[robocat]

Think of all the thousands of tiny snippets of text and single Unicode characters that make up a UI. You definitely don't want to be able to select snippets within most controls, because selection interferes with using the control.

Examples: the text in a menu item, the text in a button, the Unicode x in a close icon, the bar between menus.

This is really noticeable in a few web applications where you can select the wrong thing and it interferes severely with using the UI (I have experienced this with Windows and Android).

Yes, you usually want to be able to select the main text. However many mobile UI frameworks just disable all selection, because that is the easiest way to also disable selection within UI controls (managing this issue is actually quite difficult from my experience writing a HTML UI framework).

[steve1977]

In other words, HTML UI frameworks are still far behind native frameworks and actually not really usable yet.

[robocat]

In other words, poorly written components don't work well: which happens in other GUI toolkits and not just HTML.

Good HTML UI frameworks don't make this mistake.

[steve1977]

Are there any good HTML UI frameworks yet?

[robocat]

So long as you don't want an OS native UI, yes I think so.

For example I use Visual Studio Code every day and the UI seems pretty good to me (panels, menus, tabs, check boxes, combos etc). I am presuming it uses a component framework (although I admit I haven't looked at the source).