WPF and Silverlight both operate on a subpixel grid. That is,
you can align elements on partial pixel boundaries, like this:
<Rectangle Margin="10.5 10.5 10 10"
Stroke="Black"
StrokeThickness="1"
Height="100"
Width="300" />
Unfortunately, for single-pixel-width elements, the result is
usually not what you want. For example, the xaml above produces
this rectangle:
You may be able to tell it's a little fuzzy. Here's a zoomed-in
view of the upper left corner:
No, probably not what you want. You specified a 1px line. Sure,
you could have simply started it on a whole pixel, but while that
is easy in this instance, when you have nested containers inside
elements inside panels inside windows, all with their own margins,
it gets pretty complicated.
WPF now
has a great UI feature that Silverlight got back in the SL3 timeframe:
Layout Rounding. Layout rounding lets you specify that you want the
shape to snap to the closest whole pixel. Rather than have a
double-width gray line, you'll get a single-width black line, but
it may be a partial pixel off from where you thought it would be.
That's the trade-off, and it's one that many folks are willing to
make.
<Rectangle Margin="10.5 10.5 10 10"
UseLayoutRounding="True"
Stroke="Black"
StrokeThickness="1"
Height="100"
Width="300" />
Here's the same rectangle with layout rounding turned on.
And here's the zoomed-in shot:
Now that's more like it!
Anti-aliasing has its place, for sure, but when you want crisp
lines, you want crisp lines. I'm happy to see this addition to WPF
4.