[docs] A few improvements

If we wrote just this much every day...

src/hb-buffer.cc

@@ -1887,6 +1887,10 @@ hb_buffer_t::sort (unsigned int start, unsigned int end, int(*compar)(const hb_g
 
 /**
  * hb_buffer_diff:
+ * @buffer: a buffer.
+ * @reference: other buffer to compare to.
+ * @dottedcircle_glyph: glyph id of U+25CC DOTTED CIRCLE, or (hb_codepont_t) -1.
+ * @position_fuzz: allowed absolute difference in position values.
  *
  * If dottedcircle_glyph is (hb_codepoint_t) -1 then %HB_BUFFER_DIFF_FLAG_DOTTED_CIRCLE_PRESENT
  * and %HB_BUFFER_DIFF_FLAG_NOTDEF_PRESENT are never returned.  This should be used by most

src/hb-buffer.h

@@ -44,7 +44,6 @@ HB_BEGIN_DECLS
  * hb_glyph_info_t:
  * @codepoint: either a Unicode code point (before shaping) or a glyph index
  *             (after shaping).
- * @mask: 
  * @cluster: the index of the character in the original text that corresponds
  *           to this #hb_glyph_info_t, or whatever the client passes to
  *           hb_buffer_add(). More than one #hb_glyph_info_t can have the same
@@ -59,11 +58,13 @@ HB_BEGIN_DECLS
  *
  * The #hb_glyph_info_t is the structure that holds information about the
  * glyphs and their relation to input text.
- *
  */
-typedef struct hb_glyph_info_t {
+typedef struct hb_glyph_info_t
+{
   hb_codepoint_t codepoint;
-  hb_mask_t      mask; /* Holds hb_glyph_flags_t after hb_shape(), plus other things. */
+  /*< private >*/
+  hb_mask_t      mask;
+  /*< public >*/
   uint32_t       cluster;
 
   /*< private >*/
@@ -92,6 +93,7 @@ typedef struct hb_glyph_info_t {
 typedef enum { /*< flags >*/
   HB_GLYPH_FLAG_UNSAFE_TO_BREAK		= 0x00000001,
 
+  /*< private >*/
   HB_GLYPH_FLAG_DEFINED			= 0x00000001 /* OR of all defined flags */
 } hb_glyph_flags_t;
 
@@ -298,7 +300,15 @@ hb_buffer_set_flags (hb_buffer_t       *buffer,
 HB_EXTERN hb_buffer_flags_t
 hb_buffer_get_flags (hb_buffer_t *buffer);
 
-/*
+/**
+ * hb_buffer_cluster_level_t:
+ * @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES: Return cluster values grouped by graphemes into
+ *   monotone order.
+ * @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARACTERS: Return cluster values grouped into monotone order.
+ * @HB_BUFFER_CLUSTER_LEVEL_CHARACTERS: Don't group cluster values.
+ * @HB_BUFFER_CLUSTER_LEVEL_DEFAULT: Default cluster level,
+ *   equal to @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES.
+ *
  * Since: 0.9.42
  */
 typedef enum {

src/hb-face.cc

@@ -36,12 +36,12 @@
 
 
 /**
- * hb_face_count: Get number of faces on the blob
- * @blob:
+ * hb_face_count:
+ * @blob: a blob.
  *
+ * Get number of faces in a blob.
  *
- *
- * Return value: Number of faces on the blob
+ * Return value: Number of faces in @blob
  *
  * Since: 1.7.7
  **/
@@ -488,6 +488,9 @@ hb_face_get_glyph_count (const hb_face_t *face)
 /**
  * hb_face_get_table_tags:
  * @face: a face.
+ * @start_offset: index of first tag to return.
+ * @table_count: input length of @table_tags array, output number of items written.
+ * @table_tags: array to write tags into.
  *
  * Retrieves table tags for a face, if possible.
  *

src/hb-font.cc

@@ -1703,9 +1703,11 @@ hb_font_get_ppem (hb_font_t *font,
 /**
  * hb_font_set_ptem:
  * @font: a font.
- * @ptem: 
+ * @ptem: font size in points.
  *
- * Sets "point size" of the font.
+ * Sets "point size" of the font.  Set to 0 to unset.
+ *
+ * There are 72 points in an inch.
  *
  * Since: 1.6.0
  **/
@@ -1931,9 +1933,9 @@ hb_font_get_variation_glyph_trampoline (hb_font_t *font,
 /**
  * hb_font_funcs_set_glyph_func:
  * @ffuncs: font functions.
- * @func: (closure user_data) (destroy destroy) (scope notified):
- * @user_data:
- * @destroy:
+ * @func: (closure user_data) (destroy destroy) (scope notified): callback function.
+ * @user_data: data to pass to @func.
+ * @destroy: function to call when @user_data is not needed anymore.
  *
  * Deprecated.  Use hb_font_funcs_set_nominal_glyph_func() and
  * hb_font_funcs_set_variation_glyph_func() instead.