apprt/gtk: set the title on the window immediately if set (#8535)

Fixes #5934

This was never confirmed to be a real issue on GTK, but it is
theoretically possible and good hygiene in general. Typically, we'd get
the title through a binding which comes from a bindinggroup which comes
from the active surface in the active tab. All of this takes multiple
event loop ticks to settle, if you will.

This commit changes it so that if an explicit, static title is set, we
set that title on startup before the window is mapped. The syncing still
happens later, but at least the window will have a title from the
initialization.

src/apprt/gtk/class/surface.zig

@@ -496,6 +496,9 @@ pub const Surface = extern struct {
         /// if this is true, then it means the terminal is non-functional.
         @"error": bool = false,
 
+        /// The source that handles setting our child property.
+        idle_rechild: ?c_uint = null,
+
         /// A weak reference to an inspector window.
         inspector: ?*InspectorWindow = null,
 
@@ -504,6 +507,8 @@ pub const Surface = extern struct {
         context_menu: *gtk.PopoverMenu,
         drop_target: *gtk.DropTarget,
         progress_bar_overlay: *gtk.ProgressBar,
+        error_page: *adw.StatusPage,
+        terminal_page: *gtk.Overlay,
 
         pub var offset: c_int = 0;
     };
@@ -595,17 +600,6 @@ pub const Surface = extern struct {
         return @intFromBool(config.@"bell-features".border);
     }
 
-    fn closureStackChildName(
-        _: *Self,
-        error_: c_int,
-    ) callconv(.c) ?[*:0]const u8 {
-        const err = error_ != 0;
-        return if (err)
-            glib.ext.dupeZ(u8, "error")
-        else
-            glib.ext.dupeZ(u8, "terminal");
-    }
-
     pub fn toggleFullscreen(self: *Self) void {
         signals.@"toggle-fullscreen".impl.emit(
             self,
@@ -1370,6 +1364,19 @@ pub const Surface = extern struct {
             priv.progress_bar_timer = null;
         }
 
+        if (priv.idle_rechild) |v| {
+            if (glib.Source.remove(v) == 0) {
+                log.warn("unable to remove idle source", .{});
+            }
+            priv.idle_rechild = null;
+        }
+
+        // This works around a GTK double-free bug where if you bind
+        // to a top-level template child, it frees twice if the widget is
+        // also the root child of the template. By unsetting the child here,
+        // we avoid the double-free.
+        self.as(adw.Bin).setChild(null);
+
         gtk.Widget.disposeTemplate(
             self.as(gtk.Widget),
             getGObjectType(),
@@ -1651,8 +1658,26 @@ pub const Surface = extern struct {
             self.as(gtk.Widget).removeCssClass("background");
         }
 
-        // Note above: in both cases setting our error view is handled by
-        // a Gtk.Stack visible-child-name binding.
+        // We need to set our child property on an idle tick, because the
+        // error property can be triggered by signals that are in the middle
+        // of widget mapping and changing our child during that time
+        // results in a hard gtk crash.
+        if (priv.idle_rechild == null) priv.idle_rechild = glib.idleAdd(
+            onIdleRechild,
+            self,
+        );
+    }
+
+    fn onIdleRechild(ud: ?*anyopaque) callconv(.c) c_int {
+        const self: *Self = @ptrCast(@alignCast(ud orelse return 0));
+        const priv = self.private();
+        priv.idle_rechild = null;
+        if (priv.@"error") {
+            self.as(adw.Bin).setChild(priv.error_page.as(gtk.Widget));
+        } else {
+            self.as(adw.Bin).setChild(priv.terminal_page.as(gtk.Widget));
+        }
+        return 0;
     }
 
     fn propMouseHoverUrl(
@@ -2699,8 +2724,10 @@ pub const Surface = extern struct {
             class.bindTemplateChildPrivate("url_right", .{});
             class.bindTemplateChildPrivate("child_exited_overlay", .{});
             class.bindTemplateChildPrivate("context_menu", .{});
+            class.bindTemplateChildPrivate("error_page", .{});
             class.bindTemplateChildPrivate("progress_bar_overlay", .{});
             class.bindTemplateChildPrivate("resize_overlay", .{});
+            class.bindTemplateChildPrivate("terminal_page", .{});
             class.bindTemplateChildPrivate("drop_target", .{});
             class.bindTemplateChildPrivate("im_context", .{});
 
@@ -2736,7 +2763,6 @@ pub const Surface = extern struct {
             class.bindTemplateCallback("notify_mouse_shape", &propMouseShape);
             class.bindTemplateCallback("notify_bell_ringing", &propBellRinging);
             class.bindTemplateCallback("should_border_be_shown", &closureShouldBorderBeShown);
-            class.bindTemplateCallback("stack_child_name", &closureStackChildName);
 
             // Properties
             gobject.ext.registerProperties(class, &.{

src/apprt/gtk/class/window.zig

@@ -306,6 +306,13 @@ pub const Window = extern struct {
             const config = config_obj.get();
             if (config.maximize) self.as(gtk.Window).maximize();
             if (config.fullscreen) self.as(gtk.Window).fullscreen();
+
+            // If we have an explicit title set, we set that immediately
+            // so that any applications inspecting the window states see
+            // an immediate title set when the window appears, rather than
+            // waiting possibly a few event loop ticks for it to sync from
+            // the surface.
+            if (config.title) |v| self.as(gtk.Window).setTitle(v);
         }
 
         // We always sync our appearance at the end because loading our

src/apprt/gtk/ui/1.2/surface.blp

@@ -1,6 +1,155 @@
 using Gtk 4.0;
 using Adw 1;
 
+Adw.StatusPage error_page {
+  icon-name: "computer-fail-symbolic";
+  title: _("Oh, no.");
+  description: _("Unable to acquire an OpenGL context for rendering.");
+
+  child: LinkButton {
+    label: "https://ghostty.org/docs/help/gtk-opengl-context";
+    uri: "https://ghostty.org/docs/help/gtk-opengl-context";
+  };
+}
+
+Overlay terminal_page {
+  focusable: false;
+  focus-on-click: false;
+
+  child: Box {
+    hexpand: true;
+    vexpand: true;
+
+    GLArea gl_area {
+      realize => $gl_realize();
+      unrealize => $gl_unrealize();
+      render => $gl_render();
+      resize => $gl_resize();
+      hexpand: true;
+      vexpand: true;
+      focusable: true;
+      focus-on-click: true;
+      has-stencil-buffer: false;
+      has-depth-buffer: false;
+      allowed-apis: gl;
+    }
+
+    PopoverMenu context_menu {
+      closed => $context_menu_closed();
+      menu-model: context_menu_model;
+      flags: nested;
+      halign: start;
+      has-arrow: false;
+    }
+  };
+
+  [overlay]
+  ProgressBar progress_bar_overlay {
+    styles [
+      "osd",
+    ]
+
+    visible: false;
+    halign: fill;
+    valign: start;
+  }
+
+  [overlay]
+  // The "border" bell feature is implemented here as an overlay rather than
+  // just adding a border to the GLArea or other widget for two reasons.
+  // First, adding a border to an existing widget causes a resize of the
+  // widget which undesirable side effects. Second, we can make it reactive
+  // here in the blueprint with relatively little code.
+  Revealer {
+    reveal-child: bind $should_border_be_shown(template.config, template.bell-ringing) as <bool>;
+    transition-type: crossfade;
+    transition-duration: 500;
+
+    Box bell_overlay {
+      styles [
+        "bell-overlay",
+      ]
+
+      halign: fill;
+      valign: fill;
+    }
+  }
+
+  [overlay]
+  $GhosttySurfaceChildExited child_exited_overlay {
+    visible: bind template.child-exited;
+    close-request => $child_exited_close();
+  }
+
+  [overlay]
+  $GhosttyResizeOverlay resize_overlay {}
+
+  [overlay]
+  Label url_left {
+    styles [
+      "background",
+      "url-overlay",
+    ]
+
+    visible: false;
+    halign: start;
+    valign: end;
+    label: bind template.mouse-hover-url;
+
+    EventControllerMotion url_ec_motion {
+      enter => $url_mouse_enter();
+      leave => $url_mouse_leave();
+    }
+  }
+
+  [overlay]
+  Label url_right {
+    styles [
+      "background",
+      "url-overlay",
+    ]
+
+    visible: false;
+    halign: end;
+    valign: end;
+    label: bind template.mouse-hover-url;
+  }
+
+  // Event controllers for interactivity
+  EventControllerFocus {
+    enter => $focus_enter();
+    leave => $focus_leave();
+  }
+
+  EventControllerKey {
+    key-pressed => $key_pressed();
+    key-released => $key_released();
+  }
+
+  EventControllerMotion {
+    motion => $mouse_motion();
+    leave => $mouse_leave();
+  }
+
+  EventControllerScroll {
+    scroll => $scroll();
+    scroll-begin => $scroll_begin();
+    scroll-end => $scroll_end();
+    flags: both_axes;
+  }
+
+  GestureClick {
+    pressed => $mouse_down();
+    released => $mouse_up();
+    button: 0;
+  }
+
+  DropTarget drop_target {
+    drop => $drop();
+    actions: copy;
+  }
+}
+
 template $GhosttySurface: Adw.Bin {
   styles [
     "surface",
@@ -12,169 +161,14 @@ template $GhosttySurface: Adw.Bin {
   notify::mouse-hover-url => $notify_mouse_hover_url();
   notify::mouse-hidden => $notify_mouse_hidden();
   notify::mouse-shape => $notify_mouse_shape();
-
-  Stack {
-    StackPage {
-      name: "terminal";
-
-      child: Overlay {
-        focusable: false;
-        focus-on-click: false;
-
-        child: Box {
-          hexpand: true;
-          vexpand: true;
-
-          GLArea gl_area {
-            realize => $gl_realize();
-            unrealize => $gl_unrealize();
-            render => $gl_render();
-            resize => $gl_resize();
-            hexpand: true;
-            vexpand: true;
-            focusable: true;
-            focus-on-click: true;
-            has-stencil-buffer: false;
-            has-depth-buffer: false;
-            allowed-apis: gl;
-          }
-
-          PopoverMenu context_menu {
-            closed => $context_menu_closed();
-            menu-model: context_menu_model;
-            flags: nested;
-            halign: start;
-            has-arrow: false;
-          }
-        };
-
-        [overlay]
-        ProgressBar progress_bar_overlay {
-          styles [
-            "osd",
-          ]
-
-          visible: false;
-          halign: fill;
-          valign: start;
-        }
-
-        [overlay]
-        // The "border" bell feature is implemented here as an overlay rather than
-        // just adding a border to the GLArea or other widget for two reasons.
-        // First, adding a border to an existing widget causes a resize of the
-        // widget which undesirable side effects. Second, we can make it reactive
-        // here in the blueprint with relatively little code.
-        Revealer {
-          reveal-child: bind $should_border_be_shown(template.config, template.bell-ringing) as <bool>;
-          transition-type: crossfade;
-          transition-duration: 500;
-
-          Box bell_overlay {
-            styles [
-              "bell-overlay",
-            ]
-
-            halign: fill;
-            valign: fill;
-          }
-        }
-
-        [overlay]
-        $GhosttySurfaceChildExited child_exited_overlay {
-          visible: bind template.child-exited;
-          close-request => $child_exited_close();
-        }
-
-        [overlay]
-        $GhosttyResizeOverlay resize_overlay {}
-
-        [overlay]
-        Label url_left {
-          styles [
-            "background",
-            "url-overlay",
-          ]
-
-          visible: false;
-          halign: start;
-          valign: end;
-          label: bind template.mouse-hover-url;
-
-          EventControllerMotion url_ec_motion {
-            enter => $url_mouse_enter();
-            leave => $url_mouse_leave();
-          }
-        }
-
-        [overlay]
-        Label url_right {
-          styles [
-            "background",
-            "url-overlay",
-          ]
-
-          visible: false;
-          halign: end;
-          valign: end;
-          label: bind template.mouse-hover-url;
-        }
-
-        // Event controllers for interactivity
-        EventControllerFocus {
-          enter => $focus_enter();
-          leave => $focus_leave();
-        }
-
-        EventControllerKey {
-          key-pressed => $key_pressed();
-          key-released => $key_released();
-        }
-
-        EventControllerMotion {
-          motion => $mouse_motion();
-          leave => $mouse_leave();
-        }
-
-        EventControllerScroll {
-          scroll => $scroll();
-          scroll-begin => $scroll_begin();
-          scroll-end => $scroll_end();
-          flags: both_axes;
-        }
-
-        GestureClick {
-          pressed => $mouse_down();
-          released => $mouse_up();
-          button: 0;
-        }
-
-        DropTarget drop_target {
-          drop => $drop();
-          actions: copy;
-        }
-      };
-    }
-
-    StackPage {
-      name: "error";
-
-      child: Adw.StatusPage {
-        icon-name: "computer-fail-symbolic";
-        title: _("Oh, no.");
-        description: _("Unable to acquire an OpenGL context for rendering.");
-
-        child: LinkButton {
-          label: "https://ghostty.org/docs/help/gtk-opengl-context";
-          uri: "https://ghostty.org/docs/help/gtk-opengl-context";
-        };
-      };
-    }
-
-    // The order matters here: we can only set this after the stack
-    // pages above have been created.
-    visible-child-name: bind $stack_child_name(template.error) as <string>;
-  }
+  // Some history: we used to use a Stack here and swap between the
+  // terminal and error pages as needed. But a Stack doesn't play nice
+  // with our SplitTree and Gtk.Paned usage[^1]. Replacing this with
+  // a manual programmatic child swap fixed this. So if you ever change
+  // this, be sure to test many splits!
+  //
+  // [^1]: https://github.com/ghostty-org/ghostty/issues/8533
+  child: terminal_page;
 }
 
 IMMulticontext im_context {