Comment 3 for bug 877130

To begin with the second question, I specced "Installed" to be very different from "All Software" for two reasons. First, it helps avoid confusion between the two sections -- so that, for example, you don't end up flummoxed that you can't find an application you want to install because you're mistakenly looking only at the things you already have installed. Another way of solving that would be just to merge the sections, replacing "Installed" with an easy-to-find filter on "All Software". But second, "Installed" has different use cases: for example, a support technician looking up exactly which libraries you have installed, or someone with multiple machines comparing the software installed on each. (In the former case you could use the terminal, but you shouldn't have to.) The list is optimized for that kind of quick scanning, whereas All Software is optimized for browsing and will increasingly use tile views instead of lists.

As for the first question, why the list has branches, if it did not it would be either several hundred or several thousand items long, depending on whether you were currently showing technical items. (I don't remember exactly, but I think the previous list did not have that option.) I've met one designer who despises tree views, but I'm not aware of them being "notoriously awful" -- they're used in every file manager, and are perhaps unique in having had an entire software genre, outliners, based around them.

Now, tree controls work in a couple of different ways, depending on what you can do with the branches. What you describe as "how treeviews work" is how they work if branch labels are editable, as with renameable folders in a file manager. Where they are not, as in this case, a branch can and should expand and collapse by clicking anywhere on it.

There is some overlap between "All Software" and "Installed", different overlap between "Installed" and "History", different overlap again between "History" and "Reinstall Previous Purchases", and different overlap still between "Reinstall Previous Purchases" and your forthcoming account page. So it's vaguely possible that one or more of those might disappear altogether in future. But as long as "Installed" does exist, I think it should be categorized with single-click categories.