The terminal size of a mux chardev should be the same as the real
chardev, so listen for CHR_EVENT_RESIZE to be up to date.

We forward CHR_EVENT_RESIZE only to the focused frontend. This means
frontends should probably update their view of the terminal size on
receiving CHR_EVENT_MUX_IN.

Signed-off-by: Szymon Lukasz <noh4hss@gmail.com>
---
 chardev/char-mux.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/chardev/char-mux.c b/chardev/char-mux.c
index 46c44af67c..fa81f8341e 100644
--- a/chardev/char-mux.c
+++ b/chardev/char-mux.c
@@ -247,9 +247,24 @@ void mux_chr_send_all_event(Chardev *chr, QEMUChrEvent event)
     }
 }
 
+static void mux_update_winsize(Chardev *chr)
+{
+    MuxChardev *d = MUX_CHARDEV(chr);
+    uint16_t cols, rows;
+
+    qemu_chr_fe_get_winsize(&d->chr, &cols, &rows);
+    qemu_chr_resize(chr, cols, rows);
+}
+
 static void mux_chr_event(void *opaque, QEMUChrEvent event)
 {
-    mux_chr_send_all_event(CHARDEV(opaque), event);
+    Chardev *chr = CHARDEV(opaque);
+
+    if (event == CHR_EVENT_RESIZE) {
+        mux_update_winsize(chr);
+    } else {
+        mux_chr_send_all_event(chr, event);
+    }
 }
 
 static GSource *mux_chr_add_watch(Chardev *s, GIOCondition cond)
@@ -330,6 +345,7 @@ static void qemu_chr_open_mux(Chardev *chr,
      */
     *be_opened = machine_init_done;
     qemu_chr_fe_init(&d->chr, drv, errp);
+    mux_update_winsize(chr);
 }
 
 static void qemu_chr_parse_mux(QemuOpts *opts, ChardevBackend *backend,
-- 
2.27.0