Add color gamut xform helpers to GrGLSLShaderBuilder

New helper functions inject the necessary shader
function. Texture lookup functions can now insert
the gamut xform at the appropriate place, too.

As written, could be used to transform non-texture
colors (e.g. vertex colors) as well.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2180803005

Review-Url: https://codereview.chromium.org/2180803005

1 files changed, 20 insertions, 2 deletions

diff --git a/include/gpu/GrColorSpaceXform.h b/include/gpu/GrColorSpaceXform.h
index 177230c87c..c1fb166f47 100644
--- a/include/gpu/GrColorSpaceXform.h
+++ b/include/gpu/GrColorSpaceXform.h
@@ -8,6 +8,7 @@
 #ifndef GrColorSpaceXform_DEFINED
 #define GrColorSpaceXform_DEFINED
 
+#include "SkImageInfo.h"
 #include "SkRefCnt.h"
 
 class SkColorSpace;
@@ -18,15 +19,32 @@ class SkMatrix44;
   */
 class GrColorSpaceXform : public SkRefCnt {
 public:
-    GrColorSpaceXform(const SkMatrix44& srcToDst);
+    GrColorSpaceXform(const SkMatrix44& srcToDst, SkAlphaType srcAlphaType);
 
-    static sk_sp<GrColorSpaceXform> Make(SkColorSpace* src, SkColorSpace* dst);
+    static sk_sp<GrColorSpaceXform> Make(SkColorSpace* src, SkColorSpace* dst,
+                                         SkAlphaType srcAlphaType);
 
     const float* srcToDst() { return fSrcToDst; }
+    SkAlphaType alphaType() const { return fSrcAlphaType; }
+
+    /**
+     * GrGLSLFragmentProcessor::GenKey() must call this and include the returned value in its
+     * computed key.
+     */
+    static uint32_t XformKey(GrColorSpaceXform* xform) {
+        if (!xform) {
+            return 0;
+        }
+        // Code generation just depends on whether the alpha type is premul or not
+        return kPremul_SkAlphaType == xform->fSrcAlphaType ? 1 : 2;
+    }
 
 private:
     // We store the column-major form of the srcToDst matrix, for easy uploading to uniforms
     float fSrcToDst[16];
+
+    // Alpha type of the source. If it's premul, we need special handling
+    SkAlphaType fSrcAlphaType;
 };
 
 #endif