[gtk+] dnd: Pass dx/dy instead of x_root/y_root

[Benjamin Otte <otte src gnome org>]

commit 218efa62ef7e7ee20ca70c8c0735400684561838
Author: Benjamin Otte <otte redhat com>
Date:   Mon Dec 11 00:55:56 2017 +0100

    dnd: Pass dx/dy instead of x_root/y_root
    
    This way, we don't need root coordinates when computing the dnd start
    position.

 gdk/broadway/gdkdnd-broadway.c |    4 ++--
 gdk/gdkdnd.h                   |    4 ++--
 gdk/gdkwindow.c                |    4 ++--
 gdk/quartz/gdkdnd-quartz.c     |    4 ++--
 gdk/wayland/gdkdnd-wayland.c   |    4 ++--
 gdk/win32/gdkdnd-win32.c       |    9 +++++++--
 gdk/x11/gdkdnd-x11.c           |    8 ++++++--
 gtk/gtkdnd.c                   |   34 +++++++++++++++++++++++++---------
 8 files changed, 48 insertions(+), 23 deletions(-)
---
diff --git a/gdk/broadway/gdkdnd-broadway.c b/gdk/broadway/gdkdnd-broadway.c
index cbc1860..ac11be4 100644
--- a/gdk/broadway/gdkdnd-broadway.c
+++ b/gdk/broadway/gdkdnd-broadway.c
@@ -87,8 +87,8 @@ GdkDragContext *
 _gdk_broadway_window_drag_begin (GdkWindow         *window,
                                 GdkDevice         *device,
                                 GdkContentFormats *formats,
-                                 gint               x_root,
-                                 gint               y_root)
+                                 gint               dx,
+                                 gint               dy)
 {
   GdkDragContext *new_context;
 
diff --git a/gdk/gdkdnd.h b/gdk/gdkdnd.h
index f830fdc..6d7d224 100644
--- a/gdk/gdkdnd.h
+++ b/gdk/gdkdnd.h
@@ -137,8 +137,8 @@ GDK_AVAILABLE_IN_ALL
 GdkDragContext *        gdk_drag_begin                  (GdkWindow              *window,
                                                          GdkDevice              *device,
                                                          GdkContentFormats      *formats,
-                                                         gint                    x_root,
-                                                         gint                    y_root);
+                                                         gint                    dx,
+                                                         gint                    dy);
 
 GDK_AVAILABLE_IN_ALL
 gboolean        gdk_drag_drop_succeeded (GdkDragContext *context);
diff --git a/gdk/gdkwindow.c b/gdk/gdkwindow.c
index d14558d..47ec729 100644
--- a/gdk/gdkwindow.c
+++ b/gdk/gdkwindow.c
@@ -6928,8 +6928,8 @@ gdk_window_register_dnd (GdkWindow *window)
  * @window: the source window for this drag
  * @device: the device that controls this drag
  * @formats: (transfer none): the offered formats
- * @x_root: the x coordinate where the drag nominally started
- * @y_root: the y coordinate where the drag nominally started
+ * @dx: the x offset to @device's position where the drag nominally started
+ * @dy: the y offset to @device's position where the drag nominally started
  *
  * Starts a drag and creates a new drag context for it.
  *
diff --git a/gdk/quartz/gdkdnd-quartz.c b/gdk/quartz/gdkdnd-quartz.c
index fc9c338..2143848 100644
--- a/gdk/quartz/gdkdnd-quartz.c
+++ b/gdk/quartz/gdkdnd-quartz.c
@@ -36,8 +36,8 @@ GdkDragContext *
 _gdk_quartz_window_drag_begin (GdkWindow *window,
                                GdkDevice *device,
                                GList     *targets,
-                               gint       x_root,
-                               gint       y_root)
+                               gint       dx,
+                               gint       dy)
 {
   g_assert (_gdk_quartz_drag_source_context == NULL);
 
diff --git a/gdk/wayland/gdkdnd-wayland.c b/gdk/wayland/gdkdnd-wayland.c
index b64f487..ea1b6ef 100644
--- a/gdk/wayland/gdkdnd-wayland.c
+++ b/gdk/wayland/gdkdnd-wayland.c
@@ -586,8 +586,8 @@ GdkDragContext *
 _gdk_wayland_window_drag_begin (GdkWindow         *window,
                                GdkDevice         *device,
                                GdkContentFormats *formats,
-                                gint               x_root,
-                                gint               y_root)
+                                gint               dx,
+                                gint               dy)
 {
   GdkWaylandDragContext *context_wayland;
   GdkDragContext *context;
diff --git a/gdk/win32/gdkdnd-win32.c b/gdk/win32/gdkdnd-win32.c
index fbf5af6..6952807 100644
--- a/gdk/win32/gdkdnd-win32.c
+++ b/gdk/win32/gdkdnd-win32.c
@@ -2011,13 +2011,14 @@ GdkDragContext *
 _gdk_win32_window_drag_begin (GdkWindow         *window,
                               GdkDevice         *device,
                               GdkContentFormats *formats,
-                              gint               x_root,
-                              gint               y_root)
+                              gint               dx,
+                              gint               dy)
 {
   GdkDragContext *new_context;
   GdkWin32DragContext *context_win32;
   BYTE kbd_state[256];
   GdkWin32Selection *sel_win32 = _gdk_win32_selection_get ();
+  int x_root, y_root;
 
   if (!use_ole2_dnd)
     {
@@ -2050,6 +2051,10 @@ _gdk_win32_window_drag_begin (GdkWindow         *window,
       context_win32 = GDK_WIN32_DRAG_CONTEXT (new_context);
     }
 
+  gdk_device_get_position (device, &x_root, &y_root);
+  x_root += dx;
+  y_root += dy;
+
   context_win32->start_x = x_root;
   context_win32->start_y = y_root;
   context_win32->last_x = context_win32->start_x;
diff --git a/gdk/x11/gdkdnd-x11.c b/gdk/x11/gdkdnd-x11.c
index 9b626e2..1f9acd2 100644
--- a/gdk/x11/gdkdnd-x11.c
+++ b/gdk/x11/gdkdnd-x11.c
@@ -2101,10 +2101,11 @@ GdkDragContext *
 _gdk_x11_window_drag_begin (GdkWindow         *window,
                             GdkDevice         *device,
                             GdkContentFormats *formats,
-                            gint               x_root,
-                            gint               y_root)
+                            gint               dx,
+                            gint               dy)
 {
   GdkDragContext *context;
+  int x_root, y_root;
 
   context = (GdkDragContext *) g_object_new (GDK_TYPE_X11_DRAG_CONTEXT,
                                              "display", gdk_window_get_display (window),
@@ -2120,6 +2121,9 @@ _gdk_x11_window_drag_begin (GdkWindow         *window,
   context->actions = 0;
 
   gdk_drag_context_set_device (context, device);
+  gdk_device_get_position (device, &x_root, &y_root);
+  x_root += dx;
+  y_root += dy;
 
   GDK_X11_DRAG_CONTEXT (context)->start_x = x_root;
   GDK_X11_DRAG_CONTEXT (context)->start_y = y_root;
diff --git a/gtk/gtkdnd.c b/gtk/gtkdnd.c
index e613a5c..e969a37 100644
--- a/gtk/gtkdnd.c
+++ b/gtk/gtkdnd.c
@@ -1060,7 +1060,7 @@ gtk_drag_begin_internal (GtkWidget          *widget,
   GtkWidget *ipc_widget;
   GdkDevice *pointer, *keyboard;
   GdkWindow *ipc_window;
-  int start_x, start_y;
+  int dx, dy;
   GdkAtom selection;
 
   pointer = keyboard = NULL;
@@ -1106,21 +1106,37 @@ gtk_drag_begin_internal (GtkWidget          *widget,
       GtkWidget *toplevel = gtk_widget_get_toplevel (widget);
       gtk_widget_translate_coordinates (widget, toplevel,
                                         x, y, &x, &y);
-      gdk_window_get_root_coords (gtk_widget_get_window (toplevel),
-                                  x, y, &start_x, &start_y);
+      gdk_window_get_device_position (gtk_widget_get_window (toplevel),
+                                      pointer,
+                                      &dx, &dy,
+                                      NULL);
+      dx -= x;
+      dy -= y;
     }
   else if (event && gdk_event_get_event_type (event) == GDK_MOTION_NOTIFY)
     {
-      double x, y;
+      double ex, ey;
+      GtkWidget *toplevel = gtk_widget_get_toplevel (widget);
 
-      gdk_event_get_root_coords (event, &x, &y);
-      start_x = (int)x;
-      start_y = (int)y;
+      gdk_event_get_coords (event, &ex, &ey);
+      x = ex;
+      y = ey;
+      gtk_widget_translate_coordinates (widget, toplevel,
+                                        x, y, &x, &y);
+      gdk_window_get_device_position (gtk_widget_get_window (toplevel),
+                                      pointer,
+                                      &dx, &dy,
+                                      NULL);
+      dx -= x;
+      dy -= y;
     }
   else
-    gdk_device_get_position (pointer, &start_x, &start_y);
+    {
+      dx = 0;
+      dy = 0;
+    }
 
-  context = gdk_drag_begin (ipc_window, pointer, target_list, start_x, start_y);
+  context = gdk_drag_begin (ipc_window, pointer, target_list, dx, dy);
 
   if (!gdk_drag_context_manage_dnd (context, ipc_window, actions))
     {