Move fragCoord workaround declaration

This ensures that all extension directives occur before any
non-preprocessor tokens, as required by the spec (§ 3.4).

This was found by Qualcomm, and originally submitted as
https://github.com/google/skia/pull/21

Bug: b/111525079
Change-Id: I24357e4d3654e76c2dfbc067aca3088948dfa5a8
Reviewed-on: https://skia-review.googlesource.com/142697
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

1 files changed, 21 insertions, 19 deletions

diff --git a/src/sksl/SkSLGLSLCodeGenerator.cpp b/src/sksl/SkSLGLSLCodeGenerator.cpp
index 5f6fedcdb5..76e76c3271 100644
--- a/src/sksl/SkSLGLSLCodeGenerator.cpp
+++ b/src/sksl/SkSLGLSLCodeGenerator.cpp
@@ -1264,25 +1264,6 @@ void GLSLCodeGenerator::writeHeader() {
             this->writeExtension((Extension&) e);
         }
     }
-    if (!fProgram.fSettings.fCaps->canUseFragCoord()) {
-        Layout layout;
-        switch (fProgram.fKind) {
-            case Program::kVertex_Kind: {
-                Modifiers modifiers(layout, Modifiers::kOut_Flag | Modifiers::kHighp_Flag);
-                this->writeModifiers(modifiers, true);
-                this->write("vec4 sk_FragCoord_Workaround;\n");
-                break;
-            }
-            case Program::kFragment_Kind: {
-                Modifiers modifiers(layout, Modifiers::kIn_Flag | Modifiers::kHighp_Flag);
-                this->writeModifiers(modifiers, true);
-                this->write("vec4 sk_FragCoord_Workaround;\n");
-                break;
-            }
-            default:
-                break;
-        }
-    }
 }
 
 void GLSLCodeGenerator::writeProgramElement(const ProgramElement& e) {
@@ -1359,6 +1340,27 @@ bool GLSLCodeGenerator::generateCode() {
     fOut = rawOut;
 
     write_stringstream(fHeader, *rawOut);
+
+    if (!fProgram.fSettings.fCaps->canUseFragCoord()) {
+        Layout layout;
+        switch (fProgram.fKind) {
+            case Program::kVertex_Kind: {
+                Modifiers modifiers(layout, Modifiers::kOut_Flag | Modifiers::kHighp_Flag);
+                this->writeModifiers(modifiers, true);
+                this->write("vec4 sk_FragCoord_Workaround;\n");
+                break;
+            }
+            case Program::kFragment_Kind: {
+                Modifiers modifiers(layout, Modifiers::kIn_Flag | Modifiers::kHighp_Flag);
+                this->writeModifiers(modifiers, true);
+                this->write("vec4 sk_FragCoord_Workaround;\n");
+                break;
+            }
+            default:
+                break;
+        }
+    }
+
     if (this->usesPrecisionModifiers()) {
         this->writeLine("precision mediump float;");
     }