The reported width of a widget doesn't take the scrollbar into account.

[davep]

Consider the following test code:

from textual.app         import App, ComposeResult, RenderResult
from textual.containers  import Vertical
from textual.widgets     import Header, Footer
from textual.scroll_view import ScrollView
from textual.geometry    import Size

class ScrollViewPlaceHolder( ScrollView ):

    def __init__( self, height: int ):
        super().__init__()
        self._height = height

    def on_mount( self ) -> None:
        self.virtual_size = Size( self.size.width, self._height )

    def render( self ) -> RenderResult:
        return "\n".join( (
            "".join( f"{n + 1:3}"[ 0 ] for n in range( self.size.width ) ),
            "".join( f"{n + 1:3}"[ 1 ] for n in range( self.size.width ) ),
            "".join( f"{n + 1:3}"[ 2 ] for n in range( self.size.width ) ),
            "", "",
            f"Size: {self.size!r}",
            f"Virtual size: {self.virtual_size!r}",
            f"Vertical scrollbar width: {self.scrollbar_size_vertical}",
            "",
            "Text to width:",
            "-" * self.size.width,
            "Text to width minus 2:",
            "-" * ( self.size.width - 2 ),
            "Text to width minus vertical scrollbar:",
            "-" * ( self.size.width - self.scrollbar_size_vertical ),
            "Text to width minus vertical scrollbar minus 2:",
            "-" * ( self.size.width - self.scrollbar_size_vertical - 2 ),
        ) )

class ScrollViewApp( App[ None ] ):

    CSS = """
    ScrollViewPlaceHolder {
        height: 1fr;
        border: round red;
    }
    """

    def compose( self ) -> ComposeResult:
        yield Header()
        yield Vertical( ScrollViewPlaceHolder( 1 ), ScrollViewPlaceHolder( 1000 ) )
        yield Footer()

if __name__ == "__main__":
    ScrollViewApp().run()

and the output from it:

Checked with Will and the expectation is that the width should take the scrollbar width into account; but given the above it seems not.

[davep]

See #1891 work taking place towards a possible fix (not linking this as "a thing that will be fixed by that thing" just yet, but I suspect it will).

[willmcgugan]

This is as expected. You can get the size without the scrollbars with self.scrollable_content_region.size, which is possibly a verbose. We could add a scrollable_size property to expose that.

[willmcgugan]

#2175

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