Fix insertion of a space between multibyte characters

[ilotterytea]

Added a fix to correctly insert a space in strings containing multibyte characters. Previously, the space was inserted based on the character position, which caused issues with multibyte strings by attempting to insert the space between bytes of a multibyte character, leading to panics (assertion failed: self.is_char_boundary(idx)).

For example, the word apple has 5 bytes and 5 characters, so inserting a space with the old code works correctly. However, the Cyrillic word яблоко has 12 bytes and 6 characters. With the old code, inserting a space could put it inside a multibyte character, causing panic.

[rparrett]

Thanks for the detailed report.

The code just below is using a different method for inserting at a character boundary. Is one method or the other obviously superior?

I'd like to add an insert_char_at function similar to the existing remove_char_at and reuse the same code in both places.

[rparrett]

Oh right, the code below has to deal with potentially multiple chars.

I will take a closer look later tonight.

[rparrett]

Would you mind testing a solution more along these lines? It seems to work fine on my end, testing by mashing at various cursor positions with a virtual Cyrillic keyboard.

diff --git a/src/lib.rs b/src/lib.rs
index f9d94dd..3a5c17e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -441,15 +441,15 @@ fn keyboard(
 
             match input.logical_key {
                 Key::Space => {
-                    text_input.0.insert(pos, ' ');
+                    let byte_pos = byte_pos(&text_input.0, pos);
+                    text_input.0.insert(byte_pos, ' ');
                     cursor_pos.0 += 1;
 
                     cursor_timer.should_reset = true;
                 }
                 Key::Character(ref s) => {
-                    let before = text_input.0.chars().take(cursor_pos.0);
-                    let after = text_input.0.chars().skip(cursor_pos.0);
-                    text_input.0 = before.chain(s.chars()).chain(after).collect();
+                    let byte_pos = byte_pos(&text_input.0, pos);
+                    text_input.0.insert_str(byte_pos, s.as_str());
 
                     cursor_pos.0 += 1;
 
@@ -857,6 +857,14 @@ fn remove_char_at(input: &str, index: usize) -> String {
         .collect()
 }
 
+fn byte_pos(input: &str, char_pos: usize) -> usize {
+    let mut char_indices = input.char_indices();
+    char_indices
+        .nth(char_pos)
+        .map(|(pos, _)| pos)
+        .unwrap_or(input.len())
+}
+
 fn masked_value(value: &str, mask: Option<char>) -> String {
     mask.map_or_else(
         || value.to_string(),

[ilotterytea]

Thank you for the suggestion! I tested the solution you provided, and it works perfectly. 👍

[rparrett]

Great, thanks!

[rparrett]

Published in v0.9.2