function HelpCommand(Command: Integer; Data: NativeInt): Boolean;
bool __fastcall HelpCommand(int Command, NativeInt Data);
Provides access to any of the Help commands in the application programming interface (API) of native Help handling functions HTMLHelp, WinHelp, or other.
Use HelpCommand to send a command to HTMLHelp, WinHelp, or other native Help handling functions. Before sending the Help command to the native (Windows) help engine, HelpCommand generates an OnHelp event on the active form or on the TApplication object. Finally, the command is forwarded to the native Help handling functions (HTMLHelp or WinHelp) if there is no event handler for the OnHelp event.
In order for HelpCommand to work and to call the proper native Help handling function, insert in the uses clause of your application the Vcl.HtmlHelpViewer unit or another unit that provides an interface to the external Help viewer to use. The Vcl.HtmlHelpViewer unit provides a Delphi interface to the HTMLHelp Windows native Help handling function. For C++, you need to include the HTMLHelpViewer.hpp header files.
For information about the native Help handling functions (HTMLHelp or other) and about the data passed to them, see the appropriate HTMLHelp topics in the MSDN Library.