If the font is not a pixel font, it will render differently depending on your settings and the choices of the rendering engine. Subpixel rendering for the different LCD-screens, aliasing for the pixels to look smooth on low res screens, hinting for those small details to be visible in vector fonts.
Vector fonts are made of lines that can sometimes be smaller than a pixel wide. Font engines solves this in different ways. It both depend on the quality of the font and the settings of the engine. (I'm no font expert though so names might be off. But I have been playing on and off with pixel fonts and vector graphics since 30 years)
Re:The Decline of Usability
by LargoLasskhyfv on Sunday April 19, 2020 @06:24PM
(#22919294)
This is for XFCE, which has one of the simplest tools for setting the font rendering right, with instant visual feedback. At least when i used it. Even in multimonitor setups with different resolutions/orientations.
Other differences I could see from the screenshots: the comboboxes have the dropdown arrow next to instead of inside the edit control, the table headers should have a thick left and top border too, the up/down control's buttons should also have a 3D border, the scrollbar buttons shouldn't become disabled even at the end of travel, and non-top-mounted tabs have their shadow in the wrong direction and side tabs should have text rotated accordingly. I've used this UI for over two decades so it's pretty easy to see when something doesn't look quite right.