faq

Author: willmcgugan

FAQ.md

@@ -1,6 +1,8 @@
 
 # Frequently Asked Questions
 - [Does Textual support images?](#does-textual-support-images)
+- [How do I center a widget in a screen?](#how-do-i-center-a-widget-in-a-screen)
+- [How do I pass arguments to an app?](#how-do-i-pass-arguments-to-an-app)
 
 <a name="does-textual-support-images"></a>
 ## Does Textual support images?
@@ -9,6 +11,70 @@ Textual doesn't have built in support for images yet, but it is on the [Roadmap]
 
 See also the [rich-pixels](https://github.com/darrenburns/rich-pixels) project for a Rich renderable for images that works with Textual.
 
+<a name="how-do-i-center-a-widget-in-a-screen"></a>
+## How do I center a widget in a screen?
+
+To center a widget within a container use
+[`align`](https://textual.textualize.io/styles/align/). But remember that
+`align` works on the *children* of a container, it isn't something you use
+on the child you want centered.
+
+For example, here's an app that shows a `Button` in the middle of a
+`Screen`:
+
+```python
+from textual.app import App, ComposeResult
+from textual.widgets import Button
+
+class ButtonApp(App):
+
+    CSS = """
+    Screen {
+        align: center middle;
+    }
+    """
+
+    def compose(self) -> ComposeResult:
+        yield Button("PUSH ME!")
+
+if __name__ == "__main__":
+    ButtonApp().run()
+```
+
+<a name="how-do-i-pass-arguments-to-an-app"></a>
+## How do I pass arguments to an app?
+
+When creating your `App` class, override `__init__` as you would when
+inheriting normally. For example:
+
+```python
+from textual.app import App, ComposeResult
+from textual.widgets import Static
+
+class Greetings(App[None]):
+
+    def __init__(self, greeting: str="Hello", to_greet: str="World") -> None:
+        self.greeting = greeting
+        self.to_greet = to_greet
+        super().__init__()
+
+    def compose(self) -> ComposeResult:
+        yield Static(f"{self.greeting}, {self.to_greet}")
+```
+
+Then the app can be run, passing in various arguments; for example:
+
+```python
+# Running with default arguments.
+Greetings().run()
+
+# Running with a keyword arguyment.
+Greetings(to_greet="davep").run()
+
+# Running with both positional arguments.
+Greetings("Well hello", "there").run()
+```
+
 <hr>
 
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