PR summary

Following up on Issue #14081 regarding removal of focus_set() parameter call in the __init__() function of FigureCanvasTkAgg. Observed a similar focus structure in FigureFrameWx
Standard Tk widgets do not grab focus on creation, so this change would align the canvas with standard behavior.

Interestingly, I'm unable to reproduce the issue. Even after running a script I only get the output -> .!button, so I'm unable to gauge the importance of the fix. This could also be due to an upstream fix in Tkinter but that seems unlikely.

I'm also unsure of where (or if) to document the change in behavior other than the release notes.

I have also thought a great deal about the deprecation process. Any logical way to warn the user seems too noisy for FigureCanvasTkAgg. An unsuspecting user would receive a warning about focus changes even if they had no intention of interacting with the focus mechanism. (As the warning would have to be part of the __init__() )

Updated test_backend_tk::test_canvas_focus to handle two cases both of which raise warnings:

• Canvas created and packed to top-level widget (Focus - Yes)
• Canvas created, packed and shown using plt.show() (Focus - Yes)

Added @daniilS as Co-Author for initial ideas

PR checklist

• "closes FigureCanvasTkAgg.__init__ steals focus #14081" is in the body of the PR description
• new and changed code is tested
• Plotting related features are demonstrated in an example
• New Features and API Changes are noted with a directive and release note
• Documentation complies with general and docstring guidelines