On Tue, Jul 22, 2014 at 8:20 PM, Terry J. Reedy <report@bugs.python.org>
wrote:

>
> Terry J. Reedy added the comment:
>
> I reviewed code and made the following changes in uploaded file:
> Move some code and blank lines around.
> Since you left packing within mBar frame, removed
>        self.mBar.grid_columnconfigure(0, weight=1)
> Since the only thing packed in the left frame was the text frame, renamed
> makeLeftFrame to makeTextFrame, removed the left frame and returned the
> text frame to be gridded directly.  Works fine.
> Remove left_frame, graph_frame temporaries.
>
> The questions that stopped me from pushing this are about the following
> lines in makeGraphicFrame.
>
>         self._canvas = turtle.ScrolledCanvas(root,
>                                              800, 600,
>                                              self.canvwidth,
> self.canvheight)
>         turtle._Screen._canvas = self._canvas #*
>         turtle._Screen._canvas.adjustScrolls()
>         turtle._Screen._canvas._rootwindow.bind('<Configure>',
> self.onResize)
>         turtle._Screen._canvas._canvas['borderwidth'] = 0
>         turtle._Screen._canvas.grid(row=0, column=0, sticky='news') ##
>         ...
>         return  turtle._Screen._canvas
>
It seems that in all lines except #*, 'turtle._Screen._canvas' could be
> replaced by 'self._canvas' or even a 'canvas' temporary. The ## line seems
> wrong, as the parent is root and 0,0 is not where the canvas shoud be
> gridded and indeed not where it is gridded after being returned.  The demo
> seems fine after commenting out the line. So it seems that the following
> should work.
>
>         self._Screen._canvas = self._canvas = canvas = (
>                 turtle.ScrolledCanvas(
>                 root, 800, 600, self.canvwidth, self.canvheight))
>         canvas.adjustScrolls()
>         canvas._rootwindow.bind('<Configure>', self.onResize)
>         canvas._canvas['borderwidth'] = 0
>         ...
>         return  canvas
>

Yes! I like this a lot better. turtle._Screen._canvas was how the canvas
was being manipulated before. I was trying to follow the original
programmer's convention, but that works perfectly!

>
> Am I missing something?  Just curious, what is the <Configure> event? Or
> rather, what generates it?
>
>
The Configure event is triggered when the widget changes size. It is super
confusing. Look for '<Configure>' in the documentation here:

http://effbot.org/tkinterbook/tkinter-events-and-bindings.htm

I had to override Turtle's onResize metbod because the canvas wasn't
centering properly when the sash was being moved.

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> <http://bugs.python.org/issue21597>
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