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dotnet / pinvoke

A library containing all P/Invoke code so you don't have to import it every time. Maintained and updated to support the latest Windows OS.
MIT License
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User32.EndPaint overload should pass argument by reference #298

Closed dbremner closed 8 years ago

dbremner commented 8 years ago

User32.EndPaint(System.IntPtr hWnd, PInvoke.User32.PAINTSTRUCT lpPaint) function should pass its second argument as a ref. I noticed this while updating a project to 0.3.152. The associated pull request works around the problem by changing the Friendly attribute from FriendlyFlag.In to FriendlyFlag.Bidirectional.

AArnott commented 8 years ago

I'm guessing the "should pass its second argument as a ref" is only a perf optimization. And in that case, that's why the primary p/invoke signature we write for many of these methods takes a pointer:

private unsafe void SomeFunc() {
  PAINTSTRUCT ps; // initialized elsewhere.
  User32.EndPaint(hwnd, &ps);
}

If ref really is so much more convenient than the pointer approach (I'd like to learn how that is) then the caller can define a helper method that wraps the pointer usage.