For me, it's the opposite on 4.3.dev3: the main toolbar's 3 vertical dots are almost pixel-perfect while the ones in the dock are slightly blurry.

I'm using 100% editor scale with the editor in a maximized 3840×2160 window.

Non-integer spacing somewhere?

There has been a complete refactoring of the editor theme generation with emphasis on margins/spacings. Could this be a side effect?

I can certainly confirm the issue. it is difficult to visualize a comparison, but something has changed and they definitely look blurrier as a result.

Just found this today as well. Also not sure where this comes from, resizing does not fix it.

A quick comparison of versions:

My guess is that it's related to SVG_Renderer from Freetype (this file, maybe? godot/thirdparty/freetype/src/svg/ftsvg.c)
It was update here 008d3de last time, so since 4.2.1 it's probably an issue.

I'm not a C developer. Maybe @bruvzg could help us confirm this bug is related to Freetype update. By the way, sorry for bothering you (tagging).

My guess is that it's related to SVG_Renderer from Freetype (this file, maybe? godot/thirdparty/freetype/src/svg/ftsvg.c)

No, FreeType is not related to the icons in any way. Most likely it's something with icon positions (theme or control changes).

I just did a bisect and this issue seems to be a regression from #64351, cc @Rindbee
Reverting that PR fixes it for me as well.

Edit: I now only reverted the changes in the NOTIFICATION_DRAW method. Everything works still, so the problem really is somewhere in the drawing code of button.cpp

Interesting find!

Then we should look for drawing code that puts images at non-integer coordinates. This is a probable culprit.

UI toolkits of long ago may have had logic that automatically snap images and primitives to the nearest pixel. In Godot, if you draw something between pixels, it gets blurry. Rounding coords to the closest pixel after calculation may be a solution.

One suggestion would be to recommend checking the result on non-hidpi displays every time there is UI code being worked on. Perhaps add a little mention in the developer docs about that? Because someone who only works on 4K/Retina/hidpi or similar screens would never see the issue on his configuration.