142 lines
4.2 KiB
Python
142 lines
4.2 KiB
Python
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"""
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Tools for lazy loading widgets.
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"""
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from __future__ import annotations
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from textual.widget import Widget
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class Lazy(Widget):
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"""Wraps a widget so that it is mounted *lazily*.
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Lazy widgets are mounted after the first refresh. This can be used to display some parts of
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the UI very quickly, followed by the lazy widgets. Technically, this won't make anything
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faster, but it reduces the time the user sees a blank screen and will make apps feel
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more responsive.
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Making a widget lazy is beneficial for widgets which start out invisible, such as tab panes.
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Note that since lazy widgets aren't mounted immediately (by definition), they will not appear
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in queries for a brief interval until they are mounted. Your code should take this into account.
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Example:
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```python
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def compose(self) -> ComposeResult:
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yield Footer()
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with ColorTabs("Theme Colors", "Named Colors"):
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yield Content(ThemeColorButtons(), ThemeColorsView(), id="theme")
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yield Lazy(NamedColorsView())
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```
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"""
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DEFAULT_CSS = """
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Lazy {
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display: none;
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}
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"""
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def __init__(self, widget: Widget) -> None:
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"""Create a lazy widget.
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Args:
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widget: A widget that should be mounted after a refresh.
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"""
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self._replace_widget = widget
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super().__init__()
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def compose_add_child(self, widget: Widget) -> None:
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self._replace_widget.compose_add_child(widget)
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async def mount_composed_widgets(self, widgets: list[Widget]) -> None:
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parent = self.parent
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if parent is None:
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return
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assert isinstance(parent, Widget)
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async def mount() -> None:
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"""Perform the mount and discard the lazy widget."""
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await parent.mount(self._replace_widget, after=self)
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await self.remove()
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self.call_after_refresh(mount)
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class Reveal(Widget):
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"""Similar to [Lazy][textual.lazy.Lazy], but mounts children sequentially.
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This is useful when you have so many child widgets that there is a noticeable delay before
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you see anything. By mounting the children over several frames, the user will feel that
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something is happening.
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Example:
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```python
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def compose(self) -> ComposeResult:
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with lazy.Reveal(containers.VerticalScroll(can_focus=False)):
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yield Markdown(WIDGETS_MD, classes="column")
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yield Buttons()
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yield Checkboxes()
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yield Datatables()
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yield Inputs()
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yield ListViews()
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yield Logs()
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yield Sparklines()
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yield Footer()
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```
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"""
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DEFAULT_CSS = """
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Reveal {
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display: none;
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}
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"""
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def __init__(self, widget: Widget) -> None:
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"""
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Args:
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widget: A widget to mount.
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"""
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self._replace_widget = widget
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self._widgets: list[Widget] = []
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super().__init__()
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@classmethod
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def _reveal(cls, parent: Widget, widgets: list[Widget]) -> None:
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"""Reveal children lazily.
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Args:
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parent: The parent widget.
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widgets: Child widgets.
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"""
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async def check_children() -> None:
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"""Check for pending children"""
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if not widgets:
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return
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widget = widgets.pop(0)
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try:
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await parent.mount(widget)
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except Exception:
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# I think this can occur if the parent is removed before all children are added
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# Only noticed this on shutdown
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return
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if widgets:
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parent.set_timer(0.02, check_children)
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parent.call_next(check_children)
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def compose_add_child(self, widget: Widget) -> None:
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self._widgets.append(widget)
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async def mount_composed_widgets(self, widgets: list[Widget]) -> None:
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parent = self.parent
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if parent is None:
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return
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assert isinstance(parent, Widget)
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await parent.mount(self._replace_widget, after=self)
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await self.remove()
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self._reveal(self._replace_widget, self._widgets.copy())
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self._widgets.clear()
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