C API: Add SK_API, also documentation of an example.

include/c/sk_types.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_types_DEFINED
 #define sk_types_DEFINED
 
 #include <stdint.h>
 #include <stddef.h>
 
 #ifdef __cplusplus
     #define SK_C_PLUS_PLUS_BEGIN_GUARD    extern "C" {
     #define SK_C_PLUS_PLUS_END_GUARD      }
 #else
     #include <stdbool.h>
     #define SK_C_PLUS_PLUS_BEGIN_GUARD
     #define SK_C_PLUS_PLUS_END_GUARD
 #endif
 
+#ifndef SK_API
+#define SK_API
+#endif
+
 ///////////////////////////////////////////////////////////////////////////////////////
 
 SK_C_PLUS_PLUS_BEGIN_GUARD
 
 typedef uint32_t sk_color_t;
 
 #define sk_color_set_argb(a, r, g, b)   (((a) << 24) | ((r) << 16) | ((g) << 8) | (b))
 #define sk_color_get_a(c)               (((c) >> 24) & 0xFF)
 #define sk_color_get_r(c)               (((c) >> 16) & 0xFF)
 #define sk_color_get_g(c)               (((c) >>  8) & 0xFF)
@@ skipping 18 matching lines @@
 } sk_cliptype_t;
 
 typedef enum {
     UNKNOWN_SK_PIXELGEOMETRY,
     RGB_H_SK_PIXELGEOMETRY,
     BGR_H_SK_PIXELGEOMETRY,
     RGB_V_SK_PIXELGEOMETRY,
     BGR_V_SK_PIXELGEOMETRY,
 } sk_pixelgeometry_t;
 
-sk_colortype_t sk_colortype_get_default_8888();
+SK_API sk_colortype_t sk_colortype_get_default_8888();
 
 typedef struct {
     int32_t         width;
     int32_t         height;
     sk_colortype_t  colorType;
     sk_alphatype_t  alphaType;
 } sk_imageinfo_t;
 
 typedef struct {
     sk_pixelgeometry_t pixelGeometry;
@@ skipping 63 matching lines @@
     SATURATION_SK_XFERMODE_MODE,
     COLOR_SK_XFERMODE_MODE,
     LUMINOSITY_SK_XFERMODE_MODE,
 } sk_xfermode_mode_t;
 
 //////////////////////////////////////////////////////////////////////////////////////////
 
 SK_C_PLUS_PLUS_END_GUARD
 
 #endif