utf8_length: add reserve flag for reserving a trailing character

Replace unused coloffset with reserve flag, which will reserve at least
one character cell at the end. Use it for reserving a delimiter character
when use_tilde is TRUE, and avoid a second call to utf8_length().

diff --git a/tig.c b/tig.c
index 1eb028b7a5c15d8c73630209c6eec0026a1e93de..25cf31b02e18ea71de4e7fcc30b1568429f7e801 100644 (file)
--- a/tig.c
+++ b/tig.c
@@ -58,7 +58,7 @@ static void warn(const char *msg, ...);
 static void report(const char *msg, ...);
 static int read_properties(FILE *pipe, const char *separators, int (*read)(char *, size_t, char *, size_t));
 static void set_nonblocking_input(bool loading);
-static size_t utf8_length(const char *string, size_t max_width, int *coloffset, int *trimmed);
+static size_t utf8_length(const char *string, size_t max_width, int *trimmed, bool reserve);
 
 #define ABS(x)         ((x) >= 0  ? (x) : -(x))
 #define MIN(x, y)      ((x) < (y) ? (x) :  (y))
@@ -1468,14 +1468,7 @@ draw_text(struct view *view, const char *string, int max_len, int col,
                int trimmed = FALSE;
 
                if (opt_utf8) {
-                       int pad = 0;
-
-                       len = utf8_length(string, max_len, &pad, &trimmed);
-                       if (trimmed && use_tilde) {
-                               max_len -= 1;
-                               len = utf8_length(
-                                       string, max_len, &pad, &trimmed);
-                       }
+                       len = utf8_length(string, max_len, &trimmed, use_tilde);
                        n = len;
                } else {
                        len = strlen(string);
@@ -4559,19 +4552,16 @@ utf8_to_unicode(const char *string, size_t length)
 
 /* Calculates how much of string can be shown within the given maximum width
  * and sets trimmed parameter to non-zero value if all of string could not be
- * shown.
- *
- * Additionally, adds to coloffset how many many columns to move to align with
- * the expected position. Takes into account how multi-byte and double-width
- * characters will effect the cursor position.
+ * shown. If the reserve flag is TRUE, it will reserve at least one
+ * trailing character, which can be useful when drawing a delimiter.
  *
  * Returns the number of bytes to output from string to satisfy max_width. */
 static size_t
-utf8_length(const char *string, size_t max_width, int *coloffset, int *trimmed)
+utf8_length(const char *string, size_t max_width, int *trimmed, bool reserve)
 {
        const char *start = string;
        const char *end = strchr(string, '\0');
-       size_t mbwidth = 0;
+       unsigned char last_bytes = 0;
        size_t width = 0;
 
        *trimmed = 0;
@@ -4597,27 +4587,16 @@ utf8_length(const char *string, size_t max_width, int *coloffset, int *trimmed)
                width  += ucwidth;
                if (width > max_width) {
                        *trimmed = 1;
+                       if (reserve && width - ucwidth == max_width) {
+                               string -= last_bytes;
+                       }
                        break;
                }
 
-               /* The column offset collects the differences between the
-                * number of bytes encoding a character and the number of
-                * columns will be used for rendering said character.
-                *
-                * So if some character A is encoded in 2 bytes, but will be
-                * represented on the screen using only 1 byte this will and up
-                * adding 1 to the multi-byte column offset.
-                *
-                * Assumes that no double-width character can be encoding in
-                * less than two bytes. */
-               if (bytes > ucwidth)
-                       mbwidth += bytes - ucwidth;
-
                string  += bytes;
+               last_bytes = bytes;
        }
 
-       *coloffset += mbwidth;
-
        return string - start;
 }