[x] I think the box layout deserves more love. There is much more to say than what is used in the examples, e.g. alignment and nesting box layouts to produce more complex layouts. I was already planning a blog post about this subject. Maybe I should write that first so that you can see what I mean. Afterward, we can decide whether (parts of) it should be included in the book.
[x] In the paned layout section the possible values for the position of the slider are incomplete. Floats and fractions are allowed as well. See the comment in SpPanedLayout>>#positionOfSlider:.
[x] An introductory text is missing from the section on the overlay layout.
[x] A figure is missing from the section on the overlay layout.
[x] I did not try the example in the overlay layout section, but I think we can provide a better example. E.g. a tag with a number overlayed on a widget to indicate how many things need attention, like "5" on an icon that indicates an inbox. It would be a better example than the current example with "I AM THE CHILD".
[x] The example in the overlay layout section uses #asPresenter, but it has not been introduced yet.
[x] The constraints classes are mentioned in headers, and #add:withConstraints: is used in examples, but they are not explained.
[ ] The reason why "it is better not to use fixed width or padding" is not explained. Moreover, I disagree with the statement. I have a good counter-example. Let's discuss that sometime (not here in this PR). That example will be the main example in the blog post I mentioned above.
Open issues from https://github.com/SquareBracketAssociates/BuildingApplicationWithSpec2/pull/51:
SpPanedLayout>>#positionOfSlider:.#asPresenter, but it has not been introduced yet.#add:withConstraints:is used in examples, but they are not explained.