WPF PathGeometry/RotateTransform optimization
- by devinb
I am having performance issues when rendering/rotating WPF triangles
If I had a WPF triangle being displayed and it will be rotated to some degree around a centrepoint, I can do it one of two ways:
Programatically determine the points and their offset in the backend, use XAML to simply place them on the canvas where they belong, it would look like this:
<Path Stroke="Black">
<Path.Data>
<PathGeometry>
<PathFigure StartPoint ="{Binding CalculatedPointA, Mode=OneWay}">
<LineSegment Point="{Binding CalculatedPointB, Mode=OneWay}" />
<LineSegment Point="{Binding CalculatedPointC, Mode=OneWay}" />
<LineSegment Point="{Binding CalculatedPointA, Mode=OneWay}" />
</PathFigure>
</PathGeometry>
</Path.Data>
</Path>
Generate the 'same' triangle every time, and then use a RenderTransform (Rotate) to put it where it belongs. In this case, the rotation calculations are being obfuscated, because I don't have any access to how they are being done.
<Path Stroke="Black">
<Path.Data>
<PathGeometry>
<PathFigure StartPoint ="{Binding TriPointA, Mode=OneWay}">
<LineSegment Point="{Binding TriPointB, Mode=OneWay}" />
<LineSegment Point="{Binding TriPointC, Mode=OneWay}" />
<LineSegment Point="{Binding TriPointA, Mode=OneWay}" />
</PathFigure>
</PathGeometry>
</Path.Data>
<Path.RenderTransform>
<RotateTransform CenterX="{Binding Centre.X, Mode=OneWay}"
CenterY="{Binding Centre.Y, Mode=OneWay}"
Angle="{Binding Orientation, Mode=OneWay}" />
</Path.RenderTransform>
</Path>
My question is which one is faster?
I know I should test it myself but how do I measure the render time of objects with such granularity. I would need to be able to time how long the actual rendering time is for the form, but since I'm not the one that's kicking off the redraw, I don't know how to capture the start time.
