Use int when possible to calculate atlas indices in shaders.

On certain iOS devices half has a mantissa of only 10 bits, which is not
enough to perform the floating point trickery to get the lower bits
out of the "texture coordinates". Instead we use int if available, and
float if not available.

Also re-enables multitexturing for iOS and adds a sample which
stresses the issue.

Bug: skia:7285
Change-Id: I365532c7cbbcca7c7753af209bef46e05be49e11
Reviewed-on: https://skia-review.googlesource.com/71181
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>

7 files changed, 174 insertions, 24 deletions

diff --git a/gn/samples.gni b/gn/samples.gni
index 6e1bcac893..7c0d9e2617 100644
--- a/gn/samples.gni
+++ b/gn/samples.gni
@@ -48,6 +48,7 @@ samples_sources = [
   "$_samplecode/SampleFilter2.cpp",
   "$_samplecode/SampleFilterFuzz.cpp",
   "$_samplecode/SampleFilterQuality.cpp",
+  "$_samplecode/SampleFlutterAnimate.cpp",
   "$_samplecode/SampleFontScalerTest.cpp",
   "$_samplecode/SampleFuzz.cpp",
   "$_samplecode/SampleGradients.cpp",
diff --git a/samplecode/SampleFlutterAnimate.cpp b/samplecode/SampleFlutterAnimate.cpp
new file mode 100644
index 0000000000..63b453b240
--- /dev/null
+++ b/samplecode/SampleFlutterAnimate.cpp
@@ -0,0 +1,107 @@
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SampleCode.h"
+#include "SkAnimTimer.h"
+#include "SkView.h"
+#include "SkCanvas.h"
+#include "SkUtils.h"
+#include "SkColorPriv.h"
+#include "SkColorFilter.h"
+#include "SkImage.h"
+#include "SkRandom.h"
+#include "SkSystemEventTypes.h"
+#include "SkTime.h"
+#include "SkTypeface.h"
+#include "Timer.h"
+
+#if SK_SUPPORT_GPU
+#include "GrContext.h"
+#endif
+
+class FlutterAnimateView : public SampleView {
+public:
+    FlutterAnimateView() : fCurrTime(0), fResetTime(0) {}
+
+protected:
+    void onOnceBeforeDraw() override {
+        initChars();
+    }
+
+    // overrides from SkEventSink
+    bool onQuery(SkEvent* evt) override {
+        if (SampleCode::TitleQ(*evt)) {
+            SampleCode::TitleR(evt, "FlutterAnimate");
+            return true;
+        }
+
+        return this->INHERITED::onQuery(evt);
+    }
+
+    void onDrawContent(SkCanvas* canvas) override {
+        SkPaint paint;
+        paint.setTypeface(SkTypeface::MakeFromFile("/skimages/samplefont.ttf"));
+        paint.setAntiAlias(true);
+        paint.setFilterQuality(kMedium_SkFilterQuality);
+        paint.setTextSize(50);
+
+        canvas->clear(SK_ColorWHITE);
+        for (int i = 0; i < kNumChars; ++i) {
+            canvas->save();
+            double rot = fChars[i].fStartRotation + (fChars[i].fEndRotation - fChars[i].fStartRotation)*fCurrTime/kDuration;
+            canvas->translate(fChars[i].fPosition.fX + 35,fChars[i].fPosition.fY - 50);
+            canvas->rotate(rot*180.0/SK_MScalarPI);
+            canvas->translate(-35,+50);
+            canvas->drawString(fChars[i].fChar, 0, 0,
+                               paint);
+            canvas->restore();
+        }
+    }
+
+    bool onAnimate(const SkAnimTimer& timer) override {
+        fCurrTime = timer.secs() - fResetTime;
+        if (fCurrTime > kDuration) {
+            this->initChars();
+            fResetTime = timer.secs();
+            fCurrTime = 0;
+        }
+
+        return true;
+    }
+
+private:
+    void initChars() {
+        for (int i = 0; i < kNumChars; ++i) {
+            char c = fRand.nextULessThan(26) + 65;
+            fChars[i].fChar.set(&c, 1);
+            fChars[i].fPosition = SkPoint::Make(fRand.nextF()*748 + 10, fRand.nextF()*1004 + 10);
+            fChars[i].fStartRotation = fRand.nextF();
+            fChars[i].fEndRotation = fRand.nextF() * 20 - 10;
+        }
+    }
+
+    static constexpr double kDuration = 5.0;
+    double fCurrTime;
+    double fResetTime;
+    SkRandom fRand;
+
+    struct AnimatedChar {
+        SkString fChar;
+        SkPoint  fPosition;
+        SkScalar fStartRotation;
+        SkScalar fEndRotation;
+    };
+    static constexpr int kNumChars = 40;
+    AnimatedChar fChars[kNumChars];
+
+    typedef SampleView INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+static SkView* MyFactory() { return new FlutterAnimateView; }
+static SkViewRegister reg(MyFactory);
diff --git a/src/gpu/GrContext.cpp b/src/gpu/GrContext.cpp
index 68cf42ef2a..69acd15cb2 100644
--- a/src/gpu/GrContext.cpp
+++ b/src/gpu/GrContext.cpp
@@ -211,20 +211,12 @@ bool GrContext::init(const GrContextOptions& options) {
             new GrDrawingManager(this, prcOptions, atlasTextContextOptions, &fSingleOwner));
 
     GrDrawOpAtlas::AllowMultitexturing allowMultitexturing;
-    switch (options.fAllowMultipleGlyphCacheTextures) {
-        case GrContextOptions::Enable::kDefault:
-#ifdef SK_BUILD_FOR_IOS
-            allowMultitexturing = GrDrawOpAtlas::AllowMultitexturing::kNo;
-#else
-            allowMultitexturing = GrDrawOpAtlas::AllowMultitexturing::kYes;
-#endif
-            break;
-        case GrContextOptions::Enable::kNo:
-            allowMultitexturing = GrDrawOpAtlas::AllowMultitexturing::kNo;
-            break;
-        case GrContextOptions::Enable::kYes:
-            allowMultitexturing = GrDrawOpAtlas::AllowMultitexturing::kYes;
-            break;
+    if (GrContextOptions::Enable::kNo == options.fAllowMultipleGlyphCacheTextures ||
+        // multitexturing supported only if range can represent the index + texcoords fully
+        !(fCaps->shaderCaps()->floatIs32Bits() || fCaps->shaderCaps()->integerSupport())) {
+        allowMultitexturing = GrDrawOpAtlas::AllowMultitexturing::kNo;
+    } else {
+        allowMultitexturing = GrDrawOpAtlas::AllowMultitexturing::kYes;
     }
     fAtlasGlyphCache = new GrAtlasGlyphCache(this, options.fGlyphCacheTextureMaximumBytes,
                                              allowMultitexturing);
diff --git a/src/gpu/effects/GrAtlasedShaderHelpers.h b/src/gpu/effects/GrAtlasedShaderHelpers.h
index ad901411db..7fc321daa2 100644
--- a/src/gpu/effects/GrAtlasedShaderHelpers.h
+++ b/src/gpu/effects/GrAtlasedShaderHelpers.h
@@ -8,6 +8,7 @@
 #ifndef GrAtlasedShaderHelpers_DEFINED
 #define GrAtlasedShaderHelpers_DEFINED
 
+#include "GrShaderCaps.h"
 #include "glsl/GrGLSLPrimitiveProcessor.h"
 #include "glsl/GrGLSLFragmentShaderBuilder.h"
 #include "glsl/GrGLSLVarying.h"
@@ -22,17 +23,24 @@ static void append_index_uv_varyings(GrGLSLPrimitiveProcessor::EmitArgs& args,
     // This extracts the texture index and texel coordinates from the same variable
     // Packing structure: texel coordinates are multiplied by 2 (or shifted left 1)
     //                    texture index is stored as lower bits of both x and y
-    args.fVertBuilder->codeAppendf("half2 indexTexCoords = half2(%s.x, %s.y);",
-                                   inTexCoordsName, inTexCoordsName);
-    args.fVertBuilder->codeAppend("half2 intCoords = floor(0.5*indexTexCoords);");
-    args.fVertBuilder->codeAppend("half2 diff = indexTexCoords - 2.0*intCoords;");
-    args.fVertBuilder->codeAppend("half texIdx = 2.0*diff.x + diff.y;");
+    if (args.fShaderCaps->integerSupport()) {
+        args.fVertBuilder->codeAppendf("int2 signedCoords = int2(%s);", inTexCoordsName);
+        args.fVertBuilder->codeAppend("int texIdx = 2*(signedCoords.x & 0x1) + (signedCoords.y & 0x1);");
+        args.fVertBuilder->codeAppend("signedCoords >>= 1;");
+        args.fVertBuilder->codeAppend("float2 intCoords = float2(signedCoords);");
+    } else {
+        args.fVertBuilder->codeAppendf("float2 indexTexCoords = float2(%s.x, %s.y);",
+                                       inTexCoordsName, inTexCoordsName);
+        args.fVertBuilder->codeAppend("float2 intCoords = floor(0.5*indexTexCoords);");
+        args.fVertBuilder->codeAppend("float2 diff = indexTexCoords - 2.0*intCoords;");
+        args.fVertBuilder->codeAppend("float texIdx = 2.0*diff.x + diff.y;");
+    }
 
     // Multiply by 1/atlasSize to get normalized texture coordinates
     args.fVaryingHandler->addVarying("TextureCoords", uv);
     args.fVertBuilder->codeAppendf("%s = intCoords * %s;", uv->vsOut(), atlasSizeInvName);
 
-    args.fVaryingHandler->addVarying("TexIndex", texIdx);
+    args.fVaryingHandler->addFlatVarying("TexIndex", texIdx);
     args.fVertBuilder->codeAppendf("%s = texIdx;", texIdx->vsOut());
 
     if (st) {
diff --git a/src/gpu/effects/GrBitmapTextGeoProc.cpp b/src/gpu/effects/GrBitmapTextGeoProc.cpp
index d5f930fec4..4193f1d24c 100644
--- a/src/gpu/effects/GrBitmapTextGeoProc.cpp
+++ b/src/gpu/effects/GrBitmapTextGeoProc.cpp
@@ -38,7 +38,8 @@ public:
                                                           &atlasSizeInvName);
 
         GrGLSLVertToFrag uv(kFloat2_GrSLType);
-        GrGLSLVertToFrag texIdx(kHalf_GrSLType);
+        GrSLType texIdxType = args.fShaderCaps->integerSupport() ? kInt_GrSLType : kFloat_GrSLType;
+        GrGLSLVertToFrag texIdx(texIdxType);
         append_index_uv_varyings(args, btgp.inTextureCoords()->fName, atlasSizeInvName,
                                  &uv, &texIdx, nullptr);
 
diff --git a/src/gpu/effects/GrDistanceFieldGeoProc.cpp b/src/gpu/effects/GrDistanceFieldGeoProc.cpp
index aafabdeb60..3e9addef6d 100644
--- a/src/gpu/effects/GrDistanceFieldGeoProc.cpp
+++ b/src/gpu/effects/GrDistanceFieldGeoProc.cpp
@@ -78,7 +78,8 @@ public:
 
         // add varyings
         GrGLSLVertToFrag uv(kFloat2_GrSLType);
-        GrGLSLVertToFrag texIdx(kHalf_GrSLType);
+        GrSLType texIdxType = args.fShaderCaps->integerSupport() ? kInt_GrSLType : kFloat_GrSLType;
+        GrGLSLVertToFrag texIdx(texIdxType);
         GrGLSLVertToFrag st(kFloat2_GrSLType);
         append_index_uv_varyings(args, dfTexEffect.inTextureCoords()->fName, atlasSizeInvName,
                                  &uv, &texIdx, &st);
@@ -344,7 +345,8 @@ public:
                                                           &atlasSizeInvName);
 
         GrGLSLVertToFrag uv(kFloat2_GrSLType);
-        GrGLSLVertToFrag texIdx(kHalf_GrSLType);
+        GrSLType texIdxType = args.fShaderCaps->integerSupport() ? kInt_GrSLType : kFloat_GrSLType;
+        GrGLSLVertToFrag texIdx(texIdxType);
         GrGLSLVertToFrag st(kFloat2_GrSLType);
         append_index_uv_varyings(args, dfTexEffect.inTextureCoords()->fName, atlasSizeInvName,
                                  &uv, &texIdx, &st);
@@ -639,7 +641,8 @@ public:
 
         // set up varyings
         GrGLSLVertToFrag uv(kFloat2_GrSLType);
-        GrGLSLVertToFrag texIdx(kHalf_GrSLType);
+        GrSLType texIdxType = args.fShaderCaps->integerSupport() ? kInt_GrSLType : kFloat_GrSLType;
+        GrGLSLVertToFrag texIdx(texIdxType);
         GrGLSLVertToFrag st(kFloat2_GrSLType);
         append_index_uv_varyings(args, dfTexEffect.inTextureCoords()->fName, atlasSizeInvName,
                                  &uv, &texIdx, &st);
diff --git a/src/gpu/text/GrAtlasTextBlobVertexRegenerator.cpp b/src/gpu/text/GrAtlasTextBlobVertexRegenerator.cpp
index 28b2e0f0c0..81ae09a6f5 100644
--- a/src/gpu/text/GrAtlasTextBlobVertexRegenerator.cpp
+++ b/src/gpu/text/GrAtlasTextBlobVertexRegenerator.cpp
@@ -38,6 +38,9 @@ inline void regen_vertices(char* vertex, const GrGlyph* glyph, size_t vertexStri
                            bool useDistanceFields, SkScalar transX, SkScalar transY,
                            GrColor color) {
     uint16_t u0, v0, u1, v1;
+#ifdef DISPLAY_PAGE_INDEX
+    SkColor hackColor;
+#endif
     if (regenTexCoords) {
         SkASSERT(glyph);
         int width = glyph->fBounds.width();
@@ -67,6 +70,25 @@ inline void regen_vertices(char* vertex, const GrGlyph* glyph, size_t vertexStri
         u1 |= uBit;
         v1 <<= 1;
         v1 |= vBit;
+#ifdef DISPLAY_PAGE_INDEX
+        switch (pageIndex) {
+            case 0:
+                hackColor = SK_ColorGREEN;
+                break;
+            case 1:
+                hackColor = SK_ColorRED;
+                break;
+            case 2:
+                hackColor = SK_ColorMAGENTA;
+                break;
+            case 3:
+                hackColor = SK_ColorCYAN;
+                break;
+            default:
+                hackColor = SK_ColorBLACK;
+                break;
+        }
+#endif
     }
 
     // This is a bit wonky, but sometimes we have LCD text, in which case we won't have color
@@ -90,6 +112,10 @@ inline void regen_vertices(char* vertex, const GrGlyph* glyph, size_t vertexStri
         uint16_t* textureCoords = reinterpret_cast<uint16_t*>(vertex + texCoordOffset);
         textureCoords[0] = u0;
         textureCoords[1] = v0;
+#ifdef DISPLAY_PAGE_INDEX
+        SkColor* vcolor = reinterpret_cast<SkColor*>(vertex + colorOffset);
+        *vcolor = hackColor;
+#endif
     }
     vertex += vertexStride;
 
@@ -109,6 +135,10 @@ inline void regen_vertices(char* vertex, const GrGlyph* glyph, size_t vertexStri
         uint16_t* textureCoords = reinterpret_cast<uint16_t*>(vertex + texCoordOffset);
         textureCoords[0] = u0;
         textureCoords[1] = v1;
+#ifdef DISPLAY_PAGE_INDEX
+        SkColor* vcolor = reinterpret_cast<SkColor*>(vertex + colorOffset);
+        *vcolor = hackColor;
+#endif
     }
     vertex += vertexStride;
 
@@ -128,6 +158,10 @@ inline void regen_vertices(char* vertex, const GrGlyph* glyph, size_t vertexStri
         uint16_t* textureCoords = reinterpret_cast<uint16_t*>(vertex + texCoordOffset);
         textureCoords[0] = u1;
         textureCoords[1] = v0;
+#ifdef DISPLAY_PAGE_INDEX
+        SkColor* vcolor = reinterpret_cast<SkColor*>(vertex + colorOffset);
+        *vcolor = hackColor;
+#endif
     }
     vertex += vertexStride;
 
@@ -147,6 +181,10 @@ inline void regen_vertices(char* vertex, const GrGlyph* glyph, size_t vertexStri
         uint16_t* textureCoords = reinterpret_cast<uint16_t*>(vertex + texCoordOffset);
         textureCoords[0] = u1;
         textureCoords[1] = v1;
+#ifdef DISPLAY_PAGE_INDEX
+        SkColor* vcolor = reinterpret_cast<SkColor*>(vertex + colorOffset);
+        *vcolor = hackColor;
+#endif
     }
 }