Separate concept of window size from default framebuffer size

[riccardobl]

This pr makes AppSettings.getWidth/Height return the size of the default framebuffer that is usually what is expected by user code. New methods to set and get window size are added.
The change is backward compatible.

The PR removes also a workaround that caused the engine to be aware of high DPI resolution after the second frame, in my tests waiting two frames has proven to be unnecessary.

EDIT: added rescale listener that propagates the high dpi scaling. Can be used for example to multiply the size of GUI elements.

[riccardobl]

Note: I'll need to rebase this PR manually if we decide to merge #1753 since they conflict.

[stephengold]

Note: I'll need to rebase this PR manually if we decide to merge #1753 since they conflict.

We'd better integrate 1753 first then, since I'm hoping to cherry-pick 1753 into the "v3.5" branch.

[riccardobl]

Rebased. If there isn't any objection i'll merge.

[stephengold]

I need more time to study this.

[stephengold]

1. This PR adds a rescale() method to the public SystemListener interface. Since there's no default implementation, this is potentially a breaking change. Could we implement this PR with less risk of breaking existing code?
2. I like that you documented LegacyApplication.rescale() as "Internal use only". Perhaps do the same for AndroidHarness, AndroidHarnessFragment, and JmeSurfaceView.
3. The javadoc descriptions of the x and y arguments in SceneProcessor.rescale() are identical. Please mention that one is horizontal and the other is vertical. Also, "pixels" isn't the correct unit. Each arg is actually a ratio: frame-buffer pixels per window pixel, right? Also, I have the same concerns aboout SystemListener.rescale().
4. RenderManager.notifyRescale(float x, float y) needs javadoc.
5. In the javadoc for AppSettings.setWindowSize() please specify units and also document the defaults separately for each arg, i.e. width 640 pixels, height 480 pixels.
6. Why does AwtPanelsContext.rescale() throw an IllegalStateException? It looks like an unimplemented/unsupported feature, in which case UnsupportedOperationException would be more appropriate. Also, the exception should include a message describing what's unsupported (or illegal).
7. I noticed some stylistic issues, which I will enumerate in my next review.

[riccardobl]

This PR adds a rescale() method to the public SystemListener interface. Since there's no default implementation, this is potentially a breaking change. Could we implement this PR with less risk of breaking existing code?

Yes it can be implemented as a default method, they should be supported by android at this point.

Why does AwtPanelsContext.rescale() throw an IllegalStateException? It looks like an unimplemented/unsupported feature, in which case UnsupportedOperationException would be more appropriate. Also, the exception should include a message describing what's unsupported (or illegal).

I copied the reshape implementation

I like that you documented LegacyApplication.rescale() as "Internal use only". Perhaps do the same for AndroidHarness, AndroidHarnessFragment, and JmeSurfaceView.

Actually it is not internal use only, so the comment needs to be removed

[riccardobl]

Fixed.
Thanks for catching the problems with the documentation as usual, I never pay enough attention to it.

[stephengold]

I copied the reshape implementation

AwtPanelsContext.reshape() is wrong and should be improved (but not in this PR). Please correct and improve AwtPanelsContext.rescale().

[stephengold]

@riccardobl are you still available to work on this PR?

[riccardobl]

Sure. I'll fix the issues asap (tomorrow?)