What I believe is happening in your scenario is that the iframe, which the RadWindow uses to load your external content, consumes the mouse events and thus the parent page does not know you are moving the mouse with the intent to drag the RadSplitBar: http://screencast.com/t/Ok4QOHEGA
. If so - this is the way iframes work and there isn't much that can be done.
Please note that resizing the restriction zone so that the RadWindow it outside of it is an invalid scenario - the concept is that the restriction zone is the static element and the RadWIndow sets its coordinates according this element. If these coordinates change we generally have no way of knowing this.
Nevertheless I created and attached a simple page which moves the RadWindow in the restriction zone if needed. If the splitter's orientation changes this would requrie some changes in the code, yet the general logic stays the same.
The important concept is the usage of the additional div that overlays the iframe of the RadWindow so that it does not consume the events. The rest is the logic for repositioning the RadWindow.
Please examine the recording with the expected behavior: http://screencast.com/t/x56rlMpDjdQE
. If there is enough room in the restriction zone the RadWindow is correctly moved to the right. I chose to persist its vertical position and move it to the beginning of the zone. You can further extend this logic if needed.
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