Anchor icon is always visible on Windows when visible=touch after promoted to v4.3.0

[v-pegao]

Issue description

We identified a behavior change after promoted Anchorjs from v4.2.2 to v4.3.0.

We are using visible: touch as anchor options. For v4.2.2, the anchor is hover on page of Windows10, after promoted to v4.3.0, the anchor is always there instead of hover.

Here are sample pages to help understand the issue:
v4.2.2 page(hover): https://kleisauke.github.io/net-vips-tests/api/NetVips.html
v4.3.0 page(always): https://kleisauke.github.io/net-vips/api/NetVips.html

Operating System: Windows

AnchorJs version: 4.3.0

Expected Behavior:
AnchorJS links only become visible when hovering over the headings like before for Windows when visible is touch.

Actual Behavior:
AnchorJS links are always visible for Windows when visible is touch.

Note:
This behavior change seems related to the newly added condition window.TouchEvent in function isTouchDevice() with this commit

isTouchDevice() for v4.3.0:
this.isTouchDevice=function(){return Boolean("ontouchstart"in window||window.TouchEvent||window.DocumentTouch&&document instanceof DocumentTouch)}

isTouchDevice() for v4.2.2:
,this.isTouchDevice=function(){return!!("ontouchstart"in window||window.DocumentTouch&&document instanceof DocumentTouch)}

[bryanbraun]

Thanks for the detailed report. You're totally right about where that new behavior is coming from.

Unfortunately, the behavior you're seeing is intended. To quote the docs:

touch will always display anchors for devices that support touch events, and only display them via hover for devices that do not support touch events. This approximates touchscreen detection (but isn't 100% accurate).

If you're seeing the links in your browser on Windows 10, that means your browser supports touch events (more specifically, window.TouchEvent). That might mean your desktop/laptop has support for touch interface (many windows computers, like surface books, do), or that the browser would support a touch interface if it were installed on such a device.

The change that you saw in the newer AnchorJS version comes from a similar Modernizr update, which was intended to make touch event detection more accurate. You can see details on that here: Modernizr/Modernizr#2409

Ultimately, I'm comfortable leaving this feature as-is, focused on detecting touch-events, which only approximates touchscreen detection. The alternative is to remove the feature altogether (which is what Modernizr eventually did).

If you prefer the former behavior, I'd say feel free to continue using v4.2.2.

[v-pegao]

Thanks for the reply, closing the issue now

[KasparEtter]

Boolean('ontouchstart' in window || window.TouchEvent || window.DocumentTouch && document instanceof DocumentTouch) returns true in the current Chrome (Version 105.0.5195.125) on my old MacBook Pro, which doesn't have a touch screen. The new behavior is unacceptable to me, so I will have to stay on v4.2.2. 😕