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（769862113）This is an extension and not part of the main GoJS library. Note that the API for this class may change at any time. If you intend to use an extension in production, you should copy the code to your own source directory. Extensions can be found in the GoJS kit under the extensions or extensionsTS folders. See the Extensions intro page for more information.
Constructs a PortShiftingTool and sets the name for the tool.
The port being shifted.
This tool can only start if the mouse has moved enough so that it is not a click, and if the mouse down point is on a GraphObject "port" in a Spot Panel, as determined by findPort.
Start a transaction, call findPort and remember it as the "port" property, and remember the original value for the port's GraphObject.alignment property.
Restore the port's original value for GraphObject.alignment.
Stop any ongoing transaction.
During the drag, call updateAlignment in order to set the GraphObject.alignment of the port.
At the end of the drag, update the alignment of the port and finish the tool, completing a transaction.
Clear any reference to a port element.
From the GraphObject at the mouse point, search up the visual tree until we get to an object that has the GraphObject.portId property set to a non-empty string, that is in a Spot Panel, and that is not the main element of the panel (typically the first element).
This returns null if no such port is at the mouse down point.
Save the port's GraphObject.alignment as a fractional Spot in the Spot Panel that the port is in. Thus if the main element changes size, the relative positions of the ports will be maintained. But that does assume that the port must remain inside the main element -- it cannot wander away from the node. This does not modify the port's GraphObject.alignmentFocus property.
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The PortShiftingTool class lets a user move a port on a Node.
This tool only works when the Node has a port (any GraphObject) marked with a non-null and non-empty portId that is positioned in a Spot Panel, and the user holds down the Shift key. It works by modifying that port's GraphObject.alignment property.
If you want to experiment with this extension, try the Port Shifting sample.