[mutter] monitor-manager/native: Allow starting without outputs when headless

[Marge Bot <marge-bot src gnome org>]

commit 59a10cd18827100643804299874b35db31425943
Author: Jonas Ådahl <jadahl gmail com>
Date:   Mon Jan 18 22:34:04 2021 +0100

    monitor-manager/native: Allow starting without outputs when headless
    
    This will allow starting, then adding virtual outputs when needed e.g.
    via the screen cast API.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1698>

 src/backends/native/meta-backend-native.c         |  2 +
 src/backends/native/meta-monitor-manager-native.c | 48 ++++++++++++++++++++++-
 2 files changed, 49 insertions(+), 1 deletion(-)
---
diff --git a/src/backends/native/meta-backend-native.c b/src/backends/native/meta-backend-native.c
index ebd8570d07..45fb7b421d 100644
--- a/src/backends/native/meta-backend-native.c
+++ b/src/backends/native/meta-backend-native.c
@@ -212,10 +212,12 @@ static MetaMonitorManager *
 meta_backend_native_create_monitor_manager (MetaBackend *backend,
                                             GError     **error)
 {
+  MetaBackendNative *backend_native = META_BACKEND_NATIVE (backend);
   MetaMonitorManager *manager;
 
   manager = g_initable_new (META_TYPE_MONITOR_MANAGER_NATIVE, NULL, error,
                             "backend", backend,
+                            "needs-outputs", !backend_native->is_headless,
                             NULL);
   if (!manager)
     return NULL;
diff --git a/src/backends/native/meta-monitor-manager-native.c 
b/src/backends/native/meta-monitor-manager-native.c
index d0253d89ab..30a1535061 100644
--- a/src/backends/native/meta-monitor-manager-native.c
+++ b/src/backends/native/meta-monitor-manager-native.c
@@ -63,6 +63,17 @@
 #include "meta/main.h"
 #include "meta/meta-x11-errors.h"
 
+enum
+{
+  PROP_0,
+
+  PROP_NEED_OUTPUTS,
+
+  N_PROPS
+};
+
+static GParamSpec *obj_props[N_PROPS];
+
 struct _MetaMonitorManagerNative
 {
   MetaMonitorManager parent_instance;
@@ -70,6 +81,8 @@ struct _MetaMonitorManagerNative
   gulong kms_resources_changed_handler_id;
 
   GHashTable *crtc_gamma_cache;
+
+  gboolean needs_outputs;
 };
 
 struct _MetaMonitorManagerNativeClass
@@ -588,6 +601,26 @@ meta_monitor_manager_native_get_default_layout_mode (MetaMonitorManager *manager
     return META_LOGICAL_MONITOR_LAYOUT_MODE_PHYSICAL;
 }
 
+static void
+meta_monitor_manager_native_set_property (GObject      *object,
+                                          guint         prop_id,
+                                          const GValue *value,
+                                          GParamSpec   *pspec)
+{
+  MetaMonitorManagerNative *manager_native =
+    META_MONITOR_MANAGER_NATIVE (object);
+
+  switch (prop_id)
+    {
+    case PROP_NEED_OUTPUTS:
+      manager_native->needs_outputs = g_value_get_boolean (value);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+    }
+}
+
 static void
 meta_monitor_manager_native_dispose (GObject *object)
 {
@@ -625,7 +658,8 @@ meta_monitor_manager_native_initable_init (GInitable    *initable,
           break;
         }
     }
-  if (!can_have_outputs)
+
+  if (manager_native->needs_outputs && !can_have_outputs)
     {
       g_set_error (error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND,
                    "No GPUs with outputs found");
@@ -649,6 +683,7 @@ initable_iface_init (GInitableIface *initable_iface)
 static void
 meta_monitor_manager_native_init (MetaMonitorManagerNative *manager_native)
 {
+  manager_native->needs_outputs = TRUE;
 }
 
 static void
@@ -657,6 +692,7 @@ meta_monitor_manager_native_class_init (MetaMonitorManagerNativeClass *klass)
   GObjectClass *object_class = G_OBJECT_CLASS (klass);
   MetaMonitorManagerClass *manager_class = META_MONITOR_MANAGER_CLASS (klass);
 
+  object_class->set_property = meta_monitor_manager_native_set_property;
   object_class->dispose = meta_monitor_manager_native_dispose;
 
   manager_class->read_edid =
@@ -685,4 +721,14 @@ meta_monitor_manager_native_class_init (MetaMonitorManagerNativeClass *klass)
     meta_monitor_manager_native_get_max_screen_size;
   manager_class->get_default_layout_mode =
     meta_monitor_manager_native_get_default_layout_mode;
+
+  obj_props[PROP_NEED_OUTPUTS] =
+    g_param_spec_boolean ("needs-outputs",
+                          "needs-outputs",
+                          "Whether any outputs are needed for operation",
+                          TRUE,
+                          G_PARAM_WRITABLE |
+                          G_PARAM_CONSTRUCT_ONLY |
+                          G_PARAM_STATIC_STRINGS);
+  g_object_class_install_properties (object_class, N_PROPS, obj_props);
 }