstCoeffIsOne) || covIsZero) {
         if (this->getStencil().doesWrite()) {
-            return kEmitCoverage_BlendOptFlag;
+            return kDisableBlend_BlendOptFlag |
+                   kEmitCoverage_BlendOptFlag;
         } else {
             return kSkipDraw_BlendOptFlag;
         }
@@ -358,14 +359,13 @@ GrDrawState::BlendOptFlags GrDrawState::calcBlendOpts(bool forceCoverage,
             if (kOne_GrBlendCoeff == *srcCoeff) {
                 // if there is no coverage and coeffs are (1,0) then we
                 // won't need to read the dst at all, it gets replaced by src
-                *dstCoeff = kZero_GrBlendCoeff;
+                return kDisableBlend_BlendOptFlag;
-                return kNone_BlendOpt;
             } else if (kZero_GrBlendCoeff == *srcCoeff) {
                 // if the op is "clear" then we don't need to emit a color
                 // or blend, just write transparent black into the dst.
                 *srcCoeff = kOne_GrBlendCoeff;
                 *dstCoeff = kZero_GrBlendCoeff;
-                return kEmitTransBlack_BlendOptFlag;
+                return kDisableBlend_BlendOptFlag | kEmitTransBlack_BlendOptFlag;
             }
         }
     } else if (this->isCoverageDrawing()) {
@@ -399,7 +399,13 @@ GrDrawState::BlendOptFlags GrDrawState::calcBlendOpts(bool forceCoverage,
             return  kCoverageAsAlpha_BlendOptFlag;
         }
     }
-
+    if (kOne_GrBlendCoeff == *srcCoeff &&
+        kZero_GrBlendCoeff == *dstCoeff &&
+        this->willEffectReadDstColor()) {
+        // In this case the shader will fully resolve the color, coverage, and dst and we don't
+        // need blending.
+        return kDisableBlend_BlendOptFlag;
+    }
     return kNone_BlendOpt;
 }
 

src/gpu/GrDrawState.h

@@ -520,25 +520,29 @@ public:
          * Don't draw at all
          */
         kSkipDraw_BlendOptFlag          = 0x1,
+        /**
+         * Emit the src color, disable HW blending (replace dst with src)
+         */
+        kDisableBlend_BlendOptFlag      = 0x2,
         /**
          * The coverage value does not have to be computed separately from alpha, the the output
          * color can be the modulation of the two.
          */
-        kCoverageAsAlpha_BlendOptFlag   = 0x2,
+        kCoverageAsAlpha_BlendOptFlag   = 0x4,
         /**
          * Instead of emitting a src color, emit coverage in the alpha channel and r,g,b are
          * "don't cares".
          */
-        kEmitCoverage_BlendOptFlag      = 0x4,
+        kEmitCoverage_BlendOptFlag      = 0x8,
         /**
          * Emit transparent black instead of the src color, no need to compute coverage.
          */
-        kEmitTransBlack_BlendOptFlag    = 0x8,
+        kEmitTransBlack_BlendOptFlag    = 0x10,
         /**
          * Flag used to invalidate the cached BlendOptFlags, OptSrcCoeff, and OptDstCoeff cached by
          * the get BlendOpts function. 
          */
-        kInvalid_BlendOptFlag           = 0x10,
+        kInvalid_BlendOptFlag        = 0x20,
     };
     GR_DECL_BITFIELD_OPS_FRIENDS(BlendOptFlags);
 

src/gpu/GrDrawTarget.cpp

@@ -613,16 +613,24 @@ void GrDrawTarget::removeGpuTraceMarker(const GrGpuTraceMarker* marker) {
 
 ////////////////////////////////////////////////////////////////////////////////
 
+bool GrDrawTarget::willUseHWAALines() const {
+    // There is a conflict between using smooth lines and our use of premultiplied alpha. Smooth
+    // lines tweak the incoming alpha value but not in a premul-alpha way. So we only use them when
+    // our alpha is 0xff and tweaking the color for partial coverage is OK
+    if (!this->caps()->hwAALineSupport() ||
+        !this->getDrawState().isHWAntialiasState()) {
+        return false;
+    }
+    GrDrawState::BlendOptFlags opts = this->getDrawState().getBlendOpts();
+    return (GrDrawState::kDisableBlend_BlendOptFlag & opts) &&
+           (GrDrawState::kCoverageAsAlpha_BlendOptFlag & opts);
+}
+
 bool GrDrawTarget::canApplyCoverage() const {
     // we can correctly apply coverage if a) we have dual source blending
-    // or b) one of our blend optimizations applies 
+    // or b) one of our blend optimizations applies.
-    // or c) the src/dst coefficients are 1, 0 respectively.
-    GrBlendCoeff srcCoeff; 
-    GrBlendCoeff dstCoeff; 
     return this->caps()->dualSourceBlendingSupport() ||
-           GrDrawState::kNone_BlendOpt != this->getDrawState().getBlendOpts(true, &srcCoeff,
+           GrDrawState::kNone_BlendOpt != this->getDrawState().getBlendOpts(true);
-                                                                            &dstCoeff) ||
-           (kOne_GrBlendCoeff == srcCoeff && kZero_GrBlendCoeff == dstCoeff);
 }
 
 ////////////////////////////////////////////////////////////////////////////////

src/gpu/GrDrawTarget.h

@@ -112,6 +112,12 @@ public:
         return !this->canApplyCoverage();
     }
 
+    /**
+     * Given the current draw state and hw support, will HW AA lines be used (if
+     * a line primitive type is drawn)?
+     */
+    bool willUseHWAALines() const;
+
     /**
      * There are three types of "sources" of geometry (vertices and indices) for
      * draw calls made on the target. When performing an indexed draw, the

src/gpu/gl/GrGpuGL.cpp

@@ -280,8 +280,8 @@ void GrGpuGL::onResetContext(uint32_t resetBits) {
         GL_CALL(LineWidth(1));
     }
 
-    if (resetBits & kMSAAEnable_GrGLBackendState) {
+    if (resetBits & kAA_GrGLBackendState) {
-        fMSAAEnabled = kUnknown_TriState;
+        fHWAAState.invalidate();
     }
 
     fHWActiveTextureUnitIdx = -1; // invalid
@@ -2164,20 +2164,45 @@ void GrGpuGL::flushAAState(DrawType type) {
 
     const GrRenderTarget* rt = this->getDrawState().getRenderTarget();
     if (kGL_GrGLStandard == this->glStandard()) {
-        if (RT_HAS_MSAA) {
+        // ES doesn't support toggling GL_MULTISAMPLE and doesn't have
+        // smooth lines.
+        // we prefer smooth lines over multisampled lines
+        bool smoothLines = false;
+
+        if (kDrawLines_DrawType == type) {
+            smoothLines = this->willUseHWAALines();
+            if (smoothLines) {
+                if (kYes_TriState != fHWAAState.fSmoothLineEnabled) {
+                    GL_CALL(Enable(GR_GL_LINE_SMOOTH));
+                    fHWAAState.fSmoothLineEnabled = kYes_TriState;
+                    // must disable msaa to use line smoothing
+                    if (RT_HAS_MSAA &&
+                        kNo_TriState != fHWAAState.fMSAAEnabled) {
+                        GL_CALL(Disable(GR_GL_MULTISAMPLE));
+                        fHWAAState.fMSAAEnabled = kNo_TriState;
+                    }
+                }
+            } else {
+                if (kNo_TriState != fHWAAState.fSmoothLineEnabled) {
+                    GL_CALL(Disable(GR_GL_LINE_SMOOTH));
+                    fHWAAState.fSmoothLineEnabled = kNo_TriState;
+                }
+            }
+        }
+        if (!smoothLines && RT_HAS_MSAA) {
             // FIXME: GL_NV_pr doesn't seem to like MSAA disabled. The paths
             // convex hulls of each segment appear to get filled.
             bool enableMSAA = kStencilPath_DrawType == type ||
                               this->getDrawState().isHWAntialiasState();
             if (enableMSAA) {
-                if (kYes_TriState != fMSAAEnabled) {
+                if (kYes_TriState != fHWAAState.fMSAAEnabled) {
                     GL_CALL(Enable(GR_GL_MULTISAMPLE));
-                    fMSAAEnabled = kYes_TriState;
+                    fHWAAState.fMSAAEnabled = kYes_TriState;
                 }
             } else {
-                if (kNo_TriState != fMSAAEnabled) {
+                if (kNo_TriState != fHWAAState.fMSAAEnabled) {
                     GL_CALL(Disable(GR_GL_MULTISAMPLE));
-                    fMSAAEnabled = kNo_TriState;
+                    fHWAAState.fMSAAEnabled = kNo_TriState;
                 }
             }
         }
@@ -2203,9 +2228,24 @@ void GrGpuGL::flushPathStencilSettings(SkPath::FillType fill) {
 void GrGpuGL::flushBlend(bool isLines,
                          GrBlendCoeff srcCoeff,
                          GrBlendCoeff dstCoeff) {
-    // any optimization to disable blending should have already been applied and
+    if (isLines && this->willUseHWAALines()) {
-    // tweaked the coeffs to (1, 0).
+        if (kYes_TriState != fHWBlendState.fEnabled) {
-    bool blendOff = kOne_GrBlendCoeff == srcCoeff && kZero_GrBlendCoeff == dstCoeff;
+            GL_CALL(Enable(GR_GL_BLEND));
+            fHWBlendState.fEnabled = kYes_TriState;
+        }
+        if (kSA_GrBlendCoeff != fHWBlendState.fSrcCoeff ||
+            kISA_GrBlendCoeff != fHWBlendState.fDstCoeff) {
+            GL_CALL(BlendFunc(gXfermodeCoeff2Blend[kSA_GrBlendCoeff],
+                              gXfermodeCoeff2Blend[kISA_GrBlendCoeff]));
+            fHWBlendState.fSrcCoeff = kSA_GrBlendCoeff;
+            fHWBlendState.fDstCoeff = kISA_GrBlendCoeff;
+        }
+    } else {
+        // any optimization to disable blending should
+        // have already been applied and tweaked the coeffs
+        // to (1, 0).
+        bool blendOff = kOne_GrBlendCoeff == srcCoeff &&
+                        kZero_GrBlendCoeff == dstCoeff;
         if (blendOff) {
             if (kNo_TriState != fHWBlendState.fEnabled) {
                 GL_CALL(Disable(GR_GL_BLEND));
@@ -2235,6 +2275,7 @@ void GrGpuGL::flushBlend(bool isLines,
                 fHWBlendState.fConstColorValid = true;
             }
         }
+    }
 }
 
 static inline GrGLenum tile_to_gl_wrap(SkShader::TileMode tm) {

src/gpu/gl/GrGpuGL.h

@@ -443,7 +443,15 @@ private:
         }
     } fHWBlendState;
 
+    struct {
         TriState fMSAAEnabled;
+        TriState fSmoothLineEnabled;
+        void invalidate() {
+            fMSAAEnabled = kUnknown_TriState;
+            fSmoothLineEnabled = kUnknown_TriState;
+        }
+    } fHWAAState;
+
 
     GrGLProgram::MatrixState    fHWProjectionMatrixState;