Windows 10 has earned high marks for how well it handles existing applications -- a crucial issue for any new version of Windows. But there's one area in which some existing Windows apps fall flat in a way that even Windows 10 can't help them: poor or nonexistent handling of high-DPI displays,
One of the drawbacks of running Windows on a high-DPI display comes down to the size of the items. Windows 10 does include a way to manually specify the scaling level for a given display. However, such scaling only works properly for applications that are aware of it -- and even then it has limitations.
Squinting isn't a solution
Chris Mills wrote an irate piece for Gizmodo about high-DPI problems, with much of his annoyance aimed at two issues. One, many high-DPI displays are small, like those now found routinely on notebooks. On such displays, text, icons, window decorations, the whole lot are eye-achingly small. The other problem: Some desktop applications don't scale right on high-DPI displays because they simply have no idea how to do so.
For apps that aren't high-DPI aware, Microsoft has a quick and dirty fix called DPI virtualization. Windows deliberately reports the wrong DPI resolution to such apps, so their elements render as if they were on a lower-resolution display. The results are then zoomed to fit the current display.
While this trick allows UI elements like buttons and dialog boxes to appear at the right size and proportions, it also makes text blurry, icons fuzzy, and images hazy. ClearType-rendered text looks particularly bad, since the subpixel rendering used for it only works when it matches the resolution of the display.
It's the apps, stupid
Different apps manifest this problem to different degrees. Google Chrome, for instance, is acceptable when zoomed, but almost the entire Spotify UI (and Spotify's own desktop icon) is blurry and hard on the eyes. Firefox isn't bad, although the icon set used for its menus doesn't appear to be high-DPI aware, so those look less than crisp when zoomed.
Barring a smarter upscaling algorithm in Windows, the responsibility for fixing these issues falls to app devs. Aside from writing apps to be high-DPI aware, resources like icons need to be created at high resolution. Microsoft now recommends 256 by 256 pixels, rather than the 48-by-48-pixel maximum recommended in Windows XP. Cross-platform UI toolkits, like the one used by Spotify, also need to be made high-DPI aware.
These aren't quick fixes, but with both Windows 10 and high-DPI displays coming on fast, devs shouldn't skimp on ensuring desktop Windows 10 apps aren't eye-killers.