x11: Add MetaX11Stack object

This object takes care of the X11 representation of the window stack,
namely the _NET_CLIENT_LIST and _NET_CLIENT_LIST_STACKING root window
properties.

This code has been lifted from src/core/stack.c into src/x11 as it's
dependent on the X11 display availability. This also leaves MetaStack
squeaky clean of x11 specifics.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/420

1 files changed, 413 insertions, 0 deletions

diff --git a/src/x11/meta-x11-stack.c b/src/x11/meta-x11-stack.c
new file mode 100644
index 000000000..fa08fc4c5
--- /dev/null
+++ b/src/x11/meta-x11-stack.c
@@ -0,0 +1,413 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+/*
+ * Copyright (C) 2019 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include "core/frame.h"
+#include "core/stack.h"
+#include "core/window-private.h"
+#include "x11/meta-x11-display-private.h"
+#include "x11/meta-x11-stack-private.h"
+
+struct _MetaX11Stack
+{
+  GObject parent;
+  MetaX11Display *x11_display;
+
+  /*
+   * A sequence of all the Windows (X handles, not MetaWindows) of the windows
+   * we manage, sorted in order.  Suitable to be passed into _NET_CLIENT_LIST.
+   */
+  GArray *xwindows;
+
+  /*
+   * MetaWindows waiting to be added to the xwindows list, after
+   * being added to the MetaStack.
+   *
+   * The order of the elements in this list is not important; what is important
+   * is the stack_position element of each window.
+   */
+  GList *added;
+
+  /*
+   * Windows (X handles, not MetaWindows) waiting to be removed from the
+   * xwindows list, after being removed from the MetaStack.
+   *
+   * The order of the elements in this list is not important.
+   */
+  GList *removed;
+};
+
+enum
+{
+  PROP_DISPLAY = 1,
+  N_PROPS
+};
+
+static GParamSpec *pspecs[N_PROPS] = { 0 };
+
+G_DEFINE_TYPE (MetaX11Stack, meta_x11_stack, G_TYPE_OBJECT)
+
+static void
+meta_x11_stack_init (MetaX11Stack *x11_stack)
+{
+  x11_stack->xwindows = g_array_new (FALSE, FALSE, sizeof (Window));
+}
+
+static void
+meta_x11_stack_set_property (GObject      *object,
+                             guint         prop_id,
+                             const GValue *value,
+                             GParamSpec   *pspec)
+{
+  MetaX11Stack *x11_stack = META_X11_STACK (object);
+
+  switch (prop_id)
+    {
+    case PROP_DISPLAY:
+      x11_stack->x11_display = g_value_get_object (value);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+    }
+}
+
+static void
+meta_x11_stack_get_property (GObject    *object,
+                             guint       prop_id,
+                             GValue     *value,
+                             GParamSpec *pspec)
+{
+  MetaX11Stack *x11_stack = META_X11_STACK (object);
+
+  switch (prop_id)
+    {
+    case PROP_DISPLAY:
+      g_value_set_object (value, x11_stack->x11_display);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+    }
+}
+
+static void
+stack_window_added_cb (MetaStack    *stack,
+                       MetaWindow   *window,
+                       MetaX11Stack *x11_stack)
+{
+  if (window->client_type != META_WINDOW_CLIENT_TYPE_X11)
+    return;
+
+  x11_stack->added = g_list_prepend (x11_stack->added, window);
+}
+
+static void
+stack_window_removed_cb (MetaStack    *stack,
+                         MetaWindow   *window,
+                         MetaX11Stack *x11_stack)
+{
+  if (window->client_type != META_WINDOW_CLIENT_TYPE_X11)
+    return;
+
+  x11_stack->added = g_list_remove (x11_stack->added, window);
+
+  x11_stack->removed = g_list_prepend (x11_stack->removed,
+                                   GUINT_TO_POINTER (window->xwindow));
+  if (window->frame)
+    {
+      x11_stack->removed = g_list_prepend (x11_stack->removed,
+                                           GUINT_TO_POINTER (window->frame->xwindow));
+    }
+}
+
+/**
+ * stack_do_window_deletions:
+ *
+ * Go through "deleted" and take the matching windows
+ * out of "windows".
+ */
+static void
+x11_stack_do_window_deletions (MetaX11Stack *x11_stack)
+{
+  GList *tmp;
+  int i;
+
+  tmp = x11_stack->removed;
+  while (tmp != NULL)
+    {
+      Window xwindow;
+      xwindow = GPOINTER_TO_UINT (tmp->data);
+
+      /* We go from the end figuring removals are more
+       * likely to be recent.
+       */
+      i = x11_stack->xwindows->len;
+      while (i > 0)
+        {
+          --i;
+
+          /* there's no guarantee we'll actually find windows to
+           * remove, e.g. the same xwindow could have been
+           * added/removed before we ever synced, and we put
+           * both the window->xwindow and window->frame->xwindow
+           * in the removal list.
+           */
+          if (xwindow == g_array_index (x11_stack->xwindows, Window, i))
+            {
+              g_array_remove_index (x11_stack->xwindows, i);
+              goto next;
+            }
+        }
+
+    next:
+      tmp = tmp->next;
+    }
+
+  g_clear_pointer (&x11_stack->removed, g_list_free);
+}
+
+static void
+x11_stack_do_window_additions (MetaX11Stack *x11_stack)
+{
+  GList *tmp;
+  gint n_added;
+
+  n_added = g_list_length (x11_stack->added);
+  if (n_added > 0)
+    {
+      meta_topic (META_DEBUG_STACK,
+                  "Adding %d windows to sorted list\n",
+                  n_added);
+
+      /* stack->added has the most recent additions at the
+       * front of the list, so we need to reverse it
+       */
+      x11_stack->added = g_list_reverse (x11_stack->added);
+
+      tmp = x11_stack->added;
+      while (tmp != NULL)
+        {
+          MetaWindow *w;
+
+          w = tmp->data;
+          g_array_append_val (x11_stack->xwindows, w->xwindow);
+          tmp = tmp->next;
+        }
+    }
+
+  g_clear_pointer (&x11_stack->added, g_list_free);
+}
+
+/**
+ * x11_stack_sync_to_server:
+ *
+ * Order the windows on the X server to be the same as in our structure.
+ * We do this using XRestackWindows if we don't know the previous order,
+ * or XConfigureWindow on a few particular windows if we do and can figure
+ * out the minimum set of changes.  After that, we set __NET_CLIENT_LIST
+ * and __NET_CLIENT_LIST_STACKING.
+ *
+ * FIXME: Now that we have a good view of the stacking order on the server
+ * with MetaStackTracker it should be possible to do a simpler and better
+ * job of computing the minimal set of stacking requests needed.
+ */
+static void
+x11_stack_sync_to_xserver (MetaX11Stack *x11_stack)
+{
+  MetaX11Display *x11_display = x11_stack->x11_display;
+  MetaStack *stack = x11_display->display->stack;
+  GArray *x11_stacked;
+  GArray *all_root_children_stacked; /* wayland OR x11 */
+  GList *tmp;
+  GArray *hidden_stack_ids;
+  uint64_t guard_window_id;
+  GList *sorted;
+
+  meta_topic (META_DEBUG_STACK, "Syncing window stack to server\n");
+
+  /* Create stacked xwindow arrays, in bottom-to-top order
+   */
+  x11_stacked = g_array_new (FALSE, FALSE, sizeof (Window));
+
+  all_root_children_stacked = g_array_new (FALSE, FALSE, sizeof (guint64));
+  hidden_stack_ids = g_array_new (FALSE, FALSE, sizeof (guint64));
+
+  meta_topic (META_DEBUG_STACK, "Bottom to top: ");
+  meta_push_no_msg_prefix ();
+
+  sorted = meta_stack_list_windows (stack, NULL);
+
+  for (tmp = sorted; tmp; tmp = tmp->next)
+    {
+      MetaWindow *w = tmp->data;
+      guint64 top_level_window;
+      guint64 stack_id;
+
+      if (w->unmanaging)
+        continue;
+
+      meta_topic (META_DEBUG_STACK, "%u:%d - %s ",
+		  w->layer, w->stack_position, w->desc);
+
+      if (w->client_type == META_WINDOW_CLIENT_TYPE_X11)
+        g_array_append_val (x11_stacked, w->xwindow);
+
+      if (w->frame)
+	top_level_window = w->frame->xwindow;
+      else
+	top_level_window = w->xwindow;
+
+      if (w->client_type == META_WINDOW_CLIENT_TYPE_X11)
+        stack_id = top_level_window;
+      else
+        stack_id = w->stamp;
+
+      /* We don't restack hidden windows along with the rest, though they are
+       * reflected in the _NET hints. Hidden windows all get pushed below
+       * the screens fullscreen guard_window. */
+      if (w->hidden)
+	{
+          g_array_append_val (hidden_stack_ids, stack_id);
+	  continue;
+	}
+
+      g_array_append_val (all_root_children_stacked, stack_id);
+    }
+
+  meta_topic (META_DEBUG_STACK, "\n");
+  meta_pop_no_msg_prefix ();
+
+  /* The screen guard window sits above all hidden windows and acts as
+   * a barrier to input reaching these windows. */
+  guard_window_id = x11_stack->x11_display->guard_window;
+  g_array_append_val (hidden_stack_ids, guard_window_id);
+
+  /* Sync to server */
+
+  meta_topic (META_DEBUG_STACK, "Restacking %u windows\n",
+              all_root_children_stacked->len);
+
+  meta_stack_tracker_restack_managed (x11_display->display->stack_tracker,
+                                      (guint64 *)all_root_children_stacked->data,
+                                      all_root_children_stacked->len);
+  meta_stack_tracker_restack_at_bottom (x11_display->display->stack_tracker,
+                                        (guint64 *)hidden_stack_ids->data,
+                                        hidden_stack_ids->len);
+
+  /* Sync _NET_CLIENT_LIST and _NET_CLIENT_LIST_STACKING */
+
+  XChangeProperty (x11_stack->x11_display->xdisplay,
+                   x11_stack->x11_display->xroot,
+                   x11_stack->x11_display->atom__NET_CLIENT_LIST,
+                   XA_WINDOW,
+                   32, PropModeReplace,
+                   (unsigned char *) x11_stack->xwindows->data,
+                   x11_stack->xwindows->len);
+  XChangeProperty (x11_stack->x11_display->xdisplay,
+                   x11_stack->x11_display->xroot,
+                   x11_stack->x11_display->atom__NET_CLIENT_LIST_STACKING,
+                   XA_WINDOW,
+                   32, PropModeReplace,
+                   (unsigned char *) x11_stacked->data,
+                   x11_stacked->len);
+
+  g_array_free (x11_stacked, TRUE);
+  g_array_free (hidden_stack_ids, TRUE);
+  g_array_free (all_root_children_stacked, TRUE);
+  g_list_free (sorted);
+}
+
+static void
+stack_changed_cb (MetaX11Stack *x11_stack)
+{
+  /* Do removals before adds, with paranoid idea that we might re-add
+   * the same window IDs.
+   */
+  x11_stack_do_window_deletions (x11_stack);
+  x11_stack_do_window_additions (x11_stack);
+  x11_stack_sync_to_xserver (x11_stack);
+}
+
+static void
+meta_x11_stack_constructed (GObject *object)
+{
+  MetaX11Stack *x11_stack = META_X11_STACK (object);
+  MetaX11Display *x11_display = x11_stack->x11_display;
+
+  G_OBJECT_CLASS (meta_x11_stack_parent_class)->constructed (object);
+
+  g_signal_connect (x11_display->display->stack,
+                    "window-added",
+                    G_CALLBACK (stack_window_added_cb),
+                    x11_stack);
+  g_signal_connect (x11_display->display->stack,
+                    "window-removed",
+                    G_CALLBACK (stack_window_removed_cb),
+                    x11_stack);
+  g_signal_connect_swapped (x11_display->display->stack,
+                            "changed",
+                            G_CALLBACK (stack_changed_cb),
+                            x11_stack);
+}
+
+static void
+meta_x11_stack_finalize (GObject *object)
+{
+  MetaX11Stack *x11_stack = META_X11_STACK (object);
+  MetaX11Display *x11_display = x11_stack->x11_display;
+
+  if (x11_display->display && x11_display->display->stack)
+    {
+      g_signal_handlers_disconnect_by_data (x11_display->display->stack,
+                                            x11_stack);
+    }
+
+  g_array_free (x11_stack->xwindows, TRUE);
+  g_list_free (x11_stack->added);
+  g_list_free (x11_stack->removed);
+
+  G_OBJECT_CLASS (meta_x11_stack_parent_class)->finalize (object);
+}
+
+static void
+meta_x11_stack_class_init (MetaX11StackClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+
+  object_class->set_property = meta_x11_stack_set_property;
+  object_class->get_property = meta_x11_stack_get_property;
+  object_class->constructed = meta_x11_stack_constructed;
+  object_class->finalize = meta_x11_stack_finalize;
+
+  pspecs[PROP_DISPLAY] =
+    g_param_spec_object ("display",
+                         "Display",
+                         "Display",
+                         META_TYPE_X11_DISPLAY,
+                         G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY);
+
+  g_object_class_install_properties (object_class, N_PROPS, pspecs);
+}
+
+MetaX11Stack *
+meta_x11_stack_new (MetaX11Display *x11_display)
+{
+  return g_object_new (META_TYPE_X11_STACK,
+                       "display", x11_display,
+                       NULL);
+}