Added list view section demo (#206)

Author: Nokse22

src/List View with Sections/main.blp

@@ -0,0 +1,42 @@
+using Gtk 4.0;
+using Adw 1;
+
+Adw.StatusPage {
+  title: _("List View with Sections");
+  description: _("Divide items in a list view with sections");
+  valign: start;
+
+  Adw.Clamp {
+    maximum-size: 360;
+
+    Box {
+      orientation: vertical;
+      spacing: 18;
+
+      Box {
+        halign: center;
+
+        LinkButton {
+          label: _("API Reference");
+          uri: "https://docs.gtk.org/gtk4/iface.SectionModel.html";
+        }
+
+        LinkButton {
+          label: _("Documentation");
+          uri: "https://docs.gtk.org/gtk4/section-list-widget.html#sections";
+        }
+      }
+
+      ScrolledWindow {
+        height-request: 330;
+        has-frame: true;
+
+        child: ListView list_view {
+          factory: SignalListItemFactory item_factory {};
+
+          header-factory: SignalListItemFactory header_factory {};
+        };
+      }
+    }
+  }
+}

src/List View with Sections/main.json

@@ -0,0 +1,6 @@
+{
+  "category": "layout",
+  "description": "Divide items in a list view with sections",
+  "panels": ["ui", "preview"],
+  "autorun": true
+}

src/List View with Sections/main.py

@@ -0,0 +1,50 @@
+import gi
+
+gi.require_version("Gtk", "4.0")
+gi.require_version("Adw", "1")
+from gi.repository import Gtk
+import workbench
+
+list_view = workbench.builder.get_object("list_view")
+item_factory = workbench.builder.get_object("item_factory")
+header_factory = workbench.builder.get_object("header_factory")
+
+
+class CustomModel(Gtk.StringList, Gtk.SectionModel):
+    def __init__(self):
+        super().__init__()
+
+    def do_get_section(self, position):
+        start = (position // 5) * 5
+        end = start + 5
+        return (start, end)
+
+
+def on_setup_item(_, list_item):
+    list_item.set_child(Gtk.Label(margin_start=12, xalign=0))
+
+
+def on_bind_item(_, list_item):
+    item = list_item.get_item()
+    label = list_item.get_child()
+
+    label.set_label(item.get_string())
+
+
+def on_setup_header(_, list_item):
+    list_item.set_child(Gtk.Label(label="Header", xalign=0))
+
+
+custom_model = CustomModel()
+
+for i in range(0, 200):
+    custom_model.append(f"Item {i}")
+
+item_factory.connect("setup", on_setup_item)
+item_factory.connect("bind", on_bind_item)
+
+header_factory.connect("setup", on_setup_header)
+
+selection_model = Gtk.NoSelection(model=custom_model)
+
+list_view.set_model(selection_model)