Release critical or not? [was Re: strange box-offset]

[Ethan A M. <merritt@u.washington.edu>]

On Saturday 15 July 2006 01:04 am, Timoth=C3=A9e Lecomte wrote:
> this one comes from graphics.c:3408 :
>=20
> x =3D xl;
> y =3D yb;
> w =3D xr - xl + 1;
> h =3D yt - yb + 1;
> (*t->fillbox) (style, x, y, w, h);
> (*t->move) (xl, yb);
> (*t->vector) (xl, yt);
> (*t->vector) (xr, yt);
> (*t->vector) (xr, yb);
> (*t->vector) (xl, yb);
>=20
> I think these "+1" should be removed for consistency with the other uses.

I'm not so sure.
The length in pixels of a line that starts at pixel x1 and ends at pixel x2
is (x2-x1)+1.   So this code looks correct to me.  It may well be that some
terminals interpret w and h incorrectly, but that would be an error in the
individual terminal driver, not the core code.=20

I guess the fundamental question is whether "width" should be interpreted
as "number of horizontal pixels" or "x_right - x_left".  These are not
the same number.  The former makes sense if you are thinking in terms of
terminal coords (pixels); the latter makes sense if you are thinking in=20
terms of a continuous variable (plot x coordinate).

Either way, we need to audit the code to be consistent.
IMHO an off-by-one-pixel error is not release-critical, however.
If there's a simple fix to the core code that makes things more consistent,
fine.  But if we need to poke about in all the individuals drivers, let's
not do this for 4.2.

=2D-=20
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle 98195-7742