Add isSingleComponent bool to getConstantColorComponent

Initial step to allowing effects to use/output 1 or 4 color/coverage components. This cl doesn't change any current logic and all effects still assume they are working with 4 components.

BUG=skia:

Review URL: https://codereview.chromium.org/608253002

1 files changed, 42 insertions, 0 deletions

diff --git a/src/gpu/GrProcessor.cpp b/src/gpu/GrProcessor.cpp
index 45298b522d..26e00530be 100644
--- a/src/gpu/GrProcessor.cpp
+++ b/src/gpu/GrProcessor.cpp
@@ -88,4 +88,46 @@ void GrProcessor::assertEquality(const GrProcessor& other) const {
         SkASSERT(this->textureAccess(i) == other.textureAccess(i));
     }
 }
+
+void GrProcessor::InvariantOutput::validate() const {
+    if (fIsSingleComponent) {
+        SkASSERT(0 == fValidFlags || kRGBA_GrColorComponentFlags == fValidFlags);
+        if (kRGBA_GrColorComponentFlags == fValidFlags) {
+            SkASSERT(this->colorComponentsAllEqual());
+        }
+    }
+
+    SkASSERT(this->validPreMulColor());
+}
+
+bool GrProcessor::InvariantOutput::colorComponentsAllEqual() const {
+    unsigned colorA = GrColorUnpackA(fColor);
+    return(GrColorUnpackR(fColor) == colorA &&
+           GrColorUnpackG(fColor) == colorA &&
+           GrColorUnpackB(fColor) == colorA);
+}
+
+bool GrProcessor::InvariantOutput::validPreMulColor() const {
+    if (kA_GrColorComponentFlag & fValidFlags) {
+        float c[4];
+        GrColorToRGBAFloat(fColor, c);
+        if (kR_GrColorComponentFlag & fValidFlags) {
+            if (c[0] > c[3]) {
+                return false;
+            }
+        }
+        if (kG_GrColorComponentFlag & fValidFlags) {
+            if (c[1] > c[3]) {
+                return false;
+            }
+        }
+        if (kB_GrColorComponentFlag & fValidFlags) {
+            if (c[2] > c[3]) {
+                return false;
+            }
+        }
+    }
+    return true;
+}
 #endif
+