Drag-and-drop

  • Override wantsMorph:Event:, which states whether a morph being dropped will be accepted. Default accept action is to embed the morph as a submorph. 
    wantsMorph: m Event: evt = (
	m morphTypeName =
		©pieWedgeMorph©)

  • Make wedge sensitive to left mouse click: 
    leftMouseDown: evt = (
	evt shiftIsDown
	&& [owner morphTypeName=©pieChartMorph©]
		ifTrue: [evt sourceHand addMorph: self]
		False: [resend.leftMouseDown: evt ].
	self
).

  • Adds wedge to hand if in a chart and shift key is down

  • Otherwise calls default action

Drag-and-drop

Wouldn't it be nice if you could just drag wedges between pie charts? Let's implement this! The basic method to be overridden is wantsMorph:Event:. This is sent to a morph to enquire if it wants to accept a morph being dropped onto it, and we should make charts accept wedges. The argument is a ui2Event (which characterizes the mouse position, source hand and so on), which we can ignore. This method is added to the chart traits: 

	wantsMorph: m Event: evt = (
		m morphTypeName = 'pieWedgeMorph').

Now we need to make wedges mouse-sensitive, so we add this method to the wedge traits. 

	leftMouseDown: evt = (
		evt shiftIsDown
		&& [owner morphTypeName = 'pieChartMorph']
			ifTrue: [evt sourceHand addMorph: self]
			False: [resend.leftMouseDown: evt ].
		self
	).

This lets us extract a wedge by holding the shift key down while using the left mouse button. The wedge is added to the hand that clicked the button. If the wedge is not in a chart, the default left mouse activity is invoked.

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