Revert "Reland "Remove use of integers for atlas indexing""

This reverts commit 3ae2cd5ef8906947ee9189299f6f08af07bea8c2.

Reason for revert: Odd issues with fontcache-mt on Vulkan.

Original change's description:
> Reland "Remove use of integers for atlas indexing"
> 
> This is a reland of 3a8f345cf5689c6e1f22e852acfde4b8b1e5ba42
> 
> Original change's description:
> > Remove use of integers for atlas indexing
> > 
> > Bug: skia:
> > Change-Id: I7c29e90de6531a35c415f0338e23c176a7293040
> > Reviewed-on: https://skia-review.googlesource.com/c/171233
> > Reviewed-by: Brian Salomon <bsalomon@google.com>
> > Commit-Queue: Jim Van Verth <jvanverth@google.com>
> 
> Bug: skia:
> Change-Id: Ifb041f74028a119ba410e80cbfaedce34614f90b
> Reviewed-on: https://skia-review.googlesource.com/c/171539
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Jim Van Verth <jvanverth@google.com>

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

Change-Id: I82fb5073d11b52e35b6f731415e2a87f62bc8edb
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/c/171780
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
diff --git a/src/gpu/effects/GrAtlasedShaderHelpers.h b/src/gpu/effects/GrAtlasedShaderHelpers.h
index e4ebaab..a7d445a 100644
--- a/src/gpu/effects/GrAtlasedShaderHelpers.h
+++ b/src/gpu/effects/GrAtlasedShaderHelpers.h
@@ -20,19 +20,31 @@
                                      GrGLSLVarying *uv,
                                      GrGLSLVarying *texIdx,
                                      GrGLSLVarying *st) {
+    using Interpolation = GrGLSLVaryingHandler::Interpolation;
+
+    // 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("float2 indexTexCoords = float2(%s.x, %s.y);",
-                                    inTexCoordsName, inTexCoordsName);
-    args.fVertBuilder->codeAppend("float2 unormTexCoords = floor(0.5*indexTexCoords);");
-    args.fVertBuilder->codeAppend("float2 diff = indexTexCoords - 2.0*unormTexCoords;");
-    args.fVertBuilder->codeAppend("float texIdx = 2.0*diff.x + diff.y;");
+    if (args.fShaderCaps->integerSupport()) {
+        args.fVertBuilder->codeAppendf("int2 signedCoords = int2(%s.x, %s.y);",
+                                       inTexCoordsName, inTexCoordsName);
+        args.fVertBuilder->codeAppend("int texIdx = 2*(signedCoords.x & 0x1) + (signedCoords.y & 0x1);");
+        args.fVertBuilder->codeAppend("float2 unormTexCoords = float2(signedCoords.x/2, signedCoords.y/2);");
+    } else {
+        args.fVertBuilder->codeAppendf("float2 indexTexCoords = float2(%s.x, %s.y);",
+                                       inTexCoordsName, inTexCoordsName);
+        args.fVertBuilder->codeAppend("float2 unormTexCoords = floor(0.5*indexTexCoords);");
+        args.fVertBuilder->codeAppend("float2 diff = indexTexCoords - 2.0*unormTexCoords;");
+        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 = unormTexCoords * %s;", uv->vsOut(), atlasSizeInvName);
 
-    args.fVaryingHandler->addVarying("TexIndex", texIdx);
+    args.fVaryingHandler->addVarying("TexIndex", texIdx, args.fShaderCaps->integerSupport()
+                                                                 ? Interpolation::kMustBeFlat
+                                                                 : Interpolation::kCanBeFlat);
     args.fVertBuilder->codeAppendf("%s = texIdx;", texIdx->vsOut());
 
     if (st) {
diff --git a/src/gpu/effects/GrBitmapTextGeoProc.cpp b/src/gpu/effects/GrBitmapTextGeoProc.cpp
index 00743b1..c59ae4a 100644
--- a/src/gpu/effects/GrBitmapTextGeoProc.cpp
+++ b/src/gpu/effects/GrBitmapTextGeoProc.cpp
@@ -40,7 +40,8 @@
                                                           &atlasSizeInvName);
 
         GrGLSLVarying uv(kFloat2_GrSLType);
-        GrGLSLVarying texIdx(kFloat_GrSLType);
+        GrSLType texIdxType = args.fShaderCaps->integerSupport() ? kInt_GrSLType : kFloat_GrSLType;
+        GrGLSLVarying texIdx(texIdxType);
         append_index_uv_varyings(args, btgp.inTextureCoords().name(), atlasSizeInvName, &uv,
                                  &texIdx, nullptr);
 
@@ -143,8 +144,8 @@
         fInColor = {"inColor", kUByte4_norm_GrVertexAttribType, kHalf4_GrSLType};
     }
 
-    fInTextureCoords = { "inTextureCoords", kUShort2_GrVertexAttribType,
-                         caps.integerSupport() ? kUShort2_GrSLType : kFloat2_GrSLType };
+    fInTextureCoords = {"inTextureCoords", kUShort2_GrVertexAttribType,
+                        caps.integerSupport() ? kUShort2_GrSLType : kFloat2_GrSLType};
     this->setVertexAttributes(&fInPosition, 3);
 
     if (numActiveProxies) {
diff --git a/src/gpu/effects/GrDistanceFieldGeoProc.cpp b/src/gpu/effects/GrDistanceFieldGeoProc.cpp
index e448029..d6a5e84 100644
--- a/src/gpu/effects/GrDistanceFieldGeoProc.cpp
+++ b/src/gpu/effects/GrDistanceFieldGeoProc.cpp
@@ -68,7 +68,8 @@
 
         // add varyings
         GrGLSLVarying uv(kFloat2_GrSLType);
-        GrGLSLVarying texIdx(kFloat_GrSLType);
+        GrSLType texIdxType = args.fShaderCaps->integerSupport() ? kInt_GrSLType : kFloat_GrSLType;
+        GrGLSLVarying texIdx(texIdxType);
         GrGLSLVarying st(kFloat2_GrSLType);
         append_index_uv_varyings(args, dfTexEffect.inTextureCoords().name(), atlasSizeInvName, &uv,
                                  &texIdx, &st);
@@ -230,8 +231,8 @@
         fInPosition = {"inPosition", kFloat2_GrVertexAttribType, kFloat2_GrSLType};
     }
     fInColor = {"inColor", kUByte4_norm_GrVertexAttribType, kHalf4_GrSLType };
-    fInTextureCoords = { "inTextureCoords", kUShort2_GrVertexAttribType,
-                         caps.integerSupport() ? kUShort2_GrSLType : kFloat2_GrSLType };
+    fInTextureCoords = {"inTextureCoords", kUShort2_GrVertexAttribType,
+                        caps.integerSupport() ? kUShort2_GrSLType : kFloat2_GrSLType};
     this->setVertexAttributes(&fInPosition, 3);
 
     if (numProxies) {
@@ -344,7 +345,8 @@
                                                           &atlasSizeInvName);
 
         GrGLSLVarying uv(kFloat2_GrSLType);
-        GrGLSLVarying texIdx(kFloat_GrSLType);
+        GrSLType texIdxType = args.fShaderCaps->integerSupport() ? kInt_GrSLType : kFloat_GrSLType;
+        GrGLSLVarying texIdx(texIdxType);
         GrGLSLVarying st(kFloat2_GrSLType);
         append_index_uv_varyings(args, dfPathEffect.inTextureCoords().name(), atlasSizeInvName, &uv,
                                  &texIdx, &st);
@@ -521,8 +523,8 @@
 
     fInPosition = {"inPosition", kFloat2_GrVertexAttribType, kFloat2_GrSLType};
     fInColor = {"inColor", kUByte4_norm_GrVertexAttribType, kHalf4_GrSLType};
-    fInTextureCoords = { "inTextureCoords", kUShort2_GrVertexAttribType,
-                         caps.integerSupport() ? kUShort2_GrSLType : kFloat2_GrSLType };
+    fInTextureCoords = {"inTextureCoords", kUShort2_GrVertexAttribType,
+                        caps.integerSupport() ? kUShort2_GrSLType : kFloat2_GrSLType};
     this->setVertexAttributes(&fInPosition, 3);
 
     if (numProxies) {
@@ -646,7 +648,8 @@
 
         // set up varyings
         GrGLSLVarying uv(kFloat2_GrSLType);
-        GrGLSLVarying texIdx(kFloat_GrSLType);
+        GrSLType texIdxType = args.fShaderCaps->integerSupport() ? kInt_GrSLType : kFloat_GrSLType;
+        GrGLSLVarying texIdx(texIdxType);
         GrGLSLVarying st(kFloat2_GrSLType);
         append_index_uv_varyings(args, dfTexEffect.inTextureCoords().name(), atlasSizeInvName, &uv,
                                  &texIdx, &st);
@@ -840,8 +843,8 @@
         fInPosition = {"inPosition", kFloat2_GrVertexAttribType, kFloat2_GrSLType};
     }
     fInColor = {"inColor", kUByte4_norm_GrVertexAttribType, kHalf4_GrSLType};
-    fInTextureCoords = { "inTextureCoords", kUShort2_GrVertexAttribType,
-                         caps.integerSupport() ? kUShort2_GrSLType : kFloat2_GrSLType };
+    fInTextureCoords = {"inTextureCoords", kUShort2_GrVertexAttribType,
+                        caps.integerSupport() ? kUShort2_GrSLType : kFloat2_GrSLType};
     this->setVertexAttributes(&fInPosition, 3);
 
     if (numProxies) {