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If you want to get a single printable character, you can use
key; to check whether a character is available for
you can use
key– char core “key”
Receive (but do not display) one character, char.
key?– flag facility “key-question”
Determine whether a character is available. If a character is
available, flag is true; the next call to
yield the character. Once
key? returns true, subsequent
key? before calling
also return true.
If you want to process a mix of printable and non-printable
characters, you can do that with
ekey and friends.
produces a keyboard event that you have to convert into a character
ekey>char or into a key identifier with
Typical code for using EKEY looks like this:
ekey ekey>char if ( c ) ... \ do something with the character else ekey>fkey if ( key-id ) case k-up of ... endof k-f1 of ... endof k-left k-shift-mask or k-ctrl-mask or of ... endof ... endcase else ( keyboard-event ) drop \ just ignore an unknown keyboard event type then then
ekey– u facility-ext “e-key”
Receive a keyboard event u (encoding implementation-defined).
ekey>charu – u false | c true facility-ext “e-key-to-char”
Convert keyboard event u into character
c if possible.
ekey>fkeyu1 – u2 f X:ekeys “ekey>fkey”
If u1 is a keyboard event in the special key set, convert keyboard event u1 into key id u2 and return true; otherwise return u1 and false.
ekey?– flag facility-ext “e-key-question”
True if a keyboard event is available.
The key identifiers for cursor keys are:
k-left– u X:ekeys “k-left”
k-right– u X:ekeys “k-right”
k-up– u X:ekeys “k-up”
k-down– u X:ekeys “k-down”
k-home– u X:ekeys “k-home”
k-end– u X:ekeys “k-end”
k-prior– u X:ekeys “k-prior”
k-next– u X:ekeys “k-next”
k-insert– u X:ekeys “k-insert”
k-delete– u X:ekeys “k-delete”
The key identifiers for function keys (aka keypad keys) are:
k-f1– u X:ekeys “k-f1”
k-f2– u X:ekeys “k-f2”
k-f3– u X:ekeys “k-f3”
k-f4– u X:ekeys “k-f4”
k-f5– u X:ekeys “k-f5”
k-f6– u X:ekeys “k-f6”
k-f7– u X:ekeys “k-f7”
k-f8– u X:ekeys “k-f8”
k-f9– u X:ekeys “k-f9”
k-f10– u X:ekeys “k-f10”
k-f11– u X:ekeys “k-f11”
k-f12– u X:ekeys “k-f12”
k-f12 are not as widely available.
You can combine these key identifiers with masks for various shift keys:
k-shift-mask– u X:ekeys “k-shift-mask”
k-ctrl-mask– u X:ekeys “k-ctrl-mask”
k-alt-mask– u X:ekeys “k-alt-mask”
Note that, even if a Forth system has
ekey>fkey and the key
identifier words, the keys are not necessarily available or it may not
necessarily be able to report all the keys and all the possible
combinations with shift masks. Therefore, write your programs in such
a way that they are still useful even if the keys and key combinations
cannot be pressed or are not recognized.
Examples: Older keyboards often do not have an F11 and F12 key. If you run Gforth in an xterm, the xterm catches a number of combinations (e.g., <Shift-Up>), and never passes it to Gforth. Finally, Gforth currently does not recognize and report combinations with multiple shift keys (so the <shift-ctrl-left> case in the example above would never be entered).
Gforth recognizes various keys available on ANSI terminals (in MS-DOS you need the ANSI.SYS driver to get that behaviour); it works by recognizing the escape sequences that ANSI terminals send when such a key is pressed. If you have a terminal that sends other escape sequences, you will not get useful results on Gforth. Other Forth systems may work in a different way.