Calculate size when trimming RHS correctly.

1 files changed, 18 insertions, 3 deletions

diff --git a/tty.c b/tty.c
index 10ae1617..bf4c1424 100644
--- a/tty.c
+++ b/tty.c
@@ -936,8 +936,13 @@ tty_clamp_line(struct tty *tty, const struct tty_ctx *ctx, u_int px, u_int py,
 		/* Right not visible. */
 		*i = 0;
 		*x = (ctx->xoff + px) - ctx->ox;
-		*rx = nx - ((ctx->xoff + px) + nx - ctx->sx);
+		*rx = ctx->sx - *x;
 	}
+	if (*rx > nx)
+		fatalx("%s: x too big, %u > %u", __func__, *rx, nx);
+	if (nx > *rx)
+		*rx = nx;
+
 	return (1);
 }
 
@@ -1028,8 +1033,13 @@ tty_clamp_area(struct tty *tty, const struct tty_ctx *ctx, u_int px, u_int py,
 		/* Right not visible. */
 		*i = 0;
 		*x = (ctx->xoff + px) - ctx->ox;
-		*rx = nx - ((ctx->xoff + px) + nx - ctx->sx);
+		*rx = ctx->sx - *x;
 	}
+	if (*rx > nx)
+		fatalx("%s: x too big, %u > %u", __func__, *rx, nx);
+	if (nx > *rx)
+		*rx = nx;
+
 	if (yoff >= ctx->oy && yoff + ny <= ctx->oy + ctx->sy) {
 		/* All visible. */
 		*j = 0;
@@ -1049,8 +1059,13 @@ tty_clamp_area(struct tty *tty, const struct tty_ctx *ctx, u_int px, u_int py,
 		/* Right not visible. */
 		*j = 0;
 		*y = (ctx->yoff + py) - ctx->oy;
-		*ry = ny - ((ctx->yoff + py) + ny - ctx->sy);
+		*ry = ctx->sy - *y;
 	}
+	if (*ry > ny)
+		fatalx("%s: y too big, %u > %u", __func__, *ry, ny);
+	if (ny > *ry)
+		*ry = ny;
+
 	return (1);
 }