fix(app): fix garbled inline app output

[TomJGooding]

Fix garbled inline app output when inline_no_clear=True.

Currently the terminal cursor isn't actually "reset" before printing the screen contents. This doesn't matter for most inline apps as the cursor is already offset at (0, 0). But if the app contains an Input widget, this will update the cursor position so the output will be garbled.

Fixes #6064

Please review the following checklist.

• Docstrings on all new or modified functions / classes
• Updated documentation
• Updated CHANGELOG.md (where appropriate)

[TomJGooding]

Example app for testing:

from textual.app import App, ComposeResult
from textual.widgets import Input


class ExampleApp(App):
    def compose(self) -> ComposeResult:
        yield Input("Press ctrl+q to quit")

    def on_mount(self) -> None:
        # Workaround possible bug with the initial input cursor position
        # https://github.com/Textualize/textual/issues/6064#issuecomment-3217177954
        self.simulate_key("right")

        # Show the terminal cursor for debugging
        self._driver.write("\x1b[?25h")


if __name__ == "__main__":
    app = ExampleApp()
    app.run(
        inline=True,
        inline_no_clear=True,
    )

[TomJGooding]

-cursor_y + 1 will duplicate the first line in the output. But I think this was included in case the app crashes so the traceback doesn't overwrite the prompt?

[TomJGooding]

Another test app to check the prompt is correctly restored:

from textual.app import App, ComposeResult
from textual.widgets import Button

INLINE_NO_CLEAR = False

INVALID_CSS = False


class ExitRenderablesApp(App):
    CSS = "Screen { background: invalid; }" if INVALID_CSS else ""

    def compose(self) -> ComposeResult:
        yield Button.error("Runtime Error")

    def on_mount(self) -> None:
        # Show the terminal cursor for debugging
        self._driver.write("\x1b[?25h")

    def on_button_pressed(self) -> None:
        raise RuntimeError()


if __name__ == "__main__":
    app = ExitRenderablesApp()
    app.run(
        inline=True,
        inline_no_clear=INLINE_NO_CLEAR,
    )

[TomJGooding]

Currently there is an empty line after the app output, which is removed with this change. But I'm not sure if this bottom 'padding' was intentional or not, since the INLINE_PADDING attribute is the "number of blank lines above an inline app".

I've marked as ready for review - I'm annoyed that I spent so long debugging this for what might be a simple 4 line change!

[willmcgugan]

I've marked as ready for review - I'm annoyed that I spent so long debugging this for what might be a simple 4 line change!

It's not the total number of lines that counts, but knowing which 4 lines to change!