Extend composeshader to support a lerp parameter

Bug: skia:
Change-Id: I3bbb2cb8d0a84fca0309654498548ebc94d8938f
Reviewed-on: https://skia-review.googlesource.com/18460
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>

1 files changed, 16 insertions, 26 deletions

diff --git a/src/shaders/SkComposeShader.h b/src/shaders/SkComposeShader.h
index 39c43d6b77..03861009a9 100644
--- a/src/shaders/SkComposeShader.h
+++ b/src/shaders/SkComposeShader.h
@@ -11,36 +11,22 @@
 #include "SkShaderBase.h"
 #include "SkBlendMode.h"
 
-class SkColorSpacXformer;
-
-///////////////////////////////////////////////////////////////////////////////////////////
-
-/** \class SkComposeShader
-    This subclass of shader returns the composition of two other shaders, combined by
-    a xfermode.
-*/
 class SkComposeShader : public SkShaderBase {
 public:
-    /** Create a new compose shader, given shaders A, B, and a combining xfermode mode.
-        When the xfermode is called, it will be given the result from shader A as its
-        "dst", and the result from shader B as its "src".
-        mode->xfer32(sA_result, sB_result, ...)
-        @param shaderA  The colors from this shader are seen as the "dst" by the xfermode
-        @param shaderB  The colors from this shader are seen as the "src" by the xfermode
-        @param mode     The xfermode that combines the colors from the two shaders. If mode
-                        is null, then SRC_OVER is assumed.
-    */
-    SkComposeShader(sk_sp<SkShader> sA, sk_sp<SkShader> sB, SkBlendMode mode)
-        : fShaderA(std::move(sA))
-        , fShaderB(std::move(sB))
+    SkComposeShader(sk_sp<SkShader> dst, sk_sp<SkShader> src, SkBlendMode mode, float lerpT)
+        : fDst(std::move(dst))
+        , fSrc(std::move(src))
+        , fLerpT(lerpT)
         , fMode(mode)
-    {}
+    {
+        SkASSERT(lerpT >= 0 && lerpT <= 1);
+    }
 
 #if SK_SUPPORT_GPU
     sk_sp<GrFragmentProcessor> asFragmentProcessor(const AsFPArgs&) const override;
 #endif
 
-#ifdef SK_DEBUG
+#ifdef SK_DEBUGx
     SkShader* getShaderA() { return fShaderA.get(); }
     SkShader* getShaderB() { return fShaderB.get(); }
 #endif
@@ -57,12 +43,16 @@ protected:
     bool onAppendStages(SkRasterPipeline*, SkColorSpace* dstCS, SkArenaAlloc*,
                         const SkMatrix&, const SkPaint&, const SkMatrix* localM) const override;
 
-    bool isRasterPipelineOnly() const final;
+    bool isRasterPipelineOnly() const final { return true; }
 
 private:
-    sk_sp<SkShader>     fShaderA;
-    sk_sp<SkShader>     fShaderB;
-    SkBlendMode         fMode;
+    sk_sp<SkShader>     fDst;
+    sk_sp<SkShader>     fSrc;
+    const float         fLerpT;
+    const SkBlendMode   fMode;
+
+    bool isJustMode() const { return fLerpT == 1; }
+    bool isJustLerp() const { return fMode == SkBlendMode::kSrc; }
 
     typedef SkShaderBase INHERITED;
 };