[gtk+] textview: fix bug on DnD displaced limits of selection

[Daniel Boles <dboles src gnome org>]

commit c3c10edd090bb214aee517ab12a30ca3bbc26b77
Author: Nelson Benítez León <nbenitezl+gnome gmail com>
Date:   Wed Aug 2 19:03:28 2017 +0500

    textview: fix bug on DnD displaced limits of selection
    
    The fix of commit f2fd655754407103f8fb9b2c3e7586fb595ab917
    should be confined to DnD coords only, because otherwise
    it causes the start and end of the selection to be displaced.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=785736

 gtk/gtktextview.c |   10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)
---
diff --git a/gtk/gtktextview.c b/gtk/gtktextview.c
index e624d27..0b81975 100644
--- a/gtk/gtktextview.c
+++ b/gtk/gtktextview.c
@@ -8265,9 +8265,6 @@ gtk_text_view_drag_motion (GtkWidget        *widget,
       y > (target_rect.y + target_rect.height))
     return FALSE; /* outside the text window, allow parent widgets to handle event */
 
-  x -= target_rect.x;
-  y -= target_rect.y;
-
   gtk_text_view_window_to_buffer_coords (text_view,
                                          GTK_TEXT_WINDOW_WIDGET,
                                          x, y,
@@ -8327,8 +8324,11 @@ gtk_text_view_drag_motion (GtkWidget        *widget,
       gtk_text_mark_set_visible (priv->dnd_mark, FALSE);
     }
 
-  priv->dnd_x = x;
-  priv->dnd_y = y;
+  /* DnD uses text window coords, so subtract extra widget
+   * coords that happen e.g. when displaying line numbers.
+   */
+  priv->dnd_x = x - target_rect.x;
+  priv->dnd_y = y - target_rect.y;
 
   if (!priv->scroll_timeout)
   {