This gesture was only meant to react on GDK_BUTTON_PRIMARY (either
through real pointer events, or implicitly assumed from touch events),
as it used to behave before gestures. Otherwise the gtk_drag_begin*()
call assumes being triggered by button 1, and the drag misbehaves
because that button isn't really in the state mask.
https://bugzilla.gnome.org/show_bug.cgi?id=731016
priv->drag_gesture = gtk_gesture_drag_new (widget);
gtk_gesture_single_set_touch_only (GTK_GESTURE_SINGLE (priv->drag_gesture),
FALSE);
+ gtk_gesture_single_set_button (GTK_GESTURE_SINGLE (priv->drag_gesture),
+ GDK_BUTTON_PRIMARY);
gtk_event_controller_set_propagation_phase (GTK_EVENT_CONTROLLER (priv->drag_gesture),
GTK_PHASE_BUBBLE);
g_signal_connect (priv->drag_gesture, "drag-update",