Make legacy ime visuals a runtime feature

crates/eframe/Cargo.toml

@@ -101,10 +101,6 @@ wgpu = ["wgpu_no_default_features", "egui-wgpu/default"]
 ## ```
 wgpu_no_default_features = ["dep:wgpu", "dep:egui-wgpu", "dep:pollster"]
 
-## Enable the new IME composition visuals on Windows. The legacy visuals remain
-## the default on Windows due to known issues with the new implementation.
-windows_new_ime_composition_visuals = ["egui/_override_legacy_ime_composition_visuals"]
-
 ## Enables compiling for x11.
 x11 = [
   "egui-winit/x11",
@@ -189,11 +185,6 @@ objc2-app-kit = { workspace = true, default-features = false, features = [
 
 # windows:
 [target.'cfg(any(target_os = "windows"))'.dependencies]
-egui = { workspace = true, default-features = false, features = [
-  "bytemuck",
-  "legacy_ime_composition_visuals",
-] }
-
 windows-sys = { workspace = true, features = [
   "Win32_Foundation",
   "Win32_System_Com",

crates/egui/Cargo.toml

@@ -44,21 +44,6 @@ color-hex = ["epaint/color-hex"]
 ## If you plan on specifying your own fonts you may disable this feature.
 default_fonts = ["epaint/default_fonts"]
 
-## The legacy IME composition visuals have several shortcomings. Most notably,
-## they are visually identical to text selection, making it impossible to tell
-## the two apart if there is no candidate window (e.g. when using a Korean IME).
-## In addition, the cursor is always shown at the end of the composition no
-## matter where the actual cursor is, which makes composing Chinese and Japanese
-## text confusing.
-##
-## However, the new composition visuals are not yet fully reliable either. For
-## example, on Windows, `winit` currently reports an incorrect cursor position
-## for Korean IMEs: the cursor should be at the end of the composition, but
-## `winit` reports it at the beginning. Therefore, we keep the legacy visuals
-## as an option for now and plan to remove them once the new visuals work
-## correctly across all supported platforms.
-legacy_ime_composition_visuals = []
-
 ## [`mint`](https://docs.rs/mint) enables interoperability with other math libraries such as [`glam`](https://docs.rs/glam) and [`nalgebra`](https://docs.rs/nalgebra).
 mint = ["epaint/mint"]
 
@@ -77,9 +62,6 @@ serde = ["dep:serde", "epaint/serde", "accesskit/serde"]
 ## Change Vertex layout to be compatible with unity
 unity = ["epaint/unity"]
 
-## Override and disable the legacy_ime_composition_visuals feature.
-_override_legacy_ime_composition_visuals = []
-
 ## Override and disable the unity feature
 ## This exists, so that when testing with --all-features, snapshots render correctly.
 _override_unity = ["epaint/_override_unity"]

crates/egui/src/style.rs

@@ -1204,6 +1204,24 @@ pub struct ImeComposition {
 
     /// Stroke used to underline those non-active segments.
     pub inactive_underline_stroke: Stroke,
+
+    /// If `true`, IME (Input Method Editor) composition (preedit) text is rendered
+    /// the legacy way: visually indistinguishable from a text selection, with the
+    /// cursor always shown at the end of the composition.
+    ///
+    /// If `false`, egui renders proper IME composition visuals: the cursor position
+    /// inside the composition is shown, and the active conversion segment is
+    /// highlighted (using the strokes configured above) distinctly from the rest of the
+    /// composition. This makes composing Chinese, Japanese and Korean text much
+    /// clearer.
+    ///
+    /// The legacy visuals have known shortcomings, but the new visuals are not yet
+    /// fully reliable on every platform either (e.g. `winit` reports an incorrect
+    /// cursor position for Korean IMEs on Windows), so this remains configurable.
+    ///
+    /// Defaults to `true` on Windows (because of the aforementioned `winit` bug) and
+    /// to `false` everywhere else.
+    pub legacy_visuals: bool,
 }
 
 /// Shape of the handle for sliders and similar widgets.
@@ -1621,6 +1639,7 @@ impl ImeComposition {
         Self {
             active_underline_stroke,
             inactive_underline_stroke,
+            legacy_visuals: Self::default_legacy_visuals(),
         }
     }
 
@@ -1634,8 +1653,15 @@ impl ImeComposition {
         Self {
             active_underline_stroke,
             inactive_underline_stroke,
+            legacy_visuals: Self::default_legacy_visuals(),
         }
     }
+
+    /// The default of [`Self::legacy_visuals`]: `true` on Windows (where `winit`
+    /// reports an incorrect cursor position for Korean IMEs), `false` elsewhere.
+    const fn default_legacy_visuals() -> bool {
+        cfg!(windows)
+    }
 }
 
 impl Default for ImeComposition {
@@ -2168,10 +2194,17 @@ impl ImeComposition {
         let Self {
             active_underline_stroke,
             inactive_underline_stroke,
+            legacy_visuals,
         } = self;
 
         ui.label("IME composition");
 
+        ui.checkbox(legacy_visuals, "Legacy visuals").on_hover_text(
+            "If enabled, IME composition (preedit) text looks like a text selection \
+             with the cursor at the end. If disabled, the cursor position and active \
+             conversion segment are shown.",
+        );
+
         Grid::new("ime_composition").num_columns(2).show(ui, |ui| {
             ui.label("Active underline stroke");
             ui.add(active_underline_stroke);

crates/egui/src/widgets/text_edit/builder.rs

@@ -827,10 +827,7 @@ impl TextEdit<'_> {
             false
         };
 
-        let should_paint_ime_visuals_the_legacy_way = cfg!(all(
+        let should_paint_ime_visuals_the_legacy_way = ui.visuals().ime_composition.legacy_visuals;
-            feature = "legacy_ime_composition_visuals",
-            not(feature = "_override_legacy_ime_composition_visuals"),
-        ));
 
         if ui.is_rect_visible(inner_rect) {
             let has_focus = ui.memory(|mem| mem.has_focus(id));