added support for sk_ClipDistance

Change-Id: I9ea202679211b98cf98165c8609f24f9b4e14b66
Reviewed-on: https://skia-review.googlesource.com/8247
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>

5 files changed, 35 insertions, 5 deletions

diff --git a/src/sksl/SkSLCompiler.h b/src/sksl/SkSLCompiler.h
index 167f042d52..f7dcf2b5b9 100644
--- a/src/sksl/SkSLCompiler.h
+++ b/src/sksl/SkSLCompiler.h
@@ -17,9 +17,10 @@
 #include "SkSLErrorReporter.h"
 #include "SkSLIRGenerator.h"
 
-#define SK_FRAGCOLOR_BUILTIN 10001
-#define SK_FRAGCOORD_BUILTIN    15
-#define SK_VERTEXID_BUILTIN      5
+#define SK_FRAGCOLOR_BUILTIN    10001
+#define SK_FRAGCOORD_BUILTIN       15
+#define SK_VERTEXID_BUILTIN         5
+#define SK_CLIPDISTANCE_BUILTIN     3
 
 namespace SkSL {
 
diff --git a/src/sksl/SkSLGLSLCodeGenerator.cpp b/src/sksl/SkSLGLSLCodeGenerator.cpp
index 70e2e7761c..4b1eea3451 100644
--- a/src/sksl/SkSLGLSLCodeGenerator.cpp
+++ b/src/sksl/SkSLGLSLCodeGenerator.cpp
@@ -329,6 +329,9 @@ void GLSLCodeGenerator::writeVariableReference(const VariableReference& ref) {
         case SK_VERTEXID_BUILTIN:
             this->write("gl_VertexID");
             break;
+        case SK_CLIPDISTANCE_BUILTIN:
+            this->write("gl_ClipDistance");
+            break;
         default:
             this->write(ref.fVariable.fName);
     }
@@ -346,7 +349,13 @@ void GLSLCodeGenerator::writeFieldAccess(const FieldAccess& f) {
         this->writeExpression(*f.fBase, kPostfix_Precedence);
         this->write(".");
     }
-    this->write(f.fBase->fType.fields()[f.fFieldIndex].fName);
+    switch (f.fBase->fType.fields()[f.fFieldIndex].fModifiers.fLayout.fBuiltin) {
+        case SK_CLIPDISTANCE_BUILTIN:
+            this->write("gl_ClipDistance");
+            break;
+        default:
+            this->write(f.fBase->fType.fields()[f.fFieldIndex].fName);
+    }
 }
 
 void GLSLCodeGenerator::writeSwizzle(const Swizzle& swizzle) {
diff --git a/src/sksl/sksl_frag.include b/src/sksl/sksl_frag.include
index 21849866df..d65545da66 100644
--- a/src/sksl/sksl_frag.include
+++ b/src/sksl/sksl_frag.include
@@ -3,6 +3,7 @@ STRINGIFY(
 // defines built-in interfaces supported by SkiaSL fragment shaders
 
 layout(builtin=15) in vec4 sk_FragCoord;
+layout(builtin=3) float sk_ClipDistance[1];
 
 // 9999 is a temporary value that causes us to ignore these declarations beyond
 // adding them to the symbol table. This works fine in GLSL (where they do not
diff --git a/src/sksl/sksl_vert.include b/src/sksl/sksl_vert.include
index af74c0c54c..b5ccfcb2a3 100644
--- a/src/sksl/sksl_vert.include
+++ b/src/sksl/sksl_vert.include
@@ -4,7 +4,8 @@ STRINGIFY(
 
 out gl_PerVertex {
   	layout(builtin=0) vec4 gl_Position;
-  	layout(builtin=1) float gl_PointSize;
+    layout(builtin=1) float gl_PointSize;
+    layout(builtin=3) float sk_ClipDistance[1];
 };
 
 layout(builtin=5) int sk_VertexID;
diff --git a/tests/SkSLGLSLTest.cpp b/tests/SkSLGLSLTest.cpp
index 671f6d849b..a0cc7d559e 100644
--- a/tests/SkSLGLSLTest.cpp
+++ b/tests/SkSLGLSLTest.cpp
@@ -688,4 +688,22 @@ DEF_TEST(SkSLVertexID, r) {
          SkSL::Program::kVertex_Kind);
 }
 
+DEF_TEST(SkSLClipDistance, r) {
+    test(r,
+         "void main() { sk_ClipDistance[0] = 0; }",
+         *SkSL::ShaderCapsFactory::Default(),
+         "#version 400\n"
+         "void main() {\n"
+         "    gl_ClipDistance[0] = 0.0;\n"
+         "}\n",
+         SkSL::Program::kVertex_Kind);
+    test(r,
+         "void main() { sk_FragColor = vec4(sk_ClipDistance[0]); }",
+         *SkSL::ShaderCapsFactory::Default(),
+         "#version 400\n"
+         "out vec4 sk_FragColor;\n"
+         "void main() {\n"
+         "    sk_FragColor = vec4(gl_ClipDistance[0]);\n"
+         "}\n");
+}
 #endif