[texhax] MetaFont Online Display driver

[Igor Liferenko]

Hi all,

It seems strange to me that using semicolon after "showit" causes an
extra call to blankrectangle() and updatescreen() functions from
online display driver.

I added printf() calls to x11-Xt.c driver and run "showit" without and
with trailing semicolon. The logs of these runs follow.

== Run 1 ==

user at debian:/usr/local/mf$ mf '\showit'
This is METAFONT, Version 2.7182818 (TeX Live 2017) (preloaded base=mf)

initscreen called

blankrectangle called, xl=0, xr=500, yt=0, yb=400

updatescreen called

*

== Run 2 ==

user at debian:/usr/local/mf$ mf '\showit;'
This is METAFONT, Version 2.7182818 (TeX Live 2017) (preloaded base=mf)

initscreen called

blankrectangle called, xl=0, xr=500, yt=0, yb=400

updatescreen called

blankrectangle called, xl=0, xr=500, yt=0, yb=400

updatescreen called

*


Does anybody know why semicolon affects online display driver?

Regards,
Igor