Attempt to update Xfermode comments to have parallel structure.

include/core/SkXfermode.h

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkXfermode_DEFINED
@@ skipping 52 matching lines @@
         For these equations, the colors are in premultiplied state.
         If no xfermode is specified, kSrcOver is assumed.
         The modes are ordered by those that can be expressed as a pair of Coeffs, followed by those
         that aren't Coeffs but have separable r,g,b computations, and finally
         those that are not separable.
      */
     enum Mode {
         kClear_Mode,    //!< [0, 0]
         kSrc_Mode,      //!< [Sa, Sc]
         kDst_Mode,      //!< [Da, Dc]
-        kSrcOver_Mode,  //!< [Sa + Da - Sa*Da, Rc = Sc + (1 - Sa)*Dc]
-        kDstOver_Mode,  //!< [Sa + Da - Sa*Da, Rc = Dc + (1 - Da)*Sc]
+        kSrcOver_Mode,  //!< [Sa + Da * (1 - Sa), Sc + Dc * (1 - Sa)]
+        kDstOver_Mode,  //!< [Da + Sa * (1 - Da), Dc + Sc * (1 - Da)]
         kSrcIn_Mode,    //!< [Sa * Da, Sc * Da]
-        kDstIn_Mode,    //!< [Sa * Da, Sa * Dc]
+        kDstIn_Mode,    //!< [Da * Sa, Dc * Sa]
         kSrcOut_Mode,   //!< [Sa * (1 - Da), Sc * (1 - Da)]
         kDstOut_Mode,   //!< [Da * (1 - Sa), Dc * (1 - Sa)]
-        kSrcATop_Mode,  //!< [Da, Sc * Da + (1 - Sa) * Dc]
-        kDstATop_Mode,  //!< [Sa, Sa * Dc + Sc * (1 - Da)]
-        kXor_Mode,      //!< [Sa + Da - 2 * Sa * Da, Sc * (1 - Da) + (1 - Sa) * Dc]
+        kSrcATop_Mode,  //!< [Da, Sc * Da + Dc * (1 - Sa)]
+        kDstATop_Mode,  //!< [Sa, Dc * Sa + Sc * (1 - Da)]
+        kXor_Mode,      //!< [Sa + Da - 2 * Sa * Da, Sc * (1 - Da) + Dc * (1 - Sa)]
         kPlus_Mode,     //!< [Sa + Da, Sc + Dc]
         kModulate_Mode, // multiplies all components (= alpha and color)
 
         // Following blend modes are defined in the CSS Compositing standard:
         // https://dvcs.w3.org/hg/FXTF/rawfile/tip/compositing/index.html#blending
         kScreen_Mode,
         kLastCoeffMode = kScreen_Mode,
 
         kOverlay_Mode,
         kDarken_Mode,
@@ skipping 143 matching lines @@
 
 private:
     enum {
         kModeCount = kLastMode + 1
     };
 
     typedef SkFlattenable INHERITED;
 };
 
 #endif