1 import gtk
   2 
   3 rect_x = 300
   4 rect_y = 220
   5 rect_size = 80
   6 mouse_x = 0
   7 mouse_y = 0
   8 
   9 dragging = False
  10 
  11 draw_area = None
  12 
  13 def constrain_to_viewport ():
  14     global rect_x, rect_y, draw_area
  15 
  16     if rect_x < 0:
  17         rect_x = 0
  18     elif rect_x + rect_size >= draw_area.allocation.width:
  19         rect_x = draw_area.allocation.width - rect_size
  20 
  21     if rect_y < 0:
  22         rect_y = 0
  23     elif rect_y + rect_size >= draw_area.allocation.height:
  24         rect_y = draw_area.allocation.height - rect_size
  25 
  26 def expose_event_cb (widget, event):
  27     cr = widget.window.cairo_create ()
  28     cr.set_source_rgb (1, 1, 1)
  29 
  30     cr.rectangle (0, 0, widget.allocation.width, widget.allocation.height)
  31     cr.fill ()
  32 
  33     cr.set_source_rgb (1, 0, 0)
  34     cr.rectangle (rect_x, rect_y, rect_size, rect_size)
  35     cr.fill ()
  36 
  37     return False
  38 
  39 def button_press_event_cb (widget, event):
  40     global dragging, draw_area, rect_x, rect_y, mouse_x, mouse_y
  41 
  42     if (dragging or event.button != 1
  43         or event.x < rect_x or event.x >= rect_x + rect_size
  44         or event.y < rect_y or event.y >= rect_y + rect_size):
  45         return True
  46 
  47     dragging = True
  48     mouse_x = event.x
  49     mouse_y = event.y
  50 
  51     return True
  52 
  53 def button_release_event_cb (widget, event):
  54     global dragging, draw_area, rect_x, rect_y, mouse_x, mouse_y
  55 
  56     if not dragging:
  57         return True
  58 
  59     if event.button != 1:
  60         return True
  61 
  62     dragging = False
  63     return True
  64 
  65 def motion_notify_event_cb (widget, event):
  66     global dragging, draw_area, rect_x, rect_y, mouse_x, mouse_y
  67 
  68     if not dragging:
  69         return True
  70 
  71     rect_x = rect_x + event.x - mouse_x
  72     rect_y = rect_y + event.y - mouse_y
  73     constrain_to_viewport ()
  74 
  75     mouse_x = event.x
  76     mouse_y = event.y
  77 
  78     draw_area.queue_draw ()
  79 
  80     return True
  81 
  82 window = gtk.Window (gtk.WINDOW_TOPLEVEL)
  83 
  84 draw_area = gtk.DrawingArea ()
  85 draw_area.set_size_request (640, 480)
  86 draw_area.add_events (gtk.gdk.BUTTON_PRESS_MASK | gtk.gdk.BUTTON_RELEASE_MASK | gtk.gdk.POINTER_MOTION_MASK)
  87 draw_area.connect ("expose-event", expose_event_cb)
  88 draw_area.connect ("button-press-event", button_press_event_cb)
  89 draw_area.connect ("button-release-event", button_release_event_cb)
  90 draw_area.connect ("motion-notify-event", motion_notify_event_cb)
  91 
  92 window.add (draw_area)
  93 
  94 window.show_all ()
  95 
  96 gtk.main ()