Vcl.Forms.THelpEvent

• Up to Parent: Vcl.Forms

Delphi

THelpEvent = function(Command: Word; Data: THelpEventData; var CallHelp: Boolean): Boolean of object;

C++

typedef bool __fastcall (__closure *THelpEvent)(System::Word Command, NativeInt Data, bool &CallHelp);

Properties

Type	Visibility	Source	Unit	Parent
type typedef	public	Vcl.Forms.pas Vcl.Forms.hpp	Vcl.Forms	Vcl.Forms

Description

THelpEvent is the type of an OnHelp event handler.

THelpEvent includes the following parameters:

• Command, which indicates the type of Help command that was issued. Its meaning depends on the current Help system. For example, when using HTMLHelp, Command is the command used by the HTMLHelp API. For details on possible commands, see the appropriate HTMLHelp topics in the MSDN Library.

• Data, which provides additional data to describe the action of the Help system. Its value depends on the value of the Command property. Typically, Data specifies a keyword or context ID. For details, see the appropriate HTMLHelp topics in the MSDN Library.

• CallHelp is set by the event handler. If CallHelp is true when the event handler exits, the application should forward the Help command to the Help system. If the event handler handles the command, it sets CallHelp to false so that the application does not forward the Help command to the Help system.

In order for the OnHelp event handler to work properly, insert in the uses clause of your application the Vcl.HtmlHelpViewer 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 file.

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.

See Also

• Procedural types
• Creating events