Follow-up on High DPI resolution
One of the cool results of this dialog is how much interest there is in diving into the details and data behind some of the topics as expressed in the comment and emails. We’re having fun talking in more depth about these questions and observations. This post is a follow-up to the comments about high DPI resolution, application compatibility, and the general problems with readability in many situations. Allow me to introduce a program manager lead on our Desktop Graphics team, Ryan Haveson, who will expand on our discussion of graphics and Windows 7. –Steven
When we started windows 7 planning, we looked at customer data for display hardware, and we found something very interesting (and surprising). We found that roughly half of users were not configuring their PC to use the full native screen resolution. Here is a table representing data we obtained from the Windows Feedback Program which Christina talked about in an earlier post.
We don't have a way of knowing for sure why users adjust their screen resolution down, but many of the comments we’ve seen match our hypothesis that a lot of people do this to because they have difficulty reading default text on high resolutions displays. With that said, some users probably stumble into this configuration by accident; for example due to a mismatched display driver or an application that changed the resolution for some reason but did not change it back. Regardless of why the screen resolution is lower, the result is blurry text that can significantly increase eye fatigue when reading on a PC screen for a long period of time. For LCD displays, much of the blurriness is caused by the fact that they are made up of fixed pixels. In non-native resolution settings, this means that the system must render fractional pixels across fixed units, causing a blurred effect. Another reason for the relative blurriness is that when the display is not set to native resolution, we can’t properly take advantage of our ClearType text rendering technology , which most people (though not all) prefer. It is interesting to note that the loss of fidelity due to changing screen resolution is less pronounced on a CRT display than on an LCD display largely because CRTs don’t have fixed pixels the way that LCDs do. However, because of the advantages in cost and size, and the popularity of the laptop PC, LCD displays are fast gaining market share in the installed base. Another problem with running in a non-native screen resolution is that many users inadvertently configure the display to a non-native aspect ratio as well. This results in an image that is both blurry and skewed! As you can imagine, this further exacerbates the issues with eye strain.
Looking beyond text, in these scenarios the resulting fidelity for media is significantly reduced as well. With the configuration that many users have, even if their hardware is capable, they are not able to see native “high def” 720p or 1080p TV content, which corresponds to 1280x720 and 1920x1080 screen resolutions respectively. The PC monitor has traditionally been the “high definition” display device, but without addressing this problem we would be at risk of trailing the TV industry in this distinction. While it is true that only about 10% of users have a truly 1080p capable PC screen today, as these displays continue to come down in price the installed base is likely to continue to grow. And you can bet that there will be another wave of even higher fidelity content in the future which users will want to take advantage of. As an example, when displays get to 400 DPI they will be almost indistinguishable from looking at printed text on paper. Even the current generation of eBook readers with a DPI of ~170 look very much like a piece of paper behind a piece of glass
From this we see that there is a real end user benefit to tap into here. It turns out that there is existing infrastructure in Windows called “High DPI” which can be used to address this. High DPI is not a new feature for Windows 7, but it was not until Vista that the OS user-interface made significant investments in support for high DPI (beyond the infrastructure present earlier). To try this out in Vista, rt. Click desktop -> personalize and select “Adjust Font Size (DPI)” from the left hand column. Our thinking for Windows 7 was that if we enable high DPI out of the box on capable displays, we will enable users to have a full-fidelity experience and also significantly reduce eye strain for on-screen reading. There is even infrastructure available to us to detect a display’s native DPI so we can do a better job of configuring default settings out of the box. However, doing this will also open up the door to expose some issues with applications which may not be fully compatible with high DPI configurations.
One of the issues is that for GDI applications to be DPI aware, the developer must write code to scale the window frame, text size, graphical buttons, and layout to match the scaling factor specified by the DPI setting. Applications which do not do this may have some issues. Most of these issues are minor, such as mismatched font sizes, or minor layout artifacts, but some applications have major issues when run at high DPI settings.
There are some mitigations that we can do in Windows, such as automatic scaling for applications which are not declared DPI aware (see Greg Schechter’s blog on the subject), but even these mitigations have problems. In the case of automatic scaling, applications which are not DPI aware are automatically scaled by the window manager. The text size matches the user preference, but it also introduces a blurry effect for that application’s window as a result. For people who can’t read the small text without the scaling, this is a necessary feature to make the high DPI configuration useful. However, other customers may only be using applications that scale well at high DPI or may be less impacted by mismatched text sizes and may find the resulting blurry effect caused by automatic scaling to be a worse option. Without a way for the OS to detect whether an application is DPI aware on not, we have to pick a default option. It always comes back to the question of weighing the benefits and looking at the tradeoffs. In the long term, the solution is to make sure that applications know how to be resolution independent and are able to scale to fit the desired user preference, which requires support in both our tools and documentation. The challenge for a platform is to figure out how to get there over time and how to produce the best possible experience during the transition.
Short term vs. long term customer satisfaction
Using the model of high definition TV, we can see that in the long term it is desirable to have a high fidelity experience. The only problem is that even though the high DPI infrastructure has been around for several windows releases (in fact there is an MSDN article dated 2001 on making applications DPI aware), we were not sure how many applications are actually tested in these configurations. So we were faced with an un-quantified potential short term negative customer impact caused by enabling this feature more broadly. The first thing we did is to quantify the exposure. We did this by performing a test pass with over 1,000 applications in our app compat lab to see how they behave at high DPI settings. The results we found are shown below, which shows the distribution of issues for these 1000 applications.
One quick thing, when we say “bug” we mean any time software behaves in a manner inconsistent with expectations—so it can be anything from cosmetic to a crash. We categorize the severity of these bugs on a scale from 1 to 4, where Sev 1 is a really bad issue (such as a crash and/or loss of data or functionality) and Sev 4 is an issue which is quite subtle and/or very difficult to reproduce.
It turns out that most applications perform well at high DPI, and very few applications have major loss of functionality. Of course, it is not the ones that work well which we need to worry about. And if 1% of applications have major issues at high DPI, that could be a significant number. So we took a look at the bugs and put them into categories corresponding to the issue types found. Here is what we came up with:
What we found was that one of the most significant issues was with clipped UI. Looking into this deeper, it became apparent that most of these cases were in configurations where the effective screen resolution would be quite low (800x600 or lower). Based on this, we were able to design the configuration UI in such a way that we minimized the number of cases where users would configure such a low effective resolution. One by one we looked at the categories of issues and when possible, we came up with mitigations for each bucket. Of course, the best mitigation is prevention and so High DPI is a major focus for our developer engagement stories for PDC, WinHEC, and other venues coming up.
Aggregate vs. individual user data
One thing for us to look at is how many users are taking advantage of high DPI today (Vista/XP). Based on the data we have, only a very small percentage of users are currently enabling the high DPI feature. This could easily be interpreted as a clear end user message that they don’t care about this feature or have a need for this feature. An alternate explanation could be that the lack of adoption is largely because XP and Vista had only limited shell support for high DPI, and the version of IE which shipped on those platforms had significant issues with displaying mismatched font sizes and poorly scaled web pages. Also, we do know anecdotally that there are users who love this feature and have used it even before Vista. Once again, we have to make an interpretation of the data and it is not always crystal clear.
Timing: is this the right feature for the market in this point in time?
Fortunately, we don’t have a “chicken and egg” problem. The hardware is already out in the field and in the market, so it is just a matter of the OS taking advantage of it. From a software perspective, most of the top software applications are DPI aware (including browsers with improved zooming, such as IE 8), but there remain a number of applications which may not behave well at high DPI. Another key piece of data is that display resolution for LCD panels is reaching the maximum at standard DPI. For these displays, there is no reason to go beyond 1900x1200 without OS support for high DPI because the text would be too small for anyone to read. Furthermore, this resolution is already capable of playing the highest fidelity video (1080p) as well as 2 megapixel photos. The combination of existing hardware in the field, future opportunity to unlock better experiences, and the fact that the hardware is now blocked on the OS and the software speak to this being the right timing.
Looking at customer data helps us identify ways to improve the Windows experience. In this case, we saw clearly that we had an opportunity to help users easily configure their display such that they would enjoy a high fidelity experience for media as well as crisp text rendered at an appropriate size. With that said, anytime we invest in a feature that can potentially impact the ecosystem of Windows applications we want to be careful about bringing forward your investments in software. We also want to make sure that we engage our community of ISVs early and deeply so they can take advantage of the platform work we have done to seamlessly deliver those benefits to their customers. In the meantime, the internal testing we did and the data that we gathered was critically important to helping us make informed decisions along the way. High DPI is a good example of the need for the whole ecosystem to participate in a solution and how we can use the customer data in the field, along with internal testing, to determine the issues people are seeing and to help us select the best course of action.