[issue21933] Allow the user to change font sizes with the text pane of turtledemo

[Terry J. Reedy]

Terry J. Reedy added the comment:

I am aware of this because the Windows has the same behavior. As I noted in my post to #17642, I consider this behavior a tolerable glitch rather than a patch-blocking bug for turtledemo because the text is relatively short and read only, so there is no issue of needing to keep a cursor in place and visible. The issue would be different for Idle if indeed this is a tk rather than turtle problem. Also, people would typically only move a few clicks up or down, and scrolling up when already at the top of the file has no effect.  So I do not regard this as a bug for this issue and regard this as still closed unless you happen to have thought of a workaround.

If you don't have a fix now, you could open a separate issue to investigate whether the linkage is a tk, tkinter, or turtle bug.

As part of #17535, I discovered that when a Text widgets change the font size, they scroll up, down too far (or down and up too far), and back to where they should be.  This is not visible with small files like the turtle examples, but is with 3000-line files like idlelib/EditorWindow.py, especially when line numbers are enabled.  My test script attached to #17535 shows that Text indeed calls scrollbar.set 3 times.  I regard this as a tk bug.  My point here is that Text widget font size changes are a bit flaky even without the mousewheel issue.

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue21933>
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