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Editorial Team
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Asked: 2026-06-17T16:39:43+00:00

I initialize my code normally, and get a valid device / render context, and

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I initialize my code normally, and get a valid device / render context, and then store those two in a static object of type OpenGL_Display. When I then call the image update function from outside the DLL, the call to both
wglGetCurrentContext() as well as wglGetCurrentDC() return NULL.
When I call wglMakeCurrent() with the HDC and HRC stored in my class, GetLastError() will return error 170 (The requested resource is in use.)

I don’t understand how the resource could be in use from any where. Note that the code runs fine from a .exe, so it has something to do with me calling it from a C# Application, or that it is in a DLL in the first place, but for the life of me I cannot figure out why those resources are busy.

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1 Answer

  1. Editorial Team

    This error is returned when the context is active in another thread.

    Most likely is that your creation/initialisation code does a wglMakeCurrent(), but does not set the context back to NULL before returning.

    If the drawing then occurs on a different thread, it will be unable to set the context and will return ERROR_BUSY.

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