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global proc string[] callbackName(string $dragControl, int $x, int $y, int $mods)

The proc returns a string array that is transferred to the drop site. By convention the first string in the array describes the user settable message type. Controls that are application defined drag sources may ignore the callback. $mods allows testing for the key modifiers CTL and SHIFT. Possible values are 0 == No modifiers, 1 == SHIFT, 2 == CTL, 3 == CTL + SHIFT.

In Python, it is similar, but there are two ways to specify the callback. The recommended way is to pass a Python function object as the argument. In that case, the Python callback should have the form:

def callbackName( dragControl, x, y, modifiers ):

The values of these arguments are the same as those for the MEL version above.

The other way to specify the callback in Python is to specify a string to be executed. In that case, the string will have the values substituted into it via the standard Python format operator. The format values are passed in a dictionary with the keys "dragControl", "x", "y", "modifiers". The "dragControl" value is a string and the other values are integers (eg the callback string could be "print '%(dragControl)s %(x)d %(y)d %(modifiers)d'")

global proc callbackName(string $dragControl, string $dropControl, string $msgs[], int $x, int $y, int $type)

The proc receives a string array that is transferred from the drag source. The first string in the msgs array describes the user defined message type. Controls that are application defined drop sites may ignore the callback. $type can have values of 1 == Move, 2 == Copy, 3 == Link.

In Python, it is similar, but there are two ways to specify the callback. The recommended way is to pass a Python function object as the argument. In that case, the Python callback should have the form:

def pythonDropTest( dragControl, dropControl, messages, x, y, dragType ):

The values of these arguments are the same as those for the MEL version above.

The other way to specify the callback in Python is to specify a string to be executed. In that case, the string will have the values substituted into it via the standard Python format operator. The format values are passed in a dictionary with the keys "dragControl", "dropControl", "messages", "x", "y", "type". The "dragControl" value is a string and the other values are integers (eg the callback string could be "print '%(dragControl)s %(dropControl)s %(messages)r %(x)d %(y)d %(type)d'")