macOS set_ime_position fixes (#2180)

* Use NSView's inputContext instead of creating our own

This means that `set_ime_position` now properly invalidates the character coordinates.

* Make `set_ime_position` robust against moving windows

CHANGELOG.md

@@ -8,6 +8,7 @@ And please only add new entries to the top of this list, right below the `# Unre
 
 # Unreleased
 
+- macOS: Remove the need to call `set_ime_position` after moving the window.
 - Added `Window::is_visible`.
 - Added `Window::is_resizable`.
 - Added `Window::is_decorated`.

src/platform_impl/macos/util/mod.rs

@@ -147,12 +147,6 @@ pub unsafe fn superclass(this: &Object) -> &Class {
     &*superclass
 }
 
-pub unsafe fn create_input_context(view: id) -> IdRef {
-    let input_context: id = msg_send![class!(NSTextInputContext), alloc];
-    let input_context: id = msg_send![input_context, initWithClient: view];
-    IdRef::new(input_context)
-}
-
 #[allow(dead_code)]
 pub unsafe fn open_emoji_picker() {
     let () = msg_send![NSApp(), orderFrontCharacterPalette: nil];

src/platform_impl/macos/view.rs

@@ -53,7 +53,8 @@ impl Default for CursorState {
 pub(super) struct ViewState {
     ns_window: id,
     pub cursor_state: Arc<Mutex<CursorState>>,
-    ime_spot: Option<(f64, f64)>,
+    /// The position of the candidate window.
+    ime_position: LogicalPosition<f64>,
     raw_characters: Option<String>,
     pub(super) modifiers: ModifiersState,
     tracking_rect: Option<NSInteger>,
@@ -71,7 +72,8 @@ pub fn new_view(ns_window: id) -> (IdRef, Weak<Mutex<CursorState>>) {
     let state = ViewState {
         ns_window,
         cursor_state,
-        ime_spot: None,
+        // By default, open the candidate window in the top left corner
+        ime_position: LogicalPosition::new(0.0, 0.0),
         raw_characters: None,
         modifiers: Default::default(),
         tracking_rect: None,
@@ -87,14 +89,11 @@ pub fn new_view(ns_window: id) -> (IdRef, Weak<Mutex<CursorState>>) {
     }
 }
 
-pub unsafe fn set_ime_position(ns_view: id, input_context: id, x: f64, y: f64) {
+pub unsafe fn set_ime_position(ns_view: id, position: LogicalPosition<f64>) {
     let state_ptr: *mut c_void = *(*ns_view).get_mut_ivar("winitState");
     let state = &mut *(state_ptr as *mut ViewState);
-    let content_rect =
-        NSWindow::contentRectForFrameRect_(state.ns_window, NSWindow::frame(state.ns_window));
-    let base_x = content_rect.origin.x as f64;
-    let base_y = (content_rect.origin.y + content_rect.size.height) as f64;
-    state.ime_spot = Some((base_x + x, base_y - y));
+    state.ime_position = position;
+    let input_context: id = msg_send![ns_view, inputContext];
     let _: () = msg_send![input_context, invalidateCharacterCoordinates];
 }
 
@@ -480,15 +479,16 @@ extern "C" fn first_rect_for_character_range(
     unsafe {
         let state_ptr: *mut c_void = *this.get_ivar("winitState");
         let state = &mut *(state_ptr as *mut ViewState);
-        let (x, y) = state.ime_spot.unwrap_or_else(|| {
-            let content_rect = NSWindow::contentRectForFrameRect_(
-                state.ns_window,
-                NSWindow::frame(state.ns_window),
-            );
-            let x = content_rect.origin.x;
-            let y = util::bottom_left_to_top_left(content_rect);
-            (x, y)
-        });
+        let content_rect =
+            NSWindow::contentRectForFrameRect_(state.ns_window, NSWindow::frame(state.ns_window));
+        let base_x = content_rect.origin.x as f64;
+        let base_y = (content_rect.origin.y + content_rect.size.height) as f64;
+        let x = base_x + state.ime_position.x;
+        let y = base_y - state.ime_position.y;
+        // This is not ideal: We _should_ return a different position based on
+        // the currently selected character (which varies depending on the type
+        // and size of the character), but in the current `winit` API there is
+        // no way to express this. Same goes for the `NSSize`.
         NSRect::new(NSPoint::new(x as _, y as _), NSSize::new(0.0, 0.0))
     }
 }

src/platform_impl/macos/window.rs

@@ -363,7 +363,6 @@ impl Drop for SharedStateMutexGuard<'_> {
 pub struct UnownedWindow {
     pub ns_window: IdRef, // never changes
     pub ns_view: IdRef,   // never changes
-    input_context: IdRef, // never changes
     shared_state: Arc<Mutex<SharedState>>,
     decorations: AtomicBool,
     cursor_state: Weak<Mutex<CursorState>>,
@@ -398,8 +397,6 @@ impl UnownedWindow {
             ns_window.setInitialFirstResponder_(*ns_view);
         }
 
-        let input_context = unsafe { util::create_input_context(*ns_view) };
-
         let scale_factor = unsafe { NSWindow::backingScaleFactor(*ns_window) as f64 };
 
         unsafe {
@@ -442,7 +439,6 @@ impl UnownedWindow {
         let window = Arc::new(UnownedWindow {
             ns_view,
             ns_window,
-            input_context,
             shared_state: Arc::new(Mutex::new(win_attribs.into())),
             decorations: AtomicBool::new(decorations),
             cursor_state,
@@ -1046,14 +1042,7 @@ impl UnownedWindow {
     pub fn set_ime_position(&self, spot: Position) {
         let scale_factor = self.scale_factor();
         let logical_spot = spot.to_logical(scale_factor);
-        unsafe {
-            view::set_ime_position(
-                *self.ns_view,
-                *self.input_context,
-                logical_spot.x,
-                logical_spot.y,
-            );
-        }
+        unsafe { view::set_ime_position(*self.ns_view, logical_spot) };
     }
 
     #[inline]