Jeff Hobbs <jeff.ho...@gmail.com>: > On Oct 12, 9:43 am, o...@dtrx.de (Olaf Dietrich) wrote: >> >> After some somewhat heavy mouse action inside the >> canvas (with the left button pressed), the application throws: >> >> | Exception RuntimeError: 'maximum recursion depth exceeded' in <bound >> method PhotoImage.__del__ of <Tkinter.PhotoImage instance at 0x19c0998>> >> ignored >> | Exception in Tkinter callback [...] >> (and similiar ones) >> >> This error can be provoked faster by setting the recursion limit >> to lower values (e.g. 400 as in the comment above). >> >> Is there anything I can do (apart from increasing the recursion >> limit) to avoid this exception? Can I improve anything in the >> script above to make the whole thing more robust? > > It seems very heavy-handed to create 1-pixel images for drawing onto > the canvas. Any reason not to use something lighter weight?
The example was _heavily_ simplified; originally, there was a background (e.g. gray-scale) image and I was drawing lines or other shapes onto that background that should appear in color and semi-transparent on top of the background. Additionally, both background and foreground can be zoomed and scrolled, and there should be a pixel-by-pixel correspondence between the (zoomed) background pixels and the semi-transparent shapes in the foreground (as opposed to overlayed vector graphics). I could not find a more light-weight solution for these requirements. > I suspect the "self.root.update()" is the problem. Try > update_idletasks() instead, or to even avoid it if possible. You > don't want to call update in the event loop, because you are likely > reprocessing from the same call, causing the recursion. Indeed, Tk/Toplevel/Canvas.update() seems to be at the center of the problem. If I replace update() by update_idletasks(), the problem disappears, but unfortunately, considerably fewer events are recorded on the canvas (when connecting the pixels with lines, the lines become much longer with update_idletasks() than with update()). If I remove both update() and update_idletasks(), things work similarly as with update_idletasks() (the display is only marginally slower than with update_idletasks()). I wonder if there is any compromise between update() and update_idletasks(): * update(): smooth lines but recursion exception * update_idletasks(): non-smooth lines without exceptions Thanks a lot for your help Olaf -- http://mail.python.org/mailman/listinfo/python-list
