Class StylesCache

src/textual/_styles_cache.py:37–523

Responsible for rendering CSS Styles and keeping a cache of rendered lines. The render method applies border, outline, and padding set in the Styles object to widget content. The diagram below shows content (possibly from a Rich renderable) with padding and border. The labels A. B. and

@rich.repr.auto(angular=True)
class StylesCache:
    """Responsible for rendering CSS Styles and keeping a cache of rendered lines.

    The render method applies border, outline, and padding set in the Styles object to widget content.

    The diagram below shows content (possibly from a Rich renderable) with padding and border. The
    labels A. B. and C. indicate the code path (see comments in render_line below) chosen to render
    the indicated lines.

    ```
    ┏━━━━━━━━━━━━━━━━━━━━━━┓◀── A. border
    ┃                      ┃◀┐
    ┃                      ┃ └─ B. border + padding +
    ┃   Lorem ipsum dolor  ┃◀┐         border
    ┃   sit amet,          ┃ │
    ┃   consectetur        ┃ └─ C. border + padding +
    ┃   adipiscing elit,   ┃     content + padding +
    ┃   sed do eiusmod     ┃           border
    ┃   tempor incididunt  ┃
    ┃                      ┃
    ┃                      ┃
    ┗━━━━━━━━━━━━━━━━━━━━━━┛
    ```
    """

    def __init__(self) -> None:
        self._cache: dict[int, Strip] = {}
        self._dirty_lines: set[int] = set()
        self._width = 1
        self._simple_strip: Strip | None = None
        """A simple strip consisting of left border + background + right border, which may be reused in a render."""

    def __rich_repr__(self) -> rich.repr.Result:
        if self._dirty_lines:
            yield "dirty", self._dirty_lines
        yield "width", self._width, 1

    def set_dirty(self, *regions: Region) -> None:
        """Add a dirty regions."""
        if regions:
            for region in regions:
                self._dirty_lines.update(region.line_range)
        else:
            self.clear()

    def is_dirty(self, y: int) -> bool:
        """Check if a given line is dirty (needs to be rendered again).

        Args:
            y: Y coordinate of line.

        Returns:
            True if line requires a render, False if can be cached.
        """
        return y in self._dirty_lines

    def clear(self) -> None:
        """Clear the styles cache (will cause the content to re-render)."""