Why do fonts in xterm seem too big in OS X?

Question

I am using xterm on OS X 10.5. If I do:

xterm -fa "Monaco" -fs 10

it creates a xterm with much bigger fonts than Terminal.app w/ Monaco 10 point font. In fact, I have to downsize xterm to -fs 8 or so to match the window sizes. And then the 8 point font is less readable.

Shouldn't a 10 point font be a specific absolute size (i.e. proportional to 10/72 inches) no matter whether displayed in Terminal or xterm?

The terminals are both 80x24 and not anti-aliased. Also, I ran iTerm for Mac OS X and the window almost perfectly overlayed the Terminal.app window. The width was the same but the height was a little shorter.

Answer 1

I resolved the issue. There is an option you can place in .Xdefaults to set the apparent dots per inch:

Xft.dpi: 99

Of course this doesn't really change the true display device dots per inch as that is fixed by the hardware. Apparently, this number is used to "scale" the fonts.

It appears that Mac OS X runs at about 72 dpi and the default setting on xterm is 99 dpi.

The font glyphs and the windows are nearly the same size (within 1/16") when you set both term apps to 72 dpi.