Introduce virtual monitors

Virtual monitors are monitors that isn't backed by any monitor like
hardware. It would typically be backed by e.g. a remote desktop service,
or a network display.

It is currently only supported by the native backend, and whether the
X11 backend will ever see virtual monitors is an open question. This
rest of this commit message describes how it works under the native
backend.

Each virutal monitor consists of virtualized mode setting components:

 * A virtual CRTC mode (MetaCrtcModeVirtual)
 * A virtual CRTC (MetaCrtcVirtual)
 * A virtual connector (MetaOutputVirtual)

In difference to the corresponding mode setting objects that represents
KMS objects, the virtual ones isn't directly tied to a MetaGpu, other
than the CoglFramebuffer being part of the GPU context of the primary
GPU, which is the case for all monitors no matter what GPU they are
connected to. Part of the reason for this is that a MetaGpu in practice
represents a mode setting device, and its CRTCs and outputs, are all
backed by real mode setting objects, while a virtual monitor is only
backed by a framebuffer that is tied to the primary GPU. Maybe this will
be reevaluated in the future, but since a virtual monitor is not tied to
any GPU currently, so is the case for the virtual mode setting objects.

The native rendering backend, including the cursor renderer, is adapted
to handle the situation where a CRTC does not have a GPU associated with
it; this in practice means that it e.g. will not try to upload HW cursor
buffers when the cursor is only on a virtual monitor. The same applies
to the native renderer, which is made to avoid creating
MetaOnscreenNative for views that are backed by virtual CRTCs, as well
as to avoid trying to mode set on such views.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1698>

src/backends/meta-backend-types.h

@@ -59,6 +59,9 @@ typedef struct _MetaScreenCastStream MetaScreenCastStream;
 
 typedef struct _MetaWaylandCompositor MetaWaylandCompositor;
 
+typedef struct _MetaVirtualMonitor MetaVirtualMonitor;
+typedef struct _MetaVirtualMonitorInfo MetaVirtualMonitorInfo;
+
 #ifdef HAVE_REMOTE_DESKTOP
 typedef struct _MetaRemoteDesktop MetaRemoteDesktop;
 #endif

src/backends/meta-monitor-manager-private.h

@@ -261,6 +261,10 @@ struct _MetaMonitorManagerClass
 
   void (* set_output_ctm) (MetaOutput          *output,
                            const MetaOutputCtm *ctm);
+
+  MetaVirtualMonitor * (* create_virtual_monitor) (MetaMonitorManager            *manager,
+                                                   const MetaVirtualMonitorInfo  *info,
+                                                   GError                       **error);
 };
 
 META_EXPORT_TEST
@@ -388,6 +392,10 @@ gboolean           meta_monitor_manager_get_max_screen_size (MetaMonitorManager
 MetaLogicalMonitorLayoutMode
                    meta_monitor_manager_get_default_layout_mode (MetaMonitorManager *manager);
 
+MetaVirtualMonitor * meta_monitor_manager_create_virtual_monitor (MetaMonitorManager            *manager,
+                                                                  const MetaVirtualMonitorInfo  *info,
+                                                                  GError                       **error);
+
 MetaMonitorConfigManager *
                    meta_monitor_manager_get_config_manager (MetaMonitorManager *manager);
 
@@ -424,4 +432,6 @@ void meta_monitor_manager_post_init (MetaMonitorManager *manager);
 
 MetaViewportInfo * meta_monitor_manager_get_viewports (MetaMonitorManager *manager);
 
+GList * meta_monitor_manager_get_virtual_monitors (MetaMonitorManager *manager);
+
 #endif /* META_MONITOR_MANAGER_PRIVATE_H */

src/backends/meta-monitor-manager.c

@@ -53,6 +53,7 @@
 #include "backends/meta-monitor-config-manager.h"
 #include "backends/meta-orientation-manager.h"
 #include "backends/meta-output.h"
+#include "backends/meta-virtual-monitor.h"
 #include "backends/x11/meta-monitor-manager-xrandr.h"
 #include "clutter/clutter.h"
 #include "core/main-private.h"
@@ -101,6 +102,10 @@ typedef struct _MetaMonitorManagerPrivate
 {
   MetaPowerSave power_save_mode;
   gboolean      initial_orient_change_done;
+
+  GList *virtual_monitors;
+
+  gboolean shutting_down;
 } MetaMonitorManagerPrivate;
 
 G_DEFINE_TYPE_WITH_PRIVATE (MetaMonitorManager, meta_monitor_manager,
@@ -400,6 +405,16 @@ lid_is_closed_changed (MetaBackend *backend,
   meta_monitor_manager_lid_is_closed_changed (manager);
 }
 
+static void
+prepare_shutdown (MetaBackend        *backend,
+                  MetaMonitorManager *manager)
+{
+  MetaMonitorManagerPrivate *priv =
+    meta_monitor_manager_get_instance_private (manager);
+
+  priv->shutting_down = TRUE;
+}
+
 /**
  * meta_monitor_manager_is_headless:
  * @manager: A #MetaMonitorManager object
@@ -483,6 +498,60 @@ meta_monitor_manager_get_default_layout_mode (MetaMonitorManager *manager)
   return manager_class->get_default_layout_mode (manager);
 }
 
+static void
+on_virtual_monitor_destroyed (MetaVirtualMonitor *virtual_monitor,
+                              MetaMonitorManager *manager)
+{
+  MetaMonitorManagerPrivate *priv =
+    meta_monitor_manager_get_instance_private (manager);
+  MetaOutput *output;
+
+  output = meta_virtual_monitor_get_output (virtual_monitor);
+  g_message ("Removed virtual monitor %s", meta_output_get_name (output));
+  priv->virtual_monitors = g_list_remove (priv->virtual_monitors,
+                                          virtual_monitor);
+
+  if (!priv->shutting_down)
+    meta_monitor_manager_reload (manager);
+}
+
+MetaVirtualMonitor *
+meta_monitor_manager_create_virtual_monitor (MetaMonitorManager            *manager,
+                                             const MetaVirtualMonitorInfo  *info,
+                                             GError                       **error)
+{
+  MetaMonitorManagerPrivate *priv =
+    meta_monitor_manager_get_instance_private (manager);
+  MetaMonitorManagerClass *manager_class =
+    META_MONITOR_MANAGER_GET_CLASS (manager);
+  MetaVirtualMonitor *virtual_monitor;
+  MetaOutput *output;
+
+  if (!manager_class->create_virtual_monitor)
+    {
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,
+                   "Backend doesn't support creating virtual monitors");
+      return NULL;
+    }
+
+  virtual_monitor = manager_class->create_virtual_monitor (manager, info,
+                                                           error);
+  if (!virtual_monitor)
+    return NULL;
+
+  g_signal_connect (virtual_monitor, "destroy",
+                    G_CALLBACK (on_virtual_monitor_destroyed),
+                    manager);
+
+  priv->virtual_monitors = g_list_append (priv->virtual_monitors,
+                                          virtual_monitor);
+
+  output = meta_virtual_monitor_get_output (virtual_monitor);
+  g_message ("Added virtual monitor %s", meta_output_get_name (output));
+
+  return virtual_monitor;
+}
+
 static void
 meta_monitor_manager_ensure_initial_config (MetaMonitorManager *manager)
 {
@@ -896,6 +965,10 @@ meta_monitor_manager_constructed (GObject *object)
                            G_CALLBACK (lid_is_closed_changed),
                            manager, 0);
 
+  g_signal_connect (backend, "prepare-shutdown",
+                    G_CALLBACK (prepare_shutdown),
+                    manager);
+
   manager->current_switch_config = META_MONITOR_SWITCH_CONFIG_UNKNOWN;
 
   initialize_dbus_interface (manager);
@@ -905,9 +978,13 @@ static void
 meta_monitor_manager_finalize (GObject *object)
 {
   MetaMonitorManager *manager = META_MONITOR_MANAGER (object);
+  MetaMonitorManagerPrivate *priv =
+    meta_monitor_manager_get_instance_private (manager);
 
   g_list_free_full (manager->logical_monitors, g_object_unref);
 
+  g_warn_if_fail (!priv->virtual_monitors);
+
   g_clear_signal_handler (&manager->experimental_features_changed_handler_id,
                           manager->backend);
 
@@ -2894,6 +2971,18 @@ rebuild_monitors (MetaMonitorManager *manager)
             }
         }
     }
+
+  for (l = meta_monitor_manager_get_virtual_monitors (manager); l; l = l->next)
+    {
+      MetaVirtualMonitor *virtual_monitor = l->data;
+      MetaOutput *output = meta_virtual_monitor_get_output (virtual_monitor);
+      MetaMonitorNormal *monitor_normal;
+
+      monitor_normal = meta_monitor_normal_new (manager, output);
+      manager->monitors = g_list_append (manager->monitors,
+                                         monitor_normal);
+
+    }
 }
 
 void
@@ -3365,3 +3454,12 @@ meta_monitor_manager_get_viewports (MetaMonitorManager *manager)
 
   return info;
 }
+
+GList *
+meta_monitor_manager_get_virtual_monitors (MetaMonitorManager *manager)
+{
+  MetaMonitorManagerPrivate *priv =
+    meta_monitor_manager_get_instance_private (manager);
+
+  return priv->virtual_monitors;
+}

src/backends/meta-output.h

@@ -39,7 +39,8 @@ struct _MetaTileInfo
   uint32_t tile_h;
 };
 
-/* This matches the values in drm_mode.h */
+/* The first 17 matches the values in drm_mode.h, the ones starting with
+ * 1000 do not. */
 typedef enum
 {
   META_CONNECTOR_TYPE_Unknown = 0,
@@ -59,6 +60,8 @@ typedef enum
   META_CONNECTOR_TYPE_eDP = 14,
   META_CONNECTOR_TYPE_VIRTUAL = 15,
   META_CONNECTOR_TYPE_DSI = 16,
+
+  META_CONNECTOR_TYPE_META = 1000,
 } MetaConnectorType;
 
 typedef struct _MetaOutputInfo

src/backends/meta-virtual-monitor.c

@@ -0,0 +1,238 @@
+/*
+ * Copyright (C) 2021 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ *
+ */
+
+#include "config.h"
+
+#include "backends/meta-virtual-monitor.h"
+
+#include "backends/meta-crtc.h"
+#include "backends/meta-crtc-mode.h"
+#include "backends/meta-output.h"
+
+enum
+{
+  DESTROY,
+
+  N_SIGNALS
+};
+
+static guint signals[N_SIGNALS] = { 0 };
+
+enum
+{
+  PROP_0,
+
+  PROP_CRTC,
+  PROP_CRTC_MODE,
+  PROP_OUTPUT,
+
+  N_PROPS
+};
+
+static GParamSpec *obj_props[N_PROPS];
+
+typedef struct _MetaVirtualMonitorPrivate
+{
+  MetaCrtc *crtc;
+  MetaCrtcMode *crtc_mode;
+  MetaOutput *output;
+
+  gboolean is_destroyed;
+} MetaVirtualMonitorPrivate;
+
+G_DEFINE_ABSTRACT_TYPE_WITH_PRIVATE (MetaVirtualMonitor, meta_virtual_monitor,
+                                     G_TYPE_OBJECT)
+
+MetaVirtualMonitorInfo *
+meta_virtual_monitor_info_new (int         width,
+                               int         height,
+                               float       refresh_rate,
+                               const char *vendor,
+                               const char *product,
+                               const char *serial)
+{
+  MetaVirtualMonitorInfo *info;
+
+  info = g_new0 (MetaVirtualMonitorInfo, 1);
+  info->width = width;
+  info->height = height;
+  info->refresh_rate = refresh_rate;
+  info->vendor = g_strdup (vendor);
+  info->product = g_strdup (product);
+  info->serial = g_strdup (serial);
+
+  return info;
+}
+
+void
+meta_virtual_monitor_info_free (MetaVirtualMonitorInfo *info)
+{
+  g_free (info->vendor);
+  g_free (info->product);
+  g_free (info->serial);
+  g_free (info);
+}
+
+MetaCrtc *
+meta_virtual_monitor_get_crtc (MetaVirtualMonitor *virtual_monitor)
+{
+  MetaVirtualMonitorPrivate *priv =
+    meta_virtual_monitor_get_instance_private (virtual_monitor);
+
+  return priv->crtc;
+}
+
+MetaCrtcMode *
+meta_virtual_monitor_get_crtc_mode (MetaVirtualMonitor *virtual_monitor)
+{
+  MetaVirtualMonitorPrivate *priv =
+    meta_virtual_monitor_get_instance_private (virtual_monitor);
+
+  return priv->crtc_mode;
+}
+
+MetaOutput *
+meta_virtual_monitor_get_output (MetaVirtualMonitor *virtual_monitor)
+{
+  MetaVirtualMonitorPrivate *priv =
+    meta_virtual_monitor_get_instance_private (virtual_monitor);
+
+  return priv->output;
+}
+
+static void
+meta_virtual_monitor_set_property (GObject      *object,
+                                   guint         prop_id,
+                                   const GValue *value,
+                                   GParamSpec   *pspec)
+{
+  MetaVirtualMonitor *virtual_monitor = META_VIRTUAL_MONITOR (object);
+  MetaVirtualMonitorPrivate *priv =
+    meta_virtual_monitor_get_instance_private (virtual_monitor);
+
+  switch (prop_id)
+    {
+    case PROP_CRTC:
+      priv->crtc = g_value_get_object (value);
+      break;
+    case PROP_CRTC_MODE:
+      priv->crtc_mode = g_value_get_object (value);
+      break;
+    case PROP_OUTPUT:
+      priv->output = g_value_get_object (value);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+    }
+}
+
+static void
+meta_virtual_monitor_get_property (GObject    *object,
+                                   guint       prop_id,
+                                   GValue     *value,
+                                   GParamSpec *pspec)
+{
+  MetaVirtualMonitor *virtual_monitor = META_VIRTUAL_MONITOR (object);
+  MetaVirtualMonitorPrivate *priv =
+    meta_virtual_monitor_get_instance_private (virtual_monitor);
+
+  switch (prop_id)
+    {
+    case PROP_CRTC:
+      g_value_set_object (value, priv->crtc);
+      break;
+    case PROP_CRTC_MODE:
+      g_value_set_object (value, priv->crtc_mode);
+      break;
+    case PROP_OUTPUT:
+      g_value_set_object (value, priv->output);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+    }
+}
+
+static void
+meta_virtual_monitor_dispose (GObject *object)
+{
+  MetaVirtualMonitor *virtual_monitor = META_VIRTUAL_MONITOR (object);
+  MetaVirtualMonitorPrivate *priv =
+    meta_virtual_monitor_get_instance_private (virtual_monitor);
+
+  if (!priv->is_destroyed)
+    {
+      g_signal_emit (virtual_monitor, signals[DESTROY], 0);
+      priv->is_destroyed = TRUE;
+    }
+
+  g_clear_object (&priv->crtc);
+  g_clear_object (&priv->crtc_mode);
+  g_clear_object (&priv->output);
+
+  G_OBJECT_CLASS (meta_virtual_monitor_parent_class)->dispose (object);
+}
+
+static void
+meta_virtual_monitor_init (MetaVirtualMonitor *virtual_monitor)
+{
+}
+
+static void
+meta_virtual_monitor_class_init (MetaVirtualMonitorClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+
+  object_class->set_property = meta_virtual_monitor_set_property;
+  object_class->get_property = meta_virtual_monitor_get_property;
+  object_class->dispose = meta_virtual_monitor_dispose;
+
+  obj_props[PROP_CRTC] =
+    g_param_spec_object ("crtc",
+                         "crtc",
+                         "The virtual CRTC",
+                         META_TYPE_CRTC,
+                         G_PARAM_READWRITE |
+                         G_PARAM_CONSTRUCT_ONLY |
+                         G_PARAM_STATIC_STRINGS);
+  obj_props[PROP_CRTC_MODE] =
+    g_param_spec_object ("crtc-mode",
+                         "crtc-mode",
+                         "The virtual CRTC mode",
+                         META_TYPE_CRTC_MODE,
+                         G_PARAM_READWRITE |
+                         G_PARAM_CONSTRUCT_ONLY |
+                         G_PARAM_STATIC_STRINGS);
+  obj_props[PROP_OUTPUT] =
+    g_param_spec_object ("output",
+                         "output",
+                         "The virtual output",
+                         META_TYPE_OUTPUT,
+                         G_PARAM_READWRITE |
+                         G_PARAM_CONSTRUCT_ONLY |
+                         G_PARAM_STATIC_STRINGS);
+  g_object_class_install_properties (object_class, N_PROPS, obj_props);
+
+  signals[DESTROY] =
+    g_signal_new ("destroy",
+                  G_TYPE_FROM_CLASS (klass),
+                  G_SIGNAL_RUN_LAST, 0,
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 0);
+}

src/backends/meta-virtual-monitor.h

@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2021 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ *
+ */
+
+#ifndef META_VIRTUAL_MONITOR_H
+#define META_VIRTUAL_MONITOR_H
+
+#include <glib-object.h>
+
+#include "backends/meta-backend-types.h"
+#include "core/util-private.h"
+
+typedef struct _MetaVirtualMonitorInfo
+{
+  int width;
+  int height;
+  float refresh_rate;
+
+  char *vendor;
+  char *product;
+  char *serial;
+} MetaVirtualMonitorInfo;
+
+#define META_TYPE_VIRTUAL_MONITOR (meta_virtual_monitor_get_type ())
+G_DECLARE_DERIVABLE_TYPE (MetaVirtualMonitor, meta_virtual_monitor,
+                          META, VIRTUAL_MONITOR,
+                          GObject)
+
+struct _MetaVirtualMonitorClass
+{
+  GObjectClass parent_class;
+};
+
+MetaVirtualMonitorInfo * meta_virtual_monitor_info_new (int         width,
+                                                        int         height,
+                                                        float       refresh_rate,
+                                                        const char *vendor,
+                                                        const char *product,
+                                                        const char *serial);
+
+void meta_virtual_monitor_info_free (MetaVirtualMonitorInfo *info);
+
+MetaCrtc * meta_virtual_monitor_get_crtc (MetaVirtualMonitor *virtual_monitor);
+
+MetaCrtcMode * meta_virtual_monitor_get_crtc_mode (MetaVirtualMonitor *virtual_monitor);
+
+MetaOutput * meta_virtual_monitor_get_output (MetaVirtualMonitor *virtual_monitor);
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC (MetaVirtualMonitorInfo,
+                               meta_virtual_monitor_info_free)
+
+#endif /* META_VIRTUAL_MONITOR_H */

src/backends/native/meta-backend-native-types.h

@@ -27,6 +27,8 @@ typedef struct _MetaSeatImpl MetaSeatImpl;
 typedef struct _MetaKeymapNative MetaKeymapNative;
 typedef struct _MetaRendererNative MetaRendererNative;
 typedef struct _MetaGpuKms MetaGpuKms;
+typedef struct _MetaCrtcVirtual MetaCrtcVirtual;
+typedef struct _MetaCrtcModeVirtual MetaCrtcModeVirtual;
 
 typedef enum _MetaSeatNativeFlag
 {

src/backends/native/meta-crtc-mode-virtual.c

@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2021 Red Hat
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+
+#include "config.h"
+
+#include "backends/native/meta-crtc-mode-virtual.h"
+
+#include "backends/meta-virtual-monitor.h"
+
+struct _MetaCrtcModeVirtual
+{
+  MetaCrtcMode parent;
+};
+
+#define META_CRTC_MODE_VIRTUAL_ID_BIT (((uint64_t) 1) << 63)
+
+G_DEFINE_TYPE (MetaCrtcModeVirtual, meta_crtc_mode_virtual,
+               META_TYPE_CRTC_MODE)
+
+MetaCrtcModeVirtual *
+meta_crtc_mode_virtual_new (uint64_t                      id,
+                            const MetaVirtualMonitorInfo *info)
+{
+  g_autoptr (MetaCrtcModeInfo) crtc_mode_info = NULL;
+  g_autofree char *crtc_mode_name = NULL;
+  MetaCrtcModeVirtual *mode_virtual;
+
+  crtc_mode_info = meta_crtc_mode_info_new ();
+  crtc_mode_info->width = info->width;
+  crtc_mode_info->height = info->height;
+  crtc_mode_info->refresh_rate = info->refresh_rate;
+
+  crtc_mode_name = g_strdup_printf ("%dx%d@%f",
+                                    info->width,
+                                    info->height,
+                                    info->refresh_rate);
+  mode_virtual = g_object_new (META_TYPE_CRTC_MODE_VIRTUAL,
+                               "id", META_CRTC_MODE_VIRTUAL_ID_BIT | id,
+                               "name", crtc_mode_name,
+                               "info", crtc_mode_info,
+                               NULL);
+
+  return mode_virtual;
+}
+
+static void
+meta_crtc_mode_virtual_init (MetaCrtcModeVirtual *mode_virtual)
+{
+}
+
+static void
+meta_crtc_mode_virtual_class_init (MetaCrtcModeVirtualClass *klass)
+{
+}

src/backends/native/meta-crtc-mode-virtual.h

@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2021 Red Hat
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+
+#ifndef META_CRTC_MODE_VIRTUAL_H
+#define META_CRTC_MODE_VIRTUAL_H
+
+#include "backends/meta-backend-types.h"
+#include "backends/meta-crtc-mode.h"
+
+#define META_TYPE_CRTC_MODE_VIRTUAL (meta_crtc_mode_virtual_get_type ())
+G_DECLARE_FINAL_TYPE (MetaCrtcModeVirtual, meta_crtc_mode_virtual,
+                      META, CRTC_MODE_VIRTUAL,
+                      MetaCrtcMode)
+
+MetaCrtcModeVirtual * meta_crtc_mode_virtual_new (uint64_t                      id,
+                                                  const MetaVirtualMonitorInfo *info);
+
+#endif /* META_CRTC_MODE_VIRTUAL_H */

src/backends/native/meta-crtc-virtual.c

@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2021 Red Hat
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+
+#include "config.h"
+
+#include "backends/native/meta-crtc-virtual.h"
+
+struct _MetaCrtcVirtual
+{
+  MetaCrtcNative parent;
+};
+
+#define META_CRTC_VIRTUAL_ID_BIT (((uint64_t) 1) << 63)
+
+G_DEFINE_TYPE (MetaCrtcVirtual, meta_crtc_virtual, META_TYPE_CRTC_NATIVE)
+
+MetaCrtcVirtual *
+meta_crtc_virtual_new (uint64_t id)
+{
+  return g_object_new (META_TYPE_CRTC_VIRTUAL,
+                       "id", META_CRTC_VIRTUAL_ID_BIT | id,
+                       NULL);
+}
+
+static gboolean
+meta_crtc_virtual_is_transform_handled (MetaCrtcNative       *crtc_native,
+                                        MetaMonitorTransform  transform)
+{
+  return transform == META_MONITOR_TRANSFORM_NORMAL;
+}
+
+static void
+meta_crtc_virtual_init (MetaCrtcVirtual *crtc_virtual)
+{
+}
+
+static void
+meta_crtc_virtual_class_init (MetaCrtcVirtualClass *klass)
+{
+  MetaCrtcNativeClass *crtc_native_class = META_CRTC_NATIVE_CLASS (klass);
+
+  crtc_native_class->is_transform_handled =
+    meta_crtc_virtual_is_transform_handled;
+}

src/backends/native/meta-crtc-virtual.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2021 Red Hat
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+
+#ifndef META_CRTC_VIRTUAL_H
+#define META_CRTC_VIRTUAL_H
+
+#include "backends/native/meta-crtc-native.h"
+
+#define META_TYPE_CRTC_VIRTUAL (meta_crtc_virtual_get_type ())
+G_DECLARE_FINAL_TYPE (MetaCrtcVirtual, meta_crtc_virtual,
+                      META, CRTC_VIRTUAL,
+                      MetaCrtcNative)
+
+MetaCrtcVirtual * meta_crtc_virtual_new (uint64_t id);
+
+#endif /* META_CRTC_VIRTUAL_H */

src/backends/native/meta-cursor-renderer-native.c

@@ -542,6 +542,9 @@ meta_cursor_renderer_native_prepare_frame (MetaCursorRendererNative *cursor_rend
       META_POWER_SAVE_ON)
     return;
 
+  if (!meta_crtc_get_gpu (crtc))
+    return;
+
   crtc_cursor_data = ensure_crtc_cursor_data (META_CRTC_KMS (crtc));
   if (!crtc_cursor_data->hw_state_invalidated &&
       !crtc_cursor_data->needs_sync_position)
@@ -849,6 +852,9 @@ should_have_hw_cursor (MetaCursorRenderer *renderer,
   float scale;
   GList *l;
 
+  if (!gpus)
+    return FALSE;
+
   if (!cursor_sprite)
     return FALSE;
 
@@ -989,7 +995,7 @@ calculate_cursor_sprite_gpus (MetaCursorRenderer *renderer,
           MetaGpu *gpu;
 
           gpu = meta_output_get_gpu (output);
-          if (!g_list_find (gpus, gpu))
+          if (gpu && !g_list_find (gpus, gpu))
             gpus = g_list_prepend (gpus, gpu);
         }
     }

src/backends/native/meta-monitor-manager-native.c

@@ -59,6 +59,7 @@
 #include "backends/native/meta-launcher.h"
 #include "backends/native/meta-output-kms.h"
 #include "backends/native/meta-renderer-native.h"
+#include "backends/native/meta-virtual-monitor-native.h"
 #include "clutter/clutter.h"
 #include "meta/main.h"
 #include "meta/meta-x11-errors.h"
@@ -90,6 +91,8 @@ struct _MetaMonitorManagerNativeClass
   MetaMonitorManagerClass parent_class;
 };
 
+#define VIRTUAL_OUTPUT_ID_BIT (((uint64_t) 1) << 63)
+
 static void
 initable_iface_init (GInitableIface *initable_iface);
 
@@ -224,6 +227,16 @@ apply_crtc_assignments (MetaMonitorManager    *manager,
       to_configure_crtcs = g_list_concat (to_configure_crtcs, crtcs);
     }
 
+  for (l = meta_monitor_manager_get_virtual_monitors (manager); l; l = l->next)
+    {
+      MetaVirtualMonitor *virtual_monitor = l->data;
+      MetaOutput *output = meta_virtual_monitor_get_output (virtual_monitor);
+      MetaCrtc *crtc = meta_virtual_monitor_get_crtc (virtual_monitor);
+
+      to_configure_outputs = g_list_append (to_configure_outputs, output);
+      to_configure_crtcs = g_list_append (to_configure_crtcs, crtc);
+    }
+
   for (i = 0; i < n_crtcs; i++)
     {
       MetaCrtcAssignment *crtc_assignment = crtcs[i];
@@ -362,6 +375,8 @@ meta_monitor_manager_native_get_crtc_gamma (MetaMonitorManager  *manager,
   MetaKmsCrtc *kms_crtc;
   const MetaKmsCrtcState *crtc_state;
 
+  g_return_if_fail (META_IS_CRTC_KMS (crtc));
+
   kms_crtc = meta_crtc_kms_get_kms_crtc (META_CRTC_KMS (crtc));
   crtc_state = meta_kms_crtc_get_current_state (kms_crtc);
 
@@ -455,12 +470,17 @@ meta_monitor_manager_native_set_crtc_gamma (MetaMonitorManager *manager,
 {
   MetaMonitorManagerNative *manager_native =
     META_MONITOR_MANAGER_NATIVE (manager);
-  MetaCrtcKms *crtc_kms = META_CRTC_KMS (crtc);
+  MetaCrtcKms *crtc_kms;
-  MetaKmsCrtc *kms_crtc = meta_crtc_kms_get_kms_crtc (META_CRTC_KMS (crtc));
+  MetaKmsCrtc *kms_crtc;
   g_autofree char *gamma_ramp_string = NULL;
   MetaBackend *backend = meta_monitor_manager_get_backend (manager);
   ClutterStage *stage = CLUTTER_STAGE (meta_backend_get_stage (backend));
 
+  g_return_if_fail (META_IS_CRTC_KMS (crtc));
+
+  crtc_kms = META_CRTC_KMS (crtc);
+  kms_crtc = meta_crtc_kms_get_kms_crtc (META_CRTC_KMS (crtc));
+
   g_hash_table_replace (manager_native->crtc_gamma_cache,
                         GUINT_TO_POINTER (meta_crtc_get_id (crtc)),
                         meta_kms_crtc_gamma_new (kms_crtc, size,
@@ -602,6 +622,55 @@ meta_monitor_manager_native_get_default_layout_mode (MetaMonitorManager *manager
     return META_LOGICAL_MONITOR_LAYOUT_MODE_PHYSICAL;
 }
 
+static MetaVirtualMonitorNative *
+find_virtual_monitor (MetaMonitorManagerNative *manager_native,
+                      uint64_t                  id)
+{
+  MetaMonitorManager *manager = META_MONITOR_MANAGER (manager_native);
+  GList *l;
+
+  for (l = meta_monitor_manager_get_virtual_monitors (manager); l; l = l->next)
+    {
+      MetaVirtualMonitorNative *virtual_monitor_native = l->data;
+
+      if (meta_virtual_monitor_native_get_id (virtual_monitor_native) == id)
+        return virtual_monitor_native;
+    }
+
+  return NULL;
+}
+
+static uint64_t
+allocate_virtual_monitor_id (MetaMonitorManagerNative *manager_native)
+{
+  uint64_t id;
+
+  id = 0;
+
+  while (TRUE)
+    {
+      if (!find_virtual_monitor (manager_native, id))
+        return id;
+
+      id++;
+    }
+}
+
+static MetaVirtualMonitor *
+meta_monitor_manager_native_create_virtual_monitor (MetaMonitorManager            *manager,
+                                                    const MetaVirtualMonitorInfo  *info,
+                                                    GError                       **error)
+{
+  MetaMonitorManagerNative *manager_native =
+    META_MONITOR_MANAGER_NATIVE (manager);
+  MetaVirtualMonitorNative *virtual_monitor_native;
+  uint64_t id;
+
+  id = allocate_virtual_monitor_id (manager_native);
+  virtual_monitor_native = meta_virtual_monitor_native_new (id, info);
+  return META_VIRTUAL_MONITOR (virtual_monitor_native);
+}
+
 static void
 meta_monitor_manager_native_set_property (GObject      *object,
                                           guint         prop_id,
@@ -722,6 +791,8 @@ 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;
+  manager_class->create_virtual_monitor =
+    meta_monitor_manager_native_create_virtual_monitor;
 
   obj_props[PROP_NEED_OUTPUTS] =
     g_param_spec_boolean ("needs-outputs",

src/backends/native/meta-output-kms.c

@@ -270,6 +270,8 @@ init_output_modes (MetaOutputInfo    *output_info,
 static MetaConnectorType
 meta_kms_connector_type_from_drm (uint32_t drm_connector_type)
 {
+  g_warn_if_fail (drm_connector_type < META_CONNECTOR_TYPE_META);
+
   return (MetaConnectorType) drm_connector_type;
 }
 

src/backends/native/meta-output-virtual.c

@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2021 Red Hat
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+
+#include "config.h"
+
+#include "backends/native/meta-output-virtual.h"
+
+#include "backends/native/meta-crtc-mode-virtual.h"
+#include "backends/native/meta-crtc-virtual.h"
+#include "backends/meta-virtual-monitor.h"
+
+struct _MetaOutputVirtual
+{
+  MetaOutputNative parent;
+};
+
+#define META_OUTPUT_VIRTUAL_ID_BIT (((uint64_t) 1) << 63)
+
+G_DEFINE_TYPE (MetaOutputVirtual, meta_output_virtual, META_TYPE_OUTPUT_NATIVE)
+
+MetaOutputVirtual *
+meta_output_virtual_new (uint64_t                      id,
+                         const MetaVirtualMonitorInfo *info,
+                         MetaCrtcVirtual              *crtc_virtual,
+                         MetaCrtcModeVirtual          *crtc_mode_virtual)
+{
+  g_autoptr (MetaOutputInfo) output_info = NULL;
+
+  output_info = meta_output_info_new ();
+  output_info->name = g_strdup_printf ("Meta-%" G_GUINT64_FORMAT, id);
+
+  output_info->n_possible_crtcs = 1;
+  output_info->possible_crtcs = g_new0 (MetaCrtc *, 1);
+  output_info->possible_crtcs[0] = META_CRTC (crtc_virtual);
+
+  output_info->hotplug_mode_update = FALSE;
+  output_info->suggested_x = -1;
+  output_info->suggested_y = -1;
+
+  output_info->connector_type = META_CONNECTOR_TYPE_META;
+  output_info->vendor = g_strdup (info->vendor);
+  output_info->product = g_strdup (info->product);
+  output_info->serial = g_strdup (info->serial);
+
+  output_info->n_modes = 1;
+  output_info->modes = g_new0 (MetaCrtcMode *, 1);
+  output_info->modes[0] = META_CRTC_MODE (crtc_mode_virtual);
+  output_info->preferred_mode = output_info->modes[0];
+
+  return g_object_new (META_TYPE_OUTPUT_VIRTUAL,
+                       "id", META_OUTPUT_VIRTUAL_ID_BIT | id,
+                       "info", output_info,
+                       NULL);
+}
+
+static void
+meta_output_virtual_init (MetaOutputVirtual *output_virtual)
+{
+}
+
+static void
+meta_output_virtual_class_init (MetaOutputVirtualClass *klass)
+{
+}

src/backends/native/meta-output-virtual.h

@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2021 Red Hat
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+
+#ifndef META_OUTPUT_VIRTUAL_H
+#define META_OUTPUT_VIRTUAL_H
+
+#include "backends/native/meta-backend-native-types.h"
+#include "backends/native/meta-output-native.h"
+
+#define META_TYPE_OUTPUT_VIRTUAL (meta_output_virtual_get_type ())
+G_DECLARE_FINAL_TYPE (MetaOutputVirtual, meta_output_virtual,
+                      META, OUTPUT_VIRTUAL,
+                      MetaOutputNative)
+
+MetaOutputVirtual * meta_output_virtual_new (uint64_t                      id,
+                                             const MetaVirtualMonitorInfo *info,
+                                             MetaCrtcVirtual              *crtc_virtual,
+                                             MetaCrtcModeVirtual          *crtc_mode_virtual);
+
+#endif /* META_OUTPUT_VIRTUAL_H */

src/backends/native/meta-renderer-native.c

@@ -50,6 +50,7 @@
 #include "backends/meta-logical-monitor.h"
 #include "backends/native/meta-cogl-utils.h"
 #include "backends/native/meta-crtc-kms.h"
+#include "backends/native/meta-crtc-virtual.h"
 #include "backends/native/meta-kms-device.h"
 #include "backends/native/meta-kms.h"
 #include "backends/native/meta-onscreen-native.h"
@@ -1021,13 +1022,11 @@ meta_renderer_native_create_view (MetaRenderer       *renderer,
   CoglContext *cogl_context =
     cogl_context_from_renderer_native (renderer_native);
   CoglDisplay *cogl_display = cogl_context_get_display (cogl_context);
-  CoglDisplayEGL *cogl_display_egl;
-  CoglOnscreenEgl *onscreen_egl;
   const MetaCrtcConfig *crtc_config;
   const MetaCrtcModeInfo *crtc_mode_info;
   MetaMonitorTransform view_transform;
-  MetaOnscreenNative *onscreen_native;
+  g_autoptr (CoglFramebuffer) framebuffer = NULL;
-  CoglOffscreen *offscreen = NULL;
+  g_autoptr (CoglOffscreen) offscreen = NULL;
   gboolean use_shadowfb;
   float scale;
   int onscreen_width;
@@ -1042,6 +1041,10 @@ meta_renderer_native_create_view (MetaRenderer       *renderer,
   onscreen_width = crtc_mode_info->width;
   onscreen_height = crtc_mode_info->height;
 
+  if (META_IS_CRTC_KMS (crtc))
+    {
+      MetaOnscreenNative *onscreen_native;
+
       onscreen_native = meta_onscreen_native_new (renderer_native,
                                                   renderer_native->primary_gpu_kms,
                                                   output,
@@ -1053,6 +1056,27 @@ meta_renderer_native_create_view (MetaRenderer       *renderer,
       if (!cogl_framebuffer_allocate (COGL_FRAMEBUFFER (onscreen_native), &error))
         g_error ("Failed to allocate onscreen framebuffer: %s", error->message);
 
+      use_shadowfb = should_force_shadow_fb (renderer_native,
+                                             renderer_native->primary_gpu_kms);
+      framebuffer = COGL_FRAMEBUFFER (onscreen_native);
+    }
+  else
+    {
+      CoglOffscreen *virtual_onscreen;
+
+      g_assert (META_IS_CRTC_VIRTUAL (crtc));
+
+      virtual_onscreen = meta_renderer_native_create_offscreen (renderer_native,
+                                                                cogl_context,
+                                                                onscreen_width,
+                                                                onscreen_height,
+                                                                &error);
+      if (!virtual_onscreen)
+        g_error ("Failed to allocate back buffer texture: %s", error->message);
+      use_shadowfb = FALSE;
+      framebuffer = COGL_FRAMEBUFFER (virtual_onscreen);
+    }
+
   view_transform = calculate_view_transform (monitor_manager,
                                              logical_monitor,
                                              output,
@@ -1082,9 +1106,6 @@ meta_renderer_native_create_view (MetaRenderer       *renderer,
         g_error ("Failed to allocate back buffer texture: %s", error->message);
     }
 
-  use_shadowfb = should_force_shadow_fb (renderer_native,
-                                         renderer_native->primary_gpu_kms);
-
   if (meta_is_stage_views_scaled ())
     scale = meta_logical_monitor_get_scale (logical_monitor);
   else
@@ -1099,25 +1120,29 @@ meta_renderer_native_create_view (MetaRenderer       *renderer,
                        "layout", &view_layout,
                        "crtc", crtc,
                        "scale", scale,
-                       "framebuffer", onscreen_native,
+                       "framebuffer", framebuffer,
                        "offscreen", offscreen,
                        "use-shadowfb", use_shadowfb,
                        "transform", view_transform,
                        "refresh-rate", crtc_mode_info->refresh_rate,
                        NULL);
-  g_clear_object (&offscreen);
-  g_object_unref (onscreen_native);
 
-  meta_onscreen_native_set_view (COGL_ONSCREEN (onscreen_native), view);
+  if (META_IS_ONSCREEN_NATIVE (framebuffer))
+    {
+      CoglDisplayEGL *cogl_display_egl;
+      CoglOnscreenEgl *onscreen_egl;
+
+      meta_onscreen_native_set_view (COGL_ONSCREEN (framebuffer), view);
 
       /* Ensure we don't point to stale surfaces when creating the offscreen */
       cogl_display_egl = cogl_display->winsys;
-  onscreen_egl = COGL_ONSCREEN_EGL (onscreen_native);
+      onscreen_egl = COGL_ONSCREEN_EGL (framebuffer);
       egl_surface = cogl_onscreen_egl_get_egl_surface (onscreen_egl);
       _cogl_winsys_egl_make_current (cogl_display,
                                      egl_surface,
                                      egl_surface,
                                      cogl_display_egl->egl_context);
+    }
 
   return view;
 }
@@ -1165,9 +1190,16 @@ meta_renderer_native_prepare_frame (MetaRendererNative *renderer_native,
                                     ClutterFrame       *frame)
 {
   MetaCrtc *crtc = meta_renderer_view_get_crtc (view);
-  MetaCrtcKms *crtc_kms = META_CRTC_KMS (crtc);
+  MetaCrtcKms *crtc_kms;
-  MetaKmsCrtc *kms_crtc = meta_crtc_kms_get_kms_crtc (META_CRTC_KMS (crtc));
+  MetaKmsCrtc *kms_crtc;
-  MetaKmsDevice *kms_device = meta_kms_crtc_get_device (kms_crtc);;
+  MetaKmsDevice *kms_device;
+
+  if (!META_IS_CRTC_KMS (crtc))
+    return;
+
+  crtc_kms = META_CRTC_KMS (crtc);
+  kms_crtc = meta_crtc_kms_get_kms_crtc (META_CRTC_KMS (crtc));
+  kms_device = meta_kms_crtc_get_device (kms_crtc);
 
   meta_crtc_kms_maybe_set_gamma (crtc_kms, kms_device);
 }
@@ -1181,11 +1213,15 @@ meta_renderer_native_finish_frame (MetaRendererNative *renderer_native,
     {
       CoglFramebuffer *framebuffer =
         clutter_stage_view_get_onscreen (CLUTTER_STAGE_VIEW (view));
+
+      if (COGL_IS_ONSCREEN (framebuffer))
+        {
           CoglOnscreen *onscreen = COGL_ONSCREEN (framebuffer);
 
           meta_onscreen_native_finish_frame (onscreen, frame);
         }
     }
+}
 
 static gboolean
 create_secondary_egl_config (MetaEgl               *egl,

src/backends/native/meta-stage-native.c

@@ -27,6 +27,7 @@
 #include "backends/native/meta-stage-native.h"
 
 #include "backends/meta-backend-private.h"
+#include "backends/native/meta-crtc-virtual.h"
 #include "backends/native/meta-cursor-renderer-native.h"
 #include "backends/native/meta-renderer-native.h"
 #include "meta/meta-backend.h"
@@ -45,6 +46,8 @@ struct _MetaStageNative
   int64_t presented_frame_counter_complete;
 };
 
+static ClutterStageWindowInterface *clutter_stage_window_parent_iface = NULL;
+
 static void
 clutter_stage_window_iface_init (ClutterStageWindowInterface *iface);
 
@@ -126,6 +129,24 @@ meta_stage_native_prepare_frame (ClutterStageWindow *stage_window,
                                              META_RENDERER_VIEW (stage_view));
 }
 
+static void
+meta_stage_native_redraw_view (ClutterStageWindow *stage_window,
+                               ClutterStageView   *view,
+                               ClutterFrame       *frame)
+{
+  MetaCrtc *crtc;
+
+  clutter_stage_window_parent_iface->redraw_view (stage_window, view, frame);
+
+  crtc = meta_renderer_view_get_crtc (META_RENDERER_VIEW (view));
+  if (META_IS_CRTC_VIRTUAL (crtc))
+    {
+      g_warn_if_fail (!clutter_frame_has_result (frame));
+
+      clutter_frame_set_result (frame, CLUTTER_FRAME_RESULT_PENDING_PRESENTED);
+    }
+}
+
 static void
 meta_stage_native_finish_frame (ClutterStageWindow *stage_window,
                                 ClutterStageView   *stage_view,
@@ -137,6 +158,9 @@ meta_stage_native_finish_frame (ClutterStageWindow *stage_window,
   meta_renderer_native_finish_frame (META_RENDERER_NATIVE (renderer),
                                      META_RENDERER_VIEW (stage_view),
                                      frame);
+
+  if (!clutter_frame_has_result (frame))
+    clutter_frame_set_result (frame, CLUTTER_FRAME_RESULT_IDLE);
 }
 
 static void
@@ -156,9 +180,12 @@ meta_stage_native_class_init (MetaStageNativeClass *klass)
 static void
 clutter_stage_window_iface_init (ClutterStageWindowInterface *iface)
 {
+  clutter_stage_window_parent_iface = g_type_interface_peek_parent (iface);
+
   iface->can_clip_redraws = meta_stage_native_can_clip_redraws;
   iface->get_geometry = meta_stage_native_get_geometry;
   iface->get_views = meta_stage_native_get_views;
   iface->prepare_frame = meta_stage_native_prepare_frame;
+  iface->redraw_view = meta_stage_native_redraw_view;
   iface->finish_frame = meta_stage_native_finish_frame;
 }

src/backends/native/meta-virtual-monitor-native.c

@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2021 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ *
+ */
+
+#include "config.h"
+
+#include "backends/native/meta-virtual-monitor-native.h"
+
+#include "backends/native/meta-crtc-mode-virtual.h"
+#include "backends/native/meta-crtc-virtual.h"
+#include "backends/native/meta-output-virtual.h"
+
+struct _MetaVirtualMonitorNative
+{
+  MetaVirtualMonitor parent;
+
+  uint64_t id;
+};
+
+#define VIRTUAL_OUTPUT_ID_BIT (((uint64_t) 1) << 63)
+
+G_DEFINE_TYPE (MetaVirtualMonitorNative, meta_virtual_monitor_native,
+               META_TYPE_VIRTUAL_MONITOR)
+
+uint64_t
+meta_virtual_monitor_native_get_id (MetaVirtualMonitorNative *virtual_monitor_native)
+{
+  return virtual_monitor_native->id;
+}
+
+MetaVirtualMonitorNative *
+meta_virtual_monitor_native_new (uint64_t                      id,
+                                 const MetaVirtualMonitorInfo *info)
+{
+  MetaVirtualMonitorNative *virtual_monitor_native;
+  MetaCrtcVirtual *crtc_virtual;
+  MetaCrtcModeVirtual *crtc_mode_virtual;
+  MetaOutputVirtual *output_virtual;
+
+  crtc_virtual = meta_crtc_virtual_new (id);
+  crtc_mode_virtual = meta_crtc_mode_virtual_new (id, info);
+  output_virtual = meta_output_virtual_new (id, info,
+                                            crtc_virtual,
+                                            crtc_mode_virtual);
+
+  virtual_monitor_native = g_object_new (META_TYPE_VIRTUAL_MONITOR_NATIVE,
+                                         "crtc", crtc_virtual,
+                                         "crtc-mode", crtc_mode_virtual,
+                                         "output", output_virtual,
+                                         NULL);
+  virtual_monitor_native->id = id;
+
+  return virtual_monitor_native;
+}
+
+static void
+meta_virtual_monitor_native_init (MetaVirtualMonitorNative *virtual_monitor_native)
+{
+}
+
+static void
+meta_virtual_monitor_native_class_init (MetaVirtualMonitorNativeClass *klass)
+{
+}

src/backends/native/meta-virtual-monitor-native.h

@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2021 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ *
+ */
+
+#ifndef META_VIRTUAL_MONITOR_NATIVE_H
+#define META_VIRTUAL_MONITOR_NATIVE_H
+
+#include <stdint.h>
+
+#include "backends/meta-virtual-monitor.h"
+#include "backends/meta-backend-types.h"
+
+#define META_TYPE_VIRTUAL_MONITOR_NATIVE (meta_virtual_monitor_native_get_type ())
+G_DECLARE_FINAL_TYPE (MetaVirtualMonitorNative, meta_virtual_monitor_native,
+                      META, VIRTUAL_MONITOR_NATIVE,
+                      MetaVirtualMonitor)
+
+uint64_t meta_virtual_monitor_native_get_id (MetaVirtualMonitorNative *virtual_monitor_native);
+
+MetaCrtcMode * meta_virtual_monitor_native_get_crtc_mode (MetaVirtualMonitorNative *virtual_monitor_native);
+
+MetaCrtc * meta_virtual_monitor_native_get_crtc (MetaVirtualMonitorNative *virtual_monitor_native);
+
+MetaOutput * meta_virtual_monitor_native_get_output (MetaVirtualMonitorNative *virtual_monitor_native);
+
+MetaVirtualMonitorNative * meta_virtual_monitor_native_new (uint64_t                      id,
+                                                            const MetaVirtualMonitorInfo *info);
+
+#endif /* META_VIRTUAL_MONITOR_NATIVE_H */

src/meson.build

@@ -236,6 +236,8 @@ mutter_sources = [
   'backends/meta-stage-private.h',
   'backends/meta-viewport-info.c',
   'backends/meta-viewport-info.h',
+  'backends/meta-virtual-monitor.c',
+  'backends/meta-virtual-monitor.h',
   'backends/x11/cm/meta-backend-x11-cm.c',
   'backends/x11/cm/meta-backend-x11-cm.h',
   'backends/x11/cm/meta-cursor-sprite-xfixes.c',
@@ -649,6 +651,10 @@ if have_native_backend
     'backends/native/meta-crtc-native.h',
     'backends/native/meta-crtc-mode-kms.c',
     'backends/native/meta-crtc-mode-kms.h',
+    'backends/native/meta-crtc-mode-virtual.c',
+    'backends/native/meta-crtc-mode-virtual.h',
+    'backends/native/meta-crtc-virtual.c',
+    'backends/native/meta-crtc-virtual.h',
     'backends/native/meta-cursor-renderer-native.c',
     'backends/native/meta-cursor-renderer-native.h',
     'backends/native/meta-drm-buffer-dumb.c',
@@ -678,6 +684,8 @@ if have_native_backend
     'backends/native/meta-output-kms.h',
     'backends/native/meta-output-native.c',
     'backends/native/meta-output-native.h',
+    'backends/native/meta-output-virtual.c',
+    'backends/native/meta-output-virtual.h',
     'backends/native/meta-kms-connector-private.h',
     'backends/native/meta-kms-connector.c',
     'backends/native/meta-kms-connector.h',
@@ -732,6 +740,8 @@ if have_native_backend
     'backends/native/meta-udev.h',
     'backends/native/meta-virtual-input-device-native.c',
     'backends/native/meta-virtual-input-device-native.h',
+    'backends/native/meta-virtual-monitor-native.c',
+    'backends/native/meta-virtual-monitor-native.h',
     'backends/native/meta-xkb-utils.c',
     'backends/native/meta-xkb-utils.h',
     'compositor/meta-compositor-native.c',