dnd: Implement MetaDnd

Implement MetaDnd for emitting DnD signals to plugins such as gnome-shell. The
xdnd handling code comes from gnome-shell, and it is hidden behind MetaDnd now.

https://bugzilla.gnome.org/show_bug.cgi?id=765003

src/Makefile.am

@@ -174,6 +174,7 @@ libmutter_@LIBMUTTER_API_VERSION@_la_SOURCES =	\
 	compositor/meta-background-group.c	\
 	compositor/meta-cullable.c		\
 	compositor/meta-cullable.h		\
+	compositor/meta-dnd.c		\
 	compositor/meta-dnd-actor.c		\
 	compositor/meta-dnd-actor-private.h	\
 	compositor/meta-feedback-actor.c	\
@@ -430,6 +431,7 @@ libmutterinclude_headers =			\
 	meta/meta-background-image.h		\
 	meta/meta-background-group.h		\
 	meta/meta-cursor-tracker.h		\
+	meta/meta-dnd.h			\
 	meta/meta-idle-monitor.h		\
 	meta/meta-plugin.h			\
 	meta/meta-monitor-manager.h		\

src/backends/meta-backend.c

@@ -78,6 +78,7 @@ struct _MetaBackendPrivate
   int current_device_id;
 
   MetaPointerConstraint *client_pointer_constraint;
+  MetaDnd *dnd;
 };
 typedef struct _MetaBackendPrivate MetaBackendPrivate;
 
@@ -457,6 +458,8 @@ meta_backend_initable_init (GInitable     *initable,
 
   priv->cursor_tracker = g_object_new (META_TYPE_CURSOR_TRACKER, NULL);
 
+  priv->dnd = g_object_new (META_TYPE_DND, NULL);
+
   return TRUE;
 }
 
@@ -866,3 +869,19 @@ meta_backend_get_input_settings (MetaBackend *backend)
 
   return priv->input_settings;
 }
+
+/**
+ * meta_backend_get_dnd:
+ * @backend: A #MetaDnd
+ *
+ * Gets the global #MetaDnd that's managed by this backend.
+ *
+ * Returns: (transfer none): the #MetaDnd
+ */
+MetaDnd *
+meta_backend_get_dnd (MetaBackend *backend)
+{
+  MetaBackendPrivate *priv = meta_backend_get_instance_private (backend);
+
+  return priv->dnd;
+}

src/backends/meta-dnd-private.h

@@ -0,0 +1,30 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+
+/*
+ * Copyright (C) 2016 Hyungwon Hwang
+ *
+ * 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/>.
+ */
+
+#ifndef META_DND_PRIVATE__H
+#define META_DND_PRIVATE__H
+
+#include <X11/Xlib.h>
+
+gboolean meta_dnd_handle_xdnd_event (MetaBackend    *backend,
+                                     MetaCompositor *compositor,
+                                     MetaDisplay    *display,
+                                     XEvent         *xev);
+
+#endif /* META_DND_PRIVATE_H */

src/backends/x11/meta-backend-x11.c

@@ -46,6 +46,7 @@
 #include <meta/util.h>
 #include "display-private.h"
 #include "compositor/compositor-private.h"
+#include "backends/meta-dnd-private.h"
 
 struct _MetaBackendX11Private
 {
@@ -255,6 +256,9 @@ handle_host_xevent (MetaBackend *backend,
         MetaCompositor *compositor = display->compositor;
         if (meta_plugin_manager_xevent_filter (compositor->plugin_mgr, event))
           bypass_clutter = TRUE;
+
+        if (meta_dnd_handle_xdnd_event (backend, compositor, display, event))
+          bypass_clutter = TRUE;
       }
   }
 

src/compositor/meta-dnd.c

@@ -0,0 +1,171 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+/*
+ * Copyright (C) 2016 Hyungwon Hwang
+ *
+ * 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 <gdk/gdkx.h>
+
+#include "clutter/x11/clutter-x11.h"
+#include "meta/meta-backend.h"
+#include "compositor/compositor-private.h"
+#include "core/display-private.h"
+#include "backends/meta-dnd-private.h"
+#include "meta/meta-dnd.h"
+
+struct _MetaDndClass
+{
+  GObjectClass parent_class;
+};
+
+struct _MetaDnd
+{
+  GObject parent;
+};
+
+G_DEFINE_TYPE (MetaDnd, meta_dnd, G_TYPE_OBJECT);
+
+enum
+{
+  ENTER,
+  POSITION_CHANGE,
+  LEAVE,
+
+  LAST_SIGNAL
+};
+
+static guint signals[LAST_SIGNAL] = { 0 };
+
+static void
+meta_dnd_class_init (MetaDndClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+
+  signals[ENTER] =
+    g_signal_new ("dnd-enter",
+                  G_TYPE_FROM_CLASS (object_class),
+                  G_SIGNAL_RUN_LAST,
+                  0,
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 0);
+
+  signals[POSITION_CHANGE] =
+    g_signal_new ("dnd-position-change",
+                  G_TYPE_FROM_CLASS (object_class),
+                  G_SIGNAL_RUN_LAST,
+                  0,
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 2, G_TYPE_INT, G_TYPE_INT);
+
+  signals[LEAVE] =
+    g_signal_new ("dnd-leave",
+                  G_TYPE_FROM_CLASS (object_class),
+                  G_SIGNAL_RUN_LAST,
+                  0,
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 0);
+}
+
+static void
+meta_dnd_init (MetaDnd *dnd)
+{
+}
+
+static void
+meta_dnd_notify_dnd_enter (MetaDnd *dnd)
+{
+  g_signal_emit (dnd, signals[ENTER], 0);
+}
+
+static void
+meta_dnd_notify_dnd_position_change (MetaDnd *dnd,
+                                      int      x,
+                                      int      y)
+{
+  g_signal_emit (dnd, signals[POSITION_CHANGE], 0, x, y);
+}
+
+static void
+meta_dnd_notify_dnd_leave (MetaDnd *dnd)
+{
+  g_signal_emit (dnd, signals[LEAVE], 0);
+}
+
+/*
+ * Process Xdnd events
+ *
+ * We pass the position and leave events to the plugin via a signal
+ * where the actual drag & drop handling happens.
+ *
+ * http://www.freedesktop.org/wiki/Specifications/XDND
+ */
+gboolean
+meta_dnd_handle_xdnd_event (MetaBackend    *backend,
+                            MetaCompositor *compositor,
+                            MetaDisplay    *display,
+                            XEvent         *xev)
+{
+  MetaDnd *dnd = meta_backend_get_dnd (backend);
+  Window output_window = compositor->output;
+
+  if (xev->xany.type != ClientMessage)
+    return FALSE;
+
+  if (xev->xany.window != output_window &&
+      xev->xany.window != clutter_x11_get_stage_window (CLUTTER_STAGE (compositor->stage)))
+    return FALSE;
+
+  if (xev->xclient.message_type == gdk_x11_get_xatom_by_name ("XdndPosition"))
+    {
+      XEvent xevent;
+      Window src = xev->xclient.data.l[0];
+
+      memset (&xevent, 0, sizeof(xevent));
+      xevent.xany.type = ClientMessage;
+      xevent.xany.display = display->xdisplay;
+      xevent.xclient.window = src;
+      xevent.xclient.message_type = gdk_x11_get_xatom_by_name ("XdndStatus");
+      xevent.xclient.format = 32;
+      xevent.xclient.data.l[0] = output_window;
+      /* flags: bit 0: will we accept the drop? bit 1: do we want more position messages */
+      xevent.xclient.data.l[1] = 2;
+      xevent.xclient.data.l[4] = None;
+
+      XSendEvent (display->xdisplay, src, False, 0, &xevent);
+
+      meta_dnd_notify_dnd_position_change (dnd,
+                                            (int)(xev->xclient.data.l[2] >> 16),
+                                            (int)(xev->xclient.data.l[2] & 0xFFFF));
+
+      return TRUE;
+    }
+  else if (xev->xclient.message_type == gdk_x11_get_xatom_by_name ("XdndLeave"))
+    {
+      meta_dnd_notify_dnd_leave (dnd);
+
+      return TRUE;
+    }
+  else if (xev->xclient.message_type == gdk_x11_get_xatom_by_name ("XdndEnter"))
+    {
+      meta_dnd_notify_dnd_enter (dnd);
+
+      return TRUE;
+    }
+
+    return FALSE;
+}

src/meta/meta-backend.h

@@ -28,6 +28,7 @@
 #include <glib-object.h>
 
 #include <clutter/clutter.h>
+#include "meta/meta-dnd.h"
 
 typedef struct _MetaBackend        MetaBackend;
 typedef struct _MetaBackendClass   MetaBackendClass;
@@ -48,6 +49,7 @@ void meta_backend_set_numlock (MetaBackend *backend,
                                gboolean     numlock_state);
 
 ClutterActor *meta_backend_get_stage (MetaBackend *backend);
+MetaDnd      *meta_backend_get_dnd   (MetaBackend *backend);
 
 void meta_clutter_init (void);
 

src/meta/meta-dnd.h

@@ -0,0 +1,31 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+
+/*
+ * Copyright (C) 2016 Hyungwon Hwang
+ *
+ * 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/>.
+ */
+
+#ifndef META_DND_H
+#define META_DND_H
+
+#include <glib-object.h>
+#include <string.h>
+
+#include "meta/types.h"
+
+#define META_TYPE_DND (meta_dnd_get_type ())
+G_DECLARE_FINAL_TYPE (MetaDnd, meta_dnd, META, DND, GObject)
+
+#endif /* META_DND_H */

src/meta/types.h

@@ -24,6 +24,7 @@
  * MetaCompositor: (skip)
  *
  */
+typedef struct _MetaBackend     MetaBackend;
 typedef struct _MetaCompositor  MetaCompositor;
 typedef struct _MetaDisplay     MetaDisplay;
 typedef struct _MetaFrame       MetaFrame;
@@ -38,4 +39,6 @@ typedef struct _MetaGroup       MetaGroup;
 typedef struct _MetaKeyBinding  MetaKeyBinding;
 typedef struct _MetaCursorTracker MetaCursorTracker;
 
+typedef struct _MetaDnd         MetaDnd;
+
 #endif