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Comment by chrismorgan | Hacker News Reader

I have always been utterly baffled by Apple’s approach to high DPI. They ship some of the best panels around, and then they kneecap them by using the most idiotic scaling scheme imaginable that guarantees that it’s worse than a low resolution panel for some tasks that want precision and uglier on things like single pixel lines which crop up a lot in e.g. web content, because pixel precision is impossible. Microsoft managed to do it right (though mixed-DPI took a couple of attempts), despite having no real power over developers. Meanwhile, Apple, who are in a position to sternly tell their developers to do it right or their software will break (and do so far more frequently than Microsoft), … caved and did it terribly? And do they even support real mixed DPI, or do they just fake it by rendering at the higher scale and downsampling to the other?

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This doesn't gel with my experience at all. Yes, past MacBooks weren't necessarily integer scaling (with this new display the default setting and what most people use will be though as far as I understand), and non-integer scaling is not ideal. But on my last two MacBooks at least the screen is visually plenty sharp, and looks way, way, better than the regular-DPI external monitors I still have (whether the external monitor is connected to the Mac or a Windows PC). And above all, my experience with Mac is that high-DPI has actually worked from the beginning, whereas on Windows I still have some apps that break if the scaling is not set to 100%!

Even right at the start, old apps would look a bit blurry but would still at least be in the correct proportions on macOS, whereas with the Windows scaling a lot of stuff just wouldn't work!

I have no direct personal experience on high-DPI macOS. For Windows, I’ve only come across a couple of apps that claimed to support high DPI but severely mangled it, and they both got fixed before long; and a few others that had minor problems, e.g. opening windows at unscaled sizes so that you had to resize them, or rendering small icons. And to be sure there are various DPI-unaware apps, probably far more than on macOS (linked to why Apple was in the perfect position to implement and impose proper fractional scaling), but that’s not a serious problem either.

thats the issue with windows (and linux). highdpi displays are still rare (i did say: <10%), hence a lot of developers dont support it well in their applications. on mac however highdpi is the default.all apps i have used that is native macosx works fine.

Microsoft's DPI scaling is terrible. So much stuff is ugly and/or broken. (My favorite example is DPI scaling bugs that used to exist in the DPI control panel itself: https://i.imgur.com/zi80IhG.png) Mixed DPI is a huge pain because windows change size when you drag them around. WPF was supposed to fix all this, way back when that was the future. Apple's approach is much simpler and generally works better though it certainly has its downsides too.

Your example is from Windows 8, released in 2012?

Yeah it's my favorite due to the irony. But DPI scaling bugs assuredly continue to exist both in Windows and in applications. On macOS such issues are much more rare.

On most of my machines I switch to the integer scale mode, but realistically, the effect on sharpness is not too far from antialiasing in practice. I am not sure how they do compositing of media on macOS though. Theoretically they can render them on a distinct layer that corresponds to the output display pixels and directly composite that layer to avoid an additional resampling.

Windows on the other hand, does the theoretically correct thing but messes up the ecosystem (unsupported apps, multiple monitors)

They composite everything at nearest higher integer scale, with correspondingly large framebuffer (just make a screenshot of entire screen and check the dimensions). Then, during scan out, it is scaled down by output encoder.

This method does not need GPU at all and also saves memory bandwidth; no need to save scaled down framebuffer and read it out again.

Mixed DPI still doesn't work reliably for me on Windows. Lately mine has been confused with dragging windows between monitors, they'll get stuck on the border when dragging even though I can move my cursor across fine when not dragging anything.

It could be unrelated to the mixed DPI scaling, but that's what nearly all my display issues on Windows have been related to so that's my assumption.

Windows occasionally "stick" a bit when dragging between windows monitors even with the same scaling on both screens. There are a bunch of keyboard shortcuts that are very reliable though. Windows Key + Shift + Direction: left/right instantly moves windows between displays, up maximizes, down un-maximizes and then minimizes. Windows Key + left/right (so without shift) also docks windows to the left or right of the same screen, and this feature is what makes windows also "stick" when dragging them from one screen to another.

I also recommend you check your display settings. If your windows aren't the same vertical size, then your overall desktop isn't a rectangle, it'll be some other polygon, and that means there are corners between the screens that your mouse can get stuck in.

Personally, I could care less if the UI elements themselves are fuzzy when using non-integer scaling. I love high-dpi screens mainly for reading text, and as far as I can tell non-integer scaling doesn't seem to make it fuzzy? Either way, it's way less "fuzzy" than standard-dpi displays where you can actually make out pixels very easily.

IME non-integer scaling on a Mac does make text fuzzy.

Doubling the DPI of the display makes the fuzziness less noticeable of course, but someone commented on this site that the fuzziness bothers him even on a retina display, so he distinctly prefers Windows's text rendering over Mac text rendering on the same hiDPI monitor.

As noted in other comments on this page, many Windows apps are blurry when the OS is set to a scaling factor other than 1.0, but Chrome, Firefox, the new Edge browser, Emacs, VSCode and most of the apps (e.g. Settings) that ship with Windows do not have that problem.

None of the apps except VSCode that I have opened on my Linux install over the previous 3 months are fuzzy when the OS is set to a non-integer scaling factor either, though in that case I have had to learn to adapt to certain minor bugs in Chrome and Emacs.

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