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KBDLLHOOKSTRUCT structure (winuser.h)

  • Article
  • 04/02/2021

Contains information about a low-level keyboard input event.

Syntax

typedef struct tagKBDLLHOOKSTRUCT {
  DWORD     vkCode;
  DWORD     scanCode;
  DWORD     flags;
  DWORD     time;
  ULONG_PTR dwExtraInfo;
} KBDLLHOOKSTRUCT, *LPKBDLLHOOKSTRUCT, *PKBDLLHOOKSTRUCT;

Members

vkCode

Type: DWORD

A virtual-key code. The code must be a value in the range 1 to 254.

scanCode

Type: DWORD

A hardware scan code for the key.

flags

Type: DWORD

The extended-key flag, event-injected flags, context code, and transition-state flag. This member is specified as follows. An application can use the following values to test the keystroke flags. Testing LLKHF_INJECTED (bit 4) will tell you whether the event was injected. If it was, then testing LLKHF_LOWER_IL_INJECTED (bit 1) will tell you whether or not the event was injected from a process running at lower integrity level.

Value Meaning
LLKHF_EXTENDED
(KF_EXTENDED >> 8)
 Test the extended-key flag.
LLKHF_LOWER_IL_INJECTED
0x00000002
 Test the event-injected (from a process running at lower integrity level) flag.
LLKHF_INJECTED
0x00000010
 Test the event-injected (from any process) flag.
LLKHF_ALTDOWN
(KF_ALTDOWN >> 8)
 Test the context code.
LLKHF_UP
(KF_UP >> 8)
 Test the transition-state flag.
 

The following table describes the layout of this value.

Bits Description
0 Specifies whether the key is an extended key, such as a function key or a key on the numeric keypad. The value is 1 if the key is an extended key; otherwise, it is 0.
1 Specifies whether the event was injected from a process running at lower integrity level. The value is 1 if that is the case; otherwise, it is 0. Note that bit 4 is also set whenever bit 1 is set.
2-3 Reserved.
4 Specifies whether the event was injected. The value is 1 if that is the case; otherwise, it is 0. Note that bit 1 is not necessarily set when bit 4 is set.
5 The context code. The value is 1 if the ALT key is pressed; otherwise, it is 0.
6 Reserved.
7 The transition state. The value is 0 if the key is pressed and 1 if it is being released.

time

Type: DWORD

The time stamp for this message, equivalent to what GetMessageTime would return for this message.

dwExtraInfo

Type: ULONG_PTR

Additional information associated with the message.

Requirements

Requirement Value
Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Header winuser.h (include Windows.h)

See also

Conceptual

Hooks

LowLevelKeyboardProc

Reference

SetWindowsHookEx

Additional resources