When should I use SnapsToDevicePixels in WPF 4.0?
.net, snapstodevicepixels, wpf
Solution
Good answers by Spencer and Martin as to the when to align your pixels.
As to the how: I would also point out that one should in WPF 4.0 try using the property `UseLayoutRounding` instead of `SnapsToDevicePixels`.
`UseLayoutRounding` makes what you are doing compatible with Silverlight (`SnapsToDevicePixels` is not available in Silverlight) ... and Microsoft is also encouraging the use of `UseLayoutRounding` over `SnapsToDevicePixels` in its documentation.
What is the difference between the two? Well, one big difference is that `UseLayoutRounding` occurs during the layout phase while `SnapsToDevicePixels` occurs during the render phase. This makes me speculate that `UseLayoutRounding` is probably a more performant way to go (I haven't confirmed this, though).
All that being said, there will still be reasons to use `SnapsToDevicePixels`. In fact, the MSDN documentation points to one. I will add another: it is only with `SnapsToDevicePixels` that you can use guidelines for precise control.
Here are some resources on this matter (i.e. pixel snapping and clarity with images, text, and visuals):
- The MSDN Documentation for the UIElement.SnapsToDevicePixels Property.
- The MSDN Documentation for the FrameworkElement.UseLayoutRounding Property.
- Here is the old, classic post by Dwayne Need on blurry images.
- Sometimes BitmapScalingMode helps with image clarity.
- A great blog post that shows you how to actually use SnapsToDevicePixels. It can be tricky.
- A blog post by the WPF Text team about all the different improvements they added to WPF 4.0 in order to help text clarity.
- Another blog post by the WPF Text team on layout rounding.
Heh. I know my answer was a little more than what you were asking for ... but this concept (i.e. resolution independence and the resulting problems it brings and how to get over them) can often be a point of frustration when working with WPF. At the very least, I wanted to point you to the new WPF 4.0 property, `UseLayoutRounding`.
UPDATE
I just have to add since I've seen this over and over ... sometimes `SnapsToDevicePixels` works when `UseLayoutRounding` doesn't. I wish I could put a finger on why this is the case, but definitely try UseLayoutRounding first and if that doesn't work, don't hesitate to try `SnapsToDevicePixels`.
That line is so sharp it can cut you!
Problem
Can anyone suggest a guideline on when to use `SnapsToDevicePixels` in WPF 4.0? Should it only be used occasionally if there is an issue, liberally throughout an App, only on certain controls or what?