Hi,

Currently I don't see any way how to tell an element that another one has been dropped onto him. For example if I want to drag an element into a container (see example at the end).

Unfortunately in my solution i had to change the behaviour of Trachel (RTMorph), so could this be in some (better) way incorporated into Roassal (Trachel)?

My solution is making a subclass

-------------------------------------

TRAbstractMouseEvent subclass: #TRMouseDragDrop

-------------------------------------

And altering mouseDragEnd

-------------------------------------

RTMorph>>rtMouseDragEnd: evt

| ee dropEvent dropShape relativePosition |

"notify the dragged element"

ee := TRMouseDragEnd new.

ee shape: shapeBeingPointed.

ee canvas: trachelCanvas.

ee morph: self.

shapeBeingPointed announce: ee.

"notify the element onto which was the drag performed"

shapeBeingPointed = trachelCanvas

ifFalse: [ 

shapeBeingPointed element attributes

at: #rtDroppable

ifPresent: [ 

relativePosition := self relativePositionFor: evt.

dropShape := self shapeWithAction: TRMouseDragDrop forPositionInPixels: relativePosition.

dropShape = shapeBeingPointed

ifFalse: [ 

dropEvent := TRMouseDragDrop new

shape: shapeBeingPointed;

canvas: trachelCanvas;

morph: self.

dropShape announce: dropEvent ] ] ].

eventBeginingDragging := nil.

shapeBeingPointed := nil

-------------------------------------

Example (use case) is:

-------------------------------------

view := RTView new.

container := RTBox new size: 200; color: Color white; borderColor: Color black; element.

group := RTGroup new.

RTNest new on: container nest: group.

container trachelShape size: 200.

box := RTBox new size: 50; color: Color magenta; element.

box translateTo: 250 @ 0.

container @ RTDraggable.

container @ RTResizeable.

box @ RTDraggable.

box attributes at: #rtDroppable put: true.

container

when: TRMouseDragDrop

do: [ :event |

| el |

el := event shape element.

el attributes at: #container ifPresent: [

group remove: el.

].

group add: el.

el attributes at: #container put: group.

].

view canvas

when: TRMouseDragDrop

do: [ :event |

| el |

el := event shape element.

el attributes at: #container ifPresent: [ :parent |

parent remove: el.

el attributes removeKey: #container.

].

].

view

add: container;

add: box.

view open.

-------------------------------------

Also it would be nice to have an option to highlight the drop area. There is TRMouseEnter/TRMouseLeave but it fires only for the top level shape, perhaps it should for all? Or less invasive to add TRMouseDragEnter/TRMouseDragLeave which would work like regular Enter/Leave but on the next (on z-axis) shape.

Please let me know what you think.

Peter

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