From da49f6bcc30fd49efe11a3fd228bf94480a1b4b9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jean-S=C3=A9bastien=20P=C3=A9dron?= <dumbbell@FreeBSD.org>
Date: Sat, 1 Nov 2014 17:05:15 +0000
Subject: [PATCH] vt(4): Adjust the cursor position after changing the window
 size

A new terminal_set_cursor() is added: it wraps the existing
teken_set_cursor() function.

In vtbuf_grow(), the cursor position is adjusted at the end of the
function. In vt_change_font(), we call terminal_set_cursor() just after
terminal_set_winsize_blank(), while the terminal is mute.

This fixes a bug where, after loading a kernel video driver which
increases the terminal window size, the cursor remains at its old
position, in other words, in the middle of the display content.

PR:		194421
MFC after:	1 week
---
 sys/dev/vt/vt_buf.c      | 12 ++++++++++++
 sys/dev/vt/vt_core.c     |  1 +
 sys/kern/subr_terminal.c |  7 +++++++
 sys/sys/terminal.h       |  1 +
 4 files changed, 21 insertions(+)

diff --git a/sys/dev/vt/vt_buf.c b/sys/dev/vt/vt_buf.c
index cc23b3b6c99b..c3e639e8c58a 100644
--- a/sys/dev/vt/vt_buf.c
+++ b/sys/dev/vt/vt_buf.c
@@ -562,6 +562,18 @@ vtbuf_grow(struct vt_buf *vb, const term_pos_t *p, unsigned int history_size)
 		vb->vb_roffset = vb->vb_curroffset;
 	}
 
+	/* Adjust cursor position. */
+	if (vb->vb_cursor.tp_col > p->tp_col - 1)
+		/*
+		 * Move cursor to the last column, in case its previous
+		 * position is outside of the new screen area.
+		 */
+		vb->vb_cursor.tp_col = p->tp_col - 1;
+
+	if (vb->vb_curroffset > 0 || vb->vb_cursor.tp_row > p->tp_row - 1)
+		/* Move cursor to the last line on the screen. */
+		vb->vb_cursor.tp_row = p->tp_row - 1;
+
 	vtbuf_make_undirty(vb);
 	VTBUF_UNLOCK(vb);
 
diff --git a/sys/dev/vt/vt_core.c b/sys/dev/vt/vt_core.c
index 8c7d0f0e5e8e..0062b0e6da75 100644
--- a/sys/dev/vt/vt_core.c
+++ b/sys/dev/vt/vt_core.c
@@ -1532,6 +1532,7 @@ vt_change_font(struct vt_window *vw, struct vt_font *vf)
 	terminal_mute(tm, 1);
 	vtbuf_grow(&vw->vw_buf, &size, vw->vw_buf.vb_history_size);
 	terminal_set_winsize_blank(tm, &wsz, 0, NULL);
+	terminal_set_cursor(tm, &vw->vw_buf.vb_cursor);
 	terminal_mute(tm, 0);
 
 	/* Actually apply the font to the current window. */
diff --git a/sys/kern/subr_terminal.c b/sys/kern/subr_terminal.c
index 69345df56ca6..76c6cfbf6453 100644
--- a/sys/kern/subr_terminal.c
+++ b/sys/kern/subr_terminal.c
@@ -189,6 +189,13 @@ terminal_maketty(struct terminal *tm, const char *fmt, ...)
 	terminal_sync_ttysize(tm);
 }
 
+void
+terminal_set_cursor(struct terminal *tm, const term_pos_t *pos)
+{
+
+	teken_set_cursor(&tm->tm_emulator, pos);
+}
+
 void
 terminal_set_winsize_blank(struct terminal *tm, const struct winsize *size,
     int blank, const term_attr_t *attr)
diff --git a/sys/sys/terminal.h b/sys/sys/terminal.h
index 133332f4b944..6528558a8608 100644
--- a/sys/sys/terminal.h
+++ b/sys/sys/terminal.h
@@ -207,6 +207,7 @@ struct terminal {
 
 struct terminal *terminal_alloc(const struct terminal_class *tc, void *softc);
 void	terminal_maketty(struct terminal *tm, const char *fmt, ...);
+void	terminal_set_cursor(struct terminal *tm, const term_pos_t *pos);
 void	terminal_set_winsize_blank(struct terminal *tm,
     const struct winsize *size, int blank, const term_attr_t *attr);
 void	terminal_set_winsize(struct terminal *tm, const struct winsize *size);