[gtk+/gtk-3-20] gtknotebook: avoid tab dnd from content

[Carlos Soriano Sánchez <csoriano src gnome org>]

commit d6187a3dc4b7827228663689445d9f8bcb7a6868
Author: Carlos Soriano <csoriano gnome org>
Date:   Mon May 2 10:19:12 2016 +0200

    gtknotebook: avoid tab dnd from content
    
    Before commit 6c1bee2377eba8 we were setting an attribute of GtkNotebook
    to track the pressed button if the pressed button happened on the
    tab itself.
    Later in the motion handling code we were checking whether the private
    pressed button attribute was set or not in order to handle a tab dnd
    or not.
    
    In commit 6c1bee2377eba8 the code changed and set the pressed button
    variable unconditionally, which means, a motion event from within the
    tab content triggered a tab reordering.
    
    This happened only if the children hierarchy have a widget that bubbles
    up both button press event, which sets the private pressed button
    attribute; and motion events, which started the tab dnd checking the
    private pressed button attribute.
    A widget that experienced the regression was GtkListBox.
    
    In order to fix it, set the button pressed variable only when it press
    the tab itself, not the content.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=764395

 gtk/gtknotebook.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtknotebook.c b/gtk/gtknotebook.c
index 3deb5c1..d00d7e3 100644
--- a/gtk/gtknotebook.c
+++ b/gtk/gtknotebook.c
@@ -2747,8 +2747,6 @@ gtk_notebook_button_press (GtkWidget      *widget,
   if (event->button != GDK_BUTTON_PRIMARY)
     return FALSE;
 
-  priv->pressed_button = event->button;
-
   if ((tab = get_tab_at_pos (notebook, x, y)) != NULL)
     {
       GtkAllocation allocation;
@@ -2767,6 +2765,8 @@ gtk_notebook_button_press (GtkWidget      *widget,
       /* save press to possibly begin a drag */
       if (page->reorderable || page->detachable)
         {
+          priv->pressed_button = event->button;
+
           priv->mouse_x = x;
           priv->mouse_y = y;