How does WPF-Grid implement the SharedSizeGroup-behaviour?

Im trying to figure out how Grid does with size-sharing in their columns and rows. Im looking at the Grid-code with Reflector but can't find any hits. The cols/rows sharing size should f开发者_运维百科irst get a desired size and then be measured again with the max found size to get the same size to avoid just being clipped in the arrange-pass, if Im not mistaken. But I cant find any code for size-sharing at all with Reflector. Could someone explain how size sharing should be implemented roughly in a custom panel class with respect to measure and arrange?

Look at System.Windows.Controls.DefinitionBase It's values (taken from sharedscope if used) are then used in grid.SetFinalSize