font-edit: Improve the type descriptions

tools/font-edit/twin-fedit.h

@@ -35,12 +35,44 @@
 #include <string.h>
 #include <unistd.h>
 
-typedef enum _op { OpMove, OpLine, OpCurve, OpNoop } op_t;
+/* Geometric types */
 
+/*
+ * pt_t - Point in a 2-D coordinate system
+ * @x: x-component
+ * @y: y-component
+ */
 typedef struct {
     double x, y;
 } pt_t;
 
+/*
+ * pts_t - Points in a 2-D coordinate system
+ * @n: numeber of the stored points
+ * @s: size of the storage
+ * @pt: pointer of pt_ts
+ */
+typedef struct _pts_t {
+    int n;
+    int s;
+    pt_t *pt;
+} pts_t;
+
+/*
+ * spline_t - Cubic spline type
+ * @a: starting point.
+ * @b: first control point.
+ * @c: last control point.
+ * @d: ending point.
+ */
+typedef struct _spline {
+    pt_t a, b, c, d;
+} spline_t;
+
+/* Command line tpyes */
+
+typedef enum _op { OpMove, OpLine, OpCurve, OpNoop } op_t;
+
 typedef struct _cmd {
     struct _cmd *next;
     op_t op;
@@ -59,30 +91,74 @@ typedef struct _char {
     cmd_t *last;
 } char_t;
 
-typedef struct _pts_t {
-    int n;
-    int s;
-    pt_t *pt;
-} pts_t;
-
-typedef struct _spline {
-    pt_t a, b, c, d;
-} spline_t;
-
-spline_t fit(pt_t *p, int n);
+/* Geometric functions */
 
+/*
+ * new_pts() - Allocate and initialize a new point
+ *
+ * Return: pts_t type, allocated point.
+ */
 pts_t *new_pts(void);
 
+/*
+ * dispose_pts() - Free all storage used by pts_t
+ * @pts: the points to be free
+ */
 void dispose_pts(pts_t *pts);
 
+/*
+ * add_pt() - Add a point to pts_t
+ * @pts: the object that receives the added points
+ * @pt: the point to be added
+ */
 void add_pt(pts_t *pts, pt_t *pt);
 
+/*
+ * distance_to_point() - Calculate distance between two points
+ * @a: point in 2-D coordinate
+ * @b: point in 2-D coordinate
+ *
+ * Return: double type, the distance between point a and point b.
+ */
 double distance_to_point(pt_t *a, pt_t *b);
 
+/*
+ * distance_to_line() - Calculate distance from a point to a line
+ * @p: point outside the line
+ * @p1: one of the points used to calculate the line
+ * @p2: one of the points used to calculate the line
+ *
+ * Return: double type, the distance from point p to the line.
+ */
 double distance_to_line(pt_t *p, pt_t *p1, pt_t *p2);
 
+/*
+ * distance_to_segment() - Calculate shortest distance from a point
+ *                         to a line segment
+ * @p: point outside the line segment
+ * @p1: one of the points used to calculate the line segment
+ * @p2: one of the points used to calculate the line segment
+ *
+ * Return: double type, the distance from point p to the line segment.
+ */
 double distance_to_segment(pt_t *p, pt_t *p1, pt_t *p2);
 
+/*
+ * lerp() - Interpolate linearly a point between two points
+ * @a: one of the point to be interpolated
+ * @b: one of the point to be interpolated
+ *
+ * Return: pt_t type, a interpolation point by two points.
+ */
 pt_t lerp(pt_t *a, pt_t *b);
 
+/*
+ * fit() - Fit a spline within a specified tolerance
+ * @a: points
+ * @n: number of points
+ *
+ * Return: spline_t type, a cubic spline of points.
+ */
+spline_t fit(pt_t *p, int n);
+
 #endif /* _TWIN_FEDIT_H_ */