buttons: Create an ImageToggle button

This button is inspired by the Gtk.ToggleButton button, except it
changes the displayed icon when active.

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

emmental/buttons.py

@@ -78,3 +78,37 @@ class SplitButton(Gtk.Box):
     @GObject.Signal
     def clicked(self) -> None:
         """Signal that the primary button has been clicked."""
+
+
+class ImageToggle(Button):
+    """Inspired by a ToggleButton, but changes image based on state."""
+
+    active_icon_name = GObject.Property(type=str)
+    inactive_icon_name = GObject.Property(type=str)
+
+    def __init__(self, active_icon_name: str, inactive_icon_name: str,
+                 active: bool = False, **kwargs) -> None:
+        """Initialize an ImageToggle button."""
+        super().__init__(active_icon_name=active_icon_name,
+                         inactive_icon_name=inactive_icon_name,
+                         icon_name=inactive_icon_name, active=active, **kwargs)
+
+    def do_clicked(self) -> None:
+        """Handle a click event."""
+        self.active = not self.active
+
+    @GObject.Property(type=bool, default=False)
+    def active(self) -> bool:
+        """Get the active state."""
+        return self.icon_name == self.active_icon_name
+
+    @active.setter
+    def active(self, newval: bool) -> None:
+        if newval != self.active:
+            icon = self.active_icon_name if newval else self.inactive_icon_name
+            self.icon_name = icon
+            self.emit("toggled")
+
+    @GObject.Signal
+    def toggled(self) -> None:
+        """Active state has been toggled."""

tests/test_buttons.py

@@ -147,3 +147,49 @@ class TestSplitButton(unittest.TestCase):
         self.button.connect("clicked", on_click)
         self.button._primary.emit("clicked")
         on_click.assert_called_with(self.button)
+
+
+class TestImageToggle(unittest.TestCase):
+    """Test an ImageToggle button."""
+
+    def setUp(self):
+        """Set up common variables."""
+        self.button = emmental.buttons.ImageToggle("active", "inactive")
+
+    def test_init(self):
+        """Test that the ImageToggle button is configured correctly."""
+        self.assertIsInstance(self.button, emmental.buttons.Button)
+        self.assertEqual(self.button.active_icon_name, "active")
+        self.assertEqual(self.button.inactive_icon_name, "inactive")
+        self.assertEqual(self.button.icon_name, "inactive")
+        self.assertFalse(self.button.active)
+
+    def test_active(self):
+        """Test the active property."""
+        self.button.active = True
+        self.assertTrue(self.button.active)
+        self.assertEqual(self.button.icon_name, "active")
+
+        self.button.active = False
+        self.assertFalse(self.button.active)
+        self.assertEqual(self.button.icon_name, "inactive")
+
+        button2 = emmental.buttons.ImageToggle("active", "inactive",
+                                               active=True)
+        self.assertTrue(button2.active)
+
+    def test_toggle(self):
+        """Test the toggle signal."""
+        toggled = unittest.mock.Mock()
+        self.button.connect("toggled", toggled)
+
+        self.button.active = False
+        toggled.assert_not_called()
+
+        self.button.active = True
+        toggled.assert_called()
+
+        toggled.reset_mock()
+        self.button.emit("clicked")
+        self.assertFalse(self.button.active)
+        toggled.assert_called()