Clipping node in drag event

GoJS
1

Hi

Question: Is it possible to ‘clip’ a node to the bounds of a panel when dragging.

Clarification: Yes - I do mean dragging a node over a panel, not a part within a panel.

Scenario: The scenario is that I have a node drawn ‘over’ a panel. I wish to let the user drag the node but if the drag causes the dragged node to be positioned ‘outside’ the panel I want the part of the node that exceeds the bounds of the panel to become ‘clipped’ out of sight. The real world use case is a Gantt chart where the panel is the background to the chart and the node being dragged is a task bar - drag left to move back on the timeline and right to move ahead. The task should be constrained within the chart.

I wonder if this would be possible with a Group if the Placeholder could be set to have fixed bounds - possible ? I concur that the default behaviour of the placeholder flexing to encompass the grouped nodes is good, it’s just that I need it to be fixed bounds. (I read the Group placeholder explanation here See GoJS Groups -- Northwoods Software)

As a potential fall-back, I wonder if it would be possible to clip the node within the diagram assuming it is possible to stop the auto-scroll of the diagram.Is this correct ? If so are there any examples that demonstrate this feature ? This would allow me to upscale the panels to separate diagrams and achieve the clipping effect in that way.

I also appreciate that the minLocation and maxLocation can be used to constrain the drag.

2

Well, so you already know that the Diagram automatically clips everything that is outside of the viewport. I think that is what you are utilizing in your fall-back plan, yes?

But many kinds of Panels can clip their element(s) within the rectangular bounds of the panel. This is demonstrated by a few examples at GoJS Panels -- Northwoods Software and at the end of GoJS Sizing of GraphObjects -- Northwoods Software. As you might expect, this is not a “normal” thing.

So you could artificially change the sizes of Nodes (if their element(s) are fixed size) within a “SelectionMoved” DiagramEvent listener.

3

Thanks. The case I am working on needs nodes that are clipped or ‘appear’ to go behind other elements when dragged. I followed up with the idea of switching the main panels for diagrams and it seems to be the way to go. I also have to recompute some of the layout if a node is dragged out of view - though I might trade that for using the diagram auto-scroll and prepare the extra background pre-emptively.

Thanks for the pointers on panels and clipping, useful to know.