Using the Help API

Public Declare Function WinHelp Lib _
"user32" Alias "WinHelpA" _
(ByVal hwnd As Long, ByVal _
lpHelpFile As String, _
ByVal wCommand As enm_wCommand, _
ByVal dwData As Long) As Long

Public Declare Function WinHelpString _
Lib "user32" Alias "WinHelpA" _
(ByVal hwnd As Long, ByVal _
lpHelpFile As String, _
ByVal wCommand As enm_wCommand, _
ByVal strData As String) As Long

Public Declare Function WinHelpStruct _
Lib "user32" Alias "WinHelpA" _
(ByVal hwnd As Long, ByVal _
lpHelpFile As String, _
ByVal wCommand As enm_wCommand, _
ByRef udtData As Any) As Long

Public Enum enm_wCommand
HELP_CONTEXT = &H1&
HELP_QUIT = &H2&
HELP_CONTENTS = &H3&
HELP_INDEX = &H3&
HELP_HELPONHELP = &H4&
HELP_SETCONTENTS = &H5&
HELP_SETINDEX = &H5&
HELP_CONTEXTPOPUP = &H8&
HELP_FORCEFILE = &H9&
HELP_CONTEXTMENU = &HA&
HELP_FINDER = &HB&
HELP_WM_HELP = &HC&
HELP_SETPOPUP_POS = &HD&
HELP_FORCE_GID = &HE&
HELP_TAB = &HF&
HELP_KEY = &H101&
HELP_COMMAND = &H102&
HELP_PARTIALKEY = &H105&
HELP_MULTIKEY = &H201&
HELP_SETWINPOS = &H203&
End Enum

Public Type MULTIKEYHELP
mkSize As Long
mkKeylist As Byte
szKeyphrase As String * 253 
' Array length is arbitrary; may be changed
End Type

Public Type HELPWININFO
wStructSize As Long
left As Long
top As Long
width As Long
height As Long
state As enm_windowstate
rgchMember As String * 2
End Type

Public Enum enm_windowstate
SW_HIDE = 0&
SW_SHOWNORMAL = 1&
SW_SHOWMINIMIZED = 2&
SW_SHOWMAXIMIZED = 3&
SW_SHOWNOACTIVATE = 4&
SW_SHOW = 5&
SW_MINIMIZE = 6&
SW_SHOWMINNOACTIVE = 7&
SW_SHOWNA = 8&
SW_RESTORE = 9&
End Enum

I have included type-safe declarations so that we can pass strings and UDTs. The WinHelp call has these parameters:

hwnd	Handle of the window requesting Help. The WinHelp function uses this handle to keep track of which programs have requested Help. If wCommand specifies HELP_CONTEXTMENU, hwnd identifies the control requesting Help.
lpHelpFile	The name of the Help file that WinHelp is to display. The filename may be followed by an angle bracket (>) and the name of a secondary window if the topic is to be displayed in a secondary window rather than in the primary window. The name of the secondary window must have been defined previously in the [WINDOWS] section of the Help Project (.HPJ) file.
wCommand	Type of help requested. For a list of possible values and how they affect the value to place in the dwData parameter, see below.
xxxData	Additional data. The value used depends on the value of the wCommand parameter.   For a list of possible values, click here.

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This article was originally published on November 20, 2002