sys_command 捕捉以下类型的消息:<br><br>SC_CLOSE Closes the window. <br>SC_CONTEXTHELP Changes the cursor to a question mark with a pointer. If the user then clicks a control in the dialog box, the control receives a WM_HELP message. <br>SC_DEFAULT Selects the default item; the user double-clicked the window menu. <br>SC_HOTKEY Activates the window associated with the application-specified hot key. The low-order word of lParam identifies the window to activate. <br>SC_HSCROLL Scrolls horizontally. <br>SC_KEYMENU Retrieves the window menu as a result of a keystroke. <br>SC_MAXIMIZE Maximizes the window. <br>SC_MINIMIZE Minimizes the window. <br>SC_MONITORPOWER Sets the state of the display. This command supports devices that have power-saving features, such as a battery-powered personal computer.<br>lParam can have the following values:<br><br>1 means the display is going to low power.<br><br>2 means the display is being shut off.<br> <br>SC_MOUSEMENU Retrieves the window menu as a result of a mouse click. <br>SC_MOVE Moves the window. <br>SC_NEXTWINDOW Moves to the next window. <br>SC_PREVWINDOW Moves to the previous window. <br>SC_RESTORE Restores the window to its normal position and size. <br>SC_SCREENSAVE Executes the screen saver application specified in the [boot] section of the SYSTEM.INI file. <br>SC_SIZE Sizes the window. <br>SC_TASKLIST Activates the Start menu. <br>SC_VSCROLL Scrolls vertically. <br>