[457] - Immersive reading view

[TheRealAnt]

Fixes #457

• Hiding bars when scrolling down WebView & showing when scrolling up.
• Showing bars when device rotates into landscape mode.

Demo:

Demo.1.mov

[kelson42]

It‘s important to check that his fox has no unwanted side effect on macOS (iPadOS?)

[kelson42]

@TheRealAnt I like that the feature is implemented with so few lines of code

[BPerlakiH]

@TheRealAnt Currently your changes are limited to iOS / iPad OS only, so they have no effect on macOS, which is good.
There's one thing I noticed immediately, that it also applies the bar hiding on iPad OS, which is something we did not wanted.
On iPad there are multiple things that can affect the amount of scroll needed to display the content: side bar collapsing, split screen mode and so on.
My suggestion is to keep these changes limited to iOS only for now. iPad screens are already large enough, plus as we discussed earlier, there's only 1 bar on iPad:

[BPerlakiH]

This won't compile for macOS.
We do not use macCatalyst, and UIKit cannot be imported for macOS.
We do not target watchOS at all, so that is not needed.
I would suggest something like this instead:

Suggested change

	import UIKit
	enum TargetDevice {
	case nativeMac
	case iPad
	case iPhone
	case iWatch
	public static var currentDevice: Self {
	var currentDeviceModel = UIDevice.current.model
	#if targetEnvironment(macCatalyst)
	currentDeviceModel = "nativeMac"
	#elseif os(watchOS)
	currentDeviceModel = "watchOS"
	#endif
	if currentDeviceModel.starts(with: "iPhone") {
	return .iPhone
	}
	if currentDeviceModel.starts(with: "iPad") {
	return .iPad
	}
	if currentDeviceModel.starts(with: "watchOS") {
	return .iWatch
	}
	return .nativeMac
	}
	}
	#if os(iOS)
	import UIKit
	#endif
	enum Device {
	case mac
	case iPhone
	case iPad
	public static var current: Self {
	#if os(macOS)
	mac
	#else
	switch UIDevice.current.userInterfaceIdiom {
	case .pad: return iPad
	case .phone: return iPhone
	default:
	assertionFailure("unrecognised device type: \(UIDevice.current)")
	return iPhone
	}
	#endif
	}
	}

[BPerlakiH]

@TheRealAnt, @kelson42 I've updated this PR with a couple of things:

1. removed an old "hack" around the page layout, which we no longer need
2. made sure we show the bars:

• if the device is rotated (landscape/portrait)
• if the url changes (either by clicking on a link or navigating back and forth by arrows or by dragging from the side of the screen)
• if we scroll to the very top of the screen. This is a bit of a double defence, as scrolling up should also trigger this, but to be on the safe side, as it turned out it is possible to scroll and navigate at the same time