Well, I had intended to allow an explanation to reflect a specific use-case, but I suppose I can concoct something.
The app.render[] function can be called with a widget, as with a card:
Let's say we want to save a "screenshot" of only the widgets on a card, and ignore the background.
Create an image interface the size of the card, iterate over the widgets of the card, rendering each and pasting it (with transparency) onto the image, reflecting their position on the card, and then write[] that image, prompting the user for a location to save it:
i:image[card.size] each wid in card.widgets i.paste[app.render[wid] wid.pos 1] end write[i]
You could also, for example, selectively avoid rendering some of the widgets, either by "drop"-ing them from card.widgets by name before iterating over them:
each wid in ("button2","the forbidden one") drop card.widgets
# ... draw everything but those two specific ones
end
Or conditionally avoiding/permitting a certain kind of widget:
each wid in card.widgets if !wid.type~"field" # ... draw everything except for nasty fields end end
You can also use Lil's query language and/or widget naming conventions to locate widgets of interest:
each wid in extract value where value..name like "fancy_*" from card.widgets # ... draw only the widgets which are fancy end
Et cetera, et cetera. How's that?