Textual v6.0.0 broke pong

[TomJGooding]

Today I was just curious if my silly pong game built with Textual still actually worked. Apparently it does... until the latest Textual v6.0.0.

The CHANGELOG does warn of a breaking change:

Optimization to line API to avoid applying background styles to widget content. In practice this means that you can no longer rely on blank Segments automatically getting the background color.

But I'm struggling to understand how this would cause all the weird glitches and how to fix them! Perhaps there's something obvious I'm missing in #6057, but this does include quite a lot of changes.

Obviously this is just my silly experimental game, which is why I posted this as a discussion rather than creating an issue. But I wonder if the changes in the line API might have broken other application widgets too?

[willmcgugan]

Not at my desk to try, but I think the only change that may be required is to explicitly set the Style on your segments. Ie self.rich_style if you want to pull the style from CSS.

This change negates the need to do an expensive second processing of the segments.

[TomJGooding]

Thanks, adding self.rich_style seems to fix it. But I still don't really understand why the sizing/positioning now breaks without this, rather than simply the background color?

[TomJGooding]

Here's another example to illustrate. I don't understand why the widget without self.rich_style will also break the neighbouring widget?

from textual.app import App, ComposeResult
from textual.containers import HorizontalGroup
from textual.strip import Strip
from textual.widget import Widget


class GoodWidget(Widget):
    def render_line(self, y: int) -> Strip:
        return Strip.blank(
            self.size.width,
            self.rich_style,
        )


class BadWidget(Widget):
    def render_line(self, y: int) -> Strip:
        return Strip.blank(
            self.size.width,
            # self.rich_style,
        )


class ExampleApp(App):
    CSS = """
    GoodWidget, BadWidget { width: 20; height: 10; }
    GoodWidget { border: dashed $success; }
    BadWidget  { border: dashed $error;  }
    """

    def compose(self) -> ComposeResult:
        with HorizontalGroup():
            yield BadWidget()
            yield GoodWidget()

        with HorizontalGroup():
            yield GoodWidget()
            yield BadWidget()


if __name__ == "__main__":
    app = ExampleApp()
    app.run()

[willmcgugan]

Not at my keyboard atm, but if that is breaking I'd suspect Strip.blank which I did modify recently.

[TomJGooding]

Sorry, might have helped if I'd remembered to include the screenshot.

[davep]

For what it's worth, in case you hadn't noticed yet, not only does your court get a little wonky, the whole display does. Try quitting with ctrl+c for example.

[TomJGooding]

You could say the pong also broke the pings...

[TomJGooding]

Just in case anyone stumbles across this discussion, it looks like this should be fixed in:

• fix issue rendering strips with missing style #6109