MSG结构体

typedef struct tagMSG {     // msg  
   HWND hwnd;
   UINT message;
   WPARAM wParam;
   LPARAM lParam;
   DWORD time;
   POINT pt;
} MSG;

Parameters

hwnd

Identifies the window whose window procedure receives the message.

message

Specifies the message number.

wParam

Specifies additional information about the message. The exact meaning depends on the value of the message member.

lParam

Specifies additional information about the message. The exact meaning depends on the value of the message member.

time

Specifies the time at which the message was posted.

pt

Specifies the cursor position, in screen coordinates, when the message was posted.