relative-loc ( fromgadget togadget -- loc )
Factor handbook » UI framework » Building user interfaces » Gadget geometry

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Vocabulary
ui.gadgets

Inputs

fromgadget	a gadget
togadget	a gadget

Outputs

loc	a pair of integers

Word description
Outputs the location of the top-left corner of togadget relative to the coordinate system of fromgadget.

Errors
Throws an error if togadget is not contained in a child of fromgadget.

Definition

USING: accessors kernel math.vectors ;

IN: ui.gadgets

: relative-loc ( fromgadget togadget -- loc )
    2dup eq?
    [ 2drop { 0 0 } ]
    [ [ [ parent>> ] dip relative-loc ] [ drop loc>> ] 2bi v+ ]
    if ;