Need Help Implementing a Custom Drag-Swap Interaction Between MPR Views (ActionW.DRAG_SWAP)

[shivaramakrishna009]

Summary

Hi @nroduit, I am building a custom drag-swap interaction in the Weasis MPR viewer, where dragging one MPR view and dropping it onto another should swap their displayed series and image content. The feature should work the same way other mouse tools (zoom, rotate, pan, measure) do — fully integrated with the existing mouse action architecture.

I have built:

• a custom ActionW.DRAG_SWAP
• a custom DragSwapListener extending MouseActionAdapter
• a MprViewTransferHandler to implement drag-and-drop
• modifications to MprView and ImageViewerEventManager
• a swapping method inside MprController

However, despite all wiring being done, the swapping does not occur, and only a “mouseReleased” debug log appears. No drag event or drop event is firing as expected, and the TransferHandler's importData() is never reached.

I am requesting help / guidance from Weasis maintainers on where the integration might be going wrong, or if MPR views block drag-and-drop events internally.

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Expected Behavior

When drag-swap tool is active:

1. User selects MPR View A
2. Starts dragging → the app should call exportAsDrag
3. Drops onto MPR View B → importData() should trigger
4. Controller receives requestSwap(A, B)
5. Both views swap their series and current image
6. UI updates, similar to how other actions (zoom, rotate, pan) hook through the MouseActionAdapter and ActionState system

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Actual Behavior

• Dragging does not start.
• TransferHandler does not trigger.
• importData() is never called.
• DragSwapListener only logs mouseReleased.
• Other mouse actions (zoom, rotate, pan) continue to catch the events first.
• Drag-swap cursor never activates, even though the action is registered.

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What I Already Implemented

1. DragSwapListener (MouseActionAdapter + ActionState)

DragSwapListener drag = new DragSwapListener(ActionW.DRAG_SWAP);
setAction(drag);

2. Installed TransferHandler in MprView

setTransferHandler(new MprViewTransferHandler(this));

3. Registered in ImageViewerEventManager

setAction(new DragSwapListener(ActionW.DRAG_SWAP));

4. Toolbar toggle enables/disables the action.

5. MprController.requestSwap() performs series and image swap.

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Repository Impact

The issue may relate to:

• Mouse event consumption order in MPR views
• Overlay rendering layers consuming input
• Crosshair / arcball controllers overriding drag events
• Default PannerListener / CrosshairListener intercepting BUTTON1 actions
• Missing integration with Weasis MouseActions and input dispatcher

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Codebase Reference

I can provide:

• MprView.java
• MprViewTransferHandler.java
• DragSwapListener.java
• Relevant parts of ImageViewerEventManager

(Already attached below or will attach as needed.)

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Help Requested

• Is drag-and-drop supported on MPR views? Any known limitations?
• Do MPR views consume mouse events before Swing receives them?
• How can a custom action like ActionW.DRAG_SWAP cleanly override existing defaults?
• How do I integrate a new custom MouseActionAdapter so it behaves exactly like zoom/pan/rotate?
• Is there an official recommended way to implement mouse-driven view-to-view swapping?

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Environment

• Weasis version: 4.5.1
• OS: Windows 11
• JDK: 23
• Build source: Custom build of Weasis 4.x (MPR module modified)

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If the maintainers need the exact files, I can attach them immediately.

Thank you for the guidance!

[nroduit]

See #757 (comment)