display.c

/* display.c, Zepto Emacs, Public Domain, Hugh Barney, 2017, Derived from: Anthony's Editor January 93 */

#include "header.h"

/* Reverse scan for start of logical line containing offset */
point_t lnstart(buffer_t *bp, register point_t off)
{
	register char_t *p;
	do
		p = ptr(bp, --off);
	while (bp->b_buf < p && *p != '\n');
	return (bp->b_buf < p ? ++off : 0);
}

/* Forward scan for start of logical line segment containing 'finish' */
point_t segstart(buffer_t *bp, point_t start, point_t finish)
{
	char_t *p;
	int c = 0;
	point_t scan = start;

	while (scan < finish) {
		p = ptr(bp, scan);
		if (*p == '\n') {
			c = 0;
			start = scan+1;
		} else if (COLS <= c) {
			c = 0;
			start = scan;
		}
		++scan;
		c += *p == '\t' ? 8 - (c & 7) : 1;
	}
	return (c < COLS ? start : finish);
}

/* Forward scan for start of logical line segment following 'finish' */
point_t segnext(buffer_t *bp, point_t start, point_t finish)
{
	char_t *p;
	int c = 0;

	point_t scan = segstart(bp, start, finish);
	for (;;) {
		p = ptr(bp, scan);
		if (bp->b_ebuf <= p || COLS <= c)
			break;
		++scan;
		if (*p == '\n')
			break;
		c += *p == '\t' ? 8 - (c & 7) : 1;
	}
	return (p < bp->b_ebuf ? scan : pos(bp, bp->b_ebuf));
}

/* Move up one screen line */
point_t upup(buffer_t *bp, point_t off)
{
	point_t curr = lnstart(bp, off);
	point_t seg = segstart(bp, curr, off);
	if (curr < seg)
		off = segstart(bp, curr, seg-1);
	else
		off = segstart(bp, lnstart(bp,curr-1), curr-1);
	return (off);
}

/* Move down one screen line */
point_t dndn(buffer_t *bp, point_t off)
{
	return (segnext(bp, lnstart(bp,off), off));
}

/* Return the offset of a column on the specified line */
point_t lncolumn(buffer_t *bp, point_t offset, int column)
{
	int c = 0;
	char_t *p;
	while ((p = ptr(bp, offset)) < bp->b_ebuf && *p != '\n' && c < column) {
		c += *p == '\t' ? 8 - (c & 7) : 1;
		++offset;
	}
	return (offset);
}

void display()
{
	char_t *p;
	int i, j, k;
	buffer_t *bp = curbp;
	
	/* find start of screen, handle scroll up off page or top of file  */
	/* point is always within b_page and b_epage */
	if (bp->b_point < bp->b_page)
		bp->b_page = segstart(bp, lnstart(bp,bp->b_point), bp->b_point);

	/* reframe when scrolled off bottom */
	if (bp->b_epage <= bp->b_point) {
		/* Find end of screen plus one. */
		bp->b_page = dndn(bp, bp->b_point);
		/* if we scoll to EOF we show 1 blank line at bottom of screen */
		if (pos(bp, bp->b_ebuf) <= bp->b_page) {
			bp->b_page = pos(bp, bp->b_ebuf);
			i = bp->w_rows - 1;
		} else {
			i = bp->w_rows - 0;
		}
		/* Scan backwards the required number of lines. */
		while (0 < i--)
			bp->b_page = upup(bp, bp->b_page);
	}

	addstr(HIDE_CURSOR);
	clear();

	move(bp->w_top, 0); /* start from top of window */
	i = bp->w_top;
	j = 0;
	bp->b_epage = bp->b_page;
	
	/* paint screen from top of page until we hit maxline */ 
	while (1) {
		/* reached point - store the cursor position */
		if (bp->b_point == bp->b_epage) {
			bp->b_row = i;
			bp->b_col = j;
		}
		p = ptr(bp, bp->b_epage);
		if (bp->w_top + bp->w_rows <= i || bp->b_ebuf <= p) /* maxline */
			break;
		if (*p != '\r') {
			if (isprint(*p) || *p == '\t' || *p == '\n') {
				j += *p == '\t' ? 8-(j&7) : 1;
				addch(*p);
			} else {
				char *ctrl = unctrl(*p);
				j += (int) strlen(ctrl);
				addstr(ctrl);
			}
		}
		if (*p == '\n' || COLS <= j) {
			j -= COLS;
			if (j < 0)
				j = 0;
			++i;
			(*p == '\n' ? addch('\r') : addstr("\r\n"));
		}
		++bp->b_epage;
	}

	/* replacement for clrtobot() to bottom of window */
	for (k=i; k < bp->w_top + bp->w_rows; k++) {
		move(k, j); /* clear from very last char not start of line */
		clrtoeol();
		j = 0; /* thereafter start of line */
	}

	modeline(bp);
	dispmsg();
	move(bp->b_row, bp->b_col); /* set cursor */
	addstr(SHOW_CURSOR);
	refresh();
}

void modeline(buffer_t *bp)
{
	int i;
	char mch;
	
	standout();
	move(bp->w_top + bp->w_rows, 0);
	mch = ((bp->b_flags & B_MODIFIED) ? '*' : '=');
	sprintf(temp, "=%c Zepto: == %s ", mch, bp->b_fname);
	addstr(temp);

	for (i = strlen(temp) + 1; i <= COLS; i++)
		addch('=');
	standend();
}

void dispmsg()
{
	move(MSGLINE, 0);
	if (msgflag) {
		addstr(msgline);
		msgflag = FALSE;
	}
	clrtoeol();
}