[Overview][Types][Classes][Procedures and functions][Variables][Index] | Reference for unit 'LazHelpIntf' (#lcl)

# THelpViewer

[Properties (by Name)] [Methods (by Name)] [Events (by Name)]

Base class for help viewers used in the LCL help system.

## Declaration

Source position: lazhelpintf.pas line 487

`type THelpViewer = class(TComponent)`
`protected`
`procedure SetSupportedMimeTypes(); virtual;` |  | Sets the value in the SupportedMimeTypes property.
`procedure AddSupportedMimeType(); virtual;` |  | Adds the specified MIME type to the SupportedMimeTypes property.
`public`
`constructor Create(); override;` |  | Constructor for the class instance.
`destructor Destroy; override;` |  | Destructor for the class instance.
`function SupportsTableOfContents; virtual;` |  | Indicates if the help viewer can display a table of contents for the specified help node.
`procedure ShowTableOfContents(); virtual;` |  | Displays the table of contents for the specified help node.
`function SupportsMimeType(); virtual;` |  | Indicates if the specified MIME type exists in the SupportedMimeTypes property.
`function ShowNode(); virtual;` |  | Displays the help topic for the specified help node.
`procedure Hide; virtual;` |  | Hides the help viewer.
`procedure Assign(); override;` |  | Assigns property values from the specified source to the current class instance.
`procedure Load(); virtual;` |  | Loads configuration settings for the help viewer from the specified storage.
`procedure Save(); virtual;` |  | Saves configuration settings to the specified storage.
`function GetLocalizedName; virtual;` |  | Gets the localized name for the help viewer.
`procedure RegisterSelf; virtual;` |  | Registers the help viewer for use in the LCL help system.
`procedure UnregisterSelf; virtual;` |  | Unregisters the help viewer in the LCL help system.
`property SupportedMimeTypes: TStrings; [r]` |  | Contains MIME types supported in the help viewer.
`property ParameterHelp: string; [rw]` |  | Contains a help message describing how parameters are used in the help viewer.
`property StorageName: string; [rw]` |  | Indicates the storage used for configuration settings in the help viewer.
`property AutoRegister: Boolean; [rw]` |  | Indicates if the help viewer is automatically registered at run-time.
`end;`

## Inheritance

`THelpViewer` |  | Base class for help viewers used in the LCL help system.
`TComponent`
?
`TObject`

## Description

THelpViewer is a TComponent descendant that provides the interface used for help viewers in the LCL help system. THelpViewer provides properties and methods used to access and display help topics using their corresponding help nodes, including a Table of Contents. Most methods are declared as virtual and should be overridden in descendent class that handle specific MIME types.

Methods are provided to register and unregister the help viewer for a specific MIME type. The AutoRegister property controls whether the viewer is automatically registered at run-time.

Use classes like TCHMHelpViewer, THTMLHelpViewer, THTMLBrowserHelpViewer, and THelpConnector for help databases that use the specific MIME types for the respective classes.

## See also

THTMLBrowserHelpViewer |  | Implements a browser/viewer for HTML help topics.