sksl programs can now directly query GLSL caps

This adds support for querying "sk_Caps.<cap>" directly from within an SkSL program.
Combined with the existing support for collapsing 'if' statements with constant tests,
this means we can query caps using ordinary 'if' statements and the tests will 
collapse out at compile time.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4795

Change-Id: I24d716a7fe6abf1489760bf08189164264269076
Reviewed-on: https://skia-review.googlesource.com/4795
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Ben Wagner <benjaminwagner@google.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/tests/SkSLGLSLTest.cpp b/tests/SkSLGLSLTest.cpp
index 7af32bef6f..4a9338113f 100644
--- a/tests/SkSLGLSLTest.cpp
+++ b/tests/SkSLGLSLTest.cpp
@@ -524,4 +524,27 @@ DEF_TEST(SkSLStaticIf, r) {
          "}\n");
 }
 
+DEF_TEST(SkSLCaps, r) {
+    test(r,
+         "void main() {"
+         "int x;"
+         "if (sk_Caps.externalTextureSupport) x = 1;"
+         "if (sk_Caps.fbFetchSupport) x = 2;"
+         "if (sk_Caps.dropsTileOnZeroDivide && sk_Caps.texelFetchSupport) x = 3;"
+         "if (sk_Caps.dropsTileOnZeroDivide && sk_Caps.canUseAnyFunctionInShader) x = 4;"
+         "}",
+         *SkSL::GLSLCapsFactory::VariousCaps(),
+         "#version 400\n"
+         "out vec4 sk_FragColor;\n"
+         "void main() {\n"
+         "    int x;\n"
+         "    x = 1;\n"
+         "    {\n"
+         "    }\n"
+         "    x = 3;\n"
+         "    {\n"
+         "    }\n"
+         "}\n");
+}
+
 #endif