How should I pass negative values to SendMessage and Perform when they expect a NativeUInt?

Question

Suppose you have code like this:

Result.X := ACustomMemo.Perform(EM_LINEFROMCHAR, -1, 0); 

The Windows API claims \"-1\" is a valid value t

Answer 1

Casting the -1 value to WPARAM is the proper way to handle this case.

 Result.X := ACustomMemo.Perform(EM_LINEFROMCHAR, WPARAM(-1), LPARAM(0));

btw, the delphi NativeUint definition for the WPARAM type is correct, because is a unsigned 32-bit on x86 and unsigned 64-bit on x64.