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How To refresh a canvas

Posted by Achilles (Achilles), 30 August 2004
can some 1 plzzzzzzzzz help me ....... I need to refresh my canvas

widget ,  which is in a frame  ,     after some operation ( each time  i open a new file ) ............i think there's a simple command for this but I am not able

to figure it out ...................

                 help needed  urgent

Posted by admin (Graham Ellis), 31 August 2004
You're probably looking for
       update idletasks
which will update your display with immediate effect rather than waiting for all processing to finish. Unless you use this command, your display can get out of date - especially in expectk applications.

Footnote - I make a promise to review all questions within 24 hours of them being posted. Sometimes (as in this case), you'll be lucky and be answered quicker ... but in general this board should not be relied upon for urgent responses

Posted by Achilles (Achilles), 31 August 2004
Graham UPDATE is for getting new items  to canvas along with

old ones ........... here what I want is that the old items  on my canvas ( mainly lines ) should get cleared up for new items ( lines again  ) to be put up ...................................

Posted by admin (Graham Ellis), 1 September 2004
OK - so you want to delete all the existing items off the canvas rather than simply add and change existing ones?   Sorry - I did n't get that from the original question. Try
          .canvasname delete all
where .canvasname is the name of the canvas widget.

Note
a) You may still need to update idletasks as well (as a second operation)
b) If you're wanting to draw (for example) one image after another on the same set of axes, you would do better to mark each of the changeable items you draw with a tag, then just delete the tagged items.   This way you won't have to keep redrawing the structure of your graph - just the content.



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