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.

2 files changed, 11 insertions, 0 deletions

diff --git a/st.c b/st.c
index 0d35613..54af098 100644
--- a/st.c
+++ b/st.c
@@ -129,6 +129,7 @@ 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 */
@@ -1648,6 +1649,12 @@ 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);
@@ -2373,6 +2380,8 @@ 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) {
@@ -2422,6 +2431,7 @@ check_control_code:
         }
 
         tsetchar(u, &term.c.attr, term.c.x, term.c.y);
+        term.lastc = u;
 
         if (width == 2) {
                 gp->mode |= ATTR_WIDE;
diff --git a/st.info b/st.info
index d0694e2..e5393db 100644
--- a/st.info
+++ b/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,