Use TextBuffer for layouter in TextEdit instead of &str

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

@@ -21,6 +21,8 @@ use crate::{
 
 use super::{TextEditOutput, TextEditState};
 
+type LayouterFn<'t> = &'t mut dyn FnMut(&Ui, &dyn TextBuffer, f32) -> Arc<Galley>;
+
 /// A text region that the user can edit the contents of.
 ///
 /// See also [`Ui::text_edit_singleline`] and [`Ui::text_edit_multiline`].
@@ -73,7 +75,7 @@ pub struct TextEdit<'t> {
     id_salt: Option<Id>,
     font_selection: FontSelection,
     text_color: Option<Color32>,
-    layouter: Option<&'t mut dyn FnMut(&Ui, &str, f32) -> Arc<Galley>>,
+    layouter: Option<LayouterFn<'t>>,
     password: bool,
     frame: bool,
     margin: Margin,
@@ -263,16 +265,19 @@ impl<'t> TextEdit<'t> {
     /// # egui::__run_test_ui(|ui| {
     /// # let mut my_code = String::new();
     /// # fn my_memoized_highlighter(s: &str) -> egui::text::LayoutJob { Default::default() }
-    /// let mut layouter = |ui: &egui::Ui, string: &str, wrap_width: f32| {
-    ///     let mut layout_job: egui::text::LayoutJob = my_memoized_highlighter(string);
+    /// let mut layouter = |ui: &egui::Ui, buf: &dyn egui::TextBuffer, wrap_width: f32| {
+    ///     let mut layout_job: egui::text::LayoutJob = my_memoized_highlighter(buf.as_str());
     ///     layout_job.wrap.max_width = wrap_width;
     ///     ui.fonts(|f| f.layout_job(layout_job))
     /// };
     /// ui.add(egui::TextEdit::multiline(&mut my_code).layouter(&mut layouter));
     /// # });
     /// ```
     #[inline]
-    pub fn layouter(mut self, layouter: &'t mut dyn FnMut(&Ui, &str, f32) -> Arc<Galley>) -> Self {
+    pub fn layouter(
+        mut self,
+        layouter: &'t mut dyn FnMut(&Ui, &dyn TextBuffer, f32) -> Arc<Galley>,
+    ) -> Self {
         self.layouter = Some(layouter);
 
         self
@@ -518,8 +523,8 @@ impl TextEdit<'_> {
         };
 
         let font_id_clone = font_id.clone();
-        let mut default_layouter = move |ui: &Ui, text: &str, wrap_width: f32| {
-            let text = mask_if_password(password, text);
+        let mut default_layouter = move |ui: &Ui, text: &dyn TextBuffer, wrap_width: f32| {
+            let text = mask_if_password(password, text.as_str());
             let layout_job = if multiline {
                 LayoutJob::simple(text, font_id_clone.clone(), text_color, wrap_width)
             } else {
@@ -530,7 +535,7 @@ impl TextEdit<'_> {
 
         let layouter = layouter.unwrap_or(&mut default_layouter);
 
-        let mut galley = layouter(ui, text.as_str(), wrap_width);
+        let mut galley = layouter(ui, text, wrap_width);
 
         let desired_inner_width = if clip_text {
             wrap_width // visual clipping with scroll in singleline input.
@@ -883,7 +888,7 @@ fn events(
     state: &mut TextEditState,
     text: &mut dyn TextBuffer,
     galley: &mut Arc<Galley>,
-    layouter: &mut dyn FnMut(&Ui, &str, f32) -> Arc<Galley>,
+    layouter: &mut dyn FnMut(&Ui, &dyn TextBuffer, f32) -> Arc<Galley>,
     id: Id,
     wrap_width: f32,
     multiline: bool,
@@ -1098,7 +1103,7 @@ fn events(
             any_change = true;
 
             // Layout again to avoid frame delay, and to keep `text` and `galley` in sync.
-            *galley = layouter(ui, text.as_str(), wrap_width);
+            *galley = layouter(ui, text, wrap_width);
 
             // Set cursor_range using new galley:
             cursor_range = CursorRange {

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

@@ -183,6 +183,15 @@ pub trait TextBuffer {
             self.delete_selected(&CursorRange::two(min, max))
         }
     }
+
+    /// Returns a unique identifier for the implementing type.
+    ///
+    /// By default, this returns `0`, which represents an unknown type.
+    /// Implementers should override this method with a unique identifier
+    /// to enable safe downcasting.
+    fn type_id(&self) -> usize {
+        0
+    }
 }
 
 impl TextBuffer for String {

crates/egui_demo_lib/src/demo/code_editor.rs

@@ -76,12 +76,12 @@ impl crate::View for CodeEditor {
             });
         });
 
-        let mut layouter = |ui: &egui::Ui, string: &str, wrap_width: f32| {
+        let mut layouter = |ui: &egui::Ui, buf: &dyn egui::TextBuffer, wrap_width: f32| {
             let mut layout_job = egui_extras::syntax_highlighting::highlight(
                 ui.ctx(),
                 ui.style(),
                 &theme,
-                string,
+                buf.as_str(),
                 language,
             );
             layout_job.wrap.max_width = wrap_width;

crates/egui_demo_lib/src/easy_mark/easy_mark_editor.rs

@@ -80,8 +80,8 @@ impl EasyMarkEditor {
         } = self;
 
         let response = if self.highlight_editor {
-            let mut layouter = |ui: &egui::Ui, easymark: &str, wrap_width: f32| {
-                let mut layout_job = highlighter.highlight(ui.style(), easymark);
+            let mut layouter = |ui: &egui::Ui, easymark: &dyn TextBuffer, wrap_width: f32| {
+                let mut layout_job = highlighter.highlight(ui.style(), easymark.as_str());
                 layout_job.wrap.max_width = wrap_width;
                 ui.fonts(|f| f.layout_job(layout_job))
             };