ui: Print available display backends with '-display help'

We already print availabled devices with "-device help", or available
backends with "-netdev help" or "-chardev help". Let's provide a way
for the users to query the available display backends, too.

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-id: 20200108144702.29969-1-thuth@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/vl.c b/vl.c
index 158a05ed32..751401214c 100644
--- a/vl.c
+++ b/vl.c
@@ -1869,6 +1869,11 @@ static void parse_display(const char *p)
 {
     const char *opts;
 
+    if (is_help_option(p)) {
+        qemu_display_help();
+        exit(0);
+    }
+
     if (strstart(p, "sdl", &opts)) {
         /*
          * sdl DisplayType needs hand-crafted parser instead of