Package Gnumed :: Package wxpython :: Module gmRegetMixin |
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# Source Code for Module Gnumed.wxpython.gmRegetMixin

      1  """gmRegetMixin - GNUmed data change callback mixin.
      2
      3  Widget code can mix in this class as a base class and
      4  thus gain the infrastructure to update it's display
      5  when data changes. If the widget is not visible it will
      6  only schedule refetching data from the business layer.
      7  If it *is* visible it will immediately fetch and redisplay.
      8
      9  You must call cRegetOnPaintMixin.__init__() in your own
     10  __init__() after calling __init__() on the appropriate
     11  wx.Widgets class your widget inherits from.
     12
     13  You must then make sure to call _schedule_data_reget()
     14  whenever you learn of backend data changes. This will
     15  in most cases happen after you receive a gmDispatcher
     16  signal indicating a change in the backend.
     17
     18  The _populate_with_data(self) method must be overriden in the
     19  including class and must return True if the UI was successfully
     20  repopulated with content.
     21
     22  @copyright: authors
     23
     24  Template for users:
     25
     26          #-----------------------------------------------------
     27          # reget-on-paint mixin API
     28          #
     29          # remember to call
     30          #       self._schedule_data_reget()
     31          # whenever you learn of data changes from database
     32          # listener threads, dispatcher signals etc.
     33          #-----------------------------------------------------
     34          def _populate_with_data(self):
     35                  # fill the UI with data
     36                  print "need to implement _populate_with_data"
     37                  return False
     38                  return True
     39          #-----------------------------------------------------
     40  """
     41  #===========================================================================
     42  __author__ = "K.Hilbert <Karsten.Hilbert@gmx.net>"
     43  __license__ = 'GPL v2 or later (details at http://www.gnu.org)'
     44
     45  import wx
     46
     47  #===========================================================================
     48 -class cRegetOnPaintMixin:
     49          """Mixin to add redisplay_data-on-wx.EVT_PAINT aspect.
     50
     51          Any code mixing in this class will gain the mechanism
     52          to reget data on wxPaint events. The code must be an
     53          instance of a wx.Window and must implement a
     54          _populate_with_data() method. It must also call
     55          _schedule_data_reget() at appropriate times.
     56          """
     57 -        def __init__(self):
     58                  self._data_stale = True
     59                  try:
     60                          wx.EVT_PAINT(self, self.__on_paint_event)
     61                  except:
     62                          print 'you likely need to call "cRegetOnPaintMixin.__init__(self)" later in %s__init__()' % self.__class__.__name__
     63                          raise
     64          #-----------------------------------------------------
     65 -        def __on_paint_event(self, event):
     66                  """Called just before the widget is repainted.
     67
     68                  Checks whether data needs to be refetched.
     69                  """
     70                  self.__repopulate_ui()
     71                  event.Skip()
     72          #-----------------------------------------------------
     73 -        def __repopulate_ui(self):
     74                  """Checks whether data must be refetched and does so
     75
     76                  Called on different occasions such as "notebook page
     77                  raised" or "paint event received".
     78                  """
     79                  if not self._data_stale:
     80                          return True
     81                  repopulated = self._populate_with_data()
     82                  self._data_stale = (repopulated is False)
     83                  return repopulated
     84          #-----------------------------------------------------
     85          # API for child classes
     86          #-----------------------------------------------------
     87 -        def _populate_with_data(self):
     88                  """Actually fills the UI with data.
     89
     90                  This must be overridden in child classes !
     91
     92                  Must return True/False.
     93                  """
     94                  raise NotImplementedError, "[%s] _populate_with_data() not implemented" % self.__class__.__name__
     95          #-----------------------------------------------------
     96 -        def _schedule_data_reget(self):
     97                  """Flag data as stale and schedule refetch/redisplay.
     98
     99                  - if not visible schedules refetch only
    100                  - if visible redisplays immediately (virtue of Refresh()
    101                    calling __on_paint_event() if visible) thereby invoking
    102                    the actual data refetch
    103
    104                  Called by the child class whenever it learns of data changes
    105                  such as from database listener threads, dispatcher signals etc.
    106                  """
    107                  self._data_stale = True
    108
    109                  # Master Robin Dunn sayeth this is The Way(tm) but
    110                  # neither this:
    111                  #wx.GetApp().GetTopWindow().Refresh()
    112                  # nor this:
    113                  #top_parent = wx.GetTopLevelParent(self)
    114                  #top_parent.Refresh()
    115                  # appear to work as expected :-(
    116                  # The issues I have with them are:
    117                  # 1) It appears to cause refreshes "too often", eg whenever
    118                  #    *any*  child of self calls this method - but this may
    119                  #    not matter much as only those that have self._data_stale
    120                  #    set to True will trigger backend refetches.
    121                  # 2) Even this does not in all cases cause a proper redraw
    122                  #    of the visible widgets - likely because nothing has
    123                  #    really changed in them, visually.
    124
    125                  # further testing by Hilmar revealed that the
    126                  # following appears to work:
    127                  self.Refresh()
    128                  # the logic should go like this:
    129                  # database insert -> after-insert trigger
    130                  # -> notify
    131                  # -> middleware listener
    132                  # -> flush optional middleware cache
    133                  # -> dispatcher signal to frontend listener*s*
    134                  # -> frontend listeners schedule a data reget and a Refresh()
    135                  # problem: those that are not visible are refreshed, too
    136                  # FIXME: is this last assumption true ?
    137                  return True
    138          #-----------------------------------------------------
    139          # notebook plugin API if needed
    140          #-----------------------------------------------------
    141 -        def repopulate_ui(self):
    142                  """Just a glue method to make this compatible with notebook plugins."""
    143                  self.__repopulate_ui()
    144  #===========================================================================
    145  # main
    146  #---------------------------------------------------------------------------
    147  if __name__ == '__main__':
    148          print "no unit test available"
    149