help-echo in margin

[JD Smith]

Is it possible to have help-echo or mouse-face text properties work for
text or glyphs in the margin?  My initial testing has not been
promising.  This would be very useful for, e.g., getting additional
information on breakpoints (or, using a keymap to allow mouse operations
on breakpoints, e.g. right-click to delete, etc.).  Ideally fringe
bitmaps would allow such things as well.

Thanks,

JD