apprt/gtk: add ability to put tabs in the headerbar

Signed-off-by: Tristan Partin <tristan@partin.io>

src/apprt/gtk/Window.zig

@@ -289,6 +289,10 @@ pub fn init(self: *Window, app: *App) !void {
             // left and right is not supported in libadwaita.
             .top, .left, .right => c.adw_toolbar_view_add_top_bar(toolbar_view, tab_bar_widget),
             .bottom => c.adw_toolbar_view_add_bottom_bar(toolbar_view, tab_bar_widget),
+            .headerbar => {
+                c.adw_tab_bar_set_autohide(tab_bar, 0);
+                c.adw_header_bar_set_title_widget(@ptrCast(@alignCast(self.header.?)), tab_bar_widget);
+            },
         }
         c.adw_toolbar_view_set_content(toolbar_view, box);
 
@@ -334,6 +338,7 @@ pub fn init(self: *Window, app: *App) !void {
                     .top,
                     .left,
                     .right,
+                    .headerbar,
                     => c.gtk_box_prepend(
                         @ptrCast(box),
                         @ptrCast(@alignCast(tab_bar)),

src/apprt/gtk/notebook.zig

@@ -29,7 +29,7 @@ pub const Notebook = union(enum) {
         const notebook_widget: *c.GtkWidget = c.gtk_notebook_new();
         const notebook: *c.GtkNotebook = @ptrCast(notebook_widget);
         const notebook_tab_pos: c_uint = switch (app.config.@"gtk-tabs-location") {
-            .top => c.GTK_POS_TOP,
+            .top, .headerbar => c.GTK_POS_TOP,
             .bottom => c.GTK_POS_BOTTOM,
             .left => c.GTK_POS_LEFT,
             .right => c.GTK_POS_RIGHT,

src/config/Config.zig

@@ -4511,6 +4511,7 @@ pub const GtkTabsLocation = enum {
     bottom,
     left,
     right,
+    headerbar,
 };
 
 /// See adw-toolbar-style