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lib/mp-readline: Use simple VT100 commands to speed up line redraw.

This commit is contained in:
Damien George 2015-01-25 18:26:07 +00:00
parent 4b35a5464c
commit 17d299b7bd
1 changed files with 24 additions and 15 deletions
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39
lib/mp-readline/readline.c
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@ -57,6 +57,25 @@ STATIC char *str_dup_maybe(const char *str) {
return s2;
}
STATIC void move_cursor_back(uint pos) {
if (pos <= 4) {
// fast path for most common case of 1 step back
stdout_tx_strn("\b\b\b\b", pos);
} else {
char vt100_command[6];
// snprintf needs space for the terminating null character
int n = snprintf(&vt100_command[0], sizeof(vt100_command), "\x1b[%u", pos);
if (n > 0) {
vt100_command[n] = 'D'; // replace null char
stdout_tx_strn(vt100_command, n + 1);
}
}
}
STATIC void erase_line_from_cursor(void) {
stdout_tx_strn("\x1b[K", 3);
}
typedef struct _readline_t {
vstr_t *line;
int orig_line_len;
@ -66,7 +85,7 @@ typedef struct _readline_t {
char escape_seq_buf[1];
} readline_t;
readline_t rl;
STATIC readline_t rl;
int readline_process_char(int c) {
int last_line_len = rl.line->len;
@ -215,30 +234,20 @@ end_key:
}
// redraw command prompt, efficiently
// TODO we can probably use some more sophisticated VT100 commands here
if (redraw_step_back > 0) {
for (int i = 0; i < redraw_step_back; i++) {
stdout_tx_str("\b");
}
move_cursor_back(redraw_step_back);
rl.cursor_pos -= redraw_step_back;
}
if (redraw_from_cursor) {
if (rl.line->len < last_line_len) {
// erase old chars
for (int i = rl.cursor_pos; i < last_line_len; i++) {
stdout_tx_str(" ");
}
// step back
for (int i = rl.cursor_pos; i < last_line_len; i++) {
stdout_tx_str("\b");
}
// (number of chars to erase: last_line_len - rl.cursor_pos)
erase_line_from_cursor();
}
// draw new chars
stdout_tx_strn(rl.line->buf + rl.cursor_pos, rl.line->len - rl.cursor_pos);
// move cursor forward if needed (already moved forward by length of line, so move it back)
for (int i = rl.cursor_pos + redraw_step_forward; i < rl.line->len; i++) {
stdout_tx_str("\b");
}
move_cursor_back(rl.line->len - (rl.cursor_pos + redraw_step_forward));
rl.cursor_pos += redraw_step_forward;
} else if (redraw_step_forward > 0) {
// draw over old chars to move cursor forwards