How can I get the dimensions of the current font in a terminal?

Question

I am working on an ncurses application that creates some very blocky graphics using alphanum characters. I'd like to be able to detect the dimensions (specifically the aspect ratio) of the font glyphs so that I can correct for it by changing how I render my graphics (such that a square always looks like a square).

I am able to use the

void getmaxyx(WINDOW *win, int y, int x);

function in ncurses to get the size of the screen/window, but since many windows can be freely resized, it, it's not reliable. Is there a similar function (or external mechanism) for retrieving the font dimensions?

Answer 1

With xterm or compatible and provided font operation escape sequences have not been disabled:

$ xtermcontrol --get-font
DejaVu Sans Mono

That sends the <ESC>]50;?<ESC>\ escape sequence, and the terminal replies with <ESC>]50;font-name<ESC>\. See reference.

So you can also query it with zsh for instance with:

$ IFS=$';\e' read -rsd'\' -t0.2 $'font?\e]50;?\e\\' font font rest
$ typeset font
font='DejaVu Sans Mono'

allowFontOps is generally disabled by default though. You'd set the *allowFontOps: true resource to enable them or preferably keep it disabled but set *disallowedFontOps: SetFont to allow GetFont but not SetFont.

For the size, set the:

*disallowedWindowOps: 1,2,3,4,5,6,7,8,9,11,13,19,20,21,GetSelection,SetSelection,SetWinLines,SetXprop

resource, that is disallow all but GetWinSizeChars and GetWinSizePixels, then with zsh:

$ IFS=';t' read -rsdt -t0.2 $'x?\e[18t' cy cx rest
$ IFS=';t' read -rsdt -t0.2 $'x?\e[14t' y x rest
$ echo ${x}x${y} ${cx}x${cy}
1916x1012 147x38

\e[18t requests the window size in number of cells, \e[14t in number of pixels so you can get the size of a cell with:

$ printf '%gx%g\n' '1.*x/cx' '1.*y/cy'
13x26

Answer 2

Hello from the sunny Athens. Unfortunately things like font_size, or various fonts, or things like that, have unfortunately to do with loading the graphical driver for the HW and applying it as a graphical environment, that is loaded ONLY, when you use the graphical environment from Linux and not from the console (alphanumeric mode only) or using CTRL+T for enabling a terminal during a Windows session in any case. The only possibility to use different font sizes, it could be through ncurses, but according to POSIX standards, this is not possible. If you want to apply in any case different font sizes, there are many environments like processing supported by java, which will give you a solution. Greetings from Athens Kostas Vergidis