#832 sixeltek terminal: transparency and background options

[Erik Olofsen]

For those still using the "sixeltek" terminal, attached is a diff for tek.trm, for the addition of (no)transparent and background color options, which is useful if the background in a terminal is not white (or light gray).

It should compile with a recent snapshot (an "lt" instead of "rgbcolor" struct member was used in version 6.0).

A fix is to have int_error() instead of int_warn() at the end of SIXEL_options(), otherwise "set terminal" enters an infinite loop if there is an unknown option.

Finally, an unimplemented "animate" option was removed.

[Ethan Merritt]

In file included from term.h:170,
                 from term.c:1311:
../term/tek.trm: In function ‘SIXEL_text’:
../term/tek.trm:817:57: warning: self-comparison always evaluates to true [-Wtautological-compare]
  817 |                     if (n < b_xsize-1 || pc != '?' || k == k) { /* do not output empty lines */
      |                                                         ^~

What is the intent here?

[Erik Olofsen]

Thanks for catching that. It used to be k == 1, to at least have one sixel line written (and then it should now be k == ks) but from testing it seems the condition can be omitted entirely because a dash is output which moves to the next line. Incidentally, but I guess that is another ticket, the y-size should be a multiple of 6 for sixels. And setting the size to for example 640,366 the image is not complete with the "test" command; this used to be the correct with earlier gnuplot versions, before the changes regarding x and y sizes.