API Questions

[TerryRitchie]

Since I've started diving into API calls I figured a dedicated thread for API related questions would be better.

Here is my first question.

In the Wiki here: https://qb64phoenix.com/qb64wiki/index.p...ndow_Focus

It's shown how to determine the foreground window (the one in focus).

The Microsoft docs for GetForegroundWindow are located here: https://learn.microsoft.com/en-us/window...oundwindow

I noticed in the Wiki example that GetForegroundWindow is declared as an _OFFSET (%&). How was this determined? Looking at the Microsoft docs there is no indication of the type of variable returned. With other window handle (hWnd) related functions I've noticed a variable type of LONG is used. Why was _OFFSET needed here instead of LONG?

This has me confused. Any clarification would be greatly appreciated.

HWND is 4 bytes in 32 bit and 8 bytes in 64. The reason you probably see it often declared as a LONG is because many people use 32 bit QB64. Using OFFSET makes it automatically the right size for either system. From Microsoft, the declaration for GetForegroundWindow is: HWND GetForegroundWindow();
The HWND is a handle to the window. Most handles in Win32 are going to be translated best to OFFSET in QB64.

Ah, ok, so basically it's acting like an _INTEGER64 in this sense. So the rule of thumb is if a handle is returned best practice is to use _OFFSET.

Thank you for the quick reply and explanation.