Ncurses attribute A_DIM has no effect

Question

I am programming in Linux using ncurses. When I use attron() to switch on attributes, it works for all attributes except A_DIM (which is meant to yield half bright characters). A_BOLD, A_ITALIC, A_BLINK, A_UNDERLINE, A_STANDOUT - all of these have effect, but A_DIM has no any visible effect at all, no matter if I use console or xterm. What might be wrong with that?

Answer 1

It depends on the actual terminal, and on the terminal description used. For the latter, you can see immediately if it is provided by looking at the output of infocmp, e.g.,

#   Reconstructed via infocmp from file: /usr/local/ncurses/share/terminfo/x/xterm-new
xterm-new|modern xterm terminal emulator,
    am, bce, km, mc5i, mir, msgr, npc, xenl,
    colors#8, cols#80, it#8, lines#24, pairs#64,
    acsc=``aaffggiijjkkllmmnnooppqqrrssttuuvvwwxxyyzz{{||}}~~,
    bel=^G, blink=\E[5m, bold=\E[1m, cbt=\E[Z, civis=\E[?25l,
    clear=\E[H\E[2J, cnorm=\E[?12l\E[?25h, cr=^M,
    csr=\E[%i%p1%d;%p2%dr, cub=\E[%p1%dD, cub1=^H,
    cud=\E[%p1%dB, cud1=^J, cuf=\E[%p1%dC, cuf1=\E[C,
    cup=\E[%i%p1%d;%p2%dH, cuu=\E[%p1%dA, cuu1=\E[A,
    cvvis=\E[?12;25h, dch=\E[%p1%dP, dch1=\E[P, dim=\E[2m,

XTerm provides all of the video attributes (though "dim" and "italics" are relatively recent):

Linux console provides some attributes (dim for example), but not underline or italics (it uses color). The usual Linux console terminal description does not include "dim", since that has some caveats:

These screenshots use the main ncurses test-program, named ncurses (see webpage and source).