I do t know about the "some", but that is what that Apple engineer says:
Which leads to the problem of centering. I wish to center a bitmap image within a button's border. The image is 101 logical points high, and the border is 200 logical points high. With a 2x scale factor, I can center absolutely, and still be aligned to device pixels. With a 1x, 1.25, 1.33, etc. scale factor, centering will align me on a partial pixel, which looks like crap. So I have to round. Which way? If the goal is "make it look good," then the answer is "whichever way looks good," which depends on the visual style of the bezel, i.e. whether the top or bottom has more visual weight. So now we need hinting.
And that's where things start to get really nasty. In order to make things look good at arbitrary resolutions, we want to round to device pixels. But the rounding direction is not a local question! Consider what happens if we have two visual elements abutting in logical coordinates, and they round in opposite directions: now there's a device pixel between them. That's very visible: you get a pixel crack! So you have to coordinate rounding.
Question: even with hinting, is it actually possible to make a font where two glyphs align perfectly without white space between them?
WPF is a good example of a framework that attempted resolution independence and encountered this problem. Initially it has the "SnapsToDevicePixels" property, which triggers rounding behavior at draw time. But draw time is too late, because of the "abutting elements rounding in opposite directions" problem. So they introduced the "UseLayoutRounding" property, which does...something. And the guidance is basically "turn it on and see if it helps, if not, disable it." Great.
I think a way out of this is way higher DPI with some blurring as the last step. That's what print does. At 1000 or 2500 DPI nobody will notice aliasing anymore, and he blurring would take care of small cracks between objects that supposedly are abutting, make cases where two objects that shouldn't accidentally do overlap less obnoxious, etc.
Which leads to the problem of centering. I wish to center a bitmap image within a button's border. The image is 101 logical points high, and the border is 200 logical points high. With a 2x scale factor, I can center absolutely, and still be aligned to device pixels. With a 1x, 1.25, 1.33, etc. scale factor, centering will align me on a partial pixel, which looks like crap. So I have to round. Which way? If the goal is "make it look good," then the answer is "whichever way looks good," which depends on the visual style of the bezel, i.e. whether the top or bottom has more visual weight. So now we need hinting.
And that's where things start to get really nasty. In order to make things look good at arbitrary resolutions, we want to round to device pixels. But the rounding direction is not a local question! Consider what happens if we have two visual elements abutting in logical coordinates, and they round in opposite directions: now there's a device pixel between them. That's very visible: you get a pixel crack! So you have to coordinate rounding.
Question: even with hinting, is it actually possible to make a font where two glyphs align perfectly without white space between them?
WPF is a good example of a framework that attempted resolution independence and encountered this problem. Initially it has the "SnapsToDevicePixels" property, which triggers rounding behavior at draw time. But draw time is too late, because of the "abutting elements rounding in opposite directions" problem. So they introduced the "UseLayoutRounding" property, which does...something. And the guidance is basically "turn it on and see if it helps, if not, disable it." Great.
I think a way out of this is way higher DPI with some blurring as the last step. That's what print does. At 1000 or 2500 DPI nobody will notice aliasing anymore, and he blurring would take care of small cracks between objects that supposedly are abutting, make cases where two objects that shouldn't accidentally do overlap less obnoxious, etc.