Improve API headers and documentation

Improve APi documentation; each function is properly documented now.
Add a new macro LIBASS_VERSION that encodes the version in a
hexadecimal format, similar to OpenSSL.  Fix formatting of the headers.

2 files changed, 171 insertions, 61 deletions

diff --git a/libass/ass.h b/libass/ass.h
index b7eab3c..6efcc0f 100644
--- a/libass/ass.h
+++ b/libass/ass.h
@@ -25,132 +25,228 @@
 #include <stdarg.h>
 #include "ass_types.h"
 
-/// Libass renderer object. Contents are private.
+#define LIBASS_VERSION 0x00907000
+
+/* Libass renderer object. Contents are private. */
 typedef struct ass_renderer_s ass_renderer_t;
 
-/// a linked list of images produced by ass renderer
+/* A linked list of images produced by ass renderer. */
 typedef struct ass_image_s {
-    int w, h;                   // bitmap width/height
-    int stride;                 // bitmap stride
+    int w, h;                   // Bitmap width/height
+    int stride;                 // Bitmap stride
     unsigned char *bitmap;      // 1bpp stride*h alpha buffer
-    uint32_t color;             // RGBA
-    int dst_x, dst_y;           // bitmap placement inside the video frame
+    uint32_t color;             // Bitmap color and alpha, RGBA
+    int dst_x, dst_y;           // Bitmap placement inside the video frame
 
-    struct ass_image_s *next;   // linked list
+    struct ass_image_s *next;   // Next image, or NULL
 } ass_image_t;
 
-/// Hinting type
-typedef enum { ASS_HINTING_NONE = 0,
+/* Hinting type. */
+typedef enum {
+    ASS_HINTING_NONE = 0,
     ASS_HINTING_LIGHT,
     ASS_HINTING_NORMAL,
     ASS_HINTING_NATIVE
 } ass_hinting_t;
 
 /**
- * \brief initialize the library
+ * \brief Initialize the library.
  * \return library handle or NULL if failed
  */
 ass_library_t *ass_library_init(void);
 
 /**
- * \brief finalize the library
+ * \brief Finalize the library
  * \param priv library handle
  */
 void ass_library_done(ass_library_t *);
 
 /**
- * \brief set private font directory
+ * \brief Set private font directory.
  * It is used for saving embedded fonts and also in font lookup.
+ *
+ * \param priv library handle
+ * \param fonts_dir private directory for font extraction
  */
 void ass_set_fonts_dir(ass_library_t *priv, const char *fonts_dir);
 
+/**
+ * \brief Whether fonts should be extracted from track data.
+ * \param priv library handle
+ * \param extract whether to extract fonts
+ */
 void ass_set_extract_fonts(ass_library_t *priv, int extract);
 
+/**
+ * \brief Register style overrides with a library instance.
+ * The overrides should have the form [Style.]Param=Value, e.g.
+ *   SomeStyle.Font=Arial
+ *   ScaledBorderAndShadow=yes
+ *
+ * \param priv library handle
+ * \param list NULL-terminated list of strings
+ */
 void ass_set_style_overrides(ass_library_t *priv, char **list);
 
+/**
+ * \brief Explicitly process style overrides for a track.
+ * \param track track handle
+ */
 void ass_process_force_style(ass_track_t *track);
 
+/**
+ * \brief Register a callback for debug/info messages.
+ * If a callback is registered, it is called for every message emitted by
+ * libass.  The callback receives a format string and a list of arguments,
+ * to be used for the printf family of functions. Additionally, a log level
+ * from 0 (FATAL errors) to 7 (verbose DEBUG) is passed.  Usually, level 5
+ * should be used by applications.
+ * If no callback is set, all messages level < 5 are printed to stderr,
+ * prefixed with [ass].
+ *
+ * \param priv library handle
+ * \param msg_cb pointer to callback function
+ * \param data additional data, will be passed to callback
+ */
 void ass_set_message_cb(ass_library_t *priv,
                         void (*msg_cb)(int, char *, va_list *, void *),
                         void *data);
 
 /**
- * \brief initialize the renderer
+ * \brief Initialize the renderer.
  * \param priv library handle
  * \return renderer handle or NULL if failed
  */
 ass_renderer_t *ass_renderer_init(ass_library_t *);
 
 /**
- * \brief finalize the renderer
+ * \brief Finalize the renderer.
  * \param priv renderer handle
  */
 void ass_renderer_done(ass_renderer_t *priv);
 
+/**
+ * \brief Set the frame size in pixels, including margins.
+ * \param priv renderer handle
+ * \param w width
+ * \param h height
+ */
 void ass_set_frame_size(ass_renderer_t *priv, int w, int h);
+
+/**
+ * \brief Set frame margins.  These values may be negative if pan-and-scan
+ * is used.
+ * \param priv renderer handle
+ * \param t top margin
+ * \param b bottom margin
+ * \param l left margin
+ * \param r right margin
+ */
 void ass_set_margins(ass_renderer_t *priv, int t, int b, int l, int r);
+
+/**
+ * \brief Whether margins should be used for placing regular events.
+ * \param priv renderer handle
+ * \param use whether to use the margins
+ */
 void ass_set_use_margins(ass_renderer_t *priv, int use);
+
+/**
+ * \brief Set aspect ratio parameters.
+ * \param priv renderer handle
+ * \param ar physical aspect ratio
+ * \param par pixel ratio, e.g. width / height of the video
+ */
 void ass_set_aspect_ratio(ass_renderer_t *priv, double ar, double par);
+
+/**
+ * \brief Set a fixed font scaling factor.
+ * \param priv renderer handle
+ * \param font_scale scaling factor, default is 1.0
+ */
 void ass_set_font_scale(ass_renderer_t *priv, double font_scale);
+
+/**
+ * \brief Set font hinting method.
+ * \param priv renderer handle
+ * \param ht hinting method
+ */
 void ass_set_hinting(ass_renderer_t *priv, ass_hinting_t ht);
+
+/**
+ * \brief Set line spacing. Will not be scaled with frame size.
+ * \param priv renderer handle
+ * \param line_spacing line spacing in pixels
+ */
 void ass_set_line_spacing(ass_renderer_t *priv, double line_spacing);
 
 /**
- * \brief set font lookup defaults
- * \param fc bool, use fontconfig?
- * \param config path to fontconfig configuration file, or NULL. Only matters
- * if fontconfig is used
- * \param update whether fontconfig cache should be built/updated now. Make
- * sure to call ass_fonts_update later if 0! Only matters if fontconfig
- * is used.
- * \return success
+ * \brief Set font lookup defaults.
+ * \param fc whether to use fontconfig
+ * \param config path to fontconfig configuration file, or NULL.  Only relevant
+ * if fontconfig is used.
+ * \param update whether fontconfig cache should be built/updated now.  Only
+ * relevant if fontconfig is used.
  */
 void ass_set_fonts(ass_renderer_t *priv, const char *default_font,
                    const char *default_family, int fc, const char *config,
                    int update);
 
+/**
+ * \brief Update/build font cache.  This needs to be called if it was
+ * disabled when ass_set_fonts was set.
+ *
+ * \param priv renderer handle
+ * \return success
+ */
 int ass_fonts_update(ass_renderer_t *priv);
 
 /**
- * \brief render a frame, producing a list of ass_image_t
- * \param priv library
+ * \brief Render a frame, producing a list of ass_image_t.
+ * \param priv renderer handle
  * \param track subtitle track
  * \param now video timestamp in milliseconds
+ * \param detect_change will be set to 1 if a change occured compared
+ * to the last invocation
  */
 ass_image_t *ass_render_frame(ass_renderer_t *priv, ass_track_t *track,
                               long long now, int *detect_change);
 
 
-// The following functions operate on track objects and do not need an ass_renderer //
+/*
+ * The following functions operate on track objects and do not need
+ * an ass_renderer
+ */
 
 /**
- * \brief allocate a new empty track object
+ * \brief Allocate a new empty track object.
+ * \param library handle
  * \return pointer to empty track
  */
 ass_track_t *ass_new_track(ass_library_t *);
 
 /**
- * \brief deallocate track and all its child objects (styles and events)
+ * \brief Deallocate track and all its child objects (styles and events).
  * \param track track to deallocate
  */
 void ass_free_track(ass_track_t *track);
 
 /**
- * \brief allocate new style
+ * \brief Allocate new style.
  * \param track track
  * \return newly allocated style id
  */
 int ass_alloc_style(ass_track_t *track);
 
 /**
- * \brief allocate new event
+ * \brief Allocate new event.
  * \param track track
  * \return newly allocated event id
  */
 int ass_alloc_event(ass_track_t *track);
 
 /**
- * \brief delete a style
+ * \brief Delete a style.
  * \param track track
  * \param sid style id
  * Deallocates style data. Does not modify track->n_styles.
@@ -158,7 +254,7 @@ int ass_alloc_event(ass_track_t *track);
 void ass_free_style(ass_track_t *track, int sid);
 
 /**
- * \brief delete an event
+ * \brief Delete an event.
  * \param track track
  * \param eid event id
  * Deallocates event data. Does not modify track->n_events.
@@ -174,7 +270,7 @@ void ass_free_event(ass_track_t *track, int eid);
 void ass_process_data(ass_track_t *track, char *data, int size);
 
 /**
- * \brief Parse Codec Private section of subtitle stream
+ * \brief Parse Codec Private section of subtitle stream.
  * \param track target track
  * \param data string to parse
  * \param size length of data
@@ -182,19 +278,22 @@ void ass_process_data(ass_track_t *track, char *data, int size);
 void ass_process_codec_private(ass_track_t *track, char *data, int size);
 
 /**
- * \brief Parse a chunk of subtitle stream data. In Matroska, this contains exactly 1 event (or a commentary).
+ * \brief Parse a chunk of subtitle stream data. In Matroska,
+ * this contains exactly 1 event (or a commentary).
  * \param track track
  * \param data string to parse
  * \param size length of data
  * \param timecode starting time of the event (milliseconds)
  * \param duration duration of the event (milliseconds)
-*/
+ */
 void ass_process_chunk(ass_track_t *track, char *data, int size,
                        long long timecode, long long duration);
 
 /**
  * \brief Read subtitles from file.
+ * \param library library handle
  * \param fname file name
+ * \param codepage encoding (iconv format)
  * \return newly allocated track
 */
 ass_track_t *ass_read_file(ass_library_t *library, char *fname,
@@ -202,22 +301,25 @@ ass_track_t *ass_read_file(ass_library_t *library, char *fname,
 
 /**
  * \brief Read subtitles from memory.
- * \param library libass library object
+ * \param library library handle
  * \param buf pointer to subtitles text
  * \param bufsize size of buffer
- * \param codepage recode buffer contents from given codepage
+ * \param codepage encoding (iconv format)
  * \return newly allocated track
 */
 ass_track_t *ass_read_memory(ass_library_t *library, char *buf,
                              size_t bufsize, char *codepage);
 /**
- * \brief read styles from file into already initialized track
+ * \brief Read styles from file into already initialized track.
+ * \param fname file name
+ * \param codepage encoding (iconv format)
  * \return 0 on success
  */
 int ass_read_styles(ass_track_t *track, char *fname, char *codepage);
 
 /**
  * \brief Add a memory font.
+ * \param library library handle
  * \param name attachment name
  * \param data binary font data
  * \param data_size data size
@@ -226,18 +328,20 @@ void ass_add_font(ass_library_t *library, char *name, char *data,
                   int data_size);
 
 /**
- * \brief Remove all fonts stored in ass_library object
+ * \brief Remove all fonts stored in an ass_library object.
+ * \param library library handle
  */
 void ass_clear_fonts(ass_library_t *library);
 
 /**
- * \brief Calculates timeshift from now to the start of some other subtitle event, depending on movement parameter
+ * \brief Calculates timeshift from now to the start of some other subtitle
+ * event, depending on movement parameter.
  * \param track subtitle track
- * \param now current time, ms
+ * \param now current time in milliseconds
  * \param movement how many events to skip from the one currently displayed
  * +2 means "the one after the next", -1 means "previous"
- * \return timeshift, ms
+ * \return timeshift in milliseconds
  */
 long long ass_step_sub(ass_track_t *track, long long now, int movement);
 
-#endif                          /* LIBASS_ASS_H */
+#endif /* LIBASS_ASS_H */
diff --git a/libass/ass_types.h b/libass/ass_types.h
index cdea14e..fb74872 100644
--- a/libass/ass_types.h
+++ b/libass/ass_types.h
@@ -30,7 +30,7 @@
 #define HALIGN_CENTER 2
 #define HALIGN_RIGHT 3
 
-/// ass Style: line
+/* ASS Style: line */
 typedef struct ass_style_s {
     char *Name;
     char *FontName;
@@ -54,15 +54,16 @@ typedef struct ass_style_s {
     int MarginL;
     int MarginR;
     int MarginV;
-//        int AlphaLevel;
     int Encoding;
     int treat_fontname_as_pattern;
 } ass_style_t;
 
 typedef struct render_priv_s render_priv_t;
 
-/// ass_event_t corresponds to a single Dialogue line
-/// Text is stored as-is, style overrides will be parsed later
+/*
+ * ass_event_t corresponds to a single Dialogue line;
+ * text is stored as-is, style overrides will be parsed later.
+ */
 typedef struct ass_event_s {
     long long Start;            // ms
     long long Duration;         // ms
@@ -81,26 +82,31 @@ typedef struct ass_event_s {
 } ass_event_t;
 
 typedef struct parser_priv_s parser_priv_t;
-
 typedef struct ass_library_s ass_library_t;
 
-/// ass track represent either an external script or a matroska subtitle stream (no real difference between them)
-/// it can be used in rendering after the headers are parsed (i.e. events format line read)
+/*
+ * ass track represent either an external script or a matroska subtitle stream
+ * (no real difference between them); it can be used in rendering after the
+ * headers are parsed (i.e. events format line read).
+ */
 typedef struct ass_track_s {
-    int n_styles;               // amount used
-    int max_styles;             // amount allocated
+    int n_styles;           // amount used
+    int max_styles;         // amount allocated
     int n_events;
     int max_events;
-    ass_style_t *styles;        // array of styles, max_styles length, n_styles used
-    ass_event_t *events;        // the same as styles
+    ass_style_t *styles;    // array of styles, max_styles length, n_styles used
+    ass_event_t *events;    // the same as styles
 
-    char *style_format;         // style format line (everything after "Format: ")
-    char *event_format;         // event format line
+    char *style_format;     // style format line (everything after "Format: ")
+    char *event_format;     // event format line
 
-    enum { TRACK_TYPE_UNKNOWN =
-            0, TRACK_TYPE_ASS, TRACK_TYPE_SSA } track_type;
+    enum {
+        TRACK_TYPE_UNKNOWN = 0,
+        TRACK_TYPE_ASS,
+        TRACK_TYPE_SSA
+    } track_type;
 
-    // script header fields
+    // Script header fields
     int PlayResX;
     int PlayResY;
     double Timer;
@@ -108,11 +114,11 @@ typedef struct ass_track_s {
     char ScaledBorderAndShadow;
 
 
-    int default_style;          // index of default style
-    char *name;                 // file name in case of external subs, 0 for streams
+    int default_style;      // index of default style
+    char *name;             // file name in case of external subs, 0 for streams
 
     ass_library_t *library;
     parser_priv_t *parser_priv;
 } ass_track_t;
 
-#endif                          /* LIBASS_TYPES_H */
+#endif /* LIBASS_TYPES_H */