Should the app update when I save the config.xml like it does with html, css and js files?
I assume you're using PhoneGap Developer app or some form of live reload? If so, no, changing config.xml will not refresh your instance. PGDev doesn't read config.xml in the first place, so it doesn't matter. (You need to do an actual build to verify that config.xml stuff is working.)
Why is the orientation locked in portrait on windows phone even when I try to set it to landscape in config.xml?
Guessing for the same reason as above -- you're using PGDeveloper app?
Why can I scroll the app vertically on windows phone when html and body are set to 100%?
Might help to see an example of this.
Why are my viewport settings ignored on ios and android?
It would help to see some code here.
I started from a generated blank project. Why are people talking about modifying java, xml, xaml files on forums when I don't have such files in my project?
Not a clue. Can you point to some of the links you've run across? At this point you probably don't need to worry about any of that stuff yet, if ever, but it's hard to say without knowing specifics.
Hope that helps.
Thanks for the answers.
I'm using PGDeveloper app, i don't know of other options. Not reading config.xml could be the answer to many of my problems. What do you mean by actual build?
I'm trying to use a fixed viewport width to better control size of elements. (I tried with vmin but for example 6vmin of 480px means 6*4.8 which sometimes is 28px sometimes 29px)
On windows phone fixed viewport works but orientatation doesn't, also the vertical scroll is about the size of the status bar.
On android and ios the fixed viewport is ignored.
This is one of the links I ran across: [How to] Fixed page width on Android WebView or Cordova/PhoneGap (and disabling double click/tap to zoom) « Dev « Microb…
I, now, think all my problems come from the fact I'm using this PGDev app.
What other options are there?
The PhoneGap Developer app is intended as a way to rapidly test apps without having an intermediate build step. The PGDev app does, however, have its share of edge cases, some of which you're running into:
1. no support beyond pre-installed plugins (core & a few third-party)
2. doesn't pay attention to config.xml (PGDev is itself a PhoneGap app, so it has its own)
3. has its own application bundle, which sounds obvious, but means your attempts to access your own bundle assets will fail
PGDev app is great for quickly testing an idea, but if you want to know that something will work for sure, you need to create a build using either the PhoneGap CLI or PhoneGap Build. The CLI is the most flexible but also most difficult to set up (you need a Mac to build for iOS, you need native SDKs installed,e tc.). PGB is great if you don't want to maintain your own environment, but doesn't support everything the CLI does. (But it's pretty close, so not usually a big deal.)
The link you sent is old -- from 2014. PhoneGap changes quickly and often, so I would ignore that unless you have good reason.
Also, regarding fixed viewport: don't. Design responsively instead. Devices have widely varied viewport sizes, aspect ratios, etc., and with the advent of split-screen multitasking, it's even more varied. I think the effort you invest in responsive design upfront will be worth it in the end when your app still works just fine even in unexpected environs. For layout I tend to use a combination of flexbox, rem units, absolute and relative positioning, as well as media queries as necessary to fine tune. There are always limits to how far things can go, but this suffices for most things.