hi, we have a UI displaying problem and it's very hard for me to create a sample code out of since the structure is quite complicated...
we used Infragistics docking control in our app, one function is to show the graph and user can use the zoom control to see the graph details. the graph is embedded in a grid and the zoom control can control the width of the grid. so
if fully zoomed in the width can be very huge. after some experiment, I found if the width of the control is 50000-60000 or beyond range, there will be a mysterious gray layer appearing on the graph. SNOOP doesn't show such a layer existed and by tweaking
the foreground/background of various layers, I can confirm there's no such a physical property got changed either.
see the following screen shot which shows the control in the correct mode. you will notice the orange graph header and the the black transparent timeline. note that the grid width is 77592
now I zoom in further to stretch the grid width. as you see the orange header and the timeline both covered by a "gray layer" and the grid width is now 607016.

this happens while the pane is in the floating mode. if it's docked then no matter how much zoomed in (width is) the gray layer will NOT show up. I believe this is a disaplaying issue and can either be a WPF or Infragistics. I'm more
thinking to be a WPF issue although I cannot confirm.
is there a limit of how wide the grid can be supported in WPF? I came across this discussion and not sure if it's related:
https://connect.microsoft.com/VisualStudio/feedback/details/731467/disappearing-path-wp