I was tracking this in T9657 .
Basically, the acbf library needed all sorts of stuff to be able to access metadata and extra pagedata.
Given that I am not too great with QML yet, I thought I'd also update Peruse Creator, as that would demonstrate the properties can be read and written in a sensible manner.
There's still a bit to do, and some paper cuts to polish, but I am pretty far already, so hence this review request :)
What has been done:
The metadata page can now edit (almost) everything in the metadata section.
- I removed the multi-language stuff here because I suspect we are better off making a seperate translation gui?
- DocumentInfo ID is generated as a random UUID and the creation date is written upon writing, so those didn't need to be made editable.
 Body background color should proly also go here.
 I didn't add reading direction yet.
 Editing the publishing date isn't as nice as I had hoped.
 Version needs a floating point box, but QML doesn't have one, so I'll have to think about what can be done there.
Pages now have a 'edit' page, which is BookPage put into place. You can edit page info here, as well as make frames, textareas and jumps.
- Clicking once on the page will start a page area selection mode. Clicking a second time confirms the selection and asks what kind of area you want to make.
 This was done because the click+drag activates Kirigami's swipe mechanic, it is not very touch friendly however.
 Textareas still need a bit of work, they don't show up unless you've made one textarea, went back to the pages section and then go back to the page.
 Textareas will also need to create a default language layer entry to get conform files.
- you can only make rectangles right now, but we'll proly need Qt 5.11 for showing anything more complex, as that has the 'Shape' object.
- Areas will show up in the page info list, where you can edit them a little and remove them.
 The swap is kinda broken :<
 Pages should probably try to inherit the page color from the body value.
Anyway I am pretty proud of how far I've gotten :p