[ENH] OWWidget: Collapse/expand the widget on control area toggle

[ales-erjavec]

Issue

Implements gh-3144

Description of changes

Collapse/expand the widget on control area toggle by the control area width

Includes

• Code changes
• Tests
• Documentation

[codecov-io]

Codecov Report

Merging #3146 into master will increase coverage by <.01%.
The diff coverage is 84.44%.

@@            Coverage Diff             @@
##           master    #3146      +/-   ##
==========================================
+ Coverage   82.35%   82.35%   +<.01%     
==========================================
  Files         335      335              
  Lines       58256    58277      +21     
==========================================
+ Hits        47977    47995      +18     
- Misses      10279    10282       +3

[ajdapretnar]

I made a mess. I didn't realize merging #3141 also touches widget.py. Should I revert and keep this one instead?

[ales-erjavec]

No. I can rebase.

[thocevar]

There is a visible blink/movement of items in the main area when the widget moves and then shrinks. Is it perhaps possible to do this in a single update?

[ales-erjavec]

Is it perhaps possible to do this in a single update?

Probably not. This seems platform dependent.

[ajdapretnar]

I like this. I don't experience any blinking on OSX (but this is after the last commit). There is an occasional update of the plot (or at least it looks like the graph is replotted), but it doesn't bother. Not sure what would happen on bigger data set, but perhaps it is not replotting but just a small glitch. :)