From 0a9531ac6caff2ad6abfbb804ec27cade4a92e7a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Thu, 27 May 2021 20:07:28 +0200
Subject: [PATCH] vt: cache grapheme cluster width in composed struct
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* 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 |  1 +
 util.h     |  8 --------
 vt.c       | 14 ++++++++++----
 3 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/terminal.h b/terminal.h
index 45c6c98b..83406f41 100644
--- a/terminal.h
+++ b/terminal.h
@@ -87,6 +87,7 @@ struct damage {
 struct composed {
     wchar_t chars[20];
     uint8_t count;
+    int width;
 };
 
 struct row_uri_range {
diff --git a/util.h b/util.h
index af215111..aa9fc8ba 100644
--- a/util.h
+++ b/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);
-}
diff --git a/vt.c b/vt.c
index 496333d7..6ad539d7 100644
--- a/vt.c
+++ b/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 (grapheme_width > 0)
-                term_print(term, CELL_COMB_CHARS_LO + i, grapheme_width);
+            if (cc->width > 0)
+                term_print(term, CELL_COMB_CHARS_LO + i, cc->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;