Add back button and stack support to BottomSheet, enhance ViewMono, a…

…nd fix ContentBlockImage measure method

- Replaced `He.ViewSubTitle` with `Gtk.Label` for `title_label` in `BottomSheet`.
- Added `back_button` to `BottomSheet` for stack navigation.
- Introduced `sheet_stack` property in `BottomSheet` to handle stack-type content.
- Adjusted `handle_wh` margins based on `show_handle` visibility in `BottomSheet`.
- Enhanced `ViewMono` with methods to add titlebar buttons, menus, and toggles.
- Fixed `measure` method in `ContentBlockImage` to handle out parameters correctly.
- Simplified `default_scheme_variant` property in `Application` model.

lib/Models/Application.vala

@@ -74,11 +74,7 @@ public class He.Application : Gtk.Application {
      * A scheme variant to use for the application. If not set, the user's preferred scheme will be used.
      * This is especially useful for applications with their own color needs, such as media applications using the Content variant.
      */
-    private SchemeVariant? _default_scheme_variant = null;
-    public SchemeVariant? default_scheme_variant {
-        get { return _default_scheme_variant; }
-        set { _default_scheme_variant = value; update_style_manager (); }
-    }
+    public SchemeVariant? default_scheme_variant = null;
 
     private void update_style_manager () {
         if (default_accent_color != null && override_accent_color) {
@@ -91,8 +87,10 @@ public class He.Application : Gtk.Application {
 
         if (default_scheme_variant != null) {
             style_manager.scheme_variant = default_scheme_variant;
+            update_style_manager ();
         } else {
             style_manager.scheme_variant = desktop.ensor_scheme.to_variant ();
+            update_style_manager ();
         }
 
         if (override_dark_style) {

lib/Widgets/BottomSheet.vala

@@ -35,7 +35,7 @@ public class He.BottomSheet : Gtk.Widget {
     private Gtk.Widget dimming;
     private Gtk.Widget handle;
     private Gtk.Box sheet_bin;
-    private He.ViewSubTitle title_label;
+    private Gtk.Label title_label;
     private He.SpringAnimation show_animation;
     private Gtk.WindowHandle handle_wh;
     private GLib.TimeoutSource? resize_timeout;
@@ -46,6 +46,11 @@ public class He.BottomSheet : Gtk.Widget {
     private int target_height = 0;
     private int update_interval = 16; // Default for 60Hz
 
+    /**
+     * The back button in case of a stack-type content.
+     */
+    public He.Button back_button;
+
     /**
      * The sheet to display (the content).
      */
@@ -63,6 +68,28 @@ public class He.BottomSheet : Gtk.Widget {
         }
     }
 
+    /**
+     * The sheet (as a stack) to display (the content).
+     */
+    private Gtk.Stack? _sheet_stack;
+    public Gtk.Stack? sheet_stack {
+        get { return _sheet_stack; }
+        set {
+            if (sheet_stack == value)
+                return;
+
+            _sheet_stack = value;
+
+            sheet_stack.unparent (); // Avoiding stacked children
+            sheet_bin.append (sheet_stack);
+            if (value != null) {
+                back_button.set_visible (true);
+            } else {
+                back_button.set_visible (false);
+            }
+        }
+    }
+
     /**
      * The action button to use.
      */
@@ -148,6 +175,12 @@ public class He.BottomSheet : Gtk.Widget {
 
             _show_handle = value;
             handle.visible = value;
+
+            if (value) {
+                handle_wh.margin_top = 0;
+            } else {
+                handle_wh.margin_top = 24;
+            }
         }
     }
 
@@ -193,10 +226,11 @@ public class He.BottomSheet : Gtk.Widget {
         gesture_drag.drag_update.connect (on_drag_update);
         gesture_drag.drag_end.connect (on_drag_end);
 
-        title_label = new He.ViewSubTitle ();
-        title_label.valign = Gtk.Align.END;
-        title_label.halign = Gtk.Align.START;
+        title_label = new Gtk.Label ("");
+        title_label.valign = Gtk.Align.START;
+        title_label.halign = Gtk.Align.CENTER;
         title_label.hexpand = true;
+        title_label.add_css_class ("view-subtitle");
 
         var close_button = new He.Button ("window-close-symbolic", "");
         close_button.is_disclosure = true;
@@ -206,7 +240,21 @@ public class He.BottomSheet : Gtk.Widget {
             show_sheet = false;
         });
 
+        back_button = new He.Button ("pan-start-symbolic", "");
+        back_button.is_disclosure = true;
+        back_button.set_visible (false);
+        back_button.valign = Gtk.Align.START;
+        back_button.halign = Gtk.Align.START;
+        back_button.clicked.connect (() => {
+            var selected_page = sheet_stack.pages.get_selection ();
+            sheet_stack.pages.select_item (int.max (((int) selected_page.get_nth (0) - 1), 0), true);
+        });
+        if (sheet_stack.pages.is_selected (0)) {
+            back_button.set_visible (false);
+        }
+
         var title_box = new Gtk.Box (Gtk.Orientation.HORIZONTAL, 0);
+        title_box.append (back_button);
         title_box.append (title_label);
         title_box.append (close_button);
 

lib/Widgets/ContentBlockImage.vala

@@ -94,14 +94,15 @@ public class He.ContentBlockImage : He.Bin, Gtk.Buildable {
         Object (file: file);
     }
 
-    public override void measure (Gtk.Orientation orientation, int for_size, out int min, out int nat, out int min_b, out int nat_b) {
+    public override void measure (Gtk.Orientation orientation, int for_size, out int min, out int nat, out int min_b = null, out int nat_b = null) {
         double min_width, min_height, nat_width, nat_height;
         double default_size;
 
         /* for_size = 0 below is treated as -1, but we want to return zeros. */
         if (paintable == null || for_size == 0) {
             min = 0;
             nat = 0;
+            min_b = nat_b = -1;
             return;
         }
 
@@ -126,6 +127,7 @@ public class He.ContentBlockImage : He.Bin, Gtk.Buildable {
             );
             min = (int) Math.ceil (min_width);
             nat = (int) Math.ceil (nat_width);
+            min_b = nat_b = -1;
         } else {
             paintable.compute_concrete_size (
                                              0,
@@ -137,9 +139,8 @@ public class He.ContentBlockImage : He.Bin, Gtk.Buildable {
             );
             min = (int) Math.ceil (min_height);
             nat = (int) Math.ceil (nat_height);
+            min_b = nat_b = -1;
         }
-
-        min_b = nat_b = -1;
     }
 
     public override void snapshot (Gtk.Snapshot snapshot) {

lib/Widgets/ViewMono.vala

@@ -176,7 +176,7 @@ public class He.ViewMono : He.Bin, Gtk.Buildable {
     }
 
     /**
-     * Add a child to the sidebar, should only be used in the context of a UI or Blueprint file. There should be no need to use this method in code.
+     * Add a child to the view, should only be used in the context of a UI or Blueprint file. There should be no need to use this method in code.
      *
      * @since 1.0
      */
@@ -192,6 +192,42 @@ public class He.ViewMono : He.Bin, Gtk.Buildable {
         }
     }
 
+    /**
+     * Add a titlebar button to the view's appbar.
+     *
+     * @since 1.0
+     */
+    public new void add_titlebar_button (Gtk.Button child) {
+        titlebar.append (child);
+    }
+
+    /**
+     * Add a titlebar menu to the view's appbar.
+     *
+     * @since 1.0
+     */
+    public new void add_titlebar_menu (Gtk.MenuButton child) {
+        titlebar.append_menu (child);
+    }
+
+    /**
+     * Add a titlebar toggle to the view's appbar.
+     *
+     * @since 1.0
+     */
+    public new void add_titlebar_toggle (Gtk.ToggleButton child) {
+        titlebar.append_toggle (child);
+    }
+
+    /**
+     * Add a child to the view.
+     *
+     * @since 1.0
+     */
+    public new void append (Gtk.Widget child) {
+        box.append (child);
+    }
+
     static construct {
         set_layout_manager_type (typeof (Gtk.BoxLayout));
     }