Feature to change preview font size for plain/text files.

[34x]

Hi!
First of all thank you for the app and server!

In short what this pr doing:

And details:

One of my way to use Seafile on iOS it's reading and editing text files. I am using iPhone SE and standard WebView font size sometimes very difficult to read so I decided to contribute a bit to the project.

This PR contains from 2 major parts:

1. View element that display quick settings for changing font size (it's small orange box on the right bottom corner with the arrow). I decided to create this instead of putting this to common settings for two reasons: the first one - I found it's not easy to understand philosophy of settings screen at all and the second is that's much more intuitive to change font size right in context of viewing a file.

2. The second part is about actually changing the font and storing it between app launches. For storing data I used [NSUserDefaults standardUserDefaults] but not sure if it's correct or not, because in some places app uses defaults for domain and in some - standard.

For handling changes I added observer for this property in user defaults.

And for actually setting font size I used js string document.body.style.fontSize = '%@'; in the webView. Sizes are provided in % to reflect user defined settings for the system fonts and default value is 100%.

Bugs: I found that with some sizes update did not work (for example when font size changed from 400% to 420% then to 440% e.t.c.) but after closing the view and opening it again it uses correct size. I am not sure why it happens, maybe some MobileSafari specific.

Best regards
Maks

[poetwang]

thanks for contributing to the project and make the app better

[scottcc]

Agreed, this looks very nice. Incidentally, when you hit the back button you can see that the default iOS text rendering has the table view cell labels collapsed/clipped vertically. Can you confirm you're using Xcode 9?

I'd posted the clipping as #187, and we do have a branch that has those fixed too, but I'm not yet sure if there's appetite for a larger MR yet. Just looking to confirm what you see.

[34x]

@scottcc Yes, I am using Xcode 9 and table cells look weird (like half collapsing).

[scottcc]

Thanks, yeah. From what we've seen, it has to do with the top-to-bottom constraints within that cell. Appreciate the confirmation!