History list of changes needs instruction and checkboxes

[GoogleCodeExporter]

What steps will reproduce the problem?
1. On any exploration, click History
2. See the list of changes
3.

What is the expected output? What do you see instead?
It is unclear what to do with two columns of radio buttons. If possible, please 
change those to 1 column of checkboxes instead. If a user can only compare up 
to two versions, then disable the checkboxes when two are selected.

Additionally, add directions underneath the title that read "Pick any two 
versions to compare."

What operating system are you using?

Please provide any additional information below.

Original issue reported on code.google.com by sba...@google.com on 2 Jun 2015 at 8:02

[GoogleCodeExporter]

+Xinyu

I think we can just add the directions -- it seems weird to have the checkboxes 
changing state. Xinyu, what do you think?

Original comment by s...@google.com on 2 Jun 2015 at 8:42

[GoogleCodeExporter]

Having checkboxes seems slightly strange to me too, I would expect using 
checkboxes to compare any number of versions. It might help to add more 
directions, but I'm not entirely sure how to clarify the use of radio buttons, 
do you have any suggestions?

Original comment by wxy.xi...@gmail.com on 3 Jun 2015 at 3:11

[GoogleCodeExporter]

Checkboxes in survey commonly change state when you have a limited number of 
selections..Example: "Select up to 3 magazines as your free gift" (and there 
are 8 possible magazines to choose from).

The directions could read: "Choose one from each column to compare"

Additionally, you could change the background or cell color of the selected 
versions.

Checkboxes that change state when a limit is reached is the more common UI 
solution for this use case.

It would visually help identify what is happening.

Original comment by sba...@google.com on 3 Jun 2015 at 8:55