segmented_button: honour WindowControlsPosition for the tab close button

The close button of closable tabs was pinned to the trailing edge, so
enabling macOS-style window controls left the window buttons on the
left and the tab crosses on the right.

Read crate::config::window_controls_position() and, when Start, place
the close button before the tab contents and shift them accordingly.
The hit-test, the text width and the drawn icon all derive from the
same position so they stay in sync.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/widget/segmented_button/widget.rs

@@ -9,7 +9,7 @@ use crate::widget::menu::{
     self, CloseCondition, ItemHeight, ItemWidth, MenuBarState, PathHighlight, menu_roots_children,
     menu_roots_diff,
 };
-use crate::widget::{Icon, icon};
+use crate::widget::{Icon, WindowControlsPosition, icon};
 use crate::{Element, Renderer};
 use derive_setters::Setters;
 use iced::clipboard::dnd::{
@@ -1608,8 +1608,11 @@ where
                             }
                         }
 
-                        let close_button_bounds =
-                            close_bounds(bounds, f32::from(self.close_icon.size));
+                        let close_button_bounds = close_bounds(
+                            bounds,
+                            f32::from(self.close_icon.size),
+                            crate::config::window_controls_position(),
+                        );
                         let over_close_button = self.model.items[key].closable
                             && cursor_position.is_over(close_button_bounds);
 
@@ -2420,6 +2423,25 @@ where
                 }
             }
 
+            // Whether to show the close button on this tab.
+            let show_close_button =
+                (key_is_active || !self.show_close_icon_on_hover || key_is_hovered)
+                    && self.model.is_closable(key);
+
+            // Width of the icon used by the close button, which we will subtract from the text bounds.
+            let close_icon_width = if show_close_button {
+                f32::from(self.close_icon.size)
+            } else {
+                0.0
+            };
+
+            // With macOS-style controls the close button precedes the contents, so
+            // shift them right to make room for it.
+            let close_position = crate::config::window_controls_position();
+            if show_close_button && close_position == WindowControlsPosition::Start {
+                bounds.x += close_icon_width + f32::from(self.button_spacing);
+            }
+
             // Draw the image beside the text.
             if let Some(icon) = self.model.icon(key) {
                 let mut image_bounds = bounds;
@@ -2477,21 +2499,17 @@ where
                 }
             }
 
-            // Whether to show the close button on this tab.
-            let show_close_button =
-                (key_is_active || !self.show_close_icon_on_hover || key_is_hovered)
-                    && self.model.is_closable(key);
-
-            // Width of the icon used by the close button, which we will subtract from the text bounds.
-            let close_icon_width = if show_close_button {
-                f32::from(self.close_icon.size)
+            // Room reserved after the contents: only needed when the close button
+            // trails them, since a leading one is already counted in `bounds.x`.
+            let trailing_close_width = if close_position == WindowControlsPosition::End {
+                close_icon_width
             } else {
                 0.0
             };
 
             bounds.width = original_bounds.width
                 - (bounds.x - original_bounds.x)
-                - close_icon_width
+                - trailing_close_width
                 - f32::from(self.button_padding[2]);
 
             bounds.y = center_y;
@@ -2517,7 +2535,8 @@ where
 
             // Draw a close button if set.
             if show_close_button {
-                let close_button_bounds = close_bounds(original_bounds, close_icon_width);
+                let close_button_bounds =
+                    close_bounds(original_bounds, close_icon_width, close_position);
 
                 draw_icon::<Message>(
                     renderer,
@@ -3070,9 +3089,16 @@ impl From<Id> for widget::Id {
 }
 
 /// Calculates the bounds of the close button within the area of an item.
-fn close_bounds(area: Rectangle<f32>, icon_size: f32) -> Rectangle<f32> {
+fn close_bounds(
+    area: Rectangle<f32>,
+    icon_size: f32,
+    position: WindowControlsPosition,
+) -> Rectangle<f32> {
     Rectangle {
-        x: area.x + area.width - icon_size - 8.0,
+        x: match position {
+            WindowControlsPosition::Start => area.x + 8.0,
+            WindowControlsPosition::End => area.x + area.width - icon_size - 8.0,
+        },
         y: area.center_y() - (icon_size / 2.0),
         width: icon_size,
         height: icon_size,