bootstack.SplitView#

class bootstack.SplitView(orient='horizontal', *, padding=None, accent=None, surface=None, sash_thickness=None, width=None, height=None, parent=None, **kwargs)#

Bases: PublicWidgetBase

A resizable split container with panes separated by draggable sashes.

Add panes with .add() and place children inside each pane using the returned SplitPane handle. Sashes between panes can be dragged at runtime to resize them. Panes are addressable by key — enumerate them with panes, look one up with item(), place a new one next to another with add(before=) / add(after=), reorder with move(), and drop one with remove().

Parameters:

orient (Orient) – Pane arrangement — 'horizontal' (side-by-side) or 'vertical' (stacked top-to-bottom). Defaults to 'horizontal'.
padding (Padding | None) – Space in pixels between the outer border and the pane area. A single value applies to all sides; (x, y) sets the horizontal and vertical amounts. Defaults to None.
accent (AccentToken | str | None) – Color intent token applied to the sash. When omitted, the sash uses the theme’s default color.
surface (SurfaceToken | str | None) – Surface token for the pane background.
sash_thickness (int | None) – Width (horizontal split) or height (vertical split) of the draggable sash in pixels. Defaults to the theme’s standard sash size (typically 6 px).
width (int | None) – Requested width in pixels.
height (int | None) – Requested height in pixels.
parent (Any) – Override the context-stack parent.
**kwargs (Any) – Layout placement options applied by the parent container — fill, expand, anchor, margin, row, column, sticky. See Arranging Widgets.

property is_attached: bool#

Whether the widget is currently placed in its layout.

True while the widget occupies space in its parent; False after detach (or before it has ever been placed). A detached widget keeps its state and can be returned to the layout with attach.

property panes: tuple[SplitPane, ...]#: All panes in left-to-right (or top-to-bottom) order.

property sash_positions: list[int]#: Current position of every sash in pixels, in order.

property schedule: Schedule#

Scheduler tied to this widget’s lifetime.

All jobs are automatically cancelled when the widget is destroyed. First access creates the Schedule instance; subsequent accesses return the same instance.

Usage:

self.schedule.delay(500, callback)
self.schedule.every(1000, tick)
job = self.schedule.idle(refresh)
job.cancel()

add(key=None, *, before=None, after=None, weight=1, layout='column', padding=None, gap=0, horizontal_items=None, vertical_items=None, grow_items=False, columns=None, rows=None, auto_flow='row')#

Add a pane and return a handle for placing its children and controlling it.

Panes are appended in order by default. Pass before= or after= (the key of an existing pane) to place the new pane next to another one.

Parameters:

key (str | None) – Unique identifier for the pane, used with item(), move(), and remove(). Auto-generated when omitted.
before (str | None) – Place the new pane immediately before the pane with this key.
after (str | None) – Place the new pane immediately after the pane with this key. Mutually exclusive with before; omit both to append at the end.
weight (int) – Relative size weight when the container is resized. Panes with a higher weight take proportionally more space. Settable afterward via the pane’s weight property. Defaults to 1.
layout (LayoutKind) – Internal pane layout. Defaults to 'column'.
padding (Padding | None) – Space in pixels inside the pane border. Defaults to None.
gap (int) – Space in pixels between children. Defaults to 0.
horizontal_items (str | None) – How children sit on the horizontal axis — edge values 'left'/'center'/'right'/'stretch', plus 'space-*' when horizontal is the stacking axis. Defaults to 'stretch' in grid mode, 'center' in a column and 'left' in a row.
vertical_items (str | None) – How children sit on the vertical axis — edge values 'top'/'center'/'bottom'/'stretch', plus 'space-*' when vertical is the stacking axis. Defaults to 'stretch' in grid mode, 'center' in a row and 'top' in a column.
grow_items (bool) – For 'column'/'row', when True every child grows equally to share the main axis. Defaults to False.
columns (int | list[int | str] | None) – Column definitions for 'grid' layout. An integer sets the number of equal-weight columns; a list sets per-column weights or sizes (e.g. [1, 2, 'auto', '120px']).
rows (int | list[int | str] | None) – Row definitions for 'grid' layout, same format as columns.
auto_flow (AutoFlow) – Grid auto-flow direction. Defaults to 'row'.

Returns:

SplitPane — use as a context manager to place children, and as a handle to read/set weight or remove() the pane.

Raises:

KeyError – If before/after names a pane that does not exist.
ValueError – If both before and after are given.

Return type:

SplitPane

attach(**kwargs)#

Return a detached widget to its layout, optionally moving it.

With no arguments, restores the widget to exactly where detach took it from. Any layout kwargs accepted by the original placement (e.g. fill, expand, anchor, sticky, margin) override the stored options. For stacked widgets, index= sets the position among the currently attached siblings (or pass an explicit before=/after= sibling); without one, the snapshotted position is used.

Calling attach on a widget that is already attached moves it (the kwargs are re-applied). Fires on_attach.

Parameters:: **kwargs (Any) – Layout placement options to override for this placement.
Raises:: ParentResolutionError – If the widget was never placed in a layout.

capture(path, *, inset=0, settle=0.1)#

Save a picture of this widget to an image file.

Captures the area this widget occupies on screen — one widget, a whole window, or the entire application, depending on what you call it on. The file extension selects the format, so .png, .jpg, and .pdf all work.

The widget has to be visible. A capture reads pixels from the display, so the window is brought to the front first and a hidden or detached widget cannot be captured at all. Any always-on-top setting the window already had is left as it was found.

Pair it with a save dialog to let the user choose where it goes:

import bootstack as bs

def on_export():
    chosen = bs.ask_save_file(initial_file="dashboard.png")
    if chosen:
        app.capture(chosen)

Parameters:

path (str | Path) – Where to write the image. Missing parent folders are created, and the extension chooses the format.
inset (int) – Pixels to trim from every edge, zero or more. Use 2 on a whole window to drop the native border artifact.
settle (float) – Seconds to let the desktop finish repainting before the pixels are read. The default covers the common case of a dialog closing just beforehand. The interface pauses for this long, so a second click on the control that started the capture waits its turn rather than starting an overlapping one.

Returns:

The path that was written.

Raises:

BootstackError – If the widget is not visible on screen or has been scrolled out of view, if inset is negative, if no capture backend is available, or if the file cannot be written.

Return type:

Path

Added in version 0.3.0.

destroy()#

Destroy the widget and release the resources it holds.

Removes the widget from its parent, destroys its children, and cancels any pending or repeating jobs on its schedule. After this the widget must not be used again. Destroying a container destroys everything inside it.

detach()#

Remove the widget from its layout without destroying it.

The widget stops occupying space but keeps its state, children, and event bindings, ready to be returned with attach. The current position is snapshotted so a plain attach() restores it exactly — for stacked siblings this is the index among the currently attached siblings, so detaching other siblings first shifts that index.

Calling detach on a widget that is already detached, or one that was never placed in a layout, does nothing. Fires on_detach.

emit(event, *, data=None)#

Fire a named event on this widget, as if it produced the event itself.

This is how a composite widget surfaces high-level activity to its listeners, and the generic counterpart to the on_*() shorthands for firing events that have no dedicated method.

It is meant for the framework’s own events — 'change', 'select', 'input' and the rest of the data-carrying names. A handler registered through on() or an on_<event>() shorthand receives what is emitted.

Names that map onto a native event instead ('click', 'focus', 'blur', 'submit', …) are a different matter: emitting one asks the toolkit to deliver a real input event, which carries no payload and can reach handlers the widget installed for its own use. Emitting those is not a way to notify listeners, and a listener bound through on() may not see it. Drive the widget through its properties and methods instead.

Parameters:

event (str) – The event name, unprefixed — the same name you pass to on() or an on_<event>() shorthand (e.g. 'change', 'select').
data (Any) – The payload delivered to handlers. Pass the matching payload dataclass from bootstack.events — the same object an on_<event>() handler receives.

Example

from bootstack.events import ChangeEvent

field.emit("change", data=ChangeEvent(value=new_value))

item(key)#

Return the pane handle for key.

Parameters:: key (str) – Pane key.
Returns:: The SplitPane for that key — read/set its weight or remove() it.
Return type:: SplitPane

keys()#

All pane keys in order.

move(key, *, before=None, after=None)#

Move an existing pane next to another pane.

Parameters:

key (str) – The key of the pane to move.
before (str | None) – Move it immediately before the pane with this key.
after (str | None) – Move it immediately after the pane with this key. Pass exactly one of before or after.

Raises:

KeyError – If key, before, or after names a pane that does not exist.
ValueError – If not exactly one of before/after is given, or if the anchor is the pane being moved.

on(event, handler=None)#

Bind handler to event, or return a composable Stream.

With a handler — binds immediately and returns a Subscription:

sub = widget.on("change", handler)
sub.cancel()

Without a handler — returns a Stream for operator chaining. The Tk binding is created lazily when .listen() is called:

sub = widget.on("change").debounce(300).listen(handler)
sub.cancel()

Parameters:

event (str) – Event name (e.g. "change", "click").
handler (Callable[[Any], Any] | None) – Optional callback. If omitted, a Stream is returned.

Returns:

Subscription when a handler is provided; Stream otherwise.

Return type:

Stream | Subscription

on_attach(handler=None)#

Register a callback fired when the widget enters the layout.

Fires each time the widget becomes visible in its parent — on initial placement and on every attach. Pair it with on_detach to keep per-visibility resources (timers, observers) tied to the widget’s presence on screen. The handler receives a curated Event.

Parameters:: handler (Callable[[Event], Any] | None) – Called when the widget is attached. Omit to get a composable Stream.
Returns:: A cancellable Subscription when a handler is given, otherwise a Stream.
Return type:: Stream | Subscription

on_destroy(handler=None)#

Register a callback fired when the widget is destroyed.

Fires once, as the widget is torn down — the place to release resources the widget owns that aren’t cleaned up automatically (file handles, observers, external subscriptions). The handler receives a curated Event.

Parameters:: handler (Callable[[Event], Any] | None) – Called as the widget is destroyed. Omit to get a composable Stream.
Returns:: A cancellable Subscription when a handler is given, otherwise a Stream.
Return type:: Stream | Subscription

on_detach(handler=None)#

Register a callback fired when the widget leaves the layout.

Fires each time the widget stops occupying space in its parent — on detach and when an ancestor hides it. Pair it with on_attach to release per-visibility resources. The handler receives a curated Event.

Parameters:: handler (Callable[[Event], Any] | None) – Called when the widget is detached. Omit to get a composable Stream.
Returns:: A cancellable Subscription when a handler is given, otherwise a Stream.
Return type:: Stream | Subscription

on_sash_moved() → Stream#

on_sash_moved(handler: Callable[[SashMoveEvent], Any]) → Subscription

Register a callback fired when a sash drag is released.

Parameters:: handler (Callable[[SashMoveEvent], Any] | None) – Called with a SashMoveEvent carrying index (zero-based sash index) and position (pixel offset from the leading edge). Omit to get a composable Stream.
Returns:: A cancellable Subscription when a handler is given, otherwise a Stream.
Return type:: Stream | Subscription

remove(key)#

Remove a pane and destroy its content.

Parameters:: key (str) – The key assigned when the pane was added.

sash_position(index, position=None)#

Get or set the position of a sash.

Parameters:

index (int) – Zero-based sash index. A split view with n panes has n - 1 sashes.
position (int | None) – New position in pixels. If None, returns the current position.

Returns:

Current sash position in pixels when position is None.

Raises:

IndexError – If index does not refer to an existing sash.

Return type:

int | None