editor: Fix soft wrap premature wrapping with certain fonts

[errmayank]

Closes #45107

Release Notes:

• Fixed soft wrap prematurely wrapping with certain fonts

[errmayank]

Here's before/after:

Example README.md

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Ut iaculis nisi et non.

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Ut urna nibh tincidunt.

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer imperdiet quam.

[Veykril]

Thanks!

[Veykril]

Looks like this causes a test failure

cc @MrSubidubi, seems to be a test added by you, in case you have context here

[MrSubidubi]

The test very much checks what the error says, so if this fails, it is very likely that we actually have minimal scrolling with soft wrap enabled, which we should never have. Test is supposed to catch just that (we regressed there too many times).

So this might change more in the editor than it perhaps should, some calculation there might be different due to this change and would result in scrolling with soft wrap

[errmayank]

Thanks @/MrSubidubi. Tests should pass now 🙈

[Veykril]

Can you give a bit more context on this as to why this fixes the issue now?

[errmayank]

Sorry, I realized that I shouldn't have updated em_advance(), which has it's own purpose it seems.

I thought I'd make it consistent with LineWrapper::wrap_line() which uses platform_text_system.layout_line() internally for measuring rendered char width used in soft wrap calculation.

Now, I've updated the editor prepaint to use actual rendered char width instead of raw glyph advance width coming from em_advance() which could have slight differences for some fonts (looking at you, Inconsolata for Powerline)

[Veykril]

Feels like we should give this its own method like is done with em_width and em_advance for consistency

[Veykril]

Also, why does em_width not suffice here?

[Veykril]

any comment on this?

[errmayank]

Hey, apologies for the delay. Yeah i tried using em_width but it doesn't work and i'm not really sure why tbh. So i just made it match with the line wrapper calculation.