WPF/Silverlight rendering blur effect in realtime

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4.00/5 (1 vote)

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In my WPF project I've done with clicking some UI element such stuff:

C#

void vb1_click(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
    DispatcherTimer dt = new DispatcherTimer();
    dt.Interval = new TimeSpan(0, 0, 0, 0, 1000);
    dt.Tick += new System.EventHandler(dt_Tick);
    dt.Start();
}

void dt_Tick(object sender, System.EventArgs e)
{
    for(int i = 0; i < 20; i++)
    {
        this.vb2_blur_eff.Radius = (double)i;
    }
}

The main problem is: "I can't see the each step of blur-effect per second. The program is idling and when the process is complete it gives me the final step of bluring the UI element.

I don't want it, cause both program idling is looking ugly and I want actually see the rendered result at the each period.

Posted 26-Dec-12 2:41am

Oleg Orlov

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Oleksandr Kulchytskyi · Answer 1 · 2012-12-26T02:51:00

Hi i think you have choosen a bad approach with usage of Dispatcher timer, first of all read what MSDN said about it:

<br />
The DispatcherTimer is reevaluated at the top of every DispatcherTimer loop.<br />
Timers are not guaranteed to execute exactly when the time interval occurs, but they are guaranteed to not execute before the time interval occurs. This is because DispatcherTimer operations are placed on the DispatcherTimer queue like other operations. When the DispatcherTimer operation executes is dependent on the other jobs in the queue and their priorities.

Improvements::

C#

public static class ApplicationHelper
	{
		[SecurityPermissionAttribute(SecurityAction.Demand, Flags = SecurityPermissionFlag.UnmanagedCode)]
		public static void DoEvents(DispatcherPriority priority)
		{
			DispatcherFrame frame = new DispatcherFrame();
			DispatcherOperation oper = Dispatcher.CurrentDispatcher.BeginInvoke(priority,
				new DispatcherOperationCallback(ExitFrameOperation), frame);

			Dispatcher.PushFrame(frame);
			if (oper.Status != DispatcherOperationStatus.Completed)
			{
				oper.Abort();
			}
		}

		private static object ExitFrameOperation(object obj)
		{
			((DispatcherFrame)obj).Continue = false;
			return null;
		}

		[SecurityPermissionAttribute(SecurityAction.Demand, Flags = SecurityPermissionFlag.UnmanagedCode)]
		public static void DoEvents()
		{
			DoEvents(DispatcherPriority.Background);
		}
	}

So , let's summarize :

C#

void vb1_click(object sender, System.Windows.Input.MouseButtonEventArgs e)
   {
       DispatcherTimer dt = new DispatcherTimer();
       dt.Interval = new TimeSpan(0, 0, 0, 0, 1000);
       dt.Tick += new System.EventHandler(dt_Tick);
       dt.Start();
   }

   void dt_Tick(object sender, System.EventArgs e)
   {
       for(int i = 0; i < 20; i++)
       {
           this.vb2_blur_eff.Radius = (double)i;
           ApplicationHelper.DoEvents();

       }
   }