commit 201bcee38a94cce14740e759db7cc2cb35d6be49
author Jim Van Verth <jvanverth@google.com> Wed Dec 09 13:32:38 2020 -0500
committer Skia Commit-Bot <skia-commit-bot@chromium.org> Wed Dec 09 21:40:47 2020 +0000
tree 707d1c88e7755c514ae5ab01b816e91d608a17bd
parent 04e03bc1816b20ff5f0eb5d3a41ee2e725f8a953

Use full precision for QuadEdge attributes on iOS.

We're passing in QuadEdge attributes as half precision, but
kStableLargeNegativeValue is well past any value that can be handled
by half float. Increasing the precision used fixes the issues we're
seeing on iOS 14.

Bug: skia:10594
Change-Id: I650a0930cf8dd9a2369bfeeffc132c0f7f0fa79e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/342303
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>

src/gpu/ops/GrAAConvexPathRenderer.cpp

diff --git a/src/gpu/ops/GrAAConvexPathRenderer.cpp b/src/gpu/ops/GrAAConvexPathRenderer.cpp
index 2342731..192c6b2 100644
--- a/src/gpu/ops/GrAAConvexPathRenderer.cpp
+++ b/src/gpu/ops/GrAAConvexPathRenderer.cpp
@@ -568,7 +568,12 @@
             // emit attributes
             varyingHandler->emitAttributes(qe);
 
+#if defined(SK_BUILD_FOR_IOS)
+            // GL on iOS 14 needs more precision for the quadedge attributes
+            GrGLSLVarying v(kFloat4_GrSLType);
+#else
             GrGLSLVarying v(kHalf4_GrSLType);
+#endif
             varyingHandler->addVarying("QuadEdge", &v);
             vertBuilder->codeAppendf("%s = %s;", v.vsOut(), qe.fInQuadEdge.name());
 
@@ -592,13 +597,13 @@
             fragBuilder->codeAppendf("half2 duvdy = half2(dFdy(%s.xy));", v.fsIn());
             fragBuilder->codeAppendf("if (%s.z > 0.0 && %s.w > 0.0) {", v.fsIn(), v.fsIn());
             // today we know z and w are in device space. We could use derivatives
-            fragBuilder->codeAppendf("edgeAlpha = min(min(%s.z, %s.w) + 0.5, 1.0);", v.fsIn(),
+            fragBuilder->codeAppendf("edgeAlpha = half(min(min(%s.z, %s.w) + 0.5, 1.0));", v.fsIn(),
                                      v.fsIn());
             fragBuilder->codeAppendf ("} else {");
-            fragBuilder->codeAppendf("half2 gF = half2(2.0*%s.x*duvdx.x - duvdx.y,"
-                                     "               2.0*%s.x*duvdy.x - duvdy.y);",
+            fragBuilder->codeAppendf("half2 gF = half2(half(2.0*%s.x*duvdx.x - duvdx.y),"
+                                     "                 half(2.0*%s.x*duvdy.x - duvdy.y));",
                                      v.fsIn(), v.fsIn());
-            fragBuilder->codeAppendf("edgeAlpha = (%s.x*%s.x - %s.y);", v.fsIn(), v.fsIn(),
+            fragBuilder->codeAppendf("edgeAlpha = half(%s.x*%s.x - %s.y);", v.fsIn(), v.fsIn(),
                                      v.fsIn());
             fragBuilder->codeAppendf("edgeAlpha = "
                                      "saturate(0.5 - edgeAlpha / length(gF));}");
@@ -645,7 +650,12 @@
             , fUsesLocalCoords(usesLocalCoords) {
         fInPosition = {"inPosition", kFloat2_GrVertexAttribType, kFloat2_GrSLType};
         fInColor = MakeColorAttribute("inColor", wideColor);
+#if defined(SK_BUILD_FOR_IOS)
+        // GL on iOS 14 needs more precision for the quadedge attributes
+        fInQuadEdge = {"inQuadEdge", kFloat4_GrVertexAttribType, kFloat4_GrSLType};
+#else
         fInQuadEdge = {"inQuadEdge", kFloat4_GrVertexAttribType, kHalf4_GrSLType};
+#endif
         this->setVertexAttributes(&fInPosition, 3);
     }