[PATCH] ui/console: Display the 'none' backend in '-display help'

[PATCH] ui/console: Display the 'none' backend in '-display help'

[Philippe Mathieu-Daudé]

Commit c388f408b5 added the possibility to list the display
backends using '-display help'. Since the 'none' backend is
is not implemented as a DisplayChangeListenerOps, it is not
registered to the dpys[] array with qemu_display_register(),
and is not listed in the help output.

This might be confusing, as we list it in the man page:

  -display type
      Select type of display to use. This option is a replacement for
      the old style -sdl/-curses/... options. Valid values for type are

      none
          Do not display video output. The guest will still see an
          emulated graphics card, but its output will not be displayed
          to the QEMU user. This option differs from the -nographic
          option in that it only affects what is done with video
          output; -nographic also changes the destination of the serial
          and parallel port data.

Fix by manually listing the special 'none' backend in the help.

Suggested-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 ui/console.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ui/console.c b/ui/console.c
index 69339b028b..179901c35e 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -2338,6 +2338,7 @@ void qemu_display_help(void)
     int idx;
 
     printf("Available display backend types:\n");
+    printf("none\n");
     for (idx = DISPLAY_TYPE_NONE; idx < DISPLAY_TYPE__MAX; idx++) {
         if (!dpys[idx]) {
             ui_module_load_one(DisplayType_str(idx));
-- 
2.21.1

Re: [PATCH] ui/console: Display the 'none' backend in '-display help'

[Eric Blake]

On 1/20/20 1:29 PM, Philippe Mathieu-Daudé wrote:
> Commit c388f408b5 added the possibility to list the display
> backends using '-display help'. Since the 'none' backend is
> is not implemented as a DisplayChangeListenerOps, it is not
> registered to the dpys[] array with qemu_display_register(),
> and is not listed in the help output.
> 
> This might be confusing, as we list it in the man page:
> 
>    -display type
>        Select type of display to use. This option is a replacement for
>        the old style -sdl/-curses/... options. Valid values for type are
> 
>        none
>            Do not display video output. The guest will still see an
>            emulated graphics card, but its output will not be displayed
>            to the QEMU user. This option differs from the -nographic
>            option in that it only affects what is done with video
>            output; -nographic also changes the destination of the serial
>            and parallel port data.
> 
> Fix by manually listing the special 'none' backend in the help.
> 
> Suggested-by: Thomas Huth <thuth@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>   ui/console.c | 1 +
>   1 file changed, 1 insertion(+)

Reviewed-by: Eric Blake <eblake@redhat.com>

> 
> diff --git a/ui/console.c b/ui/console.c
> index 69339b028b..179901c35e 100644
> --- a/ui/console.c
> +++ b/ui/console.c
> @@ -2338,6 +2338,7 @@ void qemu_display_help(void)
>       int idx;
>   
>       printf("Available display backend types:\n");
> +    printf("none\n");
>       for (idx = DISPLAY_TYPE_NONE; idx < DISPLAY_TYPE__MAX; idx++) {
>           if (!dpys[idx]) {
>               ui_module_load_one(DisplayType_str(idx));
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

Re: [PATCH] ui/console: Display the 'none' backend in '-display help'

[Gerd Hoffmann]

On Mon, Jan 20, 2020 at 08:29:47PM +0100, Philippe Mathieu-Daudé wrote:
> Commit c388f408b5 added the possibility to list the display
> backends using '-display help'. Since the 'none' backend is
> is not implemented as a DisplayChangeListenerOps, it is not
> registered to the dpys[] array with qemu_display_register(),
> and is not listed in the help output.
> 
> This might be confusing, as we list it in the man page:
> 
>   -display type
>       Select type of display to use. This option is a replacement for
>       the old style -sdl/-curses/... options. Valid values for type are
> 
>       none
>           Do not display video output. The guest will still see an
>           emulated graphics card, but its output will not be displayed
>           to the QEMU user. This option differs from the -nographic
>           option in that it only affects what is done with video
>           output; -nographic also changes the destination of the serial
>           and parallel port data.
> 
> Fix by manually listing the special 'none' backend in the help.
> 
> Suggested-by: Thomas Huth <thuth@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Added to ui queue.

thanks,
  Gerd