Fix cursor move with wide glyphs

st would always move back 1 column,
even with wide glyhps (using more than a single column).

The glyph rune is set on its first column,
and the other ones are to 0,
so loop until we detect the start of the previous glyph.

1 files changed, 7 insertions, 3 deletions

diff --git a/st.c b/st.c
index 034954d..77c3e8a 100644
--- a/st.c
+++ b/st.c
@@ -86,8 +86,8 @@ enum escape_state {
 
 typedef struct {
         Glyph attr; /* current char attributes */
-        int x;
-        int y;
+        int x; /* terminal column */
+        int y; /* terminal row */
         char state;
 } TCursor;
 
@@ -2175,12 +2175,16 @@ tstrsequence(uchar c)
 void
 tcontrolcode(uchar ascii)
 {
+        size_t i;
+
         switch (ascii) {
         case '\t':   /* HT */
                 tputtab(1);
                 return;
         case '\b':   /* BS */
-                tmoveto(term.c.x-1, term.c.y);
+                for (i = 1; term.c.x && term.line[term.c.y][term.c.x - i].u == 0; ++i)
+                        ;
+                tmoveto(term.c.x - i, term.c.y);
                 return;
         case '\r':   /* CR */
                 tmoveto(0, term.c.y);