Select all text in DragValue when gaining focus via keyboard (#7107)

Previously, the `DragValue` widget selected all text when focus was
gained via a mouse click, but didn't when focus was gained via keyboard.


https://github.com/user-attachments/assets/5e82ca2c-0214-4201-ad2d-056dabc05e92

This PR makes both gained focus behaving the same way by selecting the
text on focus gained via keyboard.


https://github.com/user-attachments/assets/f246c779-3368-428c-a6b2-cec20dbc20a6

- [x] I have followed the instructions in the PR template

Co-authored-by: Emil Ernerfeldt <[email protected]>

Author: Azkellas

crates/egui/src/widgets/drag_value.rs

@@ -3,7 +3,7 @@
 use std::{cmp::Ordering, ops::RangeInclusive};
 
 use crate::{
-    emath, text, Button, CursorIcon, Key, Modifiers, NumExt as _, Response, RichText, Sense,
+    emath, text, Button, CursorIcon, Id, Key, Modifiers, NumExt as _, Response, RichText, Sense,
     TextEdit, TextWrapMode, Ui, Widget, WidgetInfo, MINUS_CHAR_STR,
 };
 
@@ -569,6 +569,11 @@ impl Widget for DragValue<'_> {
                     .font(text_style),
             );
 
+            // Select all text when the edit gains focus.
+            if ui.memory_mut(|mem| mem.gained_focus(id)) {
+                select_all_text(ui, id, response.id, &value_text);
+            }
+
             let update = if update_while_editing {
                 // Update when the edit content has changed.
                 response.changed()
@@ -623,12 +628,7 @@ impl Widget for DragValue<'_> {
             if response.clicked() {
                 ui.data_mut(|data| data.remove::<String>(id));
                 ui.memory_mut(|mem| mem.request_focus(id));
-                let mut state = TextEdit::load_state(ui.ctx(), id).unwrap_or_default();
-                state.cursor.set_char_range(Some(text::CCursorRange::two(
-                    text::CCursor::default(),
-                    text::CCursor::new(value_text.chars().count()),
-                )));
-                state.store(ui.ctx(), response.id);
+                select_all_text(ui, id, response.id, &value_text);
             } else if response.dragged() {
                 ui.ctx().set_cursor_icon(cursor_icon);
 
@@ -759,6 +759,16 @@ pub(crate) fn clamp_value_to_range(x: f64, range: RangeInclusive<f64>) -> f64 {
     }
 }
 
+/// Select all text in the `DragValue` text edit widget.
+fn select_all_text(ui: &Ui, widget_id: Id, response_id: Id, value_text: &str) {
+    let mut state = TextEdit::load_state(ui.ctx(), widget_id).unwrap_or_default();
+    state.cursor.set_char_range(Some(text::CCursorRange::two(
+        text::CCursor::default(),
+        text::CCursor::new(value_text.chars().count()),
+    )));
+    state.store(ui.ctx(), response_id);
+}
+
 #[cfg(test)]
 mod tests {
     use super::clamp_value_to_range;