ALG: Push/Pop at OutputDevice is used to secure e.g. MapMode over content handling. When using PUSH_MAPMODE as flag, the MapMode is to be pushed and Poped. When during this Push/Pop mapping is temporarily disabled using EnableMapMode(false), the MapMode will not survive this Push/Pop pair. Exmaple code:

const bool bWasOn(dev.IsMapModeEnabled());
dev.EnableMapMode(false);
...
dev.Push(  PUSH_MAPMODE or nothing );
...
dev.Pop();
...
dev.EnableMapMode(bWasOn);

MapMode will be default (MAP_PIXEL) and empty, mbMap will be false after Pop, true after last line above, but useless.
This is an even more dangerous trap when Push/Pop is inside a called sub-routine and it is not obvious why after temporarily disabling the mapping the MapMode is lost.