bug#16594: 24.3.50; very slow redraw when resizing windows horizontally

[Stefan Monnier]

> I checked in a fix such that mouse dragging a line doesn't occur
> pixelwise by default.

That's sad.  I thought it was one of the nicest and most immediately
beneficial part of having pixel-sized windows.

And I wonder if it's really needed: Darren's complaint seems to point at
each redisplay being slow rather than redisplay happening too many times.


        Stefan