The framework calls this member function when the user releases the middle mouse button.
Indicates whether various virtual keys are down. This parameter can be any combination of the following values:
MK_CONTROL Set if the CTRL key is down.
MK_LBUTTON Set if the left mouse button is down.
MK_RBUTTON Set if the right mouse button is down.
MK_SHIFT Set if the SHIFT key is down.
Specifies the x- and y-coordinate of the cursor. These coordinates are always relative to the upper-left corner of the window.
This member function is called by the framework to allow your application to handle a Windows message. The parameters passed to your function reflect the parameters received by the framework when the message was received. If you call the base-class implementation of this function, that implementation will use the parameters originally passed with the message and not the parameters you supply to the function.