Support Negative desired_width in TextEdit

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

@@ -306,6 +306,7 @@ impl<'t> TextEdit<'t> {
 
     /// Set to 0.0 to keep as small as possible.
     /// Set to [`f32::INFINITY`] to take up all available space (i.e. disable automatic word wrap).
+    /// Set to a negative value to subtract from the available width (e.g., `-10.0` means `available_width - 10.0`).
     #[inline]
     pub fn desired_width(mut self, desired_width: f32) -> Self {
         self.desired_width = Some(desired_width);
@@ -508,10 +509,14 @@ impl TextEdit<'_> {
         const MIN_WIDTH: f32 = 24.0; // Never make a [`TextEdit`] more narrow than this.
         let available_width = (ui.available_width() - margin.sum().x).at_least(MIN_WIDTH);
         let desired_width = desired_width.unwrap_or_else(|| ui.spacing().text_edit_width);
-        let wrap_width = if ui.layout().horizontal_justify() {
+        let wrap_width = if ui.layout().horizontal_justify() || desired_width.is_infinite() {
             available_width
-        } else {
+        } else if desired_width >= 0.0 {
             desired_width.min(available_width)
+        } else {
+            // Negative desired width: subtract from available width
+            // (e.g., -10.0 means "available_width - 10.0")
+            (available_width + desired_width).max(0.0)
         };
 
         let font_id_clone = font_id.clone();

crates/egui_demo_lib/src/demo/text_edit.rs

@@ -22,7 +22,7 @@ impl crate::Demo for TextEditDemo {
     fn show(&mut self, ctx: &egui::Context, open: &mut bool) {
         egui::Window::new(self.name())
             .open(open)
-            .resizable(false)
+            .resizable(true)
             .show(ctx, |ui| {
                 use crate::View as _;
                 self.ui(ui);
@@ -45,6 +45,21 @@ impl crate::View for TextEditDemo {
             ui.label(".");
         });
 
+        ui.separator();
+        ui.label("Singleline text edit that reserves space for a Clear button:");
+        ui.horizontal(|ui| {
+            ui.add(egui::TextEdit::singleline(text).desired_width(-50.0))
+                .on_hover_text("Resize the window to see how the TextEdit resizes.");
+            if ui
+                .add_sized([40.0, 20.0], egui::Button::new("Clear"))
+                .clicked()
+            {
+                text.clear();
+            }
+        });
+
+        ui.separator();
+        ui.label("Multiline text edit with hint text:");
         let output = egui::TextEdit::multiline(text)
             .hint_text("Type something!")
             .show(ui);