Building DPI Aware Visual Studio Extensions
- Posted: Feb 09, 2015 at 6:00AM
Are you build Visual Studio extensions? Will you do me a favor? Please consider your user's DPI.
My primary machine runs at 3K (2880x1620) and since my eyes are old, the DPI is at 200%. If you're not running a High DPI machine you may be wondering what's the problem? If you are, like Scott Hanselman, Living a High-DPI desktop lifestyle can be painful, then you KNOW the problem.
Carlos Quintero, Microsoft MVP and Visual Studio Extension ninja, recently blogged about his recent experience in the DPI and VS Extension space...
This first thing that I noticed (very horrified) when I installed Visual Studio and my MZ-Tools extension in the new MacBook Pro 13″ Retina that I purchased last month was that at 100% scaling (96 Dpi) everything looked very tiny and at 150% (144 Dpi) or 200% (192 Dpi) scaling MZ-Tools looked horrible with very wrong layouts. In some Visual Studio versions (such as VS 2008) it looked better. And since MZ-Tools also works with the VBA editor and VB6/VB5 I also tested with different results. At that point I became DPI-aware and read everything I found about Windows and DPI, which is a lot because it is quite complex and tricky. So, if you are not DPI-aware yet, I urge you to buy a retina external monitor or a retina laptop so that you can set at least 200% scaling (better than 150% scaling) to do some tests and fixes and avoid a painful experience. A “large” monitor such as the one of the iMac 27″, that I also own, doesn’t qualify if it is not the new retina model. In the future, especially with Visual Studio, two screens would be needed for better tests with “per-monitor DPI” awareness introduced by Windows 8.1 once Visual Studio supports it.
First, I will introduce some resources that explain better than me DPI-awareness and Windows OS support:
- Windows XP used a pseudo-DPI scaling (fonts and some other UI items)
- Windows Vista (and Windows 7 and Windows 8) introduced true DPI-scaling with the following notes:
- The same DPI is used in all the monitors of a computer (this is called “system DPI”).
- An application must declare through a manifest (embedded in the executable or in an .exe.manifest file, or even by code) its DPI-awareness.
- If an application lacks the manifest, or states that it is not DPI-aware, then the OS scales the application as a bitmap (something called “DPI virtualization”) while the application still thinking that is running at 100% scaling (96 dpi).
- Windows 8.1 introduced “per-monitor DPI”, where each monitor can have a different DPI and an application is notified of a change in the DPI when moved to another monitor, so that it can accommodate the new display.
Given that your extension is hosted in an application (Visual Studio), you don’t have the chance of declaring anything about the DPI awareness of your extension, you are conditioned by the DPI-awareness of the Visual Studio version that is hosting your extension.
To know the DPI-awareness of an executable (such as devenv.exe of Visual Studio) you can use these approaches:
When ensuring DPI-awareness, you need to address three aspects:
- Once the form or toolwindow is scaled, the layout of controls must be correct, that is, without overlapping controls or clipping out of boundaries.
- The size of controls that show images must be scaled according to the actual DPI. Visual Studio does this with the toolbars and menus, but you must do it for the rest of your user interface. This includes graphic buttons on your own toolbars, pictureboxes, images on treeviews, listviews, etc. For example, what at 100% scaling measures 16×16 pixels must measure 32×32 pixels at 200% scaling. At this point we are talking only about resizing the container stretching the contained image. This point and the previous one guarantee that your extension doesn’t have usability issues with clickable controls at high scaling (such as tiny toolbar buttons or checkboxes on treeviews/listviews)
- Ideally, you should provide high-resolution images for scaled containers of images of the previous step. That is, if a button holds a 32×32 image at 200% scaling, you should provide a 32×32 image and not a stretched 16×16 image. If you are a perfectionist and have a lot of time you should provide the following dimensions for the images:
- 16×16 pixels at 100% scaling (96 Dpi)
- 20×20 pixels at 125% scaling (120 Dpi)
- 24×24 pixels at 150% scaling (144 Dpi)
- 32×32 pixels at 200% scaling (192 Dpi)
- 40×40 pixels at 250% scaling (240 Dpi)
In practice, you can compromise providing just 16×16 and 32×32 resolutions and stretch images for resolutions that you don’t provide.
Now, how to provide DPI-awareness in your extension depends on the technology that you are using: it is said that it is easier with Windows Presentation Foundation (WPF) but if you created your extension back in VS 2005 chances are that you are still using Windows Forms. The good news is that you can achieve excellent DPI-awareness with Windows Forms, even with .NET Framework 2.0. I say this because in newer versions of .NET Framework (since 4.5) a Windows Forms app can opt-in for better DPI handling.
I have found several issues in the last weeks that I have been working on this and I have resolved all of them to my complete satisfaction:
High DPI is here, it's real and your next machine (if not you current) will be High DPI, so build your apps and extensions with that in mind, please....