support REP (repeat) escape sequence

The sequence \e[Nb prints the last printed char N (more) times if it's
printable, and it's ignored after newline or other control chars.

This is Ecma-048/ANSI-X3.6 sequence and not DEC VT. It's supported by
xterm, and ncurses uses it when possible, e.g. when TERM is xterm* (and
with this commit also st*).

xterm supports only codepoints<=255, possibly due to internal limits.
We support any value/codepoint which was placed in a cell.

To test:
- tput rep 65 4 -> prints 'AAAA'
- printf "\342\225\246\033[4b" -> prints U+2566 1+4 times.

README.md

@@ -1,4 +1,4 @@
-Similar to [dwm-flexipatch](https://github.com/bakkeby/dwm-flexipatch) this st 0.8.3 (453eb7, 2020-05-16) project has a different take on st patching. It uses preprocessor directives to decide whether or not to include a patch during build time. Essentially this means that this build, for better or worse, contains both the patched _and_ the original code. The aim being that you can select which patches to include and the build will contain that code and nothing more.
+Similar to [dwm-flexipatch](https://github.com/bakkeby/dwm-flexipatch) this st 0.8.3 (113da4, 2020-05-16) project has a different take on st patching. It uses preprocessor directives to decide whether or not to include a patch during build time. Essentially this means that this build, for better or worse, contains both the patched _and_ the original code. The aim being that you can select which patches to include and the build will contain that code and nothing more.
 
 For example to include the `alpha` patch then you would only need to flip this setting from 0 to 1 in [patches.h](https://github.com/bakkeby/st-flexipatch/blob/master/patches.def.h):
 ```c
@@ -15,7 +15,7 @@ Refer to [https://st.suckless.org/](https://st.suckless.org/) for details on the
 
 ### Changelog:
 
-2020-05-20 - Upgrade to 453eb7, 2020-05-09, removed visualbell 1, 2, 3 patches and force redraw after keypress due to incompatibility
+2020-05-20 - Upgrade to 113da4, 2020-05-09, removed visualbell 1, 2, 3 patches and force redraw after keypress due to incompatibility
 
 2020-04-20 - Upgrade to c279f5, 2020-04-19, and added the force redraw on pselect after key is pressed patch and the externalpipein patch
 

st.c

@@ -142,6 +142,7 @@ typedef struct {
 	int charset;  /* current charset */
 	int icharset; /* selected charset for sequence */
 	int *tabs;
+	Rune lastc;   /* last printed char outside of sequence, 0 if control */
 } Term;
 
 /* CSI Escape sequence structs */
@@ -1793,6 +1794,12 @@ csihandle(void)
 		if (csiescseq.arg[0] == 0)
 			ttywrite(vtiden, strlen(vtiden), 0);
 		break;
+	case 'b': /* REP -- if last char is printable print it <n> more times */
+		DEFAULT(csiescseq.arg[0], 1);
+		if (term.lastc)
+			while (csiescseq.arg[0]-- > 0)
+				tputc(term.lastc);
+		break;
 	case 'C': /* CUF -- Cursor <n> Forward */
 	case 'a': /* HPR -- Cursor <n> Forward */
 		DEFAULT(csiescseq.arg[0], 1);
@@ -2543,6 +2550,8 @@ check_control_code:
 		/*
 		 * control codes are not shown ever
 		 */
+		if (!term.esc)
+			term.lastc = 0;
 		return;
 	} else if (term.esc & ESC_START) {
 		if (term.esc & ESC_CSI) {
@@ -2592,6 +2601,7 @@ check_control_code:
 	}
 
 	tsetchar(u, &term.c.attr, term.c.x, term.c.y);
+	term.lastc = u;
 
 	if (width == 2) {
 		gp->mode |= ATTR_WIDE;

st.info

@@ -184,6 +184,7 @@ st-mono| simpleterm monocolor,
 # XTerm extensions
 	rmxx=\E[29m,
 	smxx=\E[9m,
+	rep=%p1%c\E[%p2%{1}%-%db,
 # tmux extensions, see TERMINFO EXTENSIONS in tmux(1)
 	Tc,
 	Ms=\E]52;%p1%s;%p2%s\007,