There is a problem with catching mouse events when using IFRAMEs also but they are also due to the way the things work. The IFRAME is actually another, separate document and it has it owns events - this being said, you come to a point that once you have gone into the IFRAME, the events belong to the other document and if you release the splitbar, the main document does not know about this event but only the document loaded in the IFRAME "understands" that the mouse button was released.
Dealing with IFRAMEs,PDF documents, Java Applets and their events is pretty complex in such scenarios and we have introduced different workaround where this is possible - e.g the RadWindow which also contains an IFRAME hides the IFRAME while it is being moved or resized in order to prevent this IFRAME to catch the mouse events and to associate them with the main page. For the RadSplitter control, everything which we can suggest in order to improve the behavior in such scenarios is the following:
- Set LiveResize="true".
- Set debug="false" in the Web.config
the Telerik team