vaapisink: add support for "display-name" property.

Add a "display-name" property to vaapisink so that the end user could
select the desired output. Keep "display-name" in-line with the existing
"display" (GstVaapiDisplayXXX type).

So, for X11 or GLX, the "display-name" is the usual display name as we
know for XOpenDisplay(); for Wayland, the "display-name" is the name used
for wl_display_connect(); and for DRM, the "display-name" is actually the
DRI device name.

https://bugzilla.gnome.org/show_bug.cgi?id=722247

gst/vaapi/gstvaapipluginbase.c

@@ -54,6 +54,25 @@ implements_interface_init (GstImplementsInterfaceClass * iface)
 #endif
 
 /* GstVideoContext interface */
+static void
+plugin_set_display (GstVaapiPluginBase * plugin, GstVaapiDisplay * display)
+{
+  const gchar *const display_name =
+      gst_vaapi_display_get_display_name (display);
+
+  if (plugin->display_name && g_strcmp0 (plugin->display_name, display_name)) {
+    GST_DEBUG_OBJECT (plugin, "incompatible display name '%s', requested '%s'",
+        display_name, plugin->display_name);
+    gst_vaapi_display_replace (&plugin->display, NULL);
+  } else {
+    GST_INFO_OBJECT (plugin, "set display %p", display);
+    gst_vaapi_display_replace (&plugin->display, display);
+    plugin->display_type = gst_vaapi_display_get_display_type (display);
+    gst_vaapi_plugin_base_set_display_name (plugin, display_name);
+  }
+  gst_vaapi_display_unref (display);
+}
+
 #if GST_CHECK_VERSION(1,1,0)
 static void
 plugin_set_context (GstElement * element, GstContext * context)
@@ -61,12 +80,8 @@ plugin_set_context (GstElement * element, GstContext * context)
   GstVaapiPluginBase *const plugin = GST_VAAPI_PLUGIN_BASE (element);
   GstVaapiDisplay *display = NULL;
 
-  if (gst_vaapi_video_context_get_display (context, &display)) {
+  if (gst_vaapi_video_context_get_display (context, &display))
-    GST_INFO_OBJECT (element, "set display %p", display);
+    plugin_set_display (plugin, display);
-    gst_vaapi_display_replace (&plugin->display, display);
-    gst_vaapi_display_unref (display);
-    plugin->display_type = gst_vaapi_display_get_display_type (display);
-  }
 }
 #else
 static void
@@ -74,9 +89,10 @@ plugin_set_context (GstVideoContext * context, const gchar * type,
     const GValue * value)
 {
   GstVaapiPluginBase *const plugin = GST_VAAPI_PLUGIN_BASE (context);
+  GstVaapiDisplay *display = NULL;
 
-  gst_vaapi_set_display (type, value, &plugin->display);
+  gst_vaapi_set_display (type, value, &display);
-  plugin->display_type = gst_vaapi_display_get_display_type (plugin->display);
+  plugin_set_display (plugin, display);
 }
 
 static void
@@ -212,6 +228,22 @@ gst_vaapi_plugin_base_set_display_type (GstVaapiPluginBase * plugin,
   plugin->display_type_req = display_type;
 }
 
+/**
+ * gst_vaapi_plugin_base_set_display_name:
+ * @plugin: a #GstVaapiPluginBase
+ * @display_name: the new display name to match
+ *
+ * Sets the name of the display to look for. The change is effective
+ * at the next call to gst_vaapi_plugin_base_ensure_display().
+ */
+void
+gst_vaapi_plugin_base_set_display_name (GstVaapiPluginBase * plugin,
+    const gchar * display_name)
+{
+  g_free (plugin->display_name);
+  plugin->display_name = g_strdup (display_name);
+}
+
 /**
  * gst_vaapi_plugin_base_ensure_display:
  * @plugin: a #GstVaapiPluginBase

gst/vaapi/gstvaapipluginbase.h

@@ -93,6 +93,8 @@ typedef struct _GstVaapiPluginBaseClass GstVaapiPluginBaseClass;
   (GST_VAAPI_PLUGIN_BASE(plugin)->display)
 #define GST_VAAPI_PLUGIN_BASE_DISPLAY_TYPE(plugin) \
   (GST_VAAPI_PLUGIN_BASE(plugin)->display_type)
+#define GST_VAAPI_PLUGIN_BASE_DISPLAY_NAME(plugin) \
+  (GST_VAAPI_PLUGIN_BASE(plugin)->display_name)
 #define GST_VAAPI_PLUGIN_BASE_DISPLAY_REPLACE(plugin, new_display) \
   (gst_vaapi_display_replace(&GST_VAAPI_PLUGIN_BASE_DISPLAY(plugin), \
        (new_display)))
@@ -137,6 +139,7 @@ struct _GstVaapiPluginBase
   GstVaapiDisplay *display;
   GstVaapiDisplayType display_type;
   GstVaapiDisplayType display_type_req;
+  gchar *display_name;
 
   GstVaapiUploader *uploader;
   gboolean uploader_used;
@@ -188,6 +191,11 @@ void
 gst_vaapi_plugin_base_set_display_type (GstVaapiPluginBase * plugin,
     GstVaapiDisplayType display_type);
 
+G_GNUC_INTERNAL
+void
+gst_vaapi_plugin_base_set_display_name (GstVaapiPluginBase * plugin,
+    const gchar * display_name);
+
 G_GNUC_INTERNAL
 gboolean
 gst_vaapi_plugin_base_ensure_display (GstVaapiPluginBase * plugin);

gst/vaapi/gstvaapipluginutil.c

@@ -90,7 +90,8 @@ static const DisplayMap g_display_map[] = {
 };
 
 static GstVaapiDisplay *
-gst_vaapi_create_display (GstVaapiDisplayType display_type)
+gst_vaapi_create_display (GstVaapiDisplayType display_type,
+    const gchar * display_name)
 {
   GstVaapiDisplay *display = NULL;
   const DisplayMap *m;
@@ -99,7 +100,7 @@ gst_vaapi_create_display (GstVaapiDisplayType display_type)
     if (display_type != GST_VAAPI_DISPLAY_TYPE_ANY && display_type != m->type)
       continue;
 
-    display = m->create_display (NULL);
+    display = m->create_display (display_name);
     if (display || display_type != GST_VAAPI_DISPLAY_TYPE_ANY)
       break;
   }
@@ -126,7 +127,7 @@ gst_vaapi_ensure_display (gpointer element, GstVaapiDisplayType type)
     return TRUE;
 
   /* If no neighboor, or application not interested, use system default */
-  display = gst_vaapi_create_display (type);
+  display = gst_vaapi_create_display (type, plugin->display_name);
   if (!display)
     return FALSE;
 

gst/vaapi/gstvaapisink.c

@@ -128,6 +128,7 @@ enum {
     PROP_0,
 
     PROP_DISPLAY_TYPE,
+    PROP_DISPLAY_NAME,
     PROP_FULLSCREEN,
     PROP_SYNCHRONOUS,
     PROP_USE_GLX,
@@ -1148,6 +1149,10 @@ gst_vaapisink_set_property(
         gst_vaapi_plugin_base_set_display_type(GST_VAAPI_PLUGIN_BASE(sink),
             g_value_get_enum(value));
         break;
+    case PROP_DISPLAY_NAME:
+        gst_vaapi_plugin_base_set_display_name(GST_VAAPI_PLUGIN_BASE(sink),
+            g_value_get_string(value));
+        break;
     case PROP_FULLSCREEN:
         sink->fullscreen = g_value_get_boolean(value);
         break;
@@ -1186,6 +1191,9 @@ gst_vaapisink_get_property(
     case PROP_DISPLAY_TYPE:
         g_value_set_enum(value, GST_VAAPI_PLUGIN_BASE_DISPLAY_TYPE(sink));
         break;
+    case PROP_DISPLAY_NAME:
+        g_value_set_string(value, GST_VAAPI_PLUGIN_BASE_DISPLAY_NAME(sink));
+        break;
     case PROP_FULLSCREEN:
         g_value_set_boolean(value, sink->fullscreen);
         break;
@@ -1277,6 +1285,15 @@ gst_vaapisink_class_init(GstVaapiSinkClass *klass)
                            GST_VAAPI_DISPLAY_TYPE_ANY,
                            G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
 
+    g_object_class_install_property
+        (object_class,
+         PROP_DISPLAY_NAME,
+         g_param_spec_string("display-name",
+                             "display name",
+                             "display name to use",
+                             NULL,
+                             G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+
 #if USE_GLX
     g_object_class_install_property
         (object_class,