Checks to see if a mouse drag starting at (start_x, start_y) and ending at (current_x, current_y) has passed the GTK+ drag threshold, and thus should trigger the beginning of a drag-and-drop operation.
X coordinate of start of drag
Y coordinate of start of drag
current X coordinate
current Y coordinate
TRUE if the drag threshold has been passed.
Checks to see if a mouse drag starting at (start_x, start_y) and ending at (current_x, current_y) has passed the GTK+ drag threshold, and thus should trigger the beginning of a drag-and-drop operation.