title: DropShadow on large object causing ScrollViewer slowdown
body: <p>I am having issues with using the DropShadowEffect on a large WPF element. I know there have been issues with this effect in the past and found a few old questions but I was wanting to make sure I had some up to date information and possibly a good solution as I have struggled to find one that isn't 9+ years old.</p>
  <p>This issue duplicates only on high resolution scenarios so when the application window is at 1080p+. It seems to be made worse by having 2 different monitors at different resolution and DPI's. My example is a 4k screen running at 250% DPI and a 1440p screen running at 125% DPI.</p>
  <p>Here is the code:</p>
  <pre><code>    &lt;Window.Resources&gt;
          &lt;Color po:Freeze=&quot;True&quot; x:Key=&quot;GrayBrush&quot; &gt;#d3d3d3&lt;/Color&gt;
          &lt;DropShadowEffect x:Key=&quot;dropShadow&quot; BlurRadius=&quot;20&quot; ShadowDepth=&quot;0&quot; Color=&quot;{StaticResource GrayBrush}&quot; po:Freeze=&quot;True&quot; /&gt;
      &lt;/Window.Resources&gt;
  
      &lt;Grid&gt;
          &lt;Rectangle Fill=&quot;LightBlue&quot; Effect=&quot;{StaticResource dropShadow}&quot; Margin=&quot;20&quot;/&gt;
      
          &lt;ScrollViewer Margin=&quot;20&quot;&gt;
              &lt;VirtualizingStackPanel&gt;
                  &lt;TextBox /&gt;
                  etc...
              &lt;/VirtualizingStackPanel&gt;
          &lt;/ScrollViewer&gt;
      &lt;/Grid&gt;
  </code></pre>
  <p>Here is a link to a sample of a rough duplication of the problem <a href="https://streetsheaver-my.sharepoint.com/:u:/g/personal/james_baker_streets-heaver_com/EZOvAo3YoIBNrmpubutuwbsBb7TRVKA2ZBqb-LaVngiINA?e=gN1qjw" rel="nofollow noreferrer">sample</a>.</p>