Question

I would like to know how I can change mouse position in MouseProc function. Specifically to keep Y-coordinate the same. This is my function:

function HookProc(nCode: Integer; MsgID: WParam; Data: LParam): LResult; stdcall;
var
begin        
  PMouseHookStruct(Data)^.pt.Y:=600;

  Result := CallNextHookEx(Hook,nCode,MsgID,Data);
end;

I thought that re-writing the MouseHookStruct Y-coord would do the trick, but apparently not.

Answer 1

You might be looking for ClipCursor Function. No need to use hooks.

Remark:
The cursor is a shared resource. If an application confines the cursor, it must release the cursor by using ClipCursor before relinquishing control to another application.
The function confines the cursor to a rectangular area on the screen.