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, 15 insertions, 0 deletions

diff --git a/ui/console.c b/ui/console.c
index ac79d67..69339b0 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -2333,6 +2333,21 @@ void qemu_display_init(DisplayState *ds, DisplayOptions *opts)
     dpys[opts->type]->init(ds, opts);
 }
 
+void qemu_display_help(void)
+{
+    int idx;
+
+    printf("Available display backend types:\n");
+    for (idx = DISPLAY_TYPE_NONE; idx < DISPLAY_TYPE__MAX; idx++) {
+        if (!dpys[idx]) {
+            ui_module_load_one(DisplayType_str(idx));
+        }
+        if (dpys[idx]) {
+            printf("%s\n",  DisplayType_str(dpys[idx]->type));
+        }
+    }
+}
+
 void qemu_chr_parse_vc(QemuOpts *opts, ChardevBackend *backend, Error **errp)
 {
     int val;