Cherry-pick char_index_for_point fix to v0.172.x (#24286)

Cole Miller , Mikayla Maki , Louis Brunner , and ben created

Manual cherry-pick of #23989 

Release Notes:

- Fixed a bug where Zed could crash with certain input sources on macOS

Co-authored-by: Mikayla Maki <mikayla@zed.dev>
Co-authored-by: Louis Brunner <louis.brunner.fr@gmail.com>
Co-authored-by: ben <ben@zed.dev>

Change summary

crates/editor/src/editor.rs                  |  32 +++
crates/editor/src/element.rs                 | 159 ++++++++-------------
crates/editor/src/mouse_context_menu.rs      |   3 
crates/gpui/examples/input.rs                |  14 +
crates/gpui/src/geometry.rs                  |  31 ++++
crates/gpui/src/input.rs                     |  19 ++
crates/gpui/src/platform.rs                  |  18 ++
crates/gpui/src/platform/mac/window.rs       |  53 +++++-
crates/terminal_view/src/terminal_element.rs |   9 +
9 files changed, 218 insertions(+), 120 deletions(-)

Detailed changes

crates/editor/src/editor.rs 🔗

@@ -63,10 +63,10 @@ pub use editor_settings::{
     CurrentLineHighlight, EditorSettings, ScrollBeyondLastLine, SearchSettings, ShowScrollbar,
 };
 pub use editor_settings_controls::*;
-use element::LineWithInvisibles;
 pub use element::{
     CursorLayout, EditorElement, HighlightedRange, HighlightedRangeLine, PointForPosition,
 };
+use element::{LineWithInvisibles, PositionMap};
 use futures::{future, FutureExt};
 use fuzzy::StringMatchCandidate;
 use zed_predict_onboarding::ZedPredictModal;
@@ -723,6 +723,7 @@ pub struct Editor {
         >,
     >,
     last_bounds: Option<Bounds<Pixels>>,
+    last_position_map: Option<Rc<PositionMap>>,
     expect_bounds_change: Option<Bounds<Pixels>>,
     tasks: BTreeMap<(BufferId, BufferRow), RunnableTasks>,
     tasks_update_task: Option<Task<()>>,
@@ -1382,6 +1383,7 @@ impl Editor {
             gutter_hovered: false,
             pixel_position_of_newest_cursor: None,
             last_bounds: None,
+            last_position_map: None,
             expect_bounds_change: None,
             gutter_dimensions: GutterDimensions::default(),
             style: None,
@@ -14095,7 +14097,7 @@ impl Editor {
             .and_then(|item| item.to_any().downcast_ref::<T>())
     }
 
-    fn character_size(&self, window: &mut Window) -> gpui::Point<Pixels> {
+    fn character_size(&self, window: &mut Window) -> gpui::Size<Pixels> {
         let text_layout_details = self.text_layout_details(window);
         let style = &text_layout_details.editor_style;
         let font_id = window.text_system().resolve_font(&style.text.font());
@@ -14109,7 +14111,7 @@ impl Editor {
             .size
             .width;
 
-        gpui::Point::new(em_width, line_height)
+        gpui::Size::new(em_width, line_height)
     }
 }
 
@@ -15610,9 +15612,9 @@ impl EntityInputHandler for Editor {
         cx: &mut Context<Self>,
     ) -> Option<gpui::Bounds<Pixels>> {
         let text_layout_details = self.text_layout_details(window);
-        let gpui::Point {
-            x: em_width,
-            y: line_height,
+        let gpui::Size {
+            width: em_width,
+            height: line_height,
         } = self.character_size(window);
 
         let snapshot = self.snapshot(window, cx);
@@ -15630,6 +15632,24 @@ impl EntityInputHandler for Editor {
             size: size(em_width, line_height),
         })
     }
+
+    fn character_index_for_point(
+        &mut self,
+        point: gpui::Point<Pixels>,
+        _window: &mut Window,
+        _cx: &mut Context<Self>,
+    ) -> Option<usize> {
+        let position_map = self.last_position_map.as_ref()?;
+        if !position_map.text_hitbox.contains(&point) {
+            return None;
+        }
+        let display_point = position_map.point_for_position(point).previous_valid;
+        let anchor = position_map
+            .snapshot
+            .display_point_to_anchor(display_point, Bias::Left);
+        let utf16_offset = anchor.to_offset_utf16(&position_map.snapshot.buffer_snapshot);
+        Some(utf16_offset.0)
+    }
 }
 
 trait SelectionExt {

crates/editor/src/element.rs 🔗

@@ -502,7 +502,6 @@ impl EditorElement {
         let position_map = layout.position_map.clone();
         window.on_key_event({
             let editor = self.editor.clone();
-            let text_hitbox = layout.text_hitbox.clone();
             move |event: &ModifiersChangedEvent, phase, window, cx| {
                 if phase != DispatchPhase::Bubble {
                     return;
@@ -511,7 +510,7 @@ impl EditorElement {
                     if editor.hover_state.focused(window, cx) {
                         return;
                     }
-                    Self::modifiers_changed(editor, event, &position_map, &text_hitbox, window, cx)
+                    Self::modifiers_changed(editor, event, &position_map, window, cx)
                 })
             }
         });
@@ -521,17 +520,16 @@ impl EditorElement {
         editor: &mut Editor,
         event: &ModifiersChangedEvent,
         position_map: &PositionMap,
-        text_hitbox: &Hitbox,
         window: &mut Window,
         cx: &mut Context<Editor>,
     ) {
         let mouse_position = window.mouse_position();
-        if !text_hitbox.is_hovered(window) {
+        if !position_map.text_hitbox.is_hovered(window) {
             return;
         }
 
         editor.update_hovered_link(
-            position_map.point_for_position(text_hitbox.bounds, mouse_position),
+            position_map.point_for_position(mouse_position),
             &position_map.snapshot,
             event.modifiers,
             window,
@@ -539,14 +537,11 @@ impl EditorElement {
         )
     }
 
-    #[allow(clippy::too_many_arguments)]
     fn mouse_left_down(
         editor: &mut Editor,
         event: &MouseDownEvent,
         hovered_hunk: Option<Range<Anchor>>,
         position_map: &PositionMap,
-        text_hitbox: &Hitbox,
-        gutter_hitbox: &Hitbox,
         line_numbers: &HashMap<MultiBufferRow, LineNumberLayout>,
         window: &mut Window,
         cx: &mut Context<Editor>,
@@ -555,6 +550,8 @@ impl EditorElement {
             return;
         }
 
+        let text_hitbox = &position_map.text_hitbox;
+        let gutter_hitbox = &position_map.gutter_hitbox;
         let mut click_count = event.click_count;
         let mut modifiers = event.modifiers;
 
@@ -611,8 +608,7 @@ impl EditorElement {
             }
         }
 
-        let point_for_position =
-            position_map.point_for_position(text_hitbox.bounds, event.position);
+        let point_for_position = position_map.point_for_position(event.position);
         let position = point_for_position.previous_valid;
         if modifiers.shift && modifiers.alt {
             editor.select(
@@ -687,15 +683,13 @@ impl EditorElement {
         editor: &mut Editor,
         event: &MouseDownEvent,
         position_map: &PositionMap,
-        text_hitbox: &Hitbox,
         window: &mut Window,
         cx: &mut Context<Editor>,
     ) {
-        if !text_hitbox.is_hovered(window) {
+        if !position_map.text_hitbox.is_hovered(window) {
             return;
         }
-        let point_for_position =
-            position_map.point_for_position(text_hitbox.bounds, event.position);
+        let point_for_position = position_map.point_for_position(event.position);
         mouse_context_menu::deploy_context_menu(
             editor,
             Some(event.position),
@@ -710,16 +704,14 @@ impl EditorElement {
         editor: &mut Editor,
         event: &MouseDownEvent,
         position_map: &PositionMap,
-        text_hitbox: &Hitbox,
         window: &mut Window,
         cx: &mut Context<Editor>,
     ) {
-        if !text_hitbox.is_hovered(window) || window.default_prevented() {
+        if !position_map.text_hitbox.is_hovered(window) || window.default_prevented() {
             return;
         }
 
-        let point_for_position =
-            position_map.point_for_position(text_hitbox.bounds, event.position);
+        let point_for_position = position_map.point_for_position(event.position);
         let position = point_for_position.previous_valid;
 
         editor.select(
@@ -737,10 +729,10 @@ impl EditorElement {
         editor: &mut Editor,
         event: &MouseUpEvent,
         position_map: &PositionMap,
-        text_hitbox: &Hitbox,
         window: &mut Window,
         cx: &mut Context<Editor>,
     ) {
+        let text_hitbox = &position_map.text_hitbox;
         let end_selection = editor.has_pending_selection();
         let pending_nonempty_selections = editor.has_pending_nonempty_selection();
 
@@ -755,7 +747,7 @@ impl EditorElement {
         };
 
         if !pending_nonempty_selections && multi_cursor_modifier && text_hitbox.is_hovered(window) {
-            let point = position_map.point_for_position(text_hitbox.bounds, event.position);
+            let point = position_map.point_for_position(event.position);
             editor.handle_click_hovered_link(point, event.modifiers, window, cx);
 
             cx.stop_propagation();
@@ -771,8 +763,7 @@ impl EditorElement {
             #[cfg(any(target_os = "linux", target_os = "freebsd"))]
             if EditorSettings::get_global(cx).middle_click_paste {
                 if let Some(text) = cx.read_from_primary().and_then(|item| item.text()) {
-                    let point_for_position =
-                        position_map.point_for_position(text_hitbox.bounds, event.position);
+                    let point_for_position = position_map.point_for_position(event.position);
                     let position = point_for_position.previous_valid;
 
                     editor.select(
@@ -795,7 +786,6 @@ impl EditorElement {
         editor: &mut Editor,
         event: &MouseMoveEvent,
         position_map: &PositionMap,
-        text_bounds: Bounds<Pixels>,
         window: &mut Window,
         cx: &mut Context<Editor>,
     ) {
@@ -803,7 +793,8 @@ impl EditorElement {
             return;
         }
 
-        let point_for_position = position_map.point_for_position(text_bounds, event.position);
+        let text_bounds = position_map.text_hitbox.bounds;
+        let point_for_position = position_map.point_for_position(event.position);
         let mut scroll_delta = gpui::Point::<f32>::default();
         let vertical_margin = position_map.line_height.min(text_bounds.size.height / 3.0);
         let top = text_bounds.origin.y + vertical_margin;
@@ -855,19 +846,18 @@ impl EditorElement {
         editor: &mut Editor,
         event: &MouseMoveEvent,
         position_map: &PositionMap,
-        text_hitbox: &Hitbox,
-        gutter_hitbox: &Hitbox,
         window: &mut Window,
         cx: &mut Context<Editor>,
     ) {
+        let text_hitbox = &position_map.text_hitbox;
+        let gutter_hitbox = &position_map.gutter_hitbox;
         let modifiers = event.modifiers;
         let gutter_hovered = gutter_hitbox.is_hovered(window);
         editor.set_gutter_hovered(gutter_hovered, cx);
 
         // Don't trigger hover popover if mouse is hovering over context menu
         if text_hitbox.is_hovered(window) {
-            let point_for_position =
-                position_map.point_for_position(text_hitbox.bounds, event.position);
+            let point_for_position = position_map.point_for_position(event.position);
 
             editor.update_hovered_link(
                 point_for_position,
@@ -3789,8 +3779,7 @@ impl EditorElement {
         window: &mut Window,
         cx: &mut App,
     ) -> Vec<AnyElement> {
-        let point_for_position =
-            position_map.point_for_position(text_hitbox.bounds, window.mouse_position());
+        let point_for_position = position_map.point_for_position(window.mouse_position());
 
         let mut controls = vec![];
 
@@ -3927,7 +3916,10 @@ impl EditorElement {
             let scroll_top = layout.position_map.snapshot.scroll_position().y;
             let gutter_bg = cx.theme().colors().editor_gutter_background;
             window.paint_quad(fill(layout.gutter_hitbox.bounds, gutter_bg));
-            window.paint_quad(fill(layout.text_hitbox.bounds, self.style.background));
+            window.paint_quad(fill(
+                layout.position_map.text_hitbox.bounds,
+                self.style.background,
+            ));
 
             if let EditorMode::Full = layout.mode {
                 let mut active_rows = layout.active_rows.iter().peekable();
@@ -3952,8 +3944,8 @@ impl EditorElement {
                                     end: layout.gutter_hitbox.right(),
                                 }),
                                 CurrentLineHighlight::Line => Some(Range {
-                                    start: layout.text_hitbox.bounds.left(),
-                                    end: layout.text_hitbox.bounds.right(),
+                                    start: layout.position_map.text_hitbox.bounds.left(),
+                                    end: layout.position_map.text_hitbox.bounds.right(),
                                 }),
                                 CurrentLineHighlight::All => Some(Range {
                                     start: layout.hitbox.left(),
@@ -4027,7 +4019,7 @@ impl EditorElement {
                     layout.position_map.snapshot.scroll_position().x * layout.position_map.em_width;
 
                 for (wrap_position, active) in layout.wrap_guides.iter() {
-                    let x = (layout.text_hitbox.origin.x
+                    let x = (layout.position_map.text_hitbox.origin.x
                         + *wrap_position
                         + layout.position_map.em_width / 2.)
                         - scroll_left;
@@ -4039,7 +4031,7 @@ impl EditorElement {
                             || scrollbar_y.as_ref().map_or(false, |sy| sy.visible)
                     };
 
-                    if x < layout.text_hitbox.origin.x
+                    if x < layout.position_map.text_hitbox.origin.x
                         || (show_scrollbars && x > self.scrollbar_left(&layout.hitbox.bounds))
                     {
                         continue;
@@ -4052,8 +4044,8 @@ impl EditorElement {
                     };
                     window.paint_quad(fill(
                         Bounds {
-                            origin: point(x, layout.text_hitbox.origin.y),
-                            size: size(px(1.), layout.text_hitbox.size.height),
+                            origin: point(x, layout.position_map.text_hitbox.origin.y),
+                            size: size(px(1.), layout.position_map.text_hitbox.size.height),
                         },
                         color,
                     ));
@@ -4428,7 +4420,7 @@ impl EditorElement {
     fn paint_text(&mut self, layout: &mut EditorLayout, window: &mut Window, cx: &mut App) {
         window.with_content_mask(
             Some(ContentMask {
-                bounds: layout.text_hitbox.bounds,
+                bounds: layout.position_map.text_hitbox.bounds,
             }),
             |window| {
                 let cursor_style = if self
@@ -4442,7 +4434,7 @@ impl EditorElement {
                 } else {
                     CursorStyle::IBeam
                 };
-                window.set_cursor_style(cursor_style, &layout.text_hitbox);
+                window.set_cursor_style(cursor_style, &layout.position_map.text_hitbox);
 
                 let invisible_display_ranges = self.paint_highlights(layout, window);
                 self.paint_lines(&invisible_display_ranges, layout, window, cx);
@@ -4464,7 +4456,7 @@ impl EditorElement {
         layout: &mut EditorLayout,
         window: &mut Window,
     ) -> SmallVec<[Range<DisplayPoint>; 32]> {
-        window.paint_layer(layout.text_hitbox.bounds, |window| {
+        window.paint_layer(layout.position_map.text_hitbox.bounds, |window| {
             let mut invisible_display_ranges = SmallVec::<[Range<DisplayPoint>; 32]>::new();
             let line_end_overshoot = 0.15 * layout.position_map.line_height;
             for (range, color) in &layout.highlighted_ranges {
@@ -4543,7 +4535,7 @@ impl EditorElement {
         // A softer than perfect black
         let redaction_color = gpui::rgb(0x0e1111);
 
-        window.paint_layer(layout.text_hitbox.bounds, |window| {
+        window.paint_layer(layout.position_map.text_hitbox.bounds, |window| {
             for range in layout.redacted_ranges.iter() {
                 self.paint_highlighted_range(
                     range.clone(),
@@ -5117,13 +5109,13 @@ impl EditorElement {
                     .collect(),
             };
 
-            highlighted_range.paint(layout.text_hitbox.bounds, window);
+            highlighted_range.paint(layout.position_map.text_hitbox.bounds, window);
         }
     }
 
     fn paint_inline_blame(&mut self, layout: &mut EditorLayout, window: &mut Window, cx: &mut App) {
         if let Some(mut inline_blame) = layout.inline_blame.take() {
-            window.paint_layer(layout.text_hitbox.bounds, |window| {
+            window.paint_layer(layout.position_map.text_hitbox.bounds, |window| {
                 inline_blame.paint(window, cx);
             })
         }
@@ -5242,8 +5234,6 @@ impl EditorElement {
         window.on_mouse_event({
             let position_map = layout.position_map.clone();
             let editor = self.editor.clone();
-            let text_hitbox = layout.text_hitbox.clone();
-            let gutter_hitbox = layout.gutter_hitbox.clone();
             let multi_buffer_range =
                 layout
                     .display_hunks
@@ -5275,32 +5265,16 @@ impl EditorElement {
                                 event,
                                 multi_buffer_range.clone(),
                                 &position_map,
-                                &text_hitbox,
-                                &gutter_hitbox,
                                 line_numbers.as_ref(),
                                 window,
                                 cx,
                             );
                         }),
                         MouseButton::Right => editor.update(cx, |editor, cx| {
-                            Self::mouse_right_down(
-                                editor,
-                                event,
-                                &position_map,
-                                &text_hitbox,
-                                window,
-                                cx,
-                            );
+                            Self::mouse_right_down(editor, event, &position_map, window, cx);
                         }),
                         MouseButton::Middle => editor.update(cx, |editor, cx| {
-                            Self::mouse_middle_down(
-                                editor,
-                                event,
-                                &position_map,
-                                &text_hitbox,
-                                window,
-                                cx,
-                            );
+                            Self::mouse_middle_down(editor, event, &position_map, window, cx);
                         }),
                         _ => {}
                     };
@@ -5311,12 +5285,11 @@ impl EditorElement {
         window.on_mouse_event({
             let editor = self.editor.clone();
             let position_map = layout.position_map.clone();
-            let text_hitbox = layout.text_hitbox.clone();
 
             move |event: &MouseUpEvent, phase, window, cx| {
                 if phase == DispatchPhase::Bubble {
                     editor.update(cx, |editor, cx| {
-                        Self::mouse_up(editor, event, &position_map, &text_hitbox, window, cx)
+                        Self::mouse_up(editor, event, &position_map, window, cx)
                     });
                 }
             }
@@ -5324,8 +5297,6 @@ impl EditorElement {
         window.on_mouse_event({
             let position_map = layout.position_map.clone();
             let editor = self.editor.clone();
-            let text_hitbox = layout.text_hitbox.clone();
-            let gutter_hitbox = layout.gutter_hitbox.clone();
 
             move |event: &MouseMoveEvent, phase, window, cx| {
                 if phase == DispatchPhase::Bubble {
@@ -5336,25 +5307,10 @@ impl EditorElement {
                         if event.pressed_button == Some(MouseButton::Left)
                             || event.pressed_button == Some(MouseButton::Middle)
                         {
-                            Self::mouse_dragged(
-                                editor,
-                                event,
-                                &position_map,
-                                text_hitbox.bounds,
-                                window,
-                                cx,
-                            )
+                            Self::mouse_dragged(editor, event, &position_map, window, cx)
                         }
 
-                        Self::mouse_moved(
-                            editor,
-                            event,
-                            &position_map,
-                            &text_hitbox,
-                            &gutter_hitbox,
-                            window,
-                            cx,
-                        )
+                        Self::mouse_moved(editor, event, &position_map, window, cx)
                     });
                 }
             }
@@ -7159,6 +7115,12 @@ impl Element for EditorElement {
                         em_width,
                         em_advance,
                         snapshot,
+                        gutter_hitbox: gutter_hitbox.clone(),
+                        text_hitbox: text_hitbox.clone(),
+                    });
+
+                    self.editor.update(cx, |editor, _| {
+                        editor.last_position_map = Some(position_map.clone())
                     });
 
                     let hunk_controls = self.layout_diff_hunk_controls(
@@ -7182,7 +7144,6 @@ impl Element for EditorElement {
                         wrap_guides,
                         indent_guides,
                         hitbox,
-                        text_hitbox,
                         gutter_hitbox,
                         display_hunks,
                         content_origin,
@@ -7354,7 +7315,6 @@ impl IntoElement for EditorElement {
 pub struct EditorLayout {
     position_map: Rc<PositionMap>,
     hitbox: Hitbox,
-    text_hitbox: Hitbox,
     gutter_hitbox: Hitbox,
     content_origin: gpui::Point<Pixels>,
     scrollbars_layout: AxisPair<Option<ScrollbarLayout>>,
@@ -7534,15 +7494,17 @@ struct CreaseTrailerLayout {
     bounds: Bounds<Pixels>,
 }
 
-struct PositionMap {
-    size: Size<Pixels>,
-    line_height: Pixels,
-    scroll_pixel_position: gpui::Point<Pixels>,
-    scroll_max: gpui::Point<f32>,
-    em_width: Pixels,
-    em_advance: Pixels,
-    line_layouts: Vec<LineWithInvisibles>,
-    snapshot: EditorSnapshot,
+pub(crate) struct PositionMap {
+    pub size: Size<Pixels>,
+    pub line_height: Pixels,
+    pub scroll_pixel_position: gpui::Point<Pixels>,
+    pub scroll_max: gpui::Point<f32>,
+    pub em_width: Pixels,
+    pub em_advance: Pixels,
+    pub line_layouts: Vec<LineWithInvisibles>,
+    pub snapshot: EditorSnapshot,
+    pub text_hitbox: Hitbox,
+    pub gutter_hitbox: Hitbox,
 }
 
 #[derive(Debug, Copy, Clone)]
@@ -7564,11 +7526,8 @@ impl PointForPosition {
 }
 
 impl PositionMap {
-    fn point_for_position(
-        &self,
-        text_bounds: Bounds<Pixels>,
-        position: gpui::Point<Pixels>,
-    ) -> PointForPosition {
+    pub(crate) fn point_for_position(&self, position: gpui::Point<Pixels>) -> PointForPosition {
+        let text_bounds = self.text_hitbox.bounds;
         let scroll_position = self.snapshot.scroll_position();
         let position = position - text_bounds.origin;
         let y = position.y.max(px(0.)).min(self.size.height);

crates/editor/src/mouse_context_menu.rs 🔗

@@ -229,9 +229,10 @@ pub fn deploy_context_menu(
             cx,
         ),
         None => {
+            let character_size = editor.character_size(window);
             let menu_position = MenuPosition::PinnedToEditor {
                 source: source_anchor,
-                offset: editor.character_size(window),
+                offset: gpui::point(character_size.width, character_size.height),
             };
             Some(MouseContextMenu::new(
                 menu_position,

crates/gpui/examples/input.rs 🔗

@@ -364,6 +364,20 @@ impl EntityInputHandler for TextInput {
             ),
         ))
     }
+
+    fn character_index_for_point(
+        &mut self,
+        point: gpui::Point<Pixels>,
+        _window: &mut Window,
+        _cx: &mut Context<Self>,
+    ) -> Option<usize> {
+        let line_point = self.last_bounds?.localize(&point)?;
+        let last_layout = self.last_layout.as_ref()?;
+
+        assert_eq!(last_layout.text, self.content);
+        let utf8_index = last_layout.index_for_x(point.x - line_point.x)?;
+        Some(self.offset_to_utf16(utf8_index))
+    }
 }
 
 struct TextElement {

crates/gpui/src/geometry.rs 🔗

@@ -217,6 +217,19 @@ impl Point<Pixels> {
     }
 }
 
+impl<T> Point<T>
+where
+    T: Sub<T, Output = T> + Debug + Clone + Default,
+{
+    /// Get the position of this point, relative to the given origin
+    pub fn relative_to(&self, origin: &Point<T>) -> Point<T> {
+        point(
+            self.x.clone() - origin.x.clone(),
+            self.y.clone() - origin.y.clone(),
+        )
+    }
+}
+
 impl<T, Rhs> Mul<Rhs> for Point<T>
 where
     T: Mul<Rhs, Output = T> + Clone + Default + Debug,
@@ -376,6 +389,13 @@ pub struct Size<T: Clone + Default + Debug> {
     pub height: T,
 }
 
+impl<T: Clone + Default + Debug> Size<T> {
+    /// Create a new Size, a synonym for [`size`]
+    pub fn new(width: T, height: T) -> Self {
+        size(width, height)
+    }
+}
+
 /// Constructs a new `Size<T>` with the provided width and height.
 ///
 /// # Arguments
@@ -1456,6 +1476,17 @@ where
     }
 }
 
+impl<T> Bounds<T>
+where
+    T: Add<T, Output = T> + PartialOrd + Clone + Default + Debug + Sub<T, Output = T>,
+{
+    /// Convert a point to the coordinate space defined by this Bounds
+    pub fn localize(&self, point: &Point<T>) -> Option<Point<T>> {
+        self.contains(point)
+            .then(|| point.relative_to(&self.origin))
+    }
+}
+
 /// Checks if the bounds represent an empty area.
 ///
 /// # Returns

crates/gpui/src/input.rs 🔗

@@ -62,6 +62,14 @@ pub trait EntityInputHandler: 'static + Sized {
         window: &mut Window,
         cx: &mut Context<Self>,
     ) -> Option<Bounds<Pixels>>;
+
+    /// See [`InputHandler::character_index_for_point`] for details
+    fn character_index_for_point(
+        &mut self,
+        point: crate::Point<Pixels>,
+        window: &mut Window,
+        cx: &mut Context<Self>,
+    ) -> Option<usize>;
 }
 
 /// The canonical implementation of [`PlatformInputHandler`]. Call [`WindowContext::handle_input`]
@@ -159,4 +167,15 @@ impl<V: EntityInputHandler> InputHandler for ElementInputHandler<V> {
             view.bounds_for_range(range_utf16, self.element_bounds, window, cx)
         })
     }
+
+    fn character_index_for_point(
+        &mut self,
+        point: crate::Point<Pixels>,
+        window: &mut Window,
+        cx: &mut App,
+    ) -> Option<usize> {
+        self.view.update(cx, |view, cx| {
+            view.character_index_for_point(point, window, cx)
+        })
+    }
 }

crates/gpui/src/platform.rs 🔗

@@ -789,6 +789,14 @@ impl PlatformInputHandler {
             cx,
         )
     }
+
+    #[allow(unused)]
+    pub fn character_index_for_point(&mut self, point: Point<Pixels>) -> Option<usize> {
+        self.cx
+            .update(|window, cx| self.handler.character_index_for_point(point, window, cx))
+            .ok()
+            .flatten()
+    }
 }
 
 /// A struct representing a selection in a text buffer, in UTF16 characters.
@@ -879,6 +887,16 @@ pub trait InputHandler: 'static {
         cx: &mut App,
     ) -> Option<Bounds<Pixels>>;
 
+    /// Get the character offset for the given point in terms of UTF16 characters
+    ///
+    /// Corresponds to [characterIndexForPoint:](https://developer.apple.com/documentation/appkit/nstextinputclient/characterindex(for:))
+    fn character_index_for_point(
+        &mut self,
+        point: Point<Pixels>,
+        window: &mut Window,
+        cx: &mut App,
+    ) -> Option<usize>;
+
     /// Allows a given input context to opt into getting raw key repeats instead of
     /// sending these to the platform.
     /// TODO: Ideally we should be able to set ApplePressAndHoldEnabled in NSUserDefaults

crates/gpui/src/platform/mac/window.rs 🔗

@@ -17,8 +17,8 @@ use cocoa::{
     },
     base::{id, nil},
     foundation::{
-        NSArray, NSAutoreleasePool, NSDictionary, NSFastEnumeration, NSInteger, NSPoint, NSRect,
-        NSSize, NSString, NSUInteger,
+        NSArray, NSAutoreleasePool, NSDictionary, NSFastEnumeration, NSInteger, NSNotFound,
+        NSPoint, NSRect, NSSize, NSString, NSUInteger,
     },
 };
 use core_graphics::display::{CGDirectDisplayID, CGPoint, CGRect};
@@ -223,6 +223,11 @@ unsafe fn build_classes() {
             accepts_first_mouse as extern "C" fn(&Object, Sel, id) -> BOOL,
         );
 
+        decl.add_method(
+            sel!(characterIndexForPoint:),
+            character_index_for_point as extern "C" fn(&Object, Sel, NSPoint) -> u64,
+        );
+
         decl.register()
     };
 }
@@ -1683,17 +1688,7 @@ extern "C" fn first_rect_for_character_range(
     range: NSRange,
     _: id,
 ) -> NSRect {
-    let frame: NSRect = unsafe {
-        let state = get_window_state(this);
-        let lock = state.lock();
-        let mut frame = NSWindow::frame(lock.native_window);
-        let content_layout_rect: CGRect = msg_send![lock.native_window, contentLayoutRect];
-        let style_mask: NSWindowStyleMask = msg_send![lock.native_window, styleMask];
-        if !style_mask.contains(NSWindowStyleMask::NSFullSizeContentViewWindowMask) {
-            frame.origin.y -= frame.size.height - content_layout_rect.size.height;
-        }
-        frame
-    };
+    let frame = get_frame(this);
     with_input_handler(this, |input_handler| {
         input_handler.bounds_for_range(range.to_range()?)
     })
@@ -1714,6 +1709,20 @@ extern "C" fn first_rect_for_character_range(
     )
 }
 
+fn get_frame(this: &Object) -> NSRect {
+    unsafe {
+        let state = get_window_state(this);
+        let lock = state.lock();
+        let mut frame = NSWindow::frame(lock.native_window);
+        let content_layout_rect: CGRect = msg_send![lock.native_window, contentLayoutRect];
+        let style_mask: NSWindowStyleMask = msg_send![lock.native_window, styleMask];
+        if !style_mask.contains(NSWindowStyleMask::NSFullSizeContentViewWindowMask) {
+            frame.origin.y -= frame.size.height - content_layout_rect.size.height;
+        }
+        frame
+    }
+}
+
 extern "C" fn insert_text(this: &Object, _: Sel, text: id, replacement_range: NSRange) {
     unsafe {
         let is_attributed_string: BOOL =
@@ -1827,6 +1836,24 @@ extern "C" fn accepts_first_mouse(this: &Object, _: Sel, _: id) -> BOOL {
     YES
 }
 
+extern "C" fn character_index_for_point(this: &Object, _: Sel, position: NSPoint) -> u64 {
+    let position = screen_point_to_gpui_point(this, position);
+    with_input_handler(this, |input_handler| {
+        input_handler.character_index_for_point(position)
+    })
+    .flatten()
+    .map(|index| index as u64)
+    .unwrap_or(NSNotFound as u64)
+}
+
+fn screen_point_to_gpui_point(this: &Object, position: NSPoint) -> Point<Pixels> {
+    let frame = get_frame(this);
+    let window_x = position.x - frame.origin.x;
+    let window_y = frame.size.height - (position.y - frame.origin.y);
+    let position = point(px(window_x as f32), px(window_y as f32));
+    position
+}
+
 extern "C" fn dragging_entered(this: &Object, _: Sel, dragging_info: id) -> NSDragOperation {
     let window_state = unsafe { get_window_state(this) };
     let position = drag_event_position(&window_state, dragging_info);

crates/terminal_view/src/terminal_element.rs 🔗

@@ -1075,6 +1075,15 @@ impl InputHandler for TerminalInputHandler {
     fn apple_press_and_hold_enabled(&mut self) -> bool {
         false
     }
+
+    fn character_index_for_point(
+        &mut self,
+        _point: Point<Pixels>,
+        _window: &mut Window,
+        _cx: &mut App,
+    ) -> Option<usize> {
+        None
+    }
 }
 
 pub fn is_blank(cell: &IndexedCell) -> bool {