Add SkOverdrawColorFilter

Uses the value in the src alpha channel to choose how
to set the dst pixel.

This is a part of a multi-part change to detect and
display gpu overdraw on Android.

CQ_INCLUDE_TRYBOTS=master.client.skia.compile:Build-Ubuntu-GCC-x86_64-Debug-NoGPU-Trybot

BUG:32370375

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=5113

Change-Id: I07040929d8a46bbadd499dccec75eebef0e11d11
Reviewed-on: https://skia-review.googlesource.com/5113
Commit-Queue: Matt Sarett <msarett@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>

6 files changed, 308 insertions, 0 deletions

diff --git a/gm/overdrawcolorfilter.cpp b/gm/overdrawcolorfilter.cpp
new file mode 100644
index 0000000000..2eba228045
--- /dev/null
+++ b/gm/overdrawcolorfilter.cpp
@@ -0,0 +1,68 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "gm.h"
+#include "SkCanvas.h"
+#include "SkOverdrawColorFilter.h"
+
+static inline void set_bitmap(SkBitmap* bitmap, uint8_t alpha) {
+    for (int y = 0; y < bitmap->height(); y++) {
+        for (int x = 0; x < bitmap->width(); x++) {
+            uint8_t* addr = bitmap->getAddr8(x, y);
+            *addr = alpha;
+        }
+    }
+
+    bitmap->notifyPixelsChanged();
+}
+
+class OverdrawColorFilter : public skiagm::GM {
+public:
+    OverdrawColorFilter() {}
+
+protected:
+    virtual SkString onShortName() override {
+        return SkString("overdrawcolorfilter");;
+    }
+
+    virtual SkISize onISize() override {
+        return SkISize::Make(200, 400);
+    }
+
+    void onDraw(SkCanvas* canvas) override {
+        static const SkPMColor colors[SkOverdrawColorFilter::kNumColors] = {
+                0x80800000, 0x80008000, 0x80000080, 0x80808000, 0x80008080, 0x80800080,
+        };
+
+        SkPaint paint;
+        sk_sp<SkColorFilter> colorFilter = SkOverdrawColorFilter::Make(colors);
+        paint.setColorFilter(colorFilter);
+
+        SkImageInfo info = SkImageInfo::MakeA8(100, 100);
+        SkBitmap bitmap;
+        bitmap.allocPixels(info);
+        set_bitmap(&bitmap, 0);
+        canvas->drawBitmap(bitmap, 0, 0, &paint);
+        set_bitmap(&bitmap, 1);
+        canvas->drawBitmap(bitmap, 0, 100, &paint);
+        set_bitmap(&bitmap, 2);
+        canvas->drawBitmap(bitmap, 0, 200, &paint);
+        set_bitmap(&bitmap, 3);
+        canvas->drawBitmap(bitmap, 0, 300, &paint);
+        set_bitmap(&bitmap, 4);
+        canvas->drawBitmap(bitmap, 100, 0, &paint);
+        set_bitmap(&bitmap, 5);
+        canvas->drawBitmap(bitmap, 100, 100, &paint);
+        set_bitmap(&bitmap, 6);
+        canvas->drawBitmap(bitmap, 100, 200, &paint);
+    }
+
+private:
+    typedef GM INHERITED;
+};
+
+DEF_GM(return new OverdrawColorFilter;)
diff --git a/gn/effects.gni b/gn/effects.gni
index 97e0f98654..3bb84aceba 100644
--- a/gn/effects.gni
+++ b/gn/effects.gni
@@ -50,6 +50,8 @@ skia_effects_sources = [
   "$_src/effects/SkMergeImageFilter.cpp",
   "$_src/effects/SkMorphologyImageFilter.cpp",
   "$_src/effects/SkOffsetImageFilter.cpp",
+  "$_src/effects/SkOverdrawColorFilter.cpp",
+  "$_src/effects/SkOverdrawColorFilter.h",
   "$_src/effects/SkPackBits.cpp",
   "$_src/effects/SkPackBits.h",
   "$_src/effects/SkPaintFlagsDrawFilter.cpp",
diff --git a/gn/gm.gni b/gn/gm.gni
index 7e70c89931..4732e0368d 100644
--- a/gn/gm.gni
+++ b/gn/gm.gni
@@ -198,6 +198,7 @@ gm_sources = [
   "$_gm/occludedrrectblur.cpp",
   "$_gm/offsetimagefilter.cpp",
   "$_gm/ovals.cpp",
+  "$_gm/overdrawcolorfilter.cpp",
   "$_gm/OverStroke.cpp",
   "$_gm/patch.cpp",
   "$_gm/patchgrid.cpp",
diff --git a/src/effects/SkOverdrawColorFilter.cpp b/src/effects/SkOverdrawColorFilter.cpp
new file mode 100644
index 0000000000..c3bcd0e616
--- /dev/null
+++ b/src/effects/SkOverdrawColorFilter.cpp
@@ -0,0 +1,181 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkOverdrawColorFilter.h"
+
+void SkOverdrawColorFilter::filterSpan(const SkPMColor src[], int count, SkPMColor dst[]) const {
+    for (int x = 0; x < count; x++) {
+        uint8_t alpha = SkGetPackedA32(src[x]);
+        if (alpha >= kNumColors) {
+            alpha = kNumColors - 1;
+        }
+
+        dst[x] = fColors[alpha];
+    }
+}
+
+void SkOverdrawColorFilter::toString(SkString* str) const {
+    str->append("SkOverdrawColorFilter (");
+    for (int i = 0; i < kNumColors; i++) {
+        str->appendf("%d: %x\n", i, fColors[i]);
+    }
+    str->append(")");
+}
+
+void SkOverdrawColorFilter::flatten(SkWriteBuffer& buffer) const {
+    buffer.writeByteArray(fColors, kNumColors * sizeof(SkPMColor));
+}
+
+sk_sp<SkFlattenable> SkOverdrawColorFilter::CreateProc(SkReadBuffer& buffer) {
+    SkPMColor colors[kNumColors];
+    size_t size = buffer.getArrayCount();
+    if (!buffer.validate(size == sizeof(colors))) {
+        return nullptr;
+    }
+    if (!buffer.readByteArray(colors, sizeof(colors))) {
+        return nullptr;
+    }
+
+    return SkOverdrawColorFilter::Make(colors);
+}
+
+SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkOverdrawColorFilter)
+    SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkOverdrawColorFilter)
+SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END
+
+#if SK_SUPPORT_GPU
+
+#include "GrFragmentProcessor.h"
+#include "GrInvariantOutput.h"
+#include "glsl/GrGLSLFragmentProcessor.h"
+#include "glsl/GrGLSLFragmentShaderBuilder.h"
+
+class OverdrawFragmentProcessor : public GrFragmentProcessor {
+public:
+    static sk_sp<GrFragmentProcessor> Make(const SkPMColor* colors);
+
+    const char* name() const override { return "Overdraw"; }
+
+private:
+    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override;
+    void onGetGLSLProcessorKey(const GrGLSLCaps&, GrProcessorKeyBuilder*) const override {}
+    bool onIsEqual(const GrFragmentProcessor&) const override;
+    void onComputeInvariantOutput(GrInvariantOutput* inout) const override;
+
+    OverdrawFragmentProcessor(const GrColor4f* colors);
+
+    GrColor4f fColors[SkOverdrawColorFilter::kNumColors];
+
+    typedef GrFragmentProcessor INHERITED;
+};
+
+class GLOverdrawFragmentProcessor : public GrGLSLFragmentProcessor {
+public:
+    GLOverdrawFragmentProcessor(const GrColor4f* colors);
+
+    void emitCode(EmitArgs&) override;
+
+protected:
+    void onSetData(const GrGLSLProgramDataManager&, const GrProcessor&) override {}
+
+private:
+    GrColor4f fColors[SkOverdrawColorFilter::kNumColors];
+
+    typedef GrGLSLFragmentProcessor INHERITED;
+};
+
+sk_sp<GrFragmentProcessor> SkOverdrawColorFilter::asFragmentProcessor(GrContext*,
+                                                                      SkColorSpace*) const {
+    return OverdrawFragmentProcessor::Make(fColors);
+}
+
+sk_sp<GrFragmentProcessor> OverdrawFragmentProcessor::Make(const SkPMColor* colors) {
+    GrColor4f grColors[SkOverdrawColorFilter::kNumColors];
+    for (int i = 0; i < SkOverdrawColorFilter::kNumColors; i++) {
+        grColors[i] = GrColor4f::FromGrColor(GrColorPackRGBA(SkGetPackedR32(colors[i]),
+                                                             SkGetPackedG32(colors[i]),
+                                                             SkGetPackedB32(colors[i]),
+                                                             SkGetPackedA32(colors[i])));
+    }
+
+    return sk_sp<OverdrawFragmentProcessor>(new OverdrawFragmentProcessor(grColors));
+}
+
+OverdrawFragmentProcessor::OverdrawFragmentProcessor(const GrColor4f* colors) {
+    this->initClassID<OverdrawFragmentProcessor>();
+    memcpy(fColors, colors, SkOverdrawColorFilter::kNumColors * sizeof(GrColor4f));
+}
+
+GrGLSLFragmentProcessor* OverdrawFragmentProcessor::onCreateGLSLInstance() const {
+    return new GLOverdrawFragmentProcessor(fColors);
+}
+
+bool OverdrawFragmentProcessor::onIsEqual(const GrFragmentProcessor& other) const {
+    const OverdrawFragmentProcessor& that = other.cast<OverdrawFragmentProcessor>();
+    return 0 == memcmp(fColors, that.fColors,
+                       sizeof(GrColor4f) * SkOverdrawColorFilter::kNumColors);
+}
+
+void OverdrawFragmentProcessor::onComputeInvariantOutput(GrInvariantOutput* inout) const {
+    inout->invalidateComponents(kRGBA_GrColorComponentFlags, GrInvariantOutput::kWill_ReadInput);
+}
+
+GLOverdrawFragmentProcessor::GLOverdrawFragmentProcessor(const GrColor4f* colors) {
+    memcpy(fColors, colors, SkOverdrawColorFilter::kNumColors * sizeof(GrColor4f));
+}
+
+void GLOverdrawFragmentProcessor::emitCode(EmitArgs& args) {
+    GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
+    if (nullptr == args.fInputColor) {
+        fragBuilder->codeAppendf("%s.rgba = vec4(%f, %f, %f, %f);", args.fOutputColor,
+                                                                    fColors[5].fRGBA[0],
+                                                                    fColors[5].fRGBA[1],
+                                                                    fColors[5].fRGBA[2],
+                                                                    fColors[5].fRGBA[3]);
+    } else {
+        fragBuilder->codeAppendf("float alpha = 255.0 * %s.a;", args.fInputColor);
+        fragBuilder->codeAppendf("if (alpha < 0.5) {");
+        fragBuilder->codeAppendf("    %s.rgba = vec4(%f, %f, %f, %f);", args.fOutputColor,
+                                                                        fColors[0].fRGBA[0],
+                                                                        fColors[0].fRGBA[1],
+                                                                        fColors[0].fRGBA[2],
+                                                                        fColors[0].fRGBA[3]);
+        fragBuilder->codeAppendf("} else if (alpha < 1.5) {");
+        fragBuilder->codeAppendf("    %s.rgba = vec4(%f, %f, %f, %f);", args.fOutputColor,
+                                                                        fColors[1].fRGBA[0],
+                                                                        fColors[1].fRGBA[1],
+                                                                        fColors[1].fRGBA[2],
+                                                                        fColors[1].fRGBA[3]);
+        fragBuilder->codeAppendf("} else if (alpha < 2.5) {");
+        fragBuilder->codeAppendf("    %s.rgba = vec4(%f, %f, %f, %f);", args.fOutputColor,
+                                                                        fColors[2].fRGBA[0],
+                                                                        fColors[2].fRGBA[1],
+                                                                        fColors[2].fRGBA[2],
+                                                                        fColors[2].fRGBA[3]);
+        fragBuilder->codeAppendf("} else if (alpha < 3.5) {");
+        fragBuilder->codeAppendf("    %s.rgba = vec4(%f, %f, %f, %f);", args.fOutputColor,
+                                                                        fColors[3].fRGBA[0],
+                                                                        fColors[3].fRGBA[1],
+                                                                        fColors[3].fRGBA[2],
+                                                                        fColors[3].fRGBA[3]);
+        fragBuilder->codeAppendf("} else if (alpha < 4.5) {");
+        fragBuilder->codeAppendf("    %s.rgba = vec4(%f, %f, %f, %f);", args.fOutputColor,
+                                                                        fColors[4].fRGBA[0],
+                                                                        fColors[4].fRGBA[1],
+                                                                        fColors[4].fRGBA[2],
+                                                                        fColors[4].fRGBA[3]);
+        fragBuilder->codeAppendf("} else {");
+        fragBuilder->codeAppendf("    %s.rgba = vec4(%f, %f, %f, %f);", args.fOutputColor,
+                                                                        fColors[5].fRGBA[0],
+                                                                        fColors[5].fRGBA[1],
+                                                                        fColors[5].fRGBA[2],
+                                                                        fColors[5].fRGBA[3]);
+        fragBuilder->codeAppendf("}");
+    }
+}
+
+#endif
diff --git a/src/effects/SkOverdrawColorFilter.h b/src/effects/SkOverdrawColorFilter.h
new file mode 100644
index 0000000000..6c5ce592f3
--- /dev/null
+++ b/src/effects/SkOverdrawColorFilter.h
@@ -0,0 +1,54 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkColorFilter.h"
+#include "../../src/core/SkReadBuffer.h"
+
+#ifndef SkOverdrawColorFilter_DEFINED
+#define SkOverdrawColorFilter_DEFINED
+
+/**
+ *  Uses the value in the src alpha channel to set the dst pixel.
+ *  0             -> fColors[0]
+ *  1             -> fColors[1]
+ *  ...
+ *  5 (or larger) -> fColors[5]
+ *
+ */
+class SkOverdrawColorFilter : public SkColorFilter {
+public:
+    static constexpr int kNumColors = 6;
+
+    static sk_sp<SkOverdrawColorFilter> Make(const SkPMColor colors[kNumColors]) {
+        return sk_sp<SkOverdrawColorFilter>(new SkOverdrawColorFilter(colors));
+    }
+
+#if SK_SUPPORT_GPU
+    sk_sp<GrFragmentProcessor> asFragmentProcessor(GrContext*, SkColorSpace*) const override;
+#endif
+
+    void filterSpan(const SkPMColor src[], int count, SkPMColor dst[]) const override;
+    void toString(SkString* str) const override;
+
+    static sk_sp<SkFlattenable> CreateProc(SkReadBuffer& buffer);
+    Factory getFactory() const override { return CreateProc; }
+    SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
+
+protected:
+    void flatten(SkWriteBuffer& buffer) const override;
+
+private:
+    SkOverdrawColorFilter(const SkPMColor colors[kNumColors]) {
+        memcpy(fColors, colors, kNumColors * sizeof(SkPMColor));
+    }
+
+    SkPMColor fColors[kNumColors];
+
+    typedef SkColorFilter INHERITED;
+};
+
+#endif // SkOverdrawColorFilter_DEFINED
diff --git a/src/ports/SkGlobalInitialization_default.cpp b/src/ports/SkGlobalInitialization_default.cpp
index 750da4af41..6b9dcacdef 100644
--- a/src/ports/SkGlobalInitialization_default.cpp
+++ b/src/ports/SkGlobalInitialization_default.cpp
@@ -40,6 +40,7 @@
 #include "SkMorphologyImageFilter.h"
 #include "SkNormalSource.h"
 #include "SkOffsetImageFilter.h"
+#include "../../src/effects/SkOverdrawColorFilter.h"
 #include "SkPaintImageFilter.h"
 #include "SkPerlinNoiseShader.h"
 #include "SkPictureImageFilter.h"
@@ -86,6 +87,7 @@ void SkFlattenable::PrivateInitializer::InitEffects() {
     SkAlphaThresholdFilter::InitializeFlattenables();
     SkArithmeticMode::InitializeFlattenables();
     SkTableColorFilter::InitializeFlattenables();
+    SkOverdrawColorFilter::InitializeFlattenables();
 
     // Shader
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkPerlinNoiseShader)