Am I a discoverer of a bug in the WPF engine?
- by bitbonk
We have a MFC 8 application compiled with /CLR that contains a larger amount of Windows Forms UserControls wich again contain WPF user controls using ElementHost. Due to the architecture of our software we can not use HwndHost directly. We observed an extremely strange behavior here that we can not make any sense of:
When the CPU load is very high during startup of the application and there are a lot live of ElementHost instances, the whole property engine completely stops working. For example animations that usually just work fine now never update the values of the bound properties, they just stay at some random value after startup. When I set a property that is not bound to anything the value is correctly stored in the dependency property (calling the getter returns the new value) but the visual representation never reflects that. I set the background to red but the background color does not change.
We tested this on a lot of different machines all running Windows XP SP2 and it is pretty reproducible.
The funny thing here is, that there is in fact one situation where the bound properties actually pickup a new value from the animation and the visual gets updated based on the property values. It is when I resize the ElementHost or when I hide and reshow the parent native control. As soon as I do this, properties that are bound to an animation pickup a new value and the visuals rerender based on the new property values - but just once - if I want to see another update I have to resize the ElementHost.
Do you have any explanation of what could be happening here or how I could approach this problem to find it out? What can I do to debug this? Is there a way I can get more information about what WPF actually does or where WPF might have crashed? To me it currently seems like a bug in WPF itself since it only happens at high CPU load at startup.
