The Game Loop and Graphics - C# Game Programming: For Serious Game Creation - page 87

HWND hWnd,
UINT wMsgFilterMin,
UINT wMsgFilterMax,
UINT wRemoveMsg
);

According to the documentation

If a message is available, the return value is nonzero.

■

If no messages are available, the return value is zero.

■

This is the perfect function to decide if there are events waiting for our particular
application.
It's not very important to understand all the details of this C function. The im-
portant thing is how the function is called from C#. To call it from C#, the
function arguments need changing from C types to the equivalent C# types.

The first argument, lpMsg is a message type. This type isn't available in C#; it
needs to be imported. The second type is a Windows handle; this is just a refer-
ence to our form. The last three arguments are all unsigned integers, which are a
standard C# type. Here's the C message structure, which is the first argument.

typedef struct {
HWND hwnd;
UINT message;
WPARAM wParam;
LPARAM lParam;
DWORD time;
POINT pt;
} MSG, *PMSG;

The structure members aren't that important; here's how to import this C type
into C#. First, include the using statement using System.Runtime.In-
teropServices; at the top of the FastLoop.cs with the other using state-
ments. This library has useful functions for importing C types and structures.

using System.Runtime.InteropServices;
using System.Windows.Forms;
namespace GameLoop
{

[StructLayout(LayoutKind.Sequential)]