Added SkSL workaround for devices which cannot safely access gl_FragCoord

This is the root cause of https://github.com/flutter/flutter/issues/13216
I've got a GM that demonstrates the bug, but only in Viewer.

Bug: skia:7410
Change-Id: Iaa1f27b10166aa09e4dc5949e5a6ca1bd14c99ac
Reviewed-on: https://skia-review.googlesource.com/93920
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/tests/SkSLGLSLTest.cpp b/tests/SkSLGLSLTest.cpp
index 1ae421f8af..9b0571bcdc 100644
--- a/tests/SkSLGLSLTest.cpp
+++ b/tests/SkSLGLSLTest.cpp
@@ -1059,6 +1059,42 @@ DEF_TEST(SkSLFragCoord, r) {
          "}\n",
          &inputs);
     REPORTER_ASSERT(r, !inputs.fRTHeight);
+
+    test(r,
+         "in float4 pos; void main() { sk_Position = pos; }",
+         *SkSL::ShaderCapsFactory::CannotUseFragCoord(),
+         "#version 400\n"
+         "out vec4 sk_FragCoord_Workaround;\n"
+         "in vec4 pos;\n"
+         "void main() {\n"
+         "    sk_FragCoord_Workaround = (gl_Position = pos);\n"
+         "}\n",
+         SkSL::Program::kVertex_Kind);
+
+    test(r,
+         "in uniform float4 sk_RTAdjust; in float4 pos; void main() { sk_Position = pos; }",
+         *SkSL::ShaderCapsFactory::CannotUseFragCoord(),
+         "#version 400\n"
+         "out vec4 sk_FragCoord_Workaround;\n"
+         "in uniform vec4 sk_RTAdjust;\n"
+         "in vec4 pos;\n"
+         "void main() {\n"
+         "    sk_FragCoord_Workaround = (gl_Position = pos);\n"
+         "    gl_Position = vec4(gl_Position.x * sk_RTAdjust.x + gl_Position.w * sk_RTAdjust.y, "
+              "gl_Position.y * sk_RTAdjust.z + gl_Position.w * sk_RTAdjust.w, 0, gl_Position.w);\n"
+         "}\n",
+         SkSL::Program::kVertex_Kind);
+
+    test(r,
+         "void main() { sk_FragColor.xy = sk_FragCoord.xy; }",
+         *SkSL::ShaderCapsFactory::CannotUseFragCoord(),
+         "#version 400\n"
+         "in vec4 sk_FragCoord_Workaround;\n"
+         "out vec4 sk_FragColor;\n"
+         "void main() {\n"
+         "    sk_FragColor.xy = vec4(sk_FragCoord_Workaround.xyz / sk_FragCoord_Workaround.w, "
+             "1.0 / sk_FragCoord_Workaround.w).xy;\n"
+         "}\n");
 }
 
 DEF_TEST(SkSLVertexID, r) {