Vocabulary
ui.gadgets

Inputs and outputs

rect	a rect
gadget	a gadget
seq	a sequence of gadgets

Generic word contract
Outputs a sequence of gadgets which potentially intersect a rectangle in the co-ordinate system of the gadget.

Notes
This does not have to be an accurate intersection test, and simply returning children>> is a valid implementation. However, an accurate intersection test reduces the amount of work done when drawing this gadget if it is partially clipped and not all children are visible.

Definition

IN: ui.gadgets

GENERIC: children-on ( rect gadget -- seq )

Methods

USING: accessors kernel ui.gadgets ;

M: gadget children-on nip children>> ;

USING: accessors kernel math.vectors sequences ui.gadgets
ui.gadgets.grids ;

M: grid children-on
dup children>> empty?
[ 2drop f ] [
[ { 0 1 } ] dip [ grid>> ] [ dim>> ] bi
[ [ loc>> vmin ] reduce ] curry fast-children-on concat
] if ;

USING: accessors kernel ui.gadgets ui.gadgets.packs ;

M: pack children-on
[ orientation>> ] [ children>> ] bi
[ loc>> ] fast-children-on ;

USING: accessors kernel ui.gadgets ui.gadgets.worlds ;

M: world children-on nip children>> ;