layout: Create an adaptable Layout widget

I'm planning to build on this widget over the next several releases.
It'll eventually be fully adaptable to window size changes made by the
user.

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

emmental/layout.py

@@ -0,0 +1,45 @@
+# Copyright 2023 (c) Anna Schumaker.
+"""Our adaptable layout that can rearrange widgets as the window is resized."""
+from gi.repository import GObject
+from gi.repository import Gtk
+from gi.repository import Adw
+
+
+class Layout(Adw.Bin):
+    """A widget that can rearrange based on window dimensions."""
+
+    show_sidebar = GObject.Property(type=bool, default=False)
+
+    wide_view = GObject.Property(type=bool, default=False)
+
+    def __init__(self, *, content: Gtk.Widget = None,
+                 sidebar: Gtk.Widget = None):
+        """Initialize our Layout widget."""
+        super().__init__()
+        self._split_view = Adw.OverlaySplitView(content=content,
+                                                sidebar=sidebar,
+                                                collapsed=not self.wide_view)
+        self.props.child = self._split_view
+
+        self.bind_property("show-sidebar", self._split_view, "show-sidebar",
+                           GObject.BindingFlags.BIDIRECTIONAL)
+        self.bind_property("wide-view", self._split_view, "collapsed",
+                           GObject.BindingFlags.INVERT_BOOLEAN)
+
+    @GObject.Property(type=Gtk.Widget)
+    def content(self) -> Gtk.Widget:
+        """Get the content widget for the Layout."""
+        return self._split_view.props.content
+
+    @content.setter
+    def content(self, widget: Gtk.Widget) -> None:
+        self._split_view.props.content = widget
+
+    @GObject.Property(type=Gtk.Widget)
+    def sidebar(self) -> Gtk.Widget:
+        """Get the sidebar widget for the Layout."""
+        return self._split_view.props.sidebar
+
+    @sidebar.setter
+    def sidebar(self, widget: Gtk.Widget) -> None:
+        self._split_view.props.sidebar = widget

tests/test_layout.py

@@ -0,0 +1,65 @@
+# Copyright 2023 (c) Anna Schumaker.
+"""Tests our adaptable layout widget."""
+import unittest
+import emmental.layout
+from gi.repository import Gtk
+from gi.repository import Adw
+
+
+class TestLayout(unittest.TestCase):
+    """Test case for our adaptable layout."""
+
+    def setUp(self):
+        """Set up common variables."""
+        self.layout = emmental.layout.Layout()
+
+    def test_init(self):
+        """Check that the layout is set up properly."""
+        self.assertIsInstance(self.layout, Adw.Bin)
+        self.assertIsInstance(self.layout._split_view, Adw.OverlaySplitView)
+        self.assertTrue(self.layout._split_view.props.collapsed)
+
+    def test_wide_view(self):
+        """Test the layout when we have a wide window."""
+        self.assertFalse(self.layout.wide_view)
+        self.assertEqual(self.layout.props.child, self.layout._split_view)
+
+        self.layout.wide_view = True
+        self.assertFalse(self.layout._split_view.props.collapsed)
+
+    def test_content(self):
+        """Test the content widget property."""
+        self.assertIsNone(self.layout.content)
+
+        widget = Gtk.Label()
+        self.layout.content = widget
+        self.assertEqual(self.layout._split_view.props.content, widget)
+        self.assertEqual(self.layout.content, widget)
+
+        widget2 = Gtk.Label()
+        layout2 = emmental.layout.Layout(content=widget2)
+        self.assertEqual(layout2.content, widget2)
+
+    def test_sidebar(self):
+        """Test the sidebar widget property."""
+        self.assertIsNone(self.layout.sidebar)
+
+        widget = Gtk.Label()
+        self.layout.sidebar = widget
+        self.assertEqual(self.layout._split_view.props.sidebar, widget)
+        self.assertEqual(self.layout.sidebar, widget)
+
+        widget2 = Gtk.Label()
+        layout2 = emmental.layout.Layout(sidebar=widget2)
+        self.assertEqual(layout2.sidebar, widget2)
+
+    def test_show_sidebar(self):
+        """Test the show-sidebar property."""
+        self.assertFalse(self.layout.show_sidebar)
+        self.assertFalse(self.layout._split_view.props.show_sidebar)
+
+        self.layout.show_sidebar = True
+        self.assertTrue(self.layout._split_view.props.show_sidebar)
+
+        self.layout._split_view.props.show_sidebar = False
+        self.assertFalse(self.layout.show_sidebar)