bug#13011: 24.2; Text flickering moving cursor with box around text enabled

[Drew Adams]

> I'd first like to hear why Drew uses negative thickness (and yet
> wants it to be positive horizontally).

IIRC, I use negative thickness mainly so the height is not increased.  I
typically do not care so much about the width (length) of a boxed word.  But I
do not want added border pixels to change the line height etc.

It really doesn't matter why or when or whether I use negative thickness.  The
question is which of these is the case:

1. The box left & right borders should be allowed to bump into the text that is
boxed.

2. Instead, the box should be shifted to the right because we have added extra
pixel(s) for the box border to the left of the text.

3. We should let users decide between #1 and #2.  For example, using a new box
attribute.

It's really not about me.  It's somewhat about how users use this today, and
what they expect.  But it's also about how users might use it (whether they do
or do not today) and what a user might expect from it.

> Also that's a hack, I can totally imagine someone using a very
> high-resolution screen with largish fonts (measured in pixels) wanting
> a -3 thickness around his hl-line box.

Me too.