move_gesture.md
In rswipl: Embed 'SWI'-'Prolog'

class move_gesture {#class-move_gesture}

A move_gesture defines the behaviour necessary to allow the user dragging a graphical object with the mouse over it's graphical device.

While dragging, the cursor is changed to a fleur

By default, the move_gesture is associated with the middle mouse-button.

move_gesture<-offset: point While active, the distance between the top-left corner of the graphical moved and the cursor. Set by ->initiate.

move_gesture->drag: event Moves the graphical using the ->do_set behaviour so that the distance between the cursor and the top-left remains the same as when the gesture was initiated.
move_gesture->initialise: button=[button_name], modifier=[modifier] Create a move_gesture, associated with a button with modifiers. Both the button and the modifiers are determined by their class-variables. One should avoid to use explicit binding of a move gesture to some button.

Defaults: button Resource defined (middle) modifiers Resource defined (none)
move_gesture->initiate: event Fills <-offset with the distance of the mouse-down event to the top-left corner of the graphical on which the move is initiated. Sets the cursor to move_gesture.cursor.
move_gesture->terminate: event Equivalent to ->drag.
move_gesture->verify: event Succeeds if the receiving graphical object has <->device not equal to @nil.