[gnome-flashback] screensaver: add GfGrab

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 069b16cd50dcdb27fec341395b16f9a1ae7297bc
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Thu Dec 12 22:38:42 2019 +0200

    screensaver: add GfGrab

 gnome-flashback/libscreensaver/Makefile.am |   2 +
 gnome-flashback/libscreensaver/gf-grab.c   | 346 +++++++++++++++++++++++++++++
 gnome-flashback/libscreensaver/gf-grab.h   |  47 ++++
 3 files changed, 395 insertions(+)
---
diff --git a/gnome-flashback/libscreensaver/Makefile.am b/gnome-flashback/libscreensaver/Makefile.am
index 701c3a8..2b27066 100644
--- a/gnome-flashback/libscreensaver/Makefile.am
+++ b/gnome-flashback/libscreensaver/Makefile.am
@@ -20,6 +20,8 @@ libscreensaver_la_CFLAGS = \
 libscreensaver_la_SOURCES = \
        gf-auth.c \
        gf-auth.h \
+       gf-grab.c \
+       gf-grab.h \
        gf-info-bar.c \
        gf-info-bar.h \
        gf-listener.c \
diff --git a/gnome-flashback/libscreensaver/gf-grab.c b/gnome-flashback/libscreensaver/gf-grab.c
new file mode 100644
index 0000000..09861cd
--- /dev/null
+++ b/gnome-flashback/libscreensaver/gf-grab.c
@@ -0,0 +1,346 @@
+/*
+ * Copyright (C) 2004-2006 William Jon McCann
+ * Copyright (C) 2019 Alberts Muktupāvels
+ *
+ * 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 3 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/>.
+ *
+ * Authors:
+ *     Alberts Muktupāvels <alberts muktupavels gmail com>
+ *     William Jon McCann <mccann jhu edu>
+ */
+
+#include "config.h"
+#include "gf-grab.h"
+
+#include <gdk/gdkx.h>
+#include <gtk/gtk.h>
+
+struct _GfGrab
+{
+  GObject    parent;
+
+  GtkWidget *invisible;
+
+  GdkWindow *grab_window;
+};
+
+G_DEFINE_TYPE (GfGrab, gf_grab, G_TYPE_OBJECT)
+
+static const char *
+grab_string (GdkGrabStatus status)
+{
+  switch (status)
+    {
+      case GDK_GRAB_SUCCESS:
+        return "GrabSuccess";
+
+      case GDK_GRAB_ALREADY_GRABBED:
+        return "AlreadyGrabbed";
+
+      case GDK_GRAB_INVALID_TIME:
+        return "GrabInvalidTime";
+
+      case GDK_GRAB_NOT_VIEWABLE:
+        return "GrabNotViewable";
+
+      case GDK_GRAB_FROZEN:
+        return "GrabFrozen";
+
+      case GDK_GRAB_FAILED:
+        return "GrabFailed";
+
+      default:
+        break;
+    }
+
+  return "unknown";
+}
+
+static void
+grab_window_reset (GfGrab *self)
+{
+  gpointer location;
+
+  if (self->grab_window == NULL)
+    return;
+
+  location = &self->grab_window;
+  g_object_remove_weak_pointer (G_OBJECT (self->grab_window), location);
+
+  self->grab_window = NULL;
+}
+
+static void
+prepare_cb (GdkSeat   *seat,
+            GdkWindow *window,
+            gpointer   user_data)
+{
+  gdk_window_show_unraised (window);
+}
+
+static GdkGrabStatus
+grab (GfGrab    *self,
+      GdkWindow *window)
+{
+  GdkDisplay *display;
+  GdkSeat *seat;
+  GdkSeatCapabilities capabilities;
+  GdkGrabStatus status;
+
+  display = gdk_window_get_display (window);
+  seat = gdk_display_get_default_seat (display);
+  capabilities = GDK_SEAT_CAPABILITY_ALL;
+
+  g_debug ("Grabbing window 0x%lx", gdk_x11_window_get_xid (window));
+
+  status = gdk_seat_grab (seat,
+                          window,
+                          capabilities,
+                          TRUE,
+                          NULL,
+                          NULL,
+                          prepare_cb,
+                          NULL);
+
+  if (status == GDK_GRAB_SUCCESS)
+    {
+      gpointer location;
+
+      grab_window_reset (self);
+      self->grab_window = window;
+
+      location = &self->grab_window;
+      g_object_add_weak_pointer (G_OBJECT (self->grab_window), location);
+    }
+
+  return status;
+}
+
+static void
+move_input_focus (GdkWindow *window)
+{
+  GdkDisplay *display;
+  Display *xdisplay;
+  Window xwindow;
+  Window old_focus;
+  int old_revert_to;
+
+  g_debug ("Moving input focus");
+
+  display = gdk_window_get_display (window);
+  xdisplay = gdk_x11_display_get_xdisplay (display);
+  xwindow = gdk_x11_window_get_xid (window);
+
+  gdk_x11_display_error_trap_push (display);
+
+  XGetInputFocus (xdisplay, &old_focus, &old_revert_to);
+  XSetInputFocus (xdisplay, xwindow, RevertToParent, CurrentTime);
+
+  gdk_x11_display_error_trap_pop_ignored (display);
+}
+
+static gboolean
+grab_window (GfGrab    *self,
+             GdkWindow *window)
+{
+  int retries;
+  int i;
+  GdkGrabStatus status;
+
+  retries = 4;
+
+  for (i = 0; i < retries; i++)
+    {
+      status = grab (self, window);
+
+      if (status == GDK_GRAB_SUCCESS)
+        return TRUE;
+
+      /* else, wait a second and try to grab again. */
+      sleep (1);
+    }
+
+  move_input_focus (window);
+
+  for (i = 0; i < retries; i++)
+    {
+      status = grab (self, window);
+
+      if (status == GDK_GRAB_SUCCESS)
+        return TRUE;
+
+      /* else, wait a second and try to grab again. */
+      sleep (1);
+    }
+
+  g_debug ("Couldn't grab window 0x%lx (%s)",
+           gdk_x11_window_get_xid (window),
+           grab_string (status));
+
+  return FALSE;
+}
+
+static gboolean
+grab_move (GfGrab    *self,
+           GdkWindow *window)
+{
+  GdkDisplay *display;
+  GdkWindow *old_window;
+  GdkGrabStatus status;
+
+  if (self->grab_window == window)
+    {
+      g_debug ("Window 0x%lx is already grabbed, skipping",
+               gdk_x11_window_get_xid (window));
+      return TRUE;
+    }
+
+  if (self->grab_window != NULL)
+    {
+      g_debug ("Moving grab from 0x%lx to 0x%lx",
+               gdk_x11_window_get_xid (self->grab_window),
+               gdk_x11_window_get_xid (window));
+    }
+  else
+    {
+      g_debug ("Grabbing window 0x%lx", gdk_x11_window_get_xid (window));
+    }
+
+  display = gdk_window_get_display (window);
+
+  g_debug ("Grabbing X server");
+  gdk_x11_display_grab (display);
+
+  old_window = self->grab_window;
+
+  gf_grab_release (self);
+  status = grab (self, window);
+
+  if (status != GDK_GRAB_SUCCESS)
+    {
+      sleep (1);
+      status = grab (self, window);
+    }
+
+  if (status != GDK_GRAB_SUCCESS && old_window != NULL)
+    {
+      g_debug ("Could not grab new window. Resuming previous grab.");
+      if (grab (self, window) != GDK_GRAB_SUCCESS)
+        g_debug ("Could not resume previous grab");
+    }
+
+  g_debug ("Ungrabbing X server");
+  gdk_x11_display_ungrab (display);
+  gdk_display_flush (display);
+
+  return (status == GDK_GRAB_SUCCESS);
+}
+
+static void
+gf_grab_finalize (GObject *object)
+{
+  GfGrab *self;
+
+  self = GF_GRAB (object);
+
+  g_clear_pointer (&self->invisible, gtk_widget_destroy);
+
+  G_OBJECT_CLASS (gf_grab_parent_class)->finalize (object);
+}
+
+static void
+gf_grab_class_init (GfGrabClass *self_class)
+{
+  GObjectClass *object_class;
+
+  object_class = G_OBJECT_CLASS (self_class);
+
+  object_class->finalize = gf_grab_finalize;
+}
+
+static void
+gf_grab_init (GfGrab *self)
+{
+  self->invisible = gtk_invisible_new ();
+  gtk_widget_show (self->invisible);
+}
+
+GfGrab *
+gf_grab_new (void)
+{
+  return g_object_new (GF_TYPE_GRAB, NULL);
+}
+
+/* this is used to grab the keyboard and mouse to the root */
+gboolean
+gf_grab_grab_root (GfGrab *self)
+{
+  GdkDisplay *display;
+  GdkScreen *screen;
+  GdkWindow *window;
+
+  g_debug ("Grabbing the root window");
+
+  display = gdk_display_get_default ();
+  screen = gdk_display_get_default_screen (display);
+  window = gdk_screen_get_root_window (screen);
+
+  return grab_window (self, window);
+}
+
+/* this is used to grab the keyboard and mouse to an offscreen window */
+gboolean
+gf_grab_grab_offscreen (GfGrab *self)
+{
+  GdkWindow *window;
+
+  window = gtk_widget_get_window (self->invisible);
+
+  return grab_window (self, window);
+}
+
+void
+gf_grab_move_to_window (GfGrab    *self,
+                        GdkWindow *window)
+{
+  GdkDisplay *display;
+  gboolean result;
+
+  display = gdk_window_get_display (window);
+
+  do
+    {
+      result = grab_move (self, window);
+      gdk_display_flush (display);
+    }
+  while (!result);
+}
+
+void
+gf_grab_release (GfGrab *self)
+{
+  GdkDisplay *display;
+  GdkSeat *seat;
+
+  g_debug ("Releasing all grabs");
+
+  display = gdk_display_get_default ();
+  seat = gdk_display_get_default_seat (display);
+
+  grab_window_reset (self);
+  gdk_seat_ungrab (seat);
+
+  gdk_display_sync (display);
+  gdk_display_flush (display);
+}
diff --git a/gnome-flashback/libscreensaver/gf-grab.h b/gnome-flashback/libscreensaver/gf-grab.h
new file mode 100644
index 0000000..6257498
--- /dev/null
+++ b/gnome-flashback/libscreensaver/gf-grab.h
@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2004-2006 William Jon McCann
+ * Copyright (C) 2019 Alberts Muktupāvels
+ *
+ * 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 3 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/>.
+ *
+ * Authors:
+ *     Alberts Muktupāvels <alberts muktupavels gmail com>
+ *     William Jon McCann <mccann jhu edu>
+ */
+
+#ifndef GF_GRAB_H
+#define GF_GRAB_H
+
+#include <gdk/gdk.h>
+#include <glib-object.h>
+
+G_BEGIN_DECLS
+
+#define GF_TYPE_GRAB (gf_grab_get_type ())
+G_DECLARE_FINAL_TYPE (GfGrab, gf_grab, GF, GRAB, GObject)
+
+GfGrab   *gf_grab_new (void);
+
+gboolean  gf_grab_grab_root      (GfGrab    *self);
+
+gboolean  gf_grab_grab_offscreen (GfGrab    *self);
+
+void      gf_grab_move_to_window (GfGrab    *self,
+                                  GdkWindow *window);
+
+void      gf_grab_release        (GfGrab    *self);
+
+G_END_DECLS
+
+#endif