The documentation for SelectObject mentions that bitmaps cannot be selected more than one DC at a time.
This is essentially due to the fact that GDI operations can be written to a bitmap image, and it would be difficult to manage multiple write operations at a time. However, all other GDI objects created after creation (with the exception of regions, but always copied) are immutable, therefore, there are no restrictions on the simultaneous allocation of several domain controllers.
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