vt: cache grapheme cluster width in composed struct

* Use regular wcswidth() to calculate the width
* Explicitly set to ‘2’ if we see a emoji variant selector
* Cache the result in the composed struct

terminal.h

@@ -87,6 +87,7 @@ struct damage {
 struct composed {
     wchar_t chars[20];
     uint8_t count;
+    int width;
 };
 
 struct row_uri_range {

util.h

@@ -35,11 +35,3 @@ sdbm_hash(const char *s)
 
     return hash;
 }
-
-#include <wchar.h>
-static inline int
-my_wcswidth(const wchar_t *s, size_t n)
-{
-    int ret = wcswidth(s, n);
-    return max(0, ret);
-}

vt.c

@@ -716,9 +716,8 @@ action_utf8_print(struct terminal *term, wchar_t wc)
             if (cc->chars[wanted_count - 1] != wc)
                 continue;
 
-            int grapheme_width = my_wcswidth(cc->chars, cc->count);
+            if (cc->width > 0)
-            if (grapheme_width > 0)
+                term_print(term, CELL_COMB_CHARS_LO + i, cc->width);
-                term_print(term, CELL_COMB_CHARS_LO + i, grapheme_width);
             return;
         }
 
@@ -732,11 +731,18 @@ action_utf8_print(struct terminal *term, wchar_t wc)
         new_cc.chars[wanted_count - 1] = wc;
 
         if (term->composed_count < CELL_COMB_CHARS_HI) {
+            /* TODO: grapheme cluster width */
+            int grapheme_width = wcswidth(new_cc.chars, new_cc.count);
+            if (new_cc.chars[new_cc.count - 1] == 0xfe0f) {
+                /* Emoji selector */
+                grapheme_width = 2;
+            }
+            new_cc.width = grapheme_width;
+
             term->composed_count++;
             term->composed = xrealloc(term->composed, term->composed_count * sizeof(term->composed[0]));
             term->composed[term->composed_count - 1] = new_cc;
 
-            int grapheme_width = my_wcswidth(new_cc.chars, new_cc.count);
             if (grapheme_width > 0)
                 term_print(term, CELL_COMB_CHARS_LO + term->composed_count - 1, grapheme_width);
             return;