Shift-drag in diagram behavious different when objects are selected

[willem-xbreeze]

If i shift + drag in a diagram when there are no selected nodes, the behaviour is to multi-select nodes based on the selected range.
If i then again shift + drag, the diagram is moved.
As a user i would expect to always multi select when pressing shift + drag and always move when pressing drag without shift.
The behaviour should not be depending on whether objects are selected or not

shiftSelect.mp4

[harmen-xb]

Retested after Theia and GLSP upgrade (#139), issue is still there.

@martin-fleck-at This looks like a GLSP client issue. Can you confirm?

[martin-fleck-at]

@harmen-xb Yeah, I can confirm that this is the behavior in GLSP, cf. https://github.com/eclipse-glsp/glsp-client/blob/daca6812b3cac934626ea056b8f0ca17c2fb61f8/packages/client/src/features/tools/marquee-selection/marquee-tool.ts#L50. It seems that it was done deliberately as shift already makes selected elements move without snapping:

Maybe the behavior could be improved by considering whether you click on an element or just the graph.

[harmen-xb]

Somewhere in time this behaviour seems to have changes between the mapping and system diagram. In the system diagram the shift doesn't seem to do anything, while in the mapping diagram shift initiates a selection. (tested with v0.2.5 of crossmodel).

The behaviour should be equal across diagrams. I also think using shift for selecting multiple nodes & edges using a rectangle selection is the most common approach across modeling tools.