From fc4287cd20ffd33f7bc97e1c8d438a12f97975ba Mon Sep 17 00:00:00 2001
From: Carlos Garnacho <carlosg@gnome.org>
Date: Fri, 21 Oct 2022 11:21:13 +0200
Subject: [PATCH] compositor: Add high level API to deal with MetaWindowDrag

This helper object (and the whole window drag operation) will be
requested to the compositor instead of created directly, and only
one of those can exist at a time, so the compositor will also
safeguard that.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2683>
---
 src/compositor/compositor-private.h |  8 +++++
 src/compositor/compositor.c         | 46 +++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/src/compositor/compositor-private.h b/src/compositor/compositor-private.h
index a95df0721..3b43c6a11 100644
--- a/src/compositor/compositor-private.h
+++ b/src/compositor/compositor-private.h
@@ -10,6 +10,7 @@
 #include "compositor/meta-compositor-view.h"
 #include "compositor/meta-plugin-manager.h"
 #include "compositor/meta-window-actor-private.h"
+#include "compositor/meta-window-drag.h"
 #include "meta/compositor.h"
 #include "meta/display.h"
 
@@ -80,6 +81,13 @@ ClutterStage * meta_compositor_get_stage (MetaCompositor *compositor);
 
 gboolean meta_compositor_is_switching_workspace (MetaCompositor *compositor);
 
+gboolean meta_compositor_drag_window (MetaCompositor *compositor,
+                                      MetaWindow     *window,
+                                      MetaGrabOp      grab_op,
+                                      uint32_t        timestamp);
+
+MetaWindowDrag * meta_compositor_get_current_window_drag (MetaCompositor *compositor);
+
 void meta_compositor_grab_begin (MetaCompositor *compositor);
 
 void meta_compositor_grab_end (MetaCompositor *compositor);
diff --git a/src/compositor/compositor.c b/src/compositor/compositor.c
index 6139b78a8..dbc4aea50 100644
--- a/src/compositor/compositor.c
+++ b/src/compositor/compositor.c
@@ -136,6 +136,8 @@ typedef struct _MetaCompositorPrivate
 
   MetaPluginManager *plugin_mgr;
 
+  MetaWindowDrag *current_drag;
+
   MetaLaters *laters;
 } MetaCompositorPrivate;
 
@@ -1673,3 +1675,47 @@ meta_compositor_get_laters (MetaCompositor *compositor)
   priv = meta_compositor_get_instance_private (compositor);
   return priv->laters;
 }
+
+static void
+on_window_drag_ended (MetaWindowDrag *window_drag,
+                      MetaCompositor *compositor)
+{
+  MetaCompositorPrivate *priv =
+    meta_compositor_get_instance_private (compositor);
+
+  g_assert (priv->current_drag == window_drag);
+  g_clear_object (&priv->current_drag);
+}
+
+gboolean
+meta_compositor_drag_window (MetaCompositor *compositor,
+                             MetaWindow     *window,
+                             MetaGrabOp      grab_op,
+                             uint32_t        timestamp)
+{
+  MetaCompositorPrivate *priv =
+    meta_compositor_get_instance_private (compositor);
+  g_autoptr (MetaWindowDrag) window_drag = NULL;
+
+  if (priv->current_drag)
+    return FALSE;
+
+  window_drag = meta_window_drag_new (window, grab_op);
+
+  if (!meta_window_drag_begin (window_drag, timestamp))
+    return FALSE;
+
+  g_signal_connect (window_drag, "ended",
+                    G_CALLBACK (on_window_drag_ended), compositor);
+  priv->current_drag = g_steal_pointer (&window_drag);
+  return TRUE;
+}
+
+MetaWindowDrag *
+meta_compositor_get_current_window_drag (MetaCompositor *compositor)
+{
+  MetaCompositorPrivate *priv =
+    meta_compositor_get_instance_private (compositor);
+
+  return priv->current_drag;
+}