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	slackline: implement ctrl+w and ctrl+l - lchat - A line oriented chat front end…
	git clone git://git.suckless.org/lchat
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	---
	commit aa7afafc6710c68811bbc33d8b781edfa8c17109
	parent 0c1a66c482d9ffa4e0e3f8fdb60aa1a02755da37
	Author: Tom Schwindl <[email protected]>
	Date: Fri, 9 Sep 2022 21:40:55 +0200

	slackline: implement ctrl+w and ctrl+l

	ctrl+w is part of the canonical line disciplines on most systems, thus
	it is convenient to implement it.

	ctrl+l is part of the emacs-mode, but generic and useful enough to be
	implemented regardless of the current mode.

	Additionally, we now check for control key combinations. This makes it
	possible to ignore "invalid" key combinations. It also helps with the
	implementation of an emacs-mode. Previously, pressing something like ctrl+f
	would insert invisible characters, which is very irritating.

	Last, it isn't weird that ctrl+u emits a NAK, since ctrl key combinations
	map the letters A-Z to the ASCII codes 1-26. "u" is the 21. character in
	the alphabet and NAK has the ASCII code 21.

	Diffstat:
	M slackline.c \| 63 +++++++++++++++++++++--------…

	1 file changed, 43 insertions(+), 20 deletions(-)
	---
	diff --git a/slackline.c b/slackline.c
	@@ -14,7 +14,7 @@
	* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
	*/

	-#include <stdbool.h>
	+#include <ctype.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	@@ -104,6 +104,30 @@ sl_postoptr(struct slackline *sl, size_t pos)
	return ptr;
	}

	+static void
	+sl_backspace(struct slackline *sl)
	+{
	+ char *ncur;
	+
	+ if (sl->rcur == 0)
	+ return;
	+
	+ ncur = sl_postoptr(sl, sl->rcur - 1);
	+
	+ if (sl->rcur < sl->rlen)
	+ memmove(ncur, sl->ptr, sl->last - sl->ptr);
	+
	+ sl->rcur--;
	+ sl->rlen--;
	+ sl->bcur = sl_postobyte(sl, sl->rcur);
	+ sl->blen = sl_postobyte(sl, sl->rlen);
	+
	+ sl->last -= sl->ptr - ncur;
	+ *sl->last = '\0';
	+
	+ sl->ptr = ncur;
	+}
	+
	int
	sl_keystroke(struct slackline *sl, int key)
	{
	@@ -192,6 +216,9 @@ sl_keystroke(struct slackline *sl, int key)
	}
	}

	+ if (!iscntrl((unsigned char) key))
	+ goto compose;
	+
	/* handle ctl keys */
	switch (key) {
	case 27: /* Escape */
	@@ -199,30 +226,26 @@ sl_keystroke(struct slackline *sl, int key)
	return 0;
	case 127: /* backspace */
	case 8: /* backspace */
	- if (sl->rcur == 0)
	- return 0;
	-
	- char *ncur = sl_postoptr(sl, sl->rcur - 1);
	-
	- if (sl->rcur < sl->rlen)
	- memmove(ncur, sl->ptr, sl->last - sl->ptr);
	-
	- sl->rcur--;
	- sl->rlen--;
	- sl->bcur = sl_postobyte(sl, sl->rcur);
	- sl->blen = sl_postobyte(sl, sl->rlen);
	-
	- sl->last -= sl->ptr - ncur;
	- *sl->last = '\0';
	-
	- sl->ptr = ncur;
	-
	+ sl_backspace(sl);
	return 0;
	- case 21: /* ctrl+u or clearline, weird that it's a NAK */
	+ case 21: /* ctrl+u -- clearline */
	sl_reset(sl);
	return 0;
	+ case 12: /* ctrl+l -- clear screen, same as clear(1) */
	+ printf("\x1b[2J\x1b[H");
	+ return 0;
	+ case 23: /* ctrl+w -- erase previous word */
	+ while (sl->rcur != 0 && isspace((unsigned char) *(sl->ptr-1)))
	+ sl_backspace(sl);
	+
	+ while (sl->rcur != 0 && !isspace((unsigned char) *(sl->ptr-1)))
	+ sl_backspace(sl);
	+ return 0;
	+ default:
	+ return 0;
	}

	+compose:
	/* byte-wise composing of UTF-8 runes */
	sl->ubuf[sl->ubuf_len++] = key;
	if (fullrune(sl->ubuf, sl->ubuf_len) == 0)