CODEWITHSUNDEEP
c++winapi
MrOlegus
MrOlegus

Reputation: 5

Where is the pt field used in the MSG structure?

MSG Message Structure:

typedef struct tagMSG {
    HWND        hwnd;
    UINT        message;
    WPARAM      wParam;
    LPARAM      lParam;
    DWORD       time;
    POINT       pt;
#ifdef _MAC
    DWORD       lPrivate;
#endif
} MSG, *PMSG, NEAR *NPMSG, FAR *LPMSG;

Why is it necessary to store cursor coordinates in a separate field if cursor coordinates are stored in lParam for mouse operation events?

Upvotes: 0

Views: 138

Answers (1)

Anders
Anders

Reputation: 101746

As noted in the comments, the current "global" mouse cursor position might not be the same as the position at the time the message was generated. The threads message queue keeps track of the time and mouse position from the window/threads point of view and simply reports it as part of the data retrieved by GetMessage.

This position can also be retried by code that does not have direct access to the MSG by calling GetMessagePos (and GetMessageTime).

Upvotes: 1

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