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slash: optimize screen refresh #13

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Merged
jledet merged 1 commit into from
Jul 7, 2025
Merged

slash: optimize screen refresh #13

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10 changes: 8 additions & 2 deletions include/slash/slash.h
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Original file line number Diff line number Diff line change
Expand Up @@ -267,10 +267,13 @@ struct slash_command {
* @line_size: Size in bytes of the line buffer.
* @prompt: Current prompt string.
* @prompt_length: Length in bytes of the prompt string.
* @prompt_print_length: Length in printable characters of the prompt string.
* @buffer: Pointer to line buffer memory.
* @cursor: Current index of cursor in line buffer.
* @cursor_screen: Current index of cursor in line buffer on screen.
* @length: Current amount of used bytes in line buffer.
* @length_screen: Current amount of used bytes in line buffer on screen.
* @refresh_full: Force a full screen refresh including prompt.
* @refresh_buffer: Force a screen refresh of buffer.
* @last_char: Last input character.
* @history_size: Size in byte of the history buffer.
* @history_depth: Number of history entries browsed back.
Expand Down Expand Up @@ -306,10 +309,13 @@ struct slash {
size_t line_size;
const char *prompt;
size_t prompt_length;
size_t prompt_print_length;
char *buffer;
size_t cursor;
size_t cursor_screen;
size_t length;
size_t length_screen;
bool refresh_full;
bool refresh_buffer;
char last_char;

/* History */
Expand Down
121 changes: 63 additions & 58 deletions src/slash.c
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Original file line number Diff line number Diff line change
Expand Up @@ -113,26 +113,6 @@ int slash_getopt(struct slash *slash, const char *opts)
}

/* Terminal handling */
static size_t slash_escaped_strlen(const char *s)
{
int len = 0;
bool escaped = false;

while (*s) {
if (escaped) {
if (*s == 'm')
escaped = false;
} else if (*s == ESC) {
escaped = true;
} else {
len++;
}
s++;
}

return len;
}

static int slash_rawmode_enable(struct slash *slash)
{
#ifdef SLASH_HAVE_TERMIOS_H
Expand Down Expand Up @@ -697,6 +677,7 @@ static void slash_complete(struct slash *slash)
if (command) {
slash_printf(slash, "\n");
slash_command_usage(slash, command);
slash->refresh_full = true;
} else {
slash_bell(slash);
}
Expand All @@ -717,6 +698,7 @@ static void slash_complete(struct slash *slash)
slash_command_description(slash, cur);
}
}
slash->refresh_full = true;
}
}

Expand Down Expand Up @@ -888,6 +870,7 @@ static bool slash_history_next(struct slash *slash)
slash->buffer[srclen] = '\0';
slash->history_cursor = src;
slash->cursor = slash->length = srclen;
slash->refresh_buffer = true;

/* Rewind if use to store buffer temporarily */
if (!slash->history_depth && slash->history_cursor != slash->history_tail)
Expand Down Expand Up @@ -917,33 +900,64 @@ static bool slash_history_previous(struct slash *slash)
slash->buffer[srclen] = '\0';
slash->history_cursor = src;
slash->cursor = slash->length = srclen;
slash->refresh_buffer = true;

return true;
}

/* Line editing */
int slash_refresh(struct slash *slash)
{
char esc[16];
const char *esc = ESCAPE("K");

if (slash->refresh_full) {
slash_putchar(slash, '\r');
if (slash_write(slash, slash->prompt, slash->prompt_length) < 0)
return -1;
if (slash_write(slash, esc, strlen(esc)) < 0)
return -1;
slash->cursor_screen = 0;
slash->length_screen = 0;
slash->refresh_full = false;
}

/* Ensure line is zero terminated */
slash->buffer[slash->length] = '\0';
if (slash->refresh_buffer) {
while (slash->cursor_screen > 0) {
slash_putchar(slash, '\b');
slash->cursor_screen--;
}
slash->refresh_buffer = false;
}

while (slash->cursor_screen != slash->cursor) {
if (slash->cursor_screen < slash->cursor) {
slash_putchar(slash, slash->buffer[slash->cursor_screen]);
slash->cursor_screen++;
} else if (slash->cursor_screen > slash->cursor) {
slash_putchar(slash, '\b');
slash->cursor_screen--;
}
}

/* Move cursor to left edge */
if (slash_putchar(slash, '\r') < 0)
return -1;
if (slash->length_screen != slash->length) {
if (slash_write(slash,
&slash->buffer[slash->cursor],
slash->length - slash->cursor) < 0)
return -1;
slash->cursor_screen = slash->length;

/* Write the prompt and the current buffer content */
if (slash_write(slash, slash->prompt, slash->prompt_length) < 0)
return -1;
if (slash_write(slash, slash->buffer, slash->length) < 0)
return -1;
if (slash->length_screen > slash->length) {
if (slash_write(slash, esc, strlen(esc)) < 0)
return -1;
}

/* Erase to the right and move cursor to original position. */
snprintf(esc, sizeof(esc), ESCAPE("K") "\r" ESCAPE("%uC"),
(unsigned int)(slash->cursor + slash->prompt_print_length));
if (slash_write(slash, esc, strlen(esc)) < 0)
return -1;
while (slash->cursor_screen > slash->cursor) {
slash_putchar(slash, '\b');
slash->cursor_screen--;
}

slash->length_screen = slash->length;
}

return 0;
}
Expand All @@ -953,30 +967,21 @@ static void slash_insert(struct slash *slash, int c)
if (slash->length + 1 > slash->line_size)
return;

/* Fast path if we're adding a character to the end of the line */
if (slash->cursor == slash->length) {
slash->buffer[slash->cursor] = c;
slash->cursor++;
slash->length++;
slash->buffer[slash->length] = '\0';
slash_putchar(slash, slash->buffer[slash->cursor - 1]);
} else {
memmove(&slash->buffer[slash->cursor + 1],
&slash->buffer[slash->cursor],
slash->length - slash->cursor);
slash->buffer[slash->cursor] = c;
slash->cursor++;
slash->length++;
slash->buffer[slash->length] = '\0';
slash_refresh(slash);
}
memmove(&slash->buffer[slash->cursor + 1],
&slash->buffer[slash->cursor],
slash->length - slash->cursor);
slash->buffer[slash->cursor] = c;
slash->cursor++;
slash->length++;
slash->buffer[slash->length] = '\0';
}

void slash_reset(struct slash *slash)
{
slash->buffer[0] = '\0';
slash->length = 0;
slash->cursor = 0;
slash->refresh_full = true;
}

static void slash_arrow_up(struct slash *slash)
Expand Down Expand Up @@ -1018,6 +1023,7 @@ void slash_clear_screen(struct slash *slash)
{
const char *esc = ESCAPE("H") ESCAPE("2J");
slash_write(slash, esc, strlen(esc));
slash->refresh_full = true;
}

static void slash_backspace(struct slash *slash)
Expand Down Expand Up @@ -1065,7 +1071,6 @@ void slash_set_prompt(struct slash *slash, const char *prompt)
{
slash->prompt = prompt;
slash->prompt_length = strlen(prompt);
slash->prompt_print_length = slash_escaped_strlen(prompt);
}

char *slash_readline(struct slash *slash)
Expand Down Expand Up @@ -1108,8 +1113,6 @@ char *slash_readline(struct slash *slash)
slash->cursor = slash->length;
}
escaped = false;

slash_refresh(slash);
} else if (iscntrl(c)) {
switch (c) {
case CONTROL('A'):
Expand Down Expand Up @@ -1141,6 +1144,7 @@ char *slash_readline(struct slash *slash)
break;
case CONTROL('K'):
slash->length = slash->cursor;
slash->buffer[slash->length] = '\0';
break;
case CONTROL('L'):
slash_clear_screen(slash);
Expand All @@ -1157,6 +1161,7 @@ char *slash_readline(struct slash *slash)
case CONTROL('U'):
slash->cursor = 0;
slash->length = 0;
slash->buffer[0] = '\0';
break;
case CONTROL('W'):
slash_delete_word(slash);
Expand All @@ -1179,13 +1184,13 @@ char *slash_readline(struct slash *slash)
/* Unknown control */
break;
}

slash_refresh(slash);
} else if (isprint(c)) {
/* Add to buffer */
slash_insert(slash, c);
}

slash_refresh(slash);

slash->last_char = c;
}

Expand Down