Cell rendering bugs

[SegHaxx]

Going to collect together cell rendering bugs here.

Looking at https://github.com/larsbrinkhoff/terminal-simulator/issues/5#issuecomment-845654823 in particular confirms something, chars should not touch the left side of the inverse cell? This is what it looks like now:

Also of note I don't see underline anywhere.

The obvious fix is to bump it to the right one dotclock, which does look nicer:

But it messes up boxdrawing:

What does a real VT100 do? Lars can you get photos of these vttest screens? :) (end of "Test of screen features")

[larsbrinkhoff]

What does a real VT100 do? Lars can you get photos of these vttest screens?

Sure, no problem. When I get back home.

I think it would be best to implement the video generation as documented in the Tech manual. I.e. the detailed process of loading data from the character ROM and feeding it through a shift register. Hopefully this should take care of making everything look exactly right.

[larsbrinkhoff]

Also of note I don't see underline anywhere.

This is currently a documented limitation of the simulator: "The Advanced Video Option is not included." This means underline or inverse video are selected from SET-UP B and can not be viewed simultaneously. The AVO adds four attribute bits per character so can display underline, inverse, dim, bright, and blink.