WPF Blur effect causing high CPU even when collapsed - wpf

Question

We have to show a legal pop-up in our WPF app. When the pop-up is shown, we use blur effect on the view below.
Recently we recognized that this is causing high GPU usage. Because of the spinner control in the background. The more active content, the more GPU usage.
We collapse this spinner when the pop-up is shown based on a property. But this doesn't help. Only when we set it to collapsed in MainWindow.xaml it works.
We tried multiple things e.g. BitmapCache and other techniques but with no success so far.
Here an example:
https://github.com/rmoergeli/BlurEffectTest.git

Answer 1

I investigated that the problem in demo code hides in your animation: it doesn't stop on changing it visibility from visible to collapsed.
So I found a solution to stop animation on being collapsed with the help of MSDN resource.
public partial class Spinner : UserControl
{
private Canvas _content;
private Storyboard _rotationStoryboard;
public Spinner()
{
// Create a name scope for the page.
NameScope.SetNameScope(this, new NameScope());
DefineContent();
SizeChanged += Spinner_SizeChanged;
IsVisibleChanged += Spinner_IsVisibleChanged;
Loaded += Spinner_Loaded;
}
private void Spinner_Loaded(object sender, RoutedEventArgs e)
{
_rotationStoryboard.Begin(this, isControllable: true);
}
private void Spinner_IsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
{
if (e.NewValue is bool isVisible && isVisible)
_rotationStoryboard.Resume(this);
else
_rotationStoryboard.Pause(this);
}
private void DefineContent()
{
_content = new Canvas();
//set content render transform origin point to center
_content.RenderTransformOrigin = new Point(0.5 , 0.5);
_content.RenderTransform = new RotateTransform(angle: 0);
// Assign the canvas a name by
// registering it with the page, so that
// it can be targeted by storyboard
// animations.
RegisterName("animatableCanvas", _content);
Content = _content;
DefineAnimatableContent();
// Create an animation and a storyboard to animate the
// canvas.
DoubleAnimation doubleAnimation = new DoubleAnimation
{
To = 360,
Duration = new Duration(TimeSpan.FromSeconds(3)),
RepeatBehavior = RepeatBehavior.Forever
};
Storyboard.SetTargetName(doubleAnimation, "animatableCanvas");
Storyboard.SetTargetProperty(doubleAnimation, new PropertyPath("RenderTransform.Angle"));
_rotationStoryboard = new Storyboard();
_rotationStoryboard.Children.Add(doubleAnimation);
}
private void DefineAnimatableContent() //renamed Refresh method
{
int n = Balls;
double size = BallSize;
_content.Children.Clear();
double x = ActualWidth / 2;
double y = ActualHeight / 2;
double r = Math.Min(x, y) - size / 2;
double doubleN = Convert.ToDouble(n);
for (int i = 1; i <= n; i++)
{
double doubleI = Convert.ToDouble(i);
double x1 = x + Math.Cos(doubleI / doubleN * 2d * Math.PI) * r - size / 2;
double y1 = y + Math.Sin(doubleI / doubleN * 2d * Math.PI) * r - size / 2;
var e = new Ellipse
{
Fill = BallBrush,
Opacity = doubleI / doubleN,
Height = size,
Width = size
};
Canvas.SetLeft(e, x1);
Canvas.SetTop(e, y1);
_content.Children.Add(e);
};
}
#region Event Handlers
private void Spinner_SizeChanged(object sender, SizeChangedEventArgs e)
{
//we dont need this anymore as we set content render transform origin point to content center
//Transform.CenterX = ActualWidth / 2;
//Transform.CenterY = ActualHeight / 2;
DefineAnimatableContent();
}
#endregion
//other logic
}
This code stops animation on changing Spiner control visibility. But sure you can pause and resume animation with any trigger you need.
N.B! Using this approach you define all the content (not only animarable parts) in code behind so you don't need Spinner.xaml resource anymore.