diff mbox series

[2/5] ui/console-vc: report to the application instead of screen rendering

Message ID 20250223145407.259924-3-r.peniaev@gmail.com (mailing list archive)
State New
Headers show
Series ui/console-vc: various fixes and improvements | expand

Commit Message

Roman Penyaev Feb. 23, 2025, 2:53 p.m. UTC 
Terminal Device Status Report (DSR) [1] should be sent to an
application, not rendered to the screen. This patch fixes rendering of
terminal report, which appears only on the graphical screen of the
terminal (console "vc") and can be reproduced by the following
command:

     echo -en '\e[6n'; IFS='[;' read -sdR _ row col; echo $row:$col

Command requests cursor position and waits for terminal response, but
instead, the response is rendered to the graphical screen and never
sent to an application.

Why bother? Busybox shell (ash) in Alpine distribution requests cursor
position on each shell prompt (once <ENTER> is pressed), which makes a
prompt on a graphical screen corrupted with repeating Cursor Position
Report (CPR) [2]:

   [root@alpine ~]# \033[57;1R]

Which is very annoying and incorrect.

[1] https://vt100.net/docs/vt100-ug/chapter3.html#DSR
[2] https://vt100.net/docs/vt100-ug/chapter3.html#CPR

Signed-off-by: Roman Penyaev <r.peniaev@gmail.com>
Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com>
Cc: qemu-devel@nongnu.org
---
 ui/console-vc.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/ui/console-vc.c b/ui/console-vc.c
index 90ff0ffda8c5..d512f57e10a9 100644
--- a/ui/console-vc.c
+++ b/ui/console-vc.c
@@ -617,10 +617,9 @@  static void vc_put_one(VCChardev *vc, int ch)
 
 static void vc_respond_str(VCChardev *vc, const char *buf)
 {
-    while (*buf) {
-        vc_put_one(vc, *buf);
-        buf++;
-    }
+    QemuTextConsole *s = vc->console;
+
+    qemu_chr_be_write(s->chr, (const uint8_t *)buf, strlen(buf));
 }
 
 /* set cursor, checking bounds */