fix some warnings, and make str_width a bit more efficient

1 files changed, 8 insertions, 4 deletions

diff --git a/src/unicode.rs b/src/unicode.rs
index 5cf597e..7897792 100644
--- a/src/unicode.rs
+++ b/src/unicode.rs
@@ -1,14 +1,18 @@
+use std::convert::TryInto as _;
 use unicode_width::UnicodeWidthChar as _;
 
 // soft hyphen is defined as width 1, but in a terminal setting it should
 // always be width 0
-pub fn char_width(c: char) -> usize {
+pub fn char_width(c: char) -> u16 {
     match c {
         '\u{00ad}' => 0,
-        _ => c.width().unwrap_or(0),
+        _ => c.width().unwrap_or(0).try_into().unwrap(),
     }
 }
 
-pub fn str_width(s: &str) -> usize {
-    s.chars().map(char_width).sum()
+// strings in this context should always be an arbitrary character followed by
+// zero or more zero-width characters, so we should only have to look at the
+// first character
+pub fn str_width(s: &str) -> u16 {
+    s.chars().next().map_or(0, char_width)
 }