> The second question is: is it possible for element to subscribe for position
> updates of another element? (I.e. element A watches for movement of element B
> and moves accordingly). I know I could add both of them to a composite shape
> or RTGroup (RTDraggable>>groupToDrag:), however I would prefer something more
> loosely coupled.
>
> In RTDraggable>>initializeElement: i found
> " element when: TRMouseDragging do: [ :e | e element translateBy: e step.
> e signalUpdate ]"
> however it is commented out so perhaps there some other way?
Yes you can. Not using events, but Trachel callbacks.
Consider the example:
-=-=-=-=-=-=-=-=-=-=-=-=
| v |
v := RTView new.
es := RTEllipse elementsOn: Collection withAllSubclasses.
v addAll: es.
es @ (RTLabelled new text: #numberOfMethods).
es @ RTPopup @ RTDraggable.
RTMetricNormalizer new
elements: es;
normalizeSize: #numberOfMethods min: 5 max: 20 using: #sqrt.
RTFlowLayout new gapSize: 15; on: es.
v
-=-=-=-=-=-=-=-=-=-=-=-=
When you move a circle, the label moves as well. There is a ‘constraint’ that
says the label sticks to the circle
The class TRConstraint contains many utility methods you may enjoy to define
constraints between elements.
For example:
TRConstraint class >> stick: aShape onTheTopLeftOf: anotherShape
| b |
self move: aShape onTheTopLeftOf: anotherShape.
b := [ :shape :step | self move: aShape onTheTopLeftOf: anotherShape ].
anotherShape addCallback: (TRTranslationCallback block: b).
anotherShape addCallback: (TRExtentCallback block: b)
Let us know if you have further question.
Cheers,
Alexandre
