Use default screen

src/textual_cookbook/recipes/architecture_patterns/use_default_screen.py

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+"""An example showing how to use a default main screen.
+
+Simple Textual apps place a lot of logic in the `App` class, but you can also
+use a `Screen` as the main screen. This example shows how to do that, and how to
+push modal screens from the main screen, and show a modal confirmation screen
+when quitting the app. You'll never leave the main screen until you quit the
+application, but you can still use the `App` class to manage a (few)
+application-wide bindings.
+
+Recipe by David Fokkema
+"""
+
+import sys
+
+from textual import on
+from textual.app import App, ComposeResult
+from textual.containers import HorizontalGroup, VerticalGroup
+from textual.screen import ModalScreen, Screen
+from textual.widgets import Button, Footer, Label
+
+
+class HelpModal(ModalScreen[None]):
+    BINDINGS = [("escape", "dismiss", "Dismiss")]
+
+    def compose(self) -> ComposeResult:
+        yield Footer()
+        yield Label("Just your regular help screen, dismiss with escape")
+
+
+class MainScreen(Screen[None]):
+    BINDINGS = [
+        ("a", "add_item", "Add Item"),
+        ("r", "remove_item", "Remove Item"),
+        ("h", "show_help", "Help"),
+    ]
+
+    items: list[str] = []
+
+    def compose(self) -> ComposeResult:
+        yield Footer()
+        yield Label()
+
+    def on_mount(self) -> None:
+        self.update_label()
+
+    def action_add_item(self) -> None:
+        self.items.append("💡")
+        self.update_label()
+
+    def action_remove_item(self) -> None:
+        if self.items:
+            self.items.pop()
+            self.update_label()
+
+    def update_label(self) -> None:
+        widget = self.query_one(Label)
+        if self.items:
+            widget.update("".join(self.items))
+        else:
+            widget.update("Empty")
+
+    def action_show_help(self) -> None:
+        self.app.push_screen(HelpModal())
+
+
+class ConfirmQuitScreen(ModalScreen[bool]):
+    BINDINGS = [("escape", "dismiss", "Dismiss")]
+
+    def compose(self) -> ComposeResult:
+        yield Footer()
+        with VerticalGroup():
+            yield Label("Are you sure you want to quit?")
+            yield HorizontalGroup(
+                Button("Yes", id="yes_button", variant="success"),
+                Button("No", id="no_button", variant="error"),
+            )
+
+    @on(Button.Pressed)
+    def confirm(self, event: Button.Pressed) -> None:
+        if event.button.id == "yes_button":
+            self.dismiss(True)
+        else:
+            self.dismiss(False)
+
+
+class MainApp(App[None]):
+    BINDINGS = [("q", "confirm_quit", "Quit")]
+
+    CSS = """
+        MainScreen Label {
+            width: 100%;
+            text-align: center;
+            padding-top: 5;
+        }
+
+        HelpModal {
+            align: center middle;
+            & Label {
+                border: $primary hkey;
+                background: $panel;
+                padding: 1 2;
+                margin-top: 3;
+            }
+        }
+
+        ConfirmQuitScreen {
+            align: center middle;
+            & VerticalGroup {
+                width: auto;
+
+                & Label {
+                    width: 100%;
+                    text-align: center;
+                }
+
+                & HorizontalGroup {
+                    width: auto;
+
+                    & Button {
+                        margin: 1 2;
+                    }
+                }
+            }
+        }
+    """
+
+    def get_default_screen(self) -> Screen[None]:
+        return MainScreen()
+
+    def action_confirm_quit(self) -> None:
+        def callback(is_confirmed: bool | None) -> None:
+            if is_confirmed:
+                self.exit()
+
+        self.push_screen(ConfirmQuitScreen(), callback=callback)
+
+
+if __name__ == "__main__":
+    app = MainApp()
+    app.run()
+    sys.exit(app.return_code)