Add "List View with a Tree" demo

src/List View with a Tree/main.blp

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+using Gtk 4.0;
+using Adw 1;
+
+Adw.StatusPage {
+  title: _("List View with a Tree");
+  description: _("Arrange items in a tree like structure");
+  valign: start;
+
+  Adw.Clamp {
+    maximum-size: 360;
+
+    Box {
+      orientation: vertical;
+      spacing: 18;
+
+      ScrolledWindow {
+        has-frame: true;
+        height-request: 320;
+
+        child: ListView list_view {
+          factory: SignalListItemFactory factory {};
+        };
+      }
+
+      Box {
+        halign: center;
+
+        LinkButton {
+          label: _("API Reference");
+          uri: "https://docs.gtk.org/gtk4/class.TreeListModel.html";
+        }
+
+        LinkButton {
+          label: _("Documentation");
+          uri: "https://docs.gtk.org/gtk4/section-list-widget.html#displaying-trees";
+        }
+      }
+    }
+  }
+}

src/List View with a Tree/main.json

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+{
+  "category": "layout",
+  "description": "Arrange items in a tree like structure",
+  "panels": ["code", "ui", "preview"],
+  "autorun": true
+}

src/List View with a Tree/main.py

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+import gi
+
+gi.require_version("Gtk", "4.0")
+gi.require_version("Adw", "1")
+from gi.repository import Gtk, GObject, Gio
+import workbench
+
+list_view = workbench.builder.get_object("list_view")
+factory = workbench.builder.get_object("factory")
+
+
+class TreeNode(GObject.Object):
+    def __init__(self, _title, _children=None):
+        super().__init__()
+        self.children = _children or []
+        self.title = _title
+
+
+class TreeWidget(Gtk.Box):
+    def __init__(self):
+        super().__init__(
+            spacing=6, margin_start=6, margin_end=12, margin_top=6, margin_bottom=6
+        )
+
+        self.expander = Gtk.TreeExpander.new()
+
+        self.label = Gtk.Label(xalign=0, ellipsize=3)
+
+        self.append(self.expander)
+        self.append(self.label)
+
+
+def create_model_func(item):
+    if item.children == []:
+        return None
+    child_model = Gio.ListStore.new(TreeNode)
+    for child in item.children:
+        child_model.append(child)
+    return child_model
+
+
+def on_setup(_, list_item):
+    list_item.set_child(TreeWidget())
+
+
+def on_bind(_, list_item):
+    list_row = list_item.get_item()
+    widget = list_item.get_child()
+    item = list_row.get_item()
+
+    widget.expander.set_list_row(list_row)
+    widget.label.set_label(item.title)
+
+
+factory.connect("setup", on_setup)
+factory.connect("bind", on_bind)
+
+root_model = TreeNode(
+    "Root",
+    [
+        TreeNode("Child 1", [TreeNode("Child 1.1", []), TreeNode("Child 1.2", [])]),
+        TreeNode(
+            "Child 2",
+            [
+                TreeNode("Child 2.1", []),
+                TreeNode("Child 2.2", []),
+                TreeNode("Child 2.3", [TreeNode("Child 3.1", [])]),
+            ],
+        ),
+    ],
+)
+
+tree_model = Gio.ListStore.new(TreeNode)
+tree_model.append(root_model)
+
+tree_list_model = Gtk.TreeListModel.new(tree_model, False, True, create_model_func)
+tree_list_model.set_autoexpand(False)
+
+selection_model = Gtk.NoSelection(model=tree_list_model)
+
+list_view.set_model(selection_model)