ui/console: move console compatibility check to dcl_display_console()

The current checks are done at registration time only. However, if a DCL
has no specific console specified, it may be switched dynamically with
console_select() later on.

Let's move the checks when displaychangelistener_display_console() is
called, which includes registration time and remains fatal if the
specified console is incompatible.

Note: we may want to display the compatibility error to the DCL, this is
left for a future improvement.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>

ui/console.c

@@ -148,6 +148,8 @@ static DisplayState *get_alloc_displaystate(void);
 static void text_console_update_cursor_timer(void);
 static void text_console_update_cursor(void *opaque);
 static bool displaychangelistener_has_dmabuf(DisplayChangeListener *dcl);
+static bool console_compatible_with(QemuConsole *con,
+                                    DisplayChangeListener *dcl, Error **errp);
 
 static void gui_update(void *opaque)
 {
@@ -1057,13 +1059,14 @@ static void console_putchar(QemuConsole *s, int ch)
 }
 
 static void displaychangelistener_display_console(DisplayChangeListener *dcl,
-                                                  QemuConsole *con)
+                                                  QemuConsole *con,
+                                                  Error **errp)
 {
     static const char nodev[] =
         "This VM has no graphic display device.";
     static DisplaySurface *dummy;
 
-    if (!con) {
+    if (!con || !console_compatible_with(con, dcl, errp)) {
         if (!dcl->ops->dpy_gfx_switch) {
             return;
         }
@@ -1114,7 +1117,7 @@ void console_select(unsigned int index)
                 if (dcl->con != NULL) {
                     continue;
                 }
-                displaychangelistener_display_console(dcl, s);
+                displaychangelistener_display_console(dcl, s, NULL);
             }
         }
         if (ds->have_text) {
@@ -1475,8 +1478,8 @@ static bool displaychangelistener_has_dmabuf(DisplayChangeListener *dcl)
     return false;
 }
 
-static bool dpy_compatible_with(QemuConsole *con,
-                                DisplayChangeListener *dcl, Error **errp)
+static bool console_compatible_with(QemuConsole *con,
+                                    DisplayChangeListener *dcl, Error **errp)
 {
     int flags;
 
@@ -1522,10 +1525,6 @@ void register_displaychangelistener(DisplayChangeListener *dcl)
 
     assert(!dcl->ds);
 
-    if (dcl->con) {
-        dpy_compatible_with(dcl->con, dcl, &error_fatal);
-    }
-
     trace_displaychangelistener_register(dcl, dcl->ops->dpy_name);
     dcl->ds = get_alloc_displaystate();
     QLIST_INSERT_HEAD(&dcl->ds->listeners, dcl, next);
@@ -1536,7 +1535,7 @@ void register_displaychangelistener(DisplayChangeListener *dcl)
     } else {
         con = active_console;
     }
-    displaychangelistener_display_console(dcl, con);
+    displaychangelistener_display_console(dcl, con, dcl->con ? &error_fatal : NULL);
     text_console_update_cursor(NULL);
 }