Refresh line with single write to avoid flickering.
Escape sequences and actual content to write to the terminal is now
accumulated into an heap allocated buffer that is flushed with a single
write at the end. This avoids a flickering effect making linenoise more
professional looking ;-)
diff --git a/linenoise.c b/linenoise.c
index c690477..514ed89 100644
--- a/linenoise.c
+++ b/linenoise.c
@@ -318,6 +318,33 @@
/* =========================== Line editing ================================= */
+/* We define a very simple "append buffer" structure, that is an heap
+ * allocated string where we can append to. This is useful in order to
+ * write all the escape sequences in a buffer and flush them to the standard
+ * output in a single call, to avoid flickering effects. */
+struct abuf {
+ char *b;
+ int len;
+};
+
+static void abInit(struct abuf *ab) {
+ ab->b = NULL;
+ ab->len = 0;
+}
+
+static void abAppend(struct abuf *ab, const char *s, int len) {
+ char *new = realloc(ab->b,ab->len+len);
+
+ if (new == NULL) return;
+ memcpy(new+ab->len,s,len);
+ ab->b = new;
+ ab->len += len;
+}
+
+static void abFree(struct abuf *ab) {
+ free(ab->b);
+}
+
/* Single line low level line refresh.
*
* Rewrite the currently edited line accordingly to the buffer content,
@@ -329,6 +356,7 @@
char *buf = l->buf;
size_t len = l->len;
size_t pos = l->pos;
+ struct abuf ab;
while((plen+pos) >= l->cols) {
buf++;
@@ -339,18 +367,21 @@
len--;
}
+ abInit(&ab);
/* Cursor to left edge */
snprintf(seq,64,"\x1b[0G");
- if (write(fd,seq,strlen(seq)) == -1) return;
+ abAppend(&ab,seq,strlen(seq));
/* Write the prompt and the current buffer content */
- if (write(fd,l->prompt,strlen(l->prompt)) == -1) return;
- if (write(fd,buf,len) == -1) return;
+ abAppend(&ab,l->prompt,strlen(l->prompt));
+ abAppend(&ab,buf,len);
/* Erase to right */
snprintf(seq,64,"\x1b[0K");
- if (write(fd,seq,strlen(seq)) == -1) return;
+ abAppend(&ab,seq,strlen(seq));
/* Move cursor to original position. */
snprintf(seq,64,"\x1b[0G\x1b[%dC", (int)(pos+plen));
- if (write(fd,seq,strlen(seq)) == -1) return;
+ abAppend(&ab,seq,strlen(seq));
+ if (write(fd,ab.b,ab.len) == -1) {} /* Can't recover from write error. */
+ abFree(&ab);
}
/* Multi line low level line refresh.
@@ -365,6 +396,7 @@
int rpos2; /* rpos after refresh. */
int old_rows = l->maxrows;
int fd = l->fd, j;
+ struct abuf ab;
/* Update maxrows if needed. */
if (rows > (int)l->maxrows) l->maxrows = rows;
@@ -377,12 +409,13 @@
/* First step: clear all the lines used before. To do so start by
* going to the last row. */
+ abInit(&ab);
if (old_rows-rpos > 0) {
#ifdef LN_DEBUG
fprintf(fp,", go down %d", old_rows-rpos);
#endif
snprintf(seq,64,"\x1b[%dB", old_rows-rpos);
- if (write(fd,seq,strlen(seq)) == -1) return;
+ abAppend(&ab,seq,strlen(seq));
}
/* Now for every row clear it, go up. */
@@ -391,7 +424,7 @@
fprintf(fp,", clear+up");
#endif
snprintf(seq,64,"\x1b[0G\x1b[0K\x1b[1A");
- if (write(fd,seq,strlen(seq)) == -1) return;
+ abAppend(&ab,seq,strlen(seq));
}
/* Clean the top line. */
@@ -399,11 +432,11 @@
fprintf(fp,", clear");
#endif
snprintf(seq,64,"\x1b[0G\x1b[0K");
- if (write(fd,seq,strlen(seq)) == -1) return;
+ abAppend(&ab,seq,strlen(seq));
/* Write the prompt and the current buffer content */
- if (write(fd,l->prompt,strlen(l->prompt)) == -1) return;
- if (write(fd,l->buf,l->len) == -1) return;
+ abAppend(&ab,l->prompt,strlen(l->prompt));
+ abAppend(&ab,l->buf,l->len);
/* If we are at the very end of the screen with our prompt, we need to
* emit a newline and move the prompt to the first column. */
@@ -414,9 +447,9 @@
#ifdef LN_DEBUG
fprintf(fp,", <newline>");
#endif
- if (write(fd,"\n",1) == -1) return;
+ abAppend(&ab,"\n",1);
snprintf(seq,64,"\x1b[0G");
- if (write(fd,seq,strlen(seq)) == -1) return;
+ abAppend(&ab,seq,strlen(seq));
rows++;
if (rows > (int)l->maxrows) l->maxrows = rows;
}
@@ -432,14 +465,14 @@
fprintf(fp,", go-up %d", rows-rpos2);
#endif
snprintf(seq,64,"\x1b[%dA", rows-rpos2);
- if (write(fd,seq,strlen(seq)) == -1) return;
+ abAppend(&ab,seq,strlen(seq));
}
/* Set column. */
#ifdef LN_DEBUG
fprintf(fp,", set col %d", 1+((plen+(int)l->pos) % (int)l->cols));
#endif
snprintf(seq,64,"\x1b[%dG", 1+((plen+(int)l->pos) % (int)l->cols));
- if (write(fd,seq,strlen(seq)) == -1) return;
+ abAppend(&ab,seq,strlen(seq));
l->oldpos = l->pos;
@@ -447,6 +480,9 @@
fprintf(fp,"\n");
fclose(fp);
#endif
+
+ if (write(fd,ab.b,ab.len) == -1) {} /* Can't recover from write error. */
+ abFree(&ab);
}
/* Calls the two low level functions refreshSingleLine() or
