[Wayland] Add support for xdg-toplevel-tag-v1 protocol

Implementation of the https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/238 wayland protocol.
It allows to identify unique toplevels (windows) in order to set their initial size and position

Author: Sunderland93

src/core/window-private.h

@@ -203,6 +203,8 @@ struct _MetaWindow
   char *sm_client_id;
   char *wm_client_machine;
 
+  char *tag;
+
   char *startup_id;
   char *muffin_hints;
   char *sandboxed_app_id;
@@ -912,4 +914,7 @@ gboolean meta_window_is_focus_async (MetaWindow *window);
 gboolean meta_window_calculate_bounds (MetaWindow *window,
                                        int        *bounds_width,
                                        int        *bounds_height);
+
+void meta_window_set_tag (MetaWindow *window,
+                          const char *tag);
 #endif

src/core/window.c

@@ -219,6 +219,7 @@ enum
   PROP_PROGRESS_PULSE,
   PROP_TILE_MODE,
   PROP_OPACITY,
+  PROP_TAG,
   PROP_LAST,
 };
 
@@ -352,6 +353,7 @@ meta_window_finalize (GObject *object)
   g_free (window->gtk_app_menu_object_path);
   g_free (window->gtk_menubar_object_path);
   g_free (window->placement.rule);
+  g_free (window->tag);
 
   G_OBJECT_CLASS (meta_window_parent_class)->finalize (object);
 }
@@ -453,6 +455,9 @@ meta_window_get_property(GObject         *object,
     case PROP_OPACITY:
       g_value_set_uint (value, win->opacity);
       break;
+    case PROP_TAG:
+      g_value_set_string (value, win->tag);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -674,6 +679,12 @@ meta_window_class_init (MetaWindowClass *klass)
                        0xFF,
                        G_PARAM_READABLE | G_PARAM_STATIC_STRINGS);
 
+  obj_props[PROP_TAG] =
+    g_param_spec_string ("tag", NULL, NULL,
+                         NULL,
+                         G_PARAM_READABLE | G_PARAM_EXPLICIT_NOTIFY |
+                         G_PARAM_STATIC_STRINGS);
+
   g_object_class_install_properties (object_class, PROP_LAST, obj_props);
 
   window_signals[WORKSPACE_CHANGED] =
@@ -9534,3 +9545,29 @@ meta_window_calculate_bounds (MetaWindow *window,
       return FALSE;
     }
 }
+
+void
+meta_window_set_tag (MetaWindow *window,
+                     const char *tag)
+{
+  if (g_set_str (&window->tag, tag))
+    g_object_notify_by_pspec (G_OBJECT (window), obj_props[PROP_TAG]);
+}
+
+/**
+ * meta_window_get_tag:
+ * @window: A #MetaWindow
+ *
+ * Get a tag associated to the window.
+ * Under wayland the tag can be set using the toplevel tag protocol,
+ * and under x11 it falls back to using `NET_WM_WINDOW_TAG` atom.
+ *
+ * Returns: (nullable): An associated toplevel tag
+ */
+const char *
+meta_window_get_tag (MetaWindow *window)
+{
+  g_return_val_if_fail (META_IS_WINDOW (window), NULL);
+
+  return window->tag;
+}

src/meson.build

@@ -589,6 +589,8 @@ if have_wayland
     'wayland/meta-wayland-xdg-shell.h',
     'wayland/meta-wayland-xdg-dialog.c',
     'wayland/meta-wayland-xdg-dialog.h',
+    'wayland/meta-wayland-xdg-toplevel-tag.c',
+    'wayland/meta-wayland-xdg-toplevel-tag.h',
     'wayland/meta-window-wayland.c',
     'wayland/meta-window-wayland.h',
     'wayland/meta-window-xwayland.c',
@@ -814,6 +816,7 @@ if have_wayland
     ['xdg-foreign', 'unstable', 'v2', ],
     ['xdg-output', 'unstable', 'v1', ],
     ['xdg-shell', 'stable', ],
+    ['xdg-toplevel-tag', 'staging', 'v1', ],
     ['xwayland-keyboard-grab', 'unstable', 'v1', ],
   ]
   if have_wayland_eglstream

src/meta/window.h

@@ -469,4 +469,7 @@ void meta_window_set_opacity              (MetaWindow *window,
 META_EXPORT
 guint8 meta_window_get_opacity              (MetaWindow *window);
 
+META_EXPORT
+const char * meta_window_get_tag (MetaWindow *window);
+
 #endif

src/wayland/meta-wayland-versions.h

@@ -57,5 +57,6 @@
 #define META_XDG_ACTIVATION_V1_VERSION 1
 #define META_XDG_DIALOG_VERSION             1
 #define META_ZWP_PRIMARY_SELECTION_V1_VERSION 1
+#define META_XDG_TOPLEVEL_TAG_V1_VERSION 1
 
 #endif

src/wayland/meta-wayland-xdg-toplevel-tag.c

@@ -0,0 +1,109 @@
+/*
+ * Copyright (C) 2024 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, see <http://www.gnu.org/licenses/>.
+ *
+ * Written by:
+ *     Bilal Elmoussaoui <[email protected]>
+ */
+
+#include "config.h"
+
+#include "wayland/meta-wayland-xdg-toplevel-tag.h"
+
+#include <wayland-server.h>
+
+#include "wayland/meta-wayland-private.h"
+#include "wayland/meta-wayland-versions.h"
+#include "wayland/meta-wayland-xdg-shell.h"
+
+#include "xdg-toplevel-tag-v1-server-protocol.h"
+
+static void
+xdg_toplevel_tag_manager_destroy (struct wl_client   *client,
+                                  struct wl_resource *resource)
+{
+    wl_resource_destroy (resource);
+}
+
+static void
+xdg_toplevel_tag_manager_set_toplevel_tag (struct wl_client   *client,
+                                           struct wl_resource *resource,
+
+
+
+
+                                           struct wl_resource *toplevel_resource,
+                                           const char         *tag)
+{
+    MetaWaylandXdgToplevel *xdg_toplevel;
+    MetaWaylandSurfaceRole *surface_role;
+    MetaWaylandSurface *surface;
+    MetaWindow *window;
+
+    if (!toplevel_resource)
+        return;
+
+    xdg_toplevel = wl_resource_get_user_data (toplevel_resource);
+    surface_role = META_WAYLAND_SURFACE_ROLE (xdg_toplevel);
+    surface = meta_wayland_surface_role_get_surface (surface_role);
+    window = meta_wayland_surface_get_window (surface);
+
+    meta_window_set_tag (window, tag);
+}
+
+static void
+xdg_toplevel_tag_manager_set_toplevel_tag_description (struct wl_client   *client,
+                                                       struct wl_resource *resource,
+                                                       struct wl_resource *toplevel,
+                                                       const char         *tag_description)
+{
+    /* We don't make use of the toplevel tag description */
+}
+
+static const struct xdg_toplevel_tag_manager_v1_interface meta_xdg_toplevel_tag_interface = {
+    xdg_toplevel_tag_manager_destroy,
+    xdg_toplevel_tag_manager_set_toplevel_tag,
+    xdg_toplevel_tag_manager_set_toplevel_tag_description,
+};
+
+
+static void
+bind_xdg_toplevel_tag (struct wl_client *client,
+                       void             *data,
+                       uint32_t          version,
+                       uint32_t          id)
+{
+    struct wl_resource *resource;
+
+    resource = wl_resource_create (client,
+                                   &xdg_toplevel_tag_manager_v1_interface,
+                                   META_XDG_TOPLEVEL_TAG_V1_VERSION,
+                                   id);
+
+    wl_resource_set_implementation (resource,
+                                    &meta_xdg_toplevel_tag_interface,
+                                    NULL, NULL);
+}
+
+void
+meta_wayland_xdg_toplevel_tag_init (MetaWaylandCompositor *compositor)
+{
+    if (wl_global_create (compositor->wayland_display,
+        &xdg_toplevel_tag_manager_v1_interface,
+        META_XDG_TOPLEVEL_TAG_V1_VERSION,
+        NULL,
+        bind_xdg_toplevel_tag) == NULL)
+        g_error ("Failed to register a global xdg-toplevel-tag object");
+}

src/wayland/meta-wayland-xdg-toplevel-tag.h

@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2024 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, see <http://www.gnu.org/licenses/>.
+ *
+ * Written by:
+ *     Bilal Elmoussaoui <[email protected]>
+ */
+
+#pragma once
+
+#include <glib.h>
+
+#include "wayland/meta-wayland-types.h"
+
+void meta_wayland_xdg_toplevel_tag_init (MetaWaylandCompositor *compositor);

src/wayland/meta-wayland.c

@@ -46,6 +46,7 @@
 #include "wayland/meta-wayland-tablet-manager.h"
 #include "wayland/meta-wayland-xdg-dialog.h"
 #include "wayland/meta-wayland-xdg-foreign.h"
+#include "wayland/meta-wayland-xdg-toplevel-tag.h"
 #include "wayland/meta-xwayland-grab-keyboard.h"
 #include "wayland/meta-xwayland-private.h"
 #include "wayland/meta-xwayland.h"
@@ -442,6 +443,7 @@ meta_wayland_compositor_setup (MetaWaylandCompositor *wayland_compositor)
   meta_wayland_text_input_init (compositor);
   meta_wayland_activation_init (compositor);
   meta_wayland_init_xdg_wm_dialog (compositor);
+  meta_wayland_xdg_toplevel_tag_init (compositor);
 
   /* Xwayland specific protocol, needs to be filtered out for all other clients */
   if (meta_xwayland_grab_keyboard_init (compositor))

src/x11/atomnames.h

@@ -180,6 +180,7 @@ item(_NET_WM_OPAQUE_REGION)
 item(_NET_WM_FRAME_DRAWN)
 item(_NET_WM_FRAME_TIMINGS)
 item(_NET_WM_WINDOW_OPACITY)
+item(_NET_WM_WINDOW_TAG)
 item(_NET_RESTACK_WINDOW)
 item(_NET_WM_XAPP_ICON_NAME)
 item(_NET_WM_XAPP_PROGRESS)

src/x11/window-props.c

@@ -418,6 +418,14 @@ reload_struts (MetaWindow    *window,
   meta_window_update_struts (window);
 }
 
+static void
+reload_toplevel_tag (MetaWindow    *window,
+                     MetaPropValue *value,
+                     gboolean       initial)
+{
+  meta_window_set_tag (window, value->v.str);
+}
+
 static void
 reload_wm_window_role (MetaWindow    *window,
                        MetaPropValue *value,
@@ -2055,6 +2063,7 @@ meta_x11_display_init_window_prop_hooks (MetaX11Display *x11_display)
     { x11_display->atom__NET_WM_STRUT_PARTIAL, META_PROP_VALUE_INVALID, reload_struts, NONE },
     { x11_display->atom__NET_WM_BYPASS_COMPOSITOR, META_PROP_VALUE_CARDINAL,  reload_bypass_compositor, LOAD_INIT | INCLUDE_OR },
     { x11_display->atom__NET_WM_WINDOW_OPACITY, META_PROP_VALUE_CARDINAL, reload_window_opacity, LOAD_INIT | INCLUDE_OR },
+    { x11_display->atom__NET_WM_WINDOW_TAG,    META_PROP_VALUE_STRING, reload_toplevel_tag, LOAD_INIT },
     { x11_display->atom__NET_WM_XAPP_ICON_NAME, META_PROP_VALUE_UTF8,     reload_theme_icon_name, LOAD_INIT | INCLUDE_OR },
     { x11_display->atom__NET_WM_XAPP_PROGRESS, META_PROP_VALUE_CARDINAL, reload_progress, LOAD_INIT | INCLUDE_OR },
     { x11_display->atom__NET_WM_XAPP_PROGRESS_PULSE, META_PROP_VALUE_CARDINAL, reload_progress_pulse, LOAD_INIT | INCLUDE_OR },