title: Catching mouse events for a custom SplitContainerDesigner
body: <p>I'm trying to create a user control that will provide a draggable splitter between two panels — exactly like SplitContainer — in a custom IDesignerHost implementation. SplitContainer itself, as far as I can tell, is not an option; it will raise an exception unless used in Visual Studio's Designer.</p>
  
  <p>My implementation would look roughly like <a href="https://stackoverflow.com/questions/2701543/winforms-alternative-to-splitcontainer/2701836#2701836">this</a>, except that I'm not receiving the necessary mouse events. I've tried event handlers, <code>On*</code> overrides and overriding <code>WndProc</code> in the user control itself, the host control, and the parent form, but I don't appear to receive <code>WM_MOUSEMOVE</code>, <code>WM_LBUTTONDOWN</code> or <code>WM_LBUTTONUP</code> events <em>anywhere</em>. Per <a href="https://connect.microsoft.com/VisualStudio/feedback/details/94689/mouse-events-consumed-not-raised-in-2-0-designers?wa=wsignin1.0" rel="nofollow noreferrer">this bug report</a>, I should be receiving <code>WM_MOUSEMOVE</code> in "the control designer"; I'm not sure what that refers to in this case.</p>
  
  <p>Any ideas how I can implement a draggable splitter?</p>