A touch, or a pen without hover, arrives on the layer and presses in the same pass.
The overlay wasn't there the pass before, so egui handed the press to the viewer and
nothing was picked. The overlay now takes such a press when it is on the layer and
off the viewer's handles, and claims it from the viewer (CLAIMED_PRIMARY), which
then neither clicks, double-clicks nor drags with it: Shift no longer toggles the
layer off, and a drag moves nothing. The claim ends with the button up.
vangel76
df01e1d75c