Documentation: C API comments in include/

include/c/sk_matrix.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 // EXPERIMENTAL EXPERIMENTAL EXPERIMENTAL EXPERIMENTAL
 // DO NOT USE -- FOR INTERNAL TESTING ONLY
 
 #ifndef sk_matrix_DEFINED
 #define sk_matrix_DEFINED
 
 #include "sk_types.h"
 
 SK_C_PLUS_PLUS_BEGIN_GUARD
 
+/** Set the matrix to identity */
 void sk_matrix_set_identity(sk_matrix_t*);
 
+/** Set the matrix to translate by (tx, ty). */
 void sk_matrix_set_translate(sk_matrix_t*, float tx, float ty);
+/**
+    Preconcats the matrix with the specified translation.
+        M' = M * T(dx, dy)
+*/
 void sk_matrix_pre_translate(sk_matrix_t*, float tx, float ty);
+/**
+    Postconcats the matrix with the specified translation.
+        M' = T(dx, dy) * M
+*/
 void sk_matrix_post_translate(sk_matrix_t*, float tx, float ty);
 
+/** Set the matrix to scale by sx and sy. */
 void sk_matrix_set_scale(sk_matrix_t*, float sx, float sy);
+/**
+    Preconcats the matrix with the specified scale.
+        M' = M * S(sx, sy)
+*/
 void sk_matrix_pre_scale(sk_matrix_t*, float sx, float sy);
+/**
+    Postconcats the matrix with the specified scale.
+        M' = S(sx, sy) * M
+*/
 void sk_matrix_post_scale(sk_matrix_t*, float sx, float sy);
 
 SK_C_PLUS_PLUS_END_GUARD
 
 #endif