You must flush GDI operations when switching between direct access and GDI access, and direct access includes other parts of GDI
A customer was running into problems when accessing the pixels of a DIB section. They used the parameter to and created two bitmaps from the same underlying memory. Those two bitmaps were then selected into corresponding DCs, and the customer found that changes to the pixels performed by writing via one DC were not visible when read from the oth...