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cmux-tui: avoid no-op deletion redraws #10984

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Merged
lawrencecchen merged 3 commits into from
Aug 27, 2026
Merged

cmux-tui: avoid no-op deletion redraws #10984

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bc01c2a
test(tui): report no-op deletions as unchanged
lawrencecchen Aug 27, 2026
f943f03
fix(tui): avoid redraws for no-op deletions
lawrencecchen Aug 27, 2026
91b73f6
test(tui): exercise forward deletion at buffer start
lawrencecchen Aug 27, 2026
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107 changes: 75 additions & 32 deletions cmux-tui/crates/cmux-tui/src/ui/input.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -76,16 +76,21 @@ impl TextInput {
InputEvent::None
}
KeyCode::Backspace if key.modifiers.contains(KeyModifiers::ALT) => {
self.delete_word_left();
InputEvent::Changed
if self.delete_word_left() { InputEvent::Changed } else { InputEvent::None }
}
KeyCode::Backspace => {
self.delete_left();
InputEvent::Changed
if self.delete_left() {
InputEvent::Changed
} else {
InputEvent::None
}
}
KeyCode::Delete => {
self.delete_right();
InputEvent::Changed
if self.delete_right() {
InputEvent::Changed
} else {
InputEvent::None
}
}
KeyCode::Char(c) if key.modifiers.contains(KeyModifiers::CONTROL) => {
self.handle_control(c)
Expand Down Expand Up @@ -155,24 +160,23 @@ impl TextInput {
'a' => self.move_start(),
'e' => self.move_end(),
'd' => {
self.delete_right();
return InputEvent::Changed;
return if self.delete_right() { InputEvent::Changed } else { InputEvent::None };
}
'w' => {
self.delete_word_left();
return InputEvent::Changed;
return if self.delete_word_left() {
InputEvent::Changed
} else {
InputEvent::None
};
}
'k' => {
self.kill_end();
return InputEvent::Changed;
return if self.kill_end() { InputEvent::Changed } else { InputEvent::None };
}
'u' => {
self.kill_start();
return InputEvent::Changed;
return if self.kill_start() { InputEvent::Changed } else { InputEvent::None };
}
'c' => {
self.clear();
return InputEvent::Changed;
return if self.clear() { InputEvent::Changed } else { InputEvent::None };
}
_ => {}
}
Expand All @@ -184,8 +188,11 @@ impl TextInput {
'b' => self.move_word_left(),
'f' => self.move_word_right(),
'd' => {
self.delete_word_right();
return InputEvent::Changed;
return if self.delete_word_right() {
InputEvent::Changed
} else {
InputEvent::None
};
}
_ => {}
}
Expand Down Expand Up @@ -222,41 +229,42 @@ impl TextInput {
self.cursor = self.word_right(self.cursor);
}

fn delete_left(&mut self) {
fn delete_left(&mut self) -> bool {
let start = self.prev_boundary(self.cursor);
self.delete_range(start, self.cursor);
self.delete_range(start, self.cursor)
}

fn delete_right(&mut self) {
fn delete_right(&mut self) -> bool {
let end = self.next_boundary(self.cursor);
self.delete_range(self.cursor, end);
self.delete_range(self.cursor, end)
}

fn delete_word_left(&mut self) {
fn delete_word_left(&mut self) -> bool {
let start = self.word_left(self.cursor);
self.delete_range(start, self.cursor);
self.delete_range(start, self.cursor)
}

fn delete_word_right(&mut self) {
fn delete_word_right(&mut self) -> bool {
let end = self.word_right(self.cursor);
self.delete_range(self.cursor, end);
self.delete_range(self.cursor, end)
}

fn kill_end(&mut self) {
self.delete_range(self.cursor, self.buffer.len());
fn kill_end(&mut self) -> bool {
self.delete_range(self.cursor, self.buffer.len())
}

fn kill_start(&mut self) {
self.delete_range(0, self.cursor);
fn kill_start(&mut self) -> bool {
self.delete_range(0, self.cursor)
}

fn delete_range(&mut self, start: usize, end: usize) {
fn delete_range(&mut self, start: usize, end: usize) -> bool {
if start >= end {
return;
return false;
}
self.buffer.replace_range(start..end, "");
self.cursor = start;
self.scroll = self.scroll.min(self.cursor);
true
}

fn word_left(&self, from: usize) -> usize {
Expand Down Expand Up @@ -438,6 +446,41 @@ mod tests {
assert_eq!(input.cursor, 3);
}

#[test]
fn deletion_reports_changed_only_when_text_was_removed() {
let no_op_keys = [
key(KeyCode::Backspace, KeyModifiers::NONE),
key(KeyCode::Delete, KeyModifiers::NONE),
key(KeyCode::Backspace, KeyModifiers::ALT),
key(KeyCode::Char('d'), KeyModifiers::CONTROL),
key(KeyCode::Char('w'), KeyModifiers::CONTROL),
key(KeyCode::Char('d'), KeyModifiers::ALT),
key(KeyCode::Char('k'), KeyModifiers::CONTROL),
key(KeyCode::Char('u'), KeyModifiers::CONTROL),
key(KeyCode::Char('c'), KeyModifiers::CONTROL),
];
for key in no_op_keys {
let mut input = text_input("");
assert_eq!(input.handle_key(&key), InputEvent::None, "{key:?}");
}

let mut input = text_input("x");
input.cursor = 1;
assert_eq!(
input.handle_key(&key(KeyCode::Backspace, KeyModifiers::NONE)),
InputEvent::Changed
);
assert!(input.buffer.is_empty());

let mut input = text_input("x");
input.cursor = 0;
assert_eq!(
input.handle_key(&key(KeyCode::Delete, KeyModifiers::NONE)),
InputEvent::Changed
);
assert!(input.buffer.is_empty());
}

#[test]
fn utf8_safe_movement_and_deletion() {
let mut input = text_input("héllo wörld");
Expand Down
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