 
 subsubsection3_5_2_2.html  subsection3_5_2.html  subsection3_5_2.html  tableofcontents3_1.html   Next: subsubsection3_5_2_2.html Display Items and Up: subsection3_5_2.html Display Items  Previous: subsection3_5_2.html Display Items    Advantages of Display Items  
It is easy to see the advantages of seperating the display items from their
  host widgets. First, the display items are easy to learn. Since they are
  the same across different types of widgets. Once you learn about a type
  of display items, you will know how to use them in all Tix widgets that
  support display items (currently these include TixHList, TixTList and the
  spreadsheet widget TixGrid, but the number is growing). In contrast, if
  you want to create a text item for the Tk widgets, you will find out that
  the listbox, text, canvas and entry widget each have a different method
  of creating and manipulating text items, and it is quite annoying to
  learn each of them individually.
   Second, the hosts widgets that use display items are extensible.
  Because of the separation of task, the host widgets are not involved
  in the implementation details of the display items. Therefore, if
  you add a new type of display items, such as a 
animation type
  that displays live video, the host widgets will gladly take them in
  and display them. You don't need to modify the existing host widgets
  at all. In contrast, if you want to display graphical images in the
  existing Tk listbox widgets, you'd better set aside 100 hours to
  rewrite it completely!
   Third, display items are good for writers of host widgets. Because
  now they just need to implement the arrangement policy of the host
  widgets. They don't need to worry about drawing at all because it is
  all handled by the display items. This is a significant saving in
  code because a widget that does not use display items has to spend
  30%of its C code to do the drawing.
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