This message is generated by the selection of items in a system menu or by a maximize or minimize button.



The enumeration SystemCommand contains the standard system command values.


low-order part The x-coordinate of the mouse when the selection was made. This value is in screen coordinates and is zero if the selection was not made with the mouse.
second part The y-coordinate of the mouse when the selection was made. If the selection was made via a system accelerator, this value is -1. If the selection was made via a mnemonic, this value is 0.



If the window processes this message, it should return zero.


The default window procedure supplies actions for each of the values occurring in the enumeration SystemCommand.

The low-order four bits of the system command value are used by the system. In order for an application to obtain the correct value it should use the bitwise and with the value 0xfff0 to mask out these bits.

The items in a system menu may be modified using the functions:

Accelerator keys that match items in the system menu are translated into this message; whereas, all other accelerator keys are translated into the message Message::Command.