為了防止用戶定義的訊息ID與系統的訊息ID衝突，MS（Microsoft）定義了一個宏WM_USER，小於WM_USER的ID被系統使用，大於WM_USER的ID被用戶使用。
基本介紹
- 中文名：WM_USER
- 防止：用戶定義與系統的訊息衝突
- 定義：宏WM_USER
- 步驟：聲明自己的訊息處理函式
- 處理函式：OnMyFirstMessage（）
MSDN定義,自定義訊息的步驟,
MSDN定義
The WM_USER constant is used by applications to help define private messages, usually of the form WM_USER+X, where X is an integer value.
#define WM_USER 0x0400RemarksThere are five ranges of message numbers:
Range | Meaning |
0 through WM_USER – 1 | Messages reserved for use by the system. |
WM_USER through 0x7FFF | Integer messages for use by private window classes. |
WM_APP through 0xBFFF | Messages available for use by applications. |
0xC000 through 0xFFFF | String messages for use by applications. |
Greater than 0xFFFF | Reserved by the system for future use. |
Message numbers in the first range (0 through WM_USER – 1) are defined by the system. Values in this range that are not explicitly defined are reserved for future use by the system.
Message numbers in the second range (WM_USER through 0x7FFF) can be defined and used by an application to send messages within a private window class. These values cannot be used to define messages that are meaningful throughout an application, because some predefined window classes already define values in this range. For example, predefined control classes such as BUTTON, EDIT, LISTBOX, and COMBOBOX may use these values. Messages in this range should not be sent to other applications unless the applications have been designed to exchange messages and to attach the same meaning to the message numbers.
Message numbers in the third range (0x8000 through 0xBFFF) are available for application to use as private messages. Message in this range do not conflict with system messages.
