display: add initial support for display attributes.

The VA display attributes are mapped to properties so that to maintain the
GStreamer terminology. Properties are to be identified by name, but internal
functions are available to lookup the property by the actual VA display
attribute type.

gst-libs/gst/vaapi/gstvaapidisplay.c

@@ -45,6 +45,12 @@ struct _GstVaapiConfig {
     GstVaapiEntrypoint  entrypoint;
 };
 
+typedef struct _GstVaapiProperty GstVaapiProperty;
+struct _GstVaapiProperty {
+    const gchar        *name;
+    VADisplayAttribute  attribute;
+};
+
 enum {
     PROP_0,
 
@@ -304,6 +310,40 @@ get_format_caps(GArray *formats)
     return out_caps;
 }
 
+/* Find display attribute */
+static const GstVaapiProperty *
+find_property(GArray *properties, const gchar *name)
+{
+    GstVaapiProperty *prop;
+    guint i;
+
+    if (!name)
+        return NULL;
+
+    for (i = 0; i < properties->len; i++) {
+        prop = &g_array_index(properties, GstVaapiProperty, i);
+        if (strcmp(prop->name, name) == 0)
+            return prop;
+    }
+    return NULL;
+}
+
+#if 0
+static const GstVaapiProperty *
+find_property_by_type(GArray *properties, VADisplayAttribType type)
+{
+    GstVaapiProperty *prop;
+    guint i;
+
+    for (i = 0; i < properties->len; i++) {
+        prop = &g_array_index(properties, GstVaapiProperty, i);
+        if (prop->attribute.type == type)
+            return prop;
+    }
+    return NULL;
+}
+#endif
+
 static void
 gst_vaapi_display_calculate_pixel_aspect_ratio(GstVaapiDisplay *display)
 {
@@ -374,6 +414,11 @@ gst_vaapi_display_destroy(GstVaapiDisplay *display)
         priv->subpicture_formats = NULL;
     }
 
+    if (priv->properties) {
+        g_array_free(priv->properties, TRUE);
+        priv->properties = NULL;
+    }
+
     if (priv->display) {
         if (!priv->parent)
             vaTerminate(priv->display);
@@ -523,9 +568,26 @@ gst_vaapi_display_create(GstVaapiDisplay *display)
     if (!vaapi_check_status(status, "vaQueryDisplayAttributes()"))
         goto end;
 
+    priv->properties = g_array_new(FALSE, FALSE, sizeof(GstVaapiProperty));
+    if (!priv->properties)
+        goto end;
+
     GST_DEBUG("%d display attributes", n);
-    for (i = 0; i < n; i++)
+    for (i = 0; i < n; i++) {
-        GST_DEBUG("  %s", string_of_VADisplayAttributeType(display_attrs[i].type));
+        VADisplayAttribute * const attr = &display_attrs[i];
+        GstVaapiProperty prop;
+
+        GST_DEBUG("  %s", string_of_VADisplayAttributeType(attr->type));
+
+        switch (attr->type) {
+        default:
+            prop.attribute.flags = 0;
+            break;
+        }
+        if (!prop.attribute.flags)
+            continue;
+        g_array_append_val(priv->properties, prop);
+    }
 
     /* VA image formats */
     formats = g_new(VAImageFormat, vaMaxNumImageFormats(priv->display));
@@ -755,6 +817,7 @@ gst_vaapi_display_init(GstVaapiDisplay *display)
     priv->encoders              = NULL;
     priv->image_formats         = NULL;
     priv->subpicture_formats    = NULL;
+    priv->properties            = NULL;
     priv->create_display        = TRUE;
 
     g_static_rec_mutex_init(&priv->mutex);
@@ -1153,3 +1216,24 @@ gst_vaapi_display_has_subpicture_format(
 
     return find_format(display->priv->subpicture_formats, format);
 }
+
+/**
+ * gst_vaapi_display_has_property:
+ * @display: a #GstVaapiDisplay
+ * @name: the property name to check
+ *
+ * Returns whether VA @display supports the requested property. The
+ * check is performed against the property @name. So, the client
+ * application may perform this check only once and cache this
+ * information.
+ *
+ * Return value: %TRUE if VA @display supports property @name
+ */
+gboolean
+gst_vaapi_display_has_property(GstVaapiDisplay *display, const gchar *name)
+{
+    g_return_val_if_fail(GST_VAAPI_IS_DISPLAY(display), FALSE);
+    g_return_val_if_fail(name, FALSE);
+
+    return find_property(display->priv->properties, name) != NULL;
+}

gst-libs/gst/vaapi/gstvaapidisplay.h

@@ -218,6 +218,9 @@ gst_vaapi_display_has_subpicture_format(
     GstVaapiImageFormat format
 );
 
+gboolean
+gst_vaapi_display_has_property(GstVaapiDisplay *display, const gchar *name);
+
 G_END_DECLS
 
 #endif /* GST_VAAPI_DISPLAY_H */

gst-libs/gst/vaapi/gstvaapidisplay_priv.h

@@ -86,6 +86,7 @@ struct _GstVaapiDisplayPrivate {
     GArray             *encoders;
     GArray             *image_formats;
     GArray             *subpicture_formats;
+    GArray             *properties;
     guint               create_display  : 1;
 };