150 lines
5.0 KiB
Python
150 lines
5.0 KiB
Python
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from __future__ import annotations
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from itertools import zip_longest
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from typing import TYPE_CHECKING
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from textual.geometry import NULL_OFFSET, Region, Size
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from textual.layout import ArrangeResult, Layout, WidgetPlacement
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if TYPE_CHECKING:
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from textual.widget import Widget
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class StreamLayout(Layout):
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"""A cut down version of the vertical layout.
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The stream layout is faster, but has a few limitations compared to the vertical layout.
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- All widgets are the full width (as if their widget is `1fr`).
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- All widgets have an effective height of `auto`.
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- `max-height` is supported, but only if it is a units value, all other extrema rules are ignored.
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- No absolute positioning.
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- No overlay: screen.
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- Layers are ignored.
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- Non TCSS styles are ignored.
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The primary use of `layout: stream` is for a long list of widgets in a scrolling container, such as
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what you might expect from a LLM chat-bot. The speed improvement will only be significant with a lot of
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child widgets, so stick to vertical layouts unless you see any slowdown.
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"""
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name = "stream"
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def __init__(self) -> None:
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self._cached_placements: list[WidgetPlacement] | None = None
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self._cached_width = 0
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super().__init__()
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def arrange(
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self, parent: Widget, children: list[Widget], size: Size, greedy: bool = True
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) -> ArrangeResult:
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parent.pre_layout(self)
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if not children:
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return []
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viewport = parent.app.viewport_size
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if size.width != self._cached_width:
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self._cached_placements = None
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previous_results = self._cached_placements or []
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layout_widgets = parent.screen._layout_widgets.get(parent, [])
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_Region = Region
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_WidgetPlacement = WidgetPlacement
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placements: list[WidgetPlacement] = []
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width = size.width
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first_child_styles = children[0].styles
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y = 0
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previous_margin = first_child_styles.margin.top
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null_offset = NULL_OFFSET
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pre_populate = bool(previous_results and layout_widgets)
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for widget, placement in zip_longest(children, previous_results):
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if pre_populate and placement is not None and widget is placement.widget:
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if widget in layout_widgets:
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pre_populate = False
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else:
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placements.append(placement)
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y = placement.region.bottom
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styles = widget.styles._base_styles
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previous_margin = styles.margin.bottom
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continue
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if widget is None:
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break
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styles = widget.styles._base_styles
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margin = styles.margin
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gutter_width, gutter_height = styles.gutter.totals
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top, right, bottom, left = margin
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y += top if top > previous_margin else previous_margin
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previous_margin = bottom
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height = (
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widget.get_content_height(size, viewport, width - gutter_width)
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+ gutter_height
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)
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if (max_height := styles.max_height) is not None and max_height.is_cells:
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height = (
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height
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if height < (max_height_value := int(max_height.value))
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else max_height_value
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)
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if (min_height := styles.min_height) is not None and min_height.is_cells:
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height = (
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height
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if height > (min_height_value := int(min_height.value))
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else min_height_value
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)
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placements.append(
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_WidgetPlacement(
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_Region(left, y, width - (left + right), height),
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null_offset,
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margin,
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widget,
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0,
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False,
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False,
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False,
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)
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)
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y += height
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self._cached_width = size.width
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self._cached_placements = placements
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return placements
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def get_content_width(self, widget: Widget, container: Size, viewport: Size) -> int:
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"""Get the optimal content width by arranging children.
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Args:
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widget: The container widget.
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container: The container size.
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viewport: The viewport size.
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Returns:
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Width of the content.
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"""
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return widget.scrollable_content_region.width
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def get_content_height(
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self, widget: Widget, container: Size, viewport: Size, width: int
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) -> int:
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"""Get the content height.
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Args:
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widget: The container widget.
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container: The container size.
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viewport: The viewport.
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width: The content width.
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Returns:
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Content height (in lines).
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"""
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if widget._nodes:
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arrangement = widget.arrange(Size(width, 0))
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height = arrangement.total_region.height
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else:
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height = 0
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return height
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