From e053bd6036331cc7d14f155614aebc20f5371d3a Mon Sep 17 00:00:00 2001
From: Luke Smith <luke@lukesmith.xyz>
Date: Tue, 10 Aug 2021 17:25:48 -0400
Subject: [PATCH] prevent losing columns on resize

---
 st.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/st.c b/st.c
index f9f8068..ceabf85 100644
--- a/st.c
+++ b/st.c
@@ -118,6 +118,7 @@ typedef struct {
 typedef struct {
 	int row;      /* nb row */
 	int col;      /* nb col */
+	int maxcol;
 	Line *line;   /* screen */
 	Line *alt;    /* alternate screen */
 	Line hist[HISTSIZE]; /* history buffer */
@@ -1311,8 +1312,8 @@ tclearregion(int x1, int y1, int x2, int y2)
 	if (y1 > y2)
 		temp = y1, y1 = y2, y2 = temp;
 
-	LIMIT(x1, 0, term.col-1);
-	LIMIT(x2, 0, term.col-1);
+	LIMIT(x1, 0, term.maxcol-1);
+	LIMIT(x2, 0, term.maxcol-1);
 	LIMIT(y1, 0, term.row-1);
 	LIMIT(y2, 0, term.row-1);
 
@@ -2607,11 +2608,18 @@ void
 tresize(int col, int row)
 {
 	int i, j;
-	int minrow = MIN(row, term.row);
-	int mincol = MIN(col, term.col);
+	int tmp;
+	int minrow, mincol;
 	int *bp;
 	TCursor c;
 
+	tmp = col;
+	if (!term.maxcol)
+		term.maxcol = term.col;
+	col = MAX(col, term.maxcol);
+	minrow = MIN(row, term.row);
+	mincol = MIN(col, term.maxcol);
+
 	if (col < 1 || row < 1) {
 		fprintf(stderr,
 		        "tresize: error resizing to %dx%d\n", col, row);
@@ -2662,17 +2670,18 @@ tresize(int col, int row)
 		term.line[i] = xmalloc(col * sizeof(Glyph));
 		term.alt[i] = xmalloc(col * sizeof(Glyph));
 	}
-	if (col > term.col) {
-		bp = term.tabs + term.col;
+	if (col > term.maxcol) {
+		bp = term.tabs + term.maxcol;
 
-		memset(bp, 0, sizeof(*term.tabs) * (col - term.col));
+		memset(bp, 0, sizeof(*term.tabs) * (col - term.maxcol));
 		while (--bp > term.tabs && !*bp)
 			/* nothing */ ;
 		for (bp += tabspaces; bp < term.tabs + col; bp += tabspaces)
 			*bp = 1;
 	}
 	/* update terminal size */
-	term.col = col;
+	term.col = tmp;
+	term.maxcol = col;
 	term.row = row;
 	/* reset scrolling region */
 	tsetscroll(0, row-1);