Incompatible Types “LongBool” and “Integer”

Question

I needed to compile the source code of Inno Media Player 0.03 which was modified by me to add a Cursor Hiding feature to it using Delphi.

I added the code to the source successfully and tried to recompile but the compiler says:

[dcc32 Error] MainUnit.pas(154): E2010 Incompatible types: 'LongBool' and 'Integer'.

What is the problem in this code?

The code I added to INNO MEDIA PLAYER:

const
  OATRUE = -1;

procedure TDirectShowPlayer.InitializeVideoWindow(WindowHandle: HWND; var Width,
  Height: Integer);
begin
  ErrorCheck(FGraphBuilder.QueryInterface(IVideoWindow, FVideoWindow));
  ErrorCheck(FVideoWindow.HideCursor(OATRUE));     **<<<ERROR IS HERE<<<**
  ...
end;

I called the IVideoWindow::HideCursor method on the FVideoWindow in the TDirectShowPlayer.InitializeVideoWindow .

The OATRUE Constant is a System.Shortint and IVideoWindow.HideCursor is a LongBool method.

Are those incompatible types or is my version of Delphi incompatible with this code that I added ?

Answer 1

On MSDN, IVideoWindow.HideCursor() is declared as taking a long as input, not a BOOL , so it should not be declared as LongBool in Delphi, it should be Longint instead. So either fix the declaration, or use a typecast:

ErrorCheck(FVideoWindow.HideCursor(BOOL(OATRUE)));

Answer 2

According to DirectShow documentation on IVideoWindow::HideCursor method signature is:

HRESULT HideCursor(
  [in] long HideCursor
);

while corresponding signature in Progdigy's Pascal translation is:

function HideCursor(HideCursor: LongBool): HResult; stdcall;

So, while your code is absolutely complies to MS specification, you have to deal with incorrect type declaration somehow. You need to typecast your constant to declared type:

ErrorCheck(FVideoWindow.HideCursor(LongBool(OATRUE)));

Note: just passing True to HideCursor might also work provided DirectShow isn't sensitive to exact values. Use with caution.