The Joys of High DPI

I recently got a new monitor at work (a Samsung SA850). It's a nice monitor and it matches the resolution of my home iMac (2560 x 1440).

The first hurdle was that I was using the on-board video and it didn't handle that high resolution. I needed a new video card. It still didn't work. Finally figured out it needed a dual-link DVI cable. Thankfully our company hardware guy dealt with all this. Just hearing about it reminded me of how much easier it is to just go buy an iMac. (And this is before all the software fun described below!)

I was hoping the new video card would raise my Windows Experience Index, but strangely, it made it worse! Before my desktop graphics was at 5.5, now it's 4.6. The gaming video index increased, but I don't do any gaming! I guess these cards are optimized for gamers. Anyone have a recommendation for a good video card for programming? (preferably low power)

Once it was working, I found the everything a little small, especially the fonts. (My eyes aren't getting any younger unfortunately.) So I played with the Windows 7 display settings. 125% was too big, so I tried a couple of custom sizes and settled on 115%. Afterwords I thought to measure the actual DPI - it was roughly 109 dpi (not exactly a "retina" display - my MacBook Pro is 220 dpi) Windows standard is 96 dpi. 109 / 96 is about 114% so my 115% setting was very close.

Note: You can adjust the size of Windows icons and their labels separately so don't go by that when choosing the scaling. (Select one, hold down the CTRL key, and then use the mouse scroll wheel)

So far so good, except now Chrome (and other programs) look "fuzzy"! It turns out, this is due to Windows DPI scaling. Taking the bitmap for a small font and just enlarging it by 115% gives crappy results. You can turn off the scaling by setting "Disable display scaling on high DPI settings" in the Compatibility section of a program's Properties. (for 32 bit but not 64 bit programs, and for local but not network drives, sigh) Of course, this may mean it goes back to smaller fonts, but you can choose font sizes within Chrome. To their credit, Firefox and Thunderbird were not fuzzy. It's hard to tell if they are actually scaling since 15% is a fairly subtle difference.

To avoid this issue, programs need to declare themselves DPI aware, either in their manifest or by calling SetProcessDPIAware. (See the MSDN article Writing High-DPI Win32 Applications)

I'm amazed that so many programs don't handle display scaling! It's not like this is something new. Sure, most people don't have high DPI monitors, but of anyone, I would expect programmers to have them, and therefore care about such things. I guess not. Even some Windows dialogs come up fuzzy!

I feel a little guilty about this. For years I've been telling people NOT to set their LCD monitor resolution lower just to get larger fonts. Leave it at its native resolution and use the Windows scaling, I tell them. But now I can see why they do it. Just using the Windows scaling gives even worse results than non-native resolutions!

Even setting scaling is an ugly user experience. (This is Windows 7) You start with Control Panel > Appearance and Personalization > Display. (searching for DPI will get you there). Notice that the title "Display" doesn't even mention anything to do with scaling, even though that's all that's on this screen. To get a custom size, you have to pick "Set custom text size (DPI)". This is the first mention of DPI. Notice that it says "text size" even though the main screen says "size of text and other items". This gives you an image of a ruler. And if you figure it out (I didn't at first) you can hold a physical ruler up to the screen and drag until they match. Unfortunately, the only way to really see what it will look like is to click OK, at which point it makes you log out (shutting down all your programs) and log back in again.

It gets worse. At the bottom of the Custom DPI Setting dialog is a check box labeled "Use Windows XP style DPI scaling". In the words of Princess Bride, "I do not think it means what you think it means". From what I could find out, this actually means something more like "Use ONLY Windows XP style DPI scaling". Or in other words, disable Windows Vista (and later) DPI virtualization. (more info in High DPI Settings in Windows) If this box is unchecked, then virtualization is actually enabled.

Then I discover that Suneido is fuzzy. Argh! I confirmed that calling SetProcessDPIAware fixed the fuzziness. But I ended up updating the manifest since that seemed like a safer approach. Mostly, Suneido was actually already "DPI aware" since it used GetDeviceCaps(hdc, GDC.LOGPIXELSY) to scale fonts. But there were a few spots that weren't scaling (e.g. tab controls). I also realized that Suneido wasn't using the best fonts. We were using "MS Sans Serif" for the default font and this is a bitmap font which scales poorly. Which is why we overrode it to use Arial for larger headings. The current standard for Windows is Segoe UI, and prior to that, Tahoma. We were using Courier New for mono-spaced code, whereas Consolas is much nicer (IMO).

So I spent a bunch of time cleaning up and modernizing the fonts in Suneido. I think the end result is a lot nicer. However, things have changed, which will mean complaints. (Yes, some of our customers complain about any kind of change, no matter how small, regardless of whether it's an improvement or not. You can't win.)

I'll end with a wish that someday we might have GUI's that are truly scalable. I realize one of the problems is bitmaps, but we could use vector graphics for icons (which is often how they're designed in the first place). Photographs and video aren't the problem - we scale them all the time. Apple is no better in this respect. They might hide the issues better than Windows, but they are still tied to certain DPI and on their mobile devices, specific screen sizes.