[bla3]

Say your UI had a one "pixel" wide vertical line. At some point, resolution becomes high enough that you need to draw it two device pixels wide. What do you do at scales in-between?

Do apps start drawing their lines wider if the default font size goes up? When? Is it consistent system wide?

[harlanlewis]

not an expert in this subject, but I believe subpixel rendering is the broad category of solution https://en.m.wikipedia.org/wiki/Subpixel_rendering

further, the “pixel” unit widely used today is quite far removed from physical pixels on consumer devices and is more similar to an abstracted “point” unit - for example, apple alone supports devices at 1x, 2x, and 3x resolutions (or pixel densities)