bootstack.Picture#

class bootstack.Picture(image=None, *, fit='contain', width=None, height=None, anchor='center', corner_radius=0, autoplay=True, loop=True, surface=None, padding=None, parent=None, **kwargs)#

Bases: PublicWidgetBase

Displays an image, scaled to fit, with optional animation.

Picture is the display widget for pictures and media — the counterpart to an Image, which is only a source handle. Hand it an Image (or a file path) and it renders the picture into a resizable area, scaling it to fit with a chosen policy. Animated GIF and WebP sources play automatically.

Unlike showing an image on a Label, a Picture is sizing-aware: it fills the space it is given and re-fits the picture as that space changes, so it works in responsive layouts.

Parameters:

  • image (Image | str | Path | None) – The picture to show — an Image handle (from bootstack.images), a file path (str or Path, opened for you), or None for an empty frame. Assign the image property later to change it.

  • fit (ImageFit) –

    How the picture is scaled into the display area. Default 'contain'.

    • 'contain' — scale to fit inside, preserving aspect ratio (letterboxing any remainder).

    • 'cover' — scale to fill, preserving aspect ratio (cropping the overflow).

    • 'fill' — stretch to fill, ignoring aspect ratio.

    • 'none' — show at natural size, no scaling.

    • 'scale-down' — like 'contain', but never enlarge past natural size.

  • width (int | None) – Fixed display width in pixels. Omit to size from the container.

  • height (int | None) – Fixed display height in pixels. Omit to size from the container.

  • anchor (Anchor) – Where the picture sits within the area when it does not fill it (with 'contain', 'scale-down', or 'none'). Default 'center'.

  • corner_radius (int) – Rounded-corner radius in pixels. 0 (default) is square.

  • autoplay (bool) – Start playing an animated source as soon as it is shown. Default True.

  • loop (bool) – Loop an animated source. Default True.

  • surface (SurfaceToken | str | None) – Background surface token used to letterbox behind the picture.

  • parent (Any) – Explicit parent widget. If omitted, the current context-stack container is used.

  • **kwargs (Any) – Layout placement options applied by the parent container (e.g. fill, expand, row, column). See Arranging Widgets.

property fit: Literal['contain', 'cover', 'fill', 'none', 'scale-down']#

The fit policy controlling how the picture is scaled into its area.

property image: Image | None#

The displayed image handle, or None when empty.

Assign an Image, a file path, or None to change what is shown.

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 is_playing: bool#

Whether an animated source is currently playing.

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()
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))
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_click() → Stream#
on_click(handler: Callable[[Event], Any]) → Subscription

Register a callback for clicks on the picture.

The handler receives a curated Event.

Parameters:

handler (Callable[[Event], Any] | None) – Called with the click Event. Omit to get a composable Stream.

Returns:

A 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_error() → Stream#
on_error(handler: Callable[[ImageErrorEvent], Any]) → Subscription

Register a callback fired when an image fails to load or decode.

The handler receives an ImageErrorEvent carrying a human-readable message.

Parameters:

handler (Callable[[ImageErrorEvent], Any] | None) – Called with the error event. Omit to get a composable Stream.

Returns:

A Subscription when a handler is given, otherwise a Stream.

Return type:

Stream | Subscription

on_load() → Stream#
on_load(handler: Callable[[ImageLoadEvent], Any]) → Subscription

Register a callback fired when an image is decoded and displayed.

The handler receives an ImageLoadEvent with the picture’s natural width, height, and frame count.

Parameters:

handler (Callable[[ImageLoadEvent], Any] | None) – Called with the load event. Omit to get a composable Stream.

Returns:

A Subscription when a handler is given, otherwise a Stream.

Return type:

Stream | Subscription

pause()#

Pause playback on the current frame.

Resume with play; the frame stays on screen meanwhile.

play()#

Start or resume playback of an animated source.

Has no effect on a still image or when already playing.

stop()#

Stop playback and reset to the first frame.