Use half-height blocks to double vertical resolution

[eddieantonio]

See Block Elements. More interesting things can be done with some of the other characters in this range, but it should be sufficient to use ▀ (U+2580)

[eddieantonio]

The plan:

▀ — foreground gets assigned above; background gets assigned below.

CSI ... 38;5;<color> ... m — foreground color
CSI ... 48;5;<color> ... m — background color

printf "\033[38;5;%03d;48;5;%03dm▀\n" $FG $BG

Assuming pixels are zero-indexed, even rows set foreground color and odd rows
set background color.

Terminate with

CSI ... 39;49 ... m

39 resets default foreground color and 49 sets default background color.

[eddieantonio]

I've got it working in the half-height branch, but the rendering is off. Turns out the half-height is too wide horizontally, and too short vertically to combine with the background color, to truly color exactly half of the square. Take a look:

(Taken in iTerm2, Build 3.1.6, 12pt Menlo, anti-aliased, 110% vertical spacing).

[eddieantonio]

It looks okay with a non-anti-aliased bitmap font, and 100% line spacing. Check it:

Edit: Here's xterm:

I think this feature might actually work for people who are not me!