adw: add option to choose toolbar style

src/apprt/gtk/Window.zig

@@ -183,6 +183,14 @@ pub fn init(self: *Window, app: *App) !void {
         }
         c.adw_toolbar_view_set_content(toolbar_view, box);
 
+        const toolbar_style: c.AdwToolbarStyle = switch (self.app.config.@"adw-toolbar-style") {
+            .flat => c.ADW_TOOLBAR_FLAT,
+            .raised => c.ADW_TOOLBAR_RAISED,
+            .@"raised-border" => c.ADW_TOOLBAR_RAISED_BORDER,
+        };
+        c.adw_toolbar_view_set_top_bar_style(toolbar_view, toolbar_style);
+        c.adw_toolbar_view_set_bottom_bar_style(toolbar_view, toolbar_style);
+
         c.adw_application_window_set_content(@ptrCast(gtk_window), @ptrCast(@alignCast(toolbar_view)));
     } else {
         // The box is our main child

src/config/Config.zig

@@ -1426,6 +1426,12 @@ keybind: Keybinds = .{},
 /// back to `top`.
 @"gtk-tabs-location": GtkTabsLocation = .top,
 
+/// Determines the appearance of the top and bottom bars when using the adwaita tab bar.
+/// If set to `flat`, top and bottom bars are flat with the terminal window.
+/// If set to `raised`, top and bottom bars cast a shadow on the terminal area.
+/// `raised-border` is similar to `raised` but the shadow is replaced with a more subtle border.
+@"adw-toolbar-style": AdwToolBarStyle = .raised,
+
 /// If `true` (default), then the Ghostty GTK tabs will be "wide." Wide tabs
 /// are the new typical Gnome style where tabs fill their available space.
 /// If you set this to `false` then tabs will only take up space they need,
@@ -4064,6 +4070,13 @@ pub const GtkTabsLocation = enum {
     right,
 };
 
+/// See adw-toolbar-style
+pub const AdwToolBarStyle = enum {
+    flat,
+    raised,
+    @"raised-border",
+};
+
 /// See mouse-shift-capture
 pub const MouseShiftCapture = enum {
     false,