Revert "Revert "Revert "Revert "Improvements to GPU dither.""""

This reverts commit f2290cb924640dfd439458a1ee5e61b31b08850f.

Reason for revert: SPIRV codegen fix has landed

Original change's description:
> Revert "Revert "Revert "Improvements to GPU dither."""
> 
> This reverts commit 0f01b2e8b5e3119e91886a2f7ec772a915d97a8c.
> 
> Reason for revert: <INSERT REASONING HERE>
> 
> Original change's description:
> > Revert "Revert "Improvements to GPU dither.""
> > 
> > This reverts commit 38fb308f3156aab1e42a61d77d08906a06263879.
> > 
> > Reason for revert: Reland with SkSL caps fix for vulkan
> > 
> > Original change's description:
> > > Revert "Improvements to GPU dither."
> > > 
> > > This reverts commit 1806e33e6a09b1361de4925d32389a01e0e2c7e7.
> > > 
> > > Reason for revert: <INSERT REASONING HERE>
> > > 
> > > Original change's description:
> > > > Improvements to GPU dither.
> > > > 
> > > > 1) Makes the range of the offset dependent on the config.
> > > > 
> > > > 2) Uses an ordered dither on GPUs that support integers in shaders.
> > > > 
> > > > 3) Enables dithering for all paints with dither flag when the color type of the dst is 4444
> > > > 
> > > > 4) Dithers r,g,b and clamps to 0,a rather than dithering all four channels (same as CPU backend).
> > > > 
> > > > Bug: skia:
> > > > Change-Id: Ie22c3adc38c6d1dbbcd97e4b7d16fc843e392c2e
> > > > Reviewed-on: https://skia-review.googlesource.com/23485
> > > > Commit-Queue: Brian Salomon <bsalomon@google.com>
> > > > Reviewed-by: Robert Phillips <robertphillips@google.com>
> > > 
> > > TBR=bsalomon@google.com,robertphillips@google.com
> > > 
> > > Change-Id: Ie82e88bd9032bf8eee745d32d9b57c335a8997c9
> > > No-Presubmit: true
> > > No-Tree-Checks: true
> > > No-Try: true
> > > Bug: skia:
> > > Reviewed-on: https://skia-review.googlesource.com/24325
> > > Reviewed-by: Brian Salomon <bsalomon@google.com>
> > > Commit-Queue: Brian Salomon <bsalomon@google.com>
> > 
> > TBR=bsalomon@google.com,robertphillips@google.com
> > 
> > Change-Id: Ic38ac276c8b88b8d993a29d1fcbfe37e84becd2a
> > No-Presubmit: true
> > No-Tree-Checks: true
> > No-Try: true
> > Bug: skia:
> > Reviewed-on: https://skia-review.googlesource.com/24282
> > Reviewed-by: Brian Salomon <bsalomon@google.com>
> > Commit-Queue: Brian Salomon <bsalomon@google.com>
> 
> TBR=bsalomon@google.com,robertphillips@google.com
> 
> Change-Id: I5ce47b06a1b451942faf9066b1a45a716b1b3f3c
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: skia:
> Reviewed-on: https://skia-review.googlesource.com/24480
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Brian Salomon <bsalomon@google.com>

TBR=bsalomon@google.com,robertphillips@google.com

Change-Id: I112df51494bc3cc832fde9c22a6532082df85a81
Reviewed-on: https://skia-review.googlesource.com/24285
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>

1 files changed, 32 insertions, 4 deletions

diff --git a/src/gpu/effects/GrDitherEffect.h b/src/gpu/effects/GrDitherEffect.h
index a996ad94c2..63c0df7eb2 100644
--- a/src/gpu/effects/GrDitherEffect.h
+++ b/src/gpu/effects/GrDitherEffect.h
@@ -18,19 +18,47 @@
 #include "effects/GrProxyMove.h"
 class GrDitherEffect : public GrFragmentProcessor {
 public:
-    static sk_sp<GrFragmentProcessor> Make() {
-        return sk_sp<GrFragmentProcessor>(new GrDitherEffect());
+    int rangeType() const { return fRangeType; }
+
+    static sk_sp<GrFragmentProcessor> Make(GrPixelConfig dstConfig) {
+        int rangeType;
+        switch (dstConfig) {
+            case kGray_8_GrPixelConfig:
+            case kRGBA_8888_GrPixelConfig:
+            case kBGRA_8888_GrPixelConfig:
+            case kSRGBA_8888_GrPixelConfig:
+            case kSBGRA_8888_GrPixelConfig:
+                rangeType = 0;
+                break;
+            case kRGB_565_GrPixelConfig:
+                rangeType = 1;
+                break;
+            case kRGBA_4444_GrPixelConfig:
+                rangeType = 2;
+                break;
+            case kUnknown_GrPixelConfig:
+            case kAlpha_half_GrPixelConfig:
+            case kRGBA_8888_sint_GrPixelConfig:
+            case kRGBA_float_GrPixelConfig:
+            case kRG_float_GrPixelConfig:
+            case kRGBA_half_GrPixelConfig:
+            case kAlpha_8_GrPixelConfig:
+                return nullptr;
+        }
+        return sk_sp<GrFragmentProcessor>(new GrDitherEffect(rangeType));
     }
     const char* name() const override { return "DitherEffect"; }
 private:
-    GrDitherEffect()
-    : INHERITED(kNone_OptimizationFlags) {
+    GrDitherEffect(int rangeType)
+    : INHERITED(kNone_OptimizationFlags)
+    , fRangeType(rangeType) {
         this->initClassID<GrDitherEffect>();
     }
     GrGLSLFragmentProcessor* onCreateGLSLInstance() const override;
     void onGetGLSLProcessorKey(const GrShaderCaps&,GrProcessorKeyBuilder*) const override;
     bool onIsEqual(const GrFragmentProcessor&) const override;
     GR_DECLARE_FRAGMENT_PROCESSOR_TEST
+    int fRangeType;
     typedef GrFragmentProcessor INHERITED;
 };
 #endif