Theme · Platform: caption buttons of their own height, titles that give way

Windows caption buttons take the bar's height less its hairline, a new
token, instead of their row's, so they keep their height beside caps
that wrap below them. A title bar's title is an Ellipsis: on Windows it
takes the free width before the buttons and gives way; a centered title
sits inset past the lights on both sides. The controls never shrink.
Tests hold a long Windows title's close button inside a 280px bar and
wrapped caps inside their row.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

TASKS.md

@@ -424,3 +424,4 @@ Per-component lines live in `tasks/`. Tags there:
 | T39a | 3 | PASS | |
 | T39b | 1 | FAIL | a long theme name pushed its badge past 280px; four-digit colors refused the theme |
 | T39b | 2 | PASS | |
+| T39c | 1 | FAIL | Windows caption buttons took their row's height; a long Windows title pushed the buttons past the bar |

examples/gallery/pages/shell/chrome.rs

@@ -59,7 +59,7 @@ pub fn title_bar(cx: &App) -> impl IntoElement + use<> {
             })),
     )
     .child(code(
-        "TitleBar::new(id) with no style leaves room for the real macOS lights.",
+        "TitleBar::new(id) with no platform leaves room for the real macOS lights.",
         cx,
     ))
 }

src/shell/chrome.rs

@@ -10,6 +10,7 @@ use smallvec::SmallVec;
 use crate::{
     primitives::{Icon, IconName},
     theme::{ActiveTheme, ControlSize, IconSize, Platform, TextSize},
+    typography::Ellipsis,
 };
 
 /// Drags the window, and zooms it on double-click.
@@ -174,7 +175,7 @@ fn caption_buttons(
     div()
         .id(id)
         .flex()
-        .h_full()
+        .flex_none()
         .children(buttons.map(|(control, icon, area)| {
             let on_close = on_close.clone();
             let group = SharedString::from(format!("caption-{control:?}"));
@@ -189,7 +190,8 @@ fn caption_buttons(
                 .items_center()
                 .justify_center()
                 .w(theme.caption_button_width())
-                .h_full()
+                .h(theme.caption_button_height())
+                .debug_selector(move || format!("caption-{control:?}"))
                 .window_control_area(area)
                 .hover(|style| style.bg(hover))
                 .on_mouse_down(MouseButton::Left, |_, window, _| window.prevent_default())
@@ -357,10 +359,11 @@ impl RenderOnce for TitleBar {
         };
         let title = self.title.map(|title| {
             div()
+                .min_w_0()
                 .text_size(theme.text_size(TextSize::Sm))
                 .font_weight(FontWeight::MEDIUM)
                 .text_color(theme.colors.fg_muted)
-                .child(title)
+                .child(Ellipsis::new(title))
         });
         let centered = style != Platform::Windows;
         let inset = theme.traffic_light_inset();
@@ -385,12 +388,15 @@ impl RenderOnce for TitleBar {
         };
         let bar = bar.children(self.leading);
         let bar = match (centered, title) {
-            (false, Some(title)) => bar.child(title),
+            (false, Some(title)) => bar.child(title.flex_1()),
             (_, title) => bar.when_some(title, |bar, title| {
                 bar.child(
                     div()
                         .absolute()
-                        .inset_0()
+                        .top_0()
+                        .bottom_0()
+                        .left(inset)
+                        .right(inset)
                         .flex()
                         .items_center()
                         .justify_center()
@@ -398,8 +404,8 @@ impl RenderOnce for TitleBar {
                 )
             }),
         };
-        bar.child(div().flex_1())
+        bar.when(centered, |bar| bar.child(div().flex_1()))
             .children(self.actions)
-            .children(trailing)
+            .children(trailing.map(|controls| div().flex_none().child(controls)))
     }
 }

src/shell/tests.rs

@@ -130,3 +130,63 @@ fn the_themes_platform_draws_the_buttons_and_the_caps(cx: &mut TestAppContext) {
         "Ctrl wider than the command mark"
     );
 }
+
+struct LongTitle;
+
+impl Render for LongTitle {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        div().w(px(280.0)).flex().flex_col().child(
+            super::TitleBar::new("bar")
+                .title("Ely — Projects at a narrow width, and more besides")
+                .platform(crate::theme::Platform::Windows),
+        )
+    }
+}
+
+/// At 280px a Windows bar's long title gives way, and its close button ends inside the bar.
+#[gpui::test]
+fn a_long_title_leaves_the_caption_buttons_in_the_bar(cx: &mut TestAppContext) {
+    cx.update(Theme::init);
+    let (_, cx) = cx.add_window_view(|_, _| LongTitle);
+    settle(cx);
+    let close = cx.debug_bounds("caption-Close").expect("a close button");
+    assert!(close.right() <= px(280.0), "{close:?} inside the bar");
+}
+
+struct Wrapped;
+
+impl Render for Wrapped {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        let windows = crate::theme::Platform::Windows;
+        div()
+            .w(px(280.0))
+            .flex()
+            .flex_col()
+            .child(
+                div()
+                    .debug_selector(|| "row".into())
+                    .flex()
+                    .flex_wrap()
+                    .items_center()
+                    .gap_3()
+                    .child(super::WindowControls::new("controls").platform(windows))
+                    .child(div().debug_selector(|| "combo".into()).child(
+                        crate::typography::KbdCombo::new("secondary-shift-k secondary-shift-s"),
+                    )),
+            )
+            .child(div().h(px(20.0)))
+    }
+}
+
+/// Caption buttons keep their own height beside caps that wrap below them, so the caps end inside the row.
+#[gpui::test]
+fn caption_buttons_keep_their_height_in_a_wrapping_row(cx: &mut TestAppContext) {
+    cx.update(Theme::init);
+    cx.update(|cx| Theme::update(cx, |theme| theme.platform = crate::theme::Platform::Windows));
+    let (_, cx) = cx.add_window_view(|_, _| Wrapped);
+    settle(cx);
+    let row = cx.debug_bounds("row").expect("the row");
+    let combo = cx.debug_bounds("combo").expect("the caps");
+    assert!(combo.top() > row.top(), "the caps wrap below the buttons");
+    assert!(combo.bottom() <= row.bottom(), "{combo:?} inside {row:?}");
+}

src/theme/tokens.rs

@@ -230,6 +230,11 @@ impl Theme {
         px_to_rems(46.0)
     }
 
+    /// A Windows caption button's height: the title bar's, less its bottom hairline.
+    pub fn caption_button_height(&self) -> Pixels {
+        self.titlebar_height().to_pixels(self.base_rem()) - px(1.0)
+    }
+
     /// Resize margin of a client-drawn window.
     pub fn window_inset(&self) -> Rems {
         px_to_rems(10.0)