Merge pull request #4979 from Textualize/app-focus-style

src/textual/app.py

@@ -312,6 +312,8 @@ class App(Generic[ReturnType], DOMNode):
     App {
         background: $background;
         color: $text;
+
+        /* When a widget is maximized */
         Screen.-maximized-view {                    
             layout: vertical !important;
             hatch: right $panel;
@@ -321,6 +323,10 @@ class App(Generic[ReturnType], DOMNode):
                 dock: initial !important;
             }
         }
+        /* Fade the header title when app is blurred */
+        &:blur HeaderTitle {           
+            text-opacity: 50%;           
+        }
     }
     *:disabled:can-focus {
         opacity: 0.7;
@@ -820,6 +826,17 @@ def _context(self) -> Generator[None, None, None]:
             active_message_pump.reset(message_pump_reset_token)
             active_app.reset(app_reset_token)
 
+    def get_pseudo_classes(self) -> Iterable[str]:
+        """Pseudo classes for a widget.
+
+        Returns:
+            Names of the pseudo classes.
+        """
+        yield "focus" if self.app_focus else "blur"
+        yield "dark" if self.dark else "light"
+        if self.is_inline:
+            yield "inline"
+
     def animate(
         self,
         attribute: str,
@@ -3617,6 +3634,7 @@ def post_mount() -> None:
 
     def _watch_app_focus(self, focus: bool) -> None:
         """Respond to changes in app focus."""
+        self.screen._update_styles()
         if focus:
             # If we've got a last-focused widget, if it still has a screen,
             # and if the screen is still the current screen and if nothing

tests/snapshot_tests/test_snapshots.py

@@ -6,6 +6,7 @@
 from rich.text import Text
 
 from tests.snapshot_tests.language_snippets import SNIPPETS
+from textual import events
 from textual.app import App, ComposeResult
 from textual.binding import Binding
 from textual.containers import Vertical
@@ -124,7 +125,9 @@ async def run_before(pilot):
         pilot.app.query(Input).first().cursor_blink = False
 
     assert snap_compare(
-        SNAPSHOT_APPS_DIR / "masked_input.py", press=["A","B","C","0","1","-","D","E"], run_before=run_before
+        SNAPSHOT_APPS_DIR / "masked_input.py",
+        press=["A", "B", "C", "0", "1", "-", "D", "E"],
+        run_before=run_before,
     )
 
 
@@ -1820,3 +1823,39 @@ def on_mount(self) -> None:
 
     # ctrl+m to maximize, escape *should* minimize
     assert snap_compare(TextAreaExample(), press=["ctrl+m", "escape"])
+
+
+def test_app_focus_style(snap_compare):
+    """Test that app blur style can be selected."""
+
+    class FocusApp(App):
+        CSS = """
+        Label {
+            padding: 1 2;
+            margin: 1 2;
+            background: $panel;
+            border: $primary;
+        }
+        App:focus {
+            .blurred {
+                visibility: hidden;
+            }
+        }
+
+        App:blur {
+            .focussed {
+                visibility: hidden;
+            }
+        }
+
+        """
+
+        def compose(self) -> ComposeResult:
+            yield Label("BLURRED", classes="blurred")
+            yield Label("FOCUSED", classes="focussed")
+
+    async def run_before(pilot: Pilot) -> None:
+        pilot.app.post_message(events.AppBlur())
+        await pilot.pause()
+
+    assert snap_compare(FocusApp(), run_before=run_before)

tests/test_test_runner.py

@@ -12,8 +12,9 @@ def on_key(self, event: events.Key) -> None:
 
     app = TestApp()
     async with app.run_test() as pilot:
-        assert (
-            str(pilot) == "<Pilot app=TestApp(title='TestApp', classes={'-dark-mode'})>"
+        assert str(pilot) in (
+            "<Pilot app=TestApp(title='TestApp', classes={'-dark-mode'}, pseudo_classes={'dark', 'focus'})>",
+            "<Pilot app=TestApp(title='TestApp', classes={'-dark-mode'}, pseudo_classes={'focus', 'dark'})>",
         )
         await pilot.press("tab", *"foo")
         await pilot.exit("bar")