bootstack.Gallery

class bootstack.Gallery(*, items=None, data_source=None, image_field='image', caption_field=None, columns='auto', tile_size=(160, 160), fit='cover', corner_radius=0, gap=8, selection_mode='none', scrollbar_variant='thin', rows=2, accent=None, surface=None, parent=None, **kwargs)

Bases: PublicWidgetBase

A scrollable, selectable grid of image thumbnails.

Gallery displays a collection of image records as a reflowing grid of thumbnails, recycling tiles so it stays efficient for large collections. It is record-native — populate it with items= (a list of dicts) or a data_source=, and read the chosen tile(s) back through selection, the same model ListView, DataTable, and Tree share.

Each record names the image to show through image_field (an Image, a file path, or a PIL image) and, optionally, a caption through caption_field. Other keys ride along in the record bag and are returned by selection and events.

Parameters:

• items (list[dict] | None) – Initial list of record dicts.

• data_source (DataSourceProtocol | None) – A data source for database- or API-backed data. Any object implementing the data-source protocol is accepted.

• image_field (str) – Record key holding the image to display in each tile — an Image handle, a file path, or a PIL image. Default 'image'.

• caption_field (str | None) – Record key for the caption shown under each thumbnail. Default None (no captions).

• columns ("int | Literal['auto']") – Number of columns, or 'auto' (default) to reflow the grid to fit the available width as it resizes.

• tile_size (tuple[int, int]) – Thumbnail size as (width, height) in pixels. Default (160, 160).

• fit (ImageFit) – How each image is scaled into its tile — 'contain', 'cover' (default), 'fill', 'none', or 'scale-down'. See Picture.

• corner_radius (int) – Rounded-corner radius for thumbnails, in pixels. Default 0.

• gap (int) – Spacing between tiles in pixels. Default 8.

• selection_mode (SelectionMode) – Tile selection behavior — 'single', 'multi', or 'none' (default). Selected tiles show an accent highlight ring.

• scrollbar_variant (ScrollbarVariant) – Scrollbar style — 'thin' (default) for a slim bar, or 'default' for the standard rounded bar.

• rows (int) – Number of tile rows used to derive the gallery’s minimum height when it sits in a container that doesn’t impose one (a scroll view, an auto-fit window). Default 2. fill/expand still grow the grid past this floor and reflow more rows in.

• accent (AccentToken | str | None) – Color intent token for the selection ring. Defaults to the theme’s primary color.

• surface (SurfaceToken | str | None) – Background surface token shown behind the tiles.

• 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 data_source: DataSourceProtocol

The underlying data source instance.

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 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()

property selection: dict | list[dict] | None

The selected record(s) — the data bag.

In 'single' mode, the selected record dict (or None). In 'multi' mode, a list of record dicts (empty when nothing is selected). Each record carries its non-displayed fields too. Read-only.

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.

clear_selection()

Deselect all tiles.

deselect_items(record_ids)

Remove the given tiles from the selection by record id.

Parameters:

record_ids (list) – Record ids to deselect.

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_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_item_activate() → Stream

on_item_activate(handler: Callable[[dict[str, Any]], Any]) → Subscription

Fired when a tile is activated (double-clicked).

The natural hook for opening a full-size viewer or detail page for the chosen record.

Parameters:

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

Returns:

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

Return type:

Stream | Subscription

on_item_click() → Stream

on_item_click(handler: Callable[[dict[str, Any]], Any]) → Subscription

Fired when a tile is clicked.

Parameters:

handler (Callable[[dict[str, Any]], Any] | None) – Called with the record dict — read fields with e["field"]. Omit to get a composable Stream.

Returns:

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

Return type:

Stream | Subscription

on_select() → Stream

on_select(handler: Callable[[Event], Any]) → Subscription

Fired when the selection changes.

Parameters:

handler (Callable[[Event], Any] | None) – Called with the curated Event; read selection for the current selection. Omit to get a composable Stream.

Returns:

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

Return type:

Stream | Subscription

reload()

Reload from the data source and refresh the grid.

scroll_to_bottom()

Scroll to the last tile.

scroll_to_top()

Scroll to the first tile.

select_all()

Select all tiles. Only effective when selection_mode='multi'.

select_items(record_ids)

Select tiles by record id.

In 'single' mode this replaces the current selection; in 'multi' mode the items are added to it.

Parameters:

record_ids (list) – Record ids of the tiles to select.