Actions can now be bound to e.g. Ctrl-Alt-A. The keybinding code also
supports other combinations of modifiers, like Shift-Ctrl-Up, but the
escape sequence decoder doesn't yet.
Don't let Ctrl-Alt-letter combinations open menus.
There is no need to check whether ev->ev == EVENT_KBD;
if decode_terminal_escape_sequence called
decode_terminal_mouse_escape_sequence, then the former neither modified
kbd.key nor passed &kbd to the latter, so kbd.key remains KBD_UNDEF.
If ev->ev was not checked, then it should not be trusted either.
So reinitialize the whole *ev if a keyboard event was indeed found.
Also list the capnames with which the escape sequences could be
read from Terminfo, and the ECMA-48 interpretations of the bytes
(parenthesized if they seem unrelated to the keys). This is in
preparation for fixing bug 96.
decode_terminal_escape_sequence() used to handle both, but
there is now a separate decode_terminal_application_key()
for ESC O. I have not yet edited decode_terminal_escape_sequence();
there may be dead code in it.
If there is e.g. ESC [ in the input buffer, combine that to Alt-[.
Check the first character too; don't blindly assume it is ESC, as
it can be NUL as well. Note this means you can no longer activate
the main menu by pressing Ctrl-@ (or Ctrl-Space on some terminals).
Otherwise, the timeout could cause ELinks to resume reading from
the terminal device while another process is still using it.
This actually happened in a test.
On entry to some functions that could resume reading from the device,
assert that the terminal has not been blocked.
