REFERENCE GUIDE

Comments31 Transition state (1 if the key is beingreleased, 0 if the key is being pressed).For WM_KEYDOWN messages, the key-transition bit (bit 31) iso and the context-code bit (bit 29) is O.Because of auto-repeat, more than one WM_KEYDOWN message mayoccur before a WM_KEYUP message is sent. The previous key state (bit30) can be used to determine whether the WM_KEYDOWN messageindicates the first down transition or a repeated down transition.For IBM Enhanced 101- and 102-key keyboards, enhanced keys are theright ALT and the right CONTROL keys on the main section of the keyboard;the INSERT, DELETE, HOME, END, PAGE UP, PAGE DOWN and DIRECTION keysin the clusters to the left of the numeric key pad; and the divide U) andENTER keys in the numeric key pad. Some other keyboards may supportthe extended-key bit in the IParam parameter.WM KEYUPThis message is sent when a nonsystem key is released. A nonsystem keyis a keyboard key that is pressed when the ALT key is not pressed, or akeyboard key that is pressed when a window has the input focus.Parameters wParam Specifies the virtual-key code of the given key.IParamContains the repeat count, scan code, key-transition code,previous key state, and context code, as shown in the followinglist:Bit0-15(low-order word)16-23(low byte ofhigh-order word)2425-2627-2829ValueRepeat count (the number of timesthe key stroke is repeated as a result of theuser holding down the key).Scan code (OEM-dependent value).Extended key, such as a function key or akey on the numeric key pad (1 if it is anextended key).Not used.Used internally by Windows.Context code (1 if the ALT key is held downwhile the key is pressed, 0 otherwise).Chapter 6, Messages directory659