feat(gpui): introduce ListState::remeasure

dino created 1 week ago

Introduce a new method `ListState::remeasure` to allow clients to
invalidate cached measurements without changing the scroll position.
This is useful when item heights may have changed (e.g., font size
changes) but the number and identity of items remains the same.

Change summary

crates/gpui/src/elements/list.rs      | 16 ++++++++++++++++
crates/settings_ui/src/settings_ui.rs |  2 +-
2 files changed, 17 insertions(+), 1 deletion(-)

Detailed changes

crates/gpui/src/elements/list.rs

@@ -254,6 +254,22 @@ impl ListState {
         self.splice(0..old_count, element_count);
     }
 
+    /// Remeasure all items without changing scroll position.
+    ///
+    /// Use this when item heights may have changed (e.g., font size changes)
+    /// but the number and identity of items remains the same.
+    pub fn remeasure(&self) {
+        let state = &mut *self.0.borrow_mut();
+        let items = state.items.clone();
+        state.measuring_behavior.reset();
+
+        let new_items = items.cursor::<Count>(()).map(|item| ListItem::Unmeasured {
+            focus_handle: item.focus_handle(),
+        });
+
+        state.items = SumTree::from_iter(new_items, ());
+    }
+
     /// The number of items in this list.
     pub fn item_count(&self) -> usize {
         self.0.borrow().items.summary().count

crates/settings_ui/src/settings_ui.rs

@@ -1389,8 +1389,8 @@ impl SettingsWindow {
             // size.
             let new_ui_font_size = ThemeSettings::get_global(cx).ui_font_size(cx);
             if new_ui_font_size != ui_font_size {
+                this.list_state.remeasure();
                 ui_font_size = new_ui_font_size;
-                this.list_state.clone().measure_all();
             }
 
             cx.notify();