Make it easy to suppress linked stream parameters

[jlstevens]

Currently, when a linked stream has lots of stream parameters, the user is forced to handle them somehow, even if it means dumping extra arguments into **kwargs in their callback.

Instead of forcing users to use **kwargs for stream values they aren't interested in, it might be nice to allow explicit suppression of these parameters. Here is one suggestion I think is reasonable:

Drag(x=0,y=0).rename(drag_count=None) # Ignore the drag_count parameter

The way this could work would be to set the parameter precedences on the stream so they get ignored before passing the values to the callback. Using rename for this purpose overloads this method slightly but I think the semantics are reasonable and it makes more sense than introducing another method.

Note that in theory this could be used to remove PointerX and PointerY (and just have PointerXY) but I think having those is still a nice convenience.

[jlstevens]

This should be easy to implement. The only thing is setting to None should set the precedence to something negative, say -1 but restoring the parameter (e.g renaming again with a string) should restore the precedence. Any original precedence value would be lost so I guess it would just restore to param's default precedence.

[jbednar]

You could do -abs(precedence), or -precedence-1, I guess, since that would be invertible...

[jlstevens]

Good idea!

[philippjfr]

Has this been documented? If so I'll close this.

[jlstevens]

I can put a stub in one of the user guides but it isn't documented currently anywhere else.

[jlstevens]

I've added a paragraph about this feature to the correspond user guide in #1537. Closing.

[github-actions]

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