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# QHelpEngineCore Class Reference
[QtHelp module]

The QHelpEngineCore class provides the core functionality of the help system. More...

Inherits QObject.

Inherited by QHelpEngine.

### Methods

- __init__ (self, QString collectionFile, QObject parent = None)
- bool addCustomFilter (self, QString filterName, QStringList attributes)
- bool autoSaveFilter (self)
- QString collectionFile (self)
- bool copyCollectionFile (self, QString fileName)
- QString currentFilter (self)
- QStringList customFilters (self)
- QVariant customValue (self, QString key, QVariant defaultValue = QVariant())
- QString documentationFileName (self, QString namespaceName)
- QString error (self)
- QByteArray fileData (self, QUrl url)
- list-of-QUrl files (self, QString namespaceName, QStringList filterAttributes, QString extensionFilter = QString())
- QStringList filterAttributes (self)
- QStringList filterAttributes (self, QString filterName)
- list-of-QStringList filterAttributeSets (self, QString namespaceName)
- QUrl findFile (self, QUrl url)
- dict-of-QString-QUrl linksForIdentifier (self, QString id)
- bool registerDocumentation (self, QString documentationFileName)
- QStringList registeredDocumentations (self)
- bool removeCustomFilter (self, QString filterName)
- bool removeCustomValue (self, QString key)
- setAutoSaveFilter (self, bool save)
- setCollectionFile (self, QString fileName)
- setCurrentFilter (self, QString filterName)
- bool setCustomValue (self, QString key, QVariant value)
- bool setupData (self)
- bool unregisterDocumentation (self, QString namespaceName)

### Static Methods

- QVariant metaData (QString documentationFileName, QString name)
- QString namespaceName (QString documentationFileName)

### Qt Signals

- void currentFilterChanged (const QString&)
- void setupFinished ()
- void setupStarted ()
- void warning (const QString&)

## Detailed Description

The QHelpEngineCore class provides the core functionality of the help system.

Before the help engine can be used, it must be initialized by calling setupData(). At the beginning of the setup process the signal setupStarted() is emitted. From this point on until the signal setupFinished() is emitted, is the help data in an undefined meaning unusable state.

The core help engine can be used to perform different tasks. By calling linksForIdentifier() the engine returns urls specifying the file locations inside the help system. The actual file data can then be retrived by calling fileData(). In contrast to all other functions in this class, linksForIdentifier() depends on the currently set custom filter. Depending on the filter, the function may return different hits.

Every help engine can contain any number of custom filters. A custom filter is defined by a name and set of filter attributes and can be added to the help engine by calling addCustomFilter(). Analogous, it is removed by calling removeCustomFilter(). customFilters() returns all defined filters.

The help engine also offers the possibility to set and read values in a persistant way comparable to ini files or Windows registry entries. For more information see setValue() or value().

This class does not offer any GUI components or functionality for indices or contents. If you need one of those use QHelpEngine instead.

When creating a custom help viewer the viewer can be configured by writing a custom collection file which could contain various keywords to be used to configure the help engine. These keywords and values and their meaning can be found in the help information for creating a custom help collection file for Assistant.

## Method Documentation

### QHelpEngineCore.__init__ (self, QString collectionFile, QObject parent = None)

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

Constructs a new core help engine with a parent. The help engine uses the information stored in the collectionFile to provide help. If the collection file does not exist yet, it'll be created.

### bool QHelpEngineCore.addCustomFilter (self, QString filterName, QStringList attributes)

Adds the new custom filter filterName. The filter attributes are specified by attributes. If the filter already exists, its attribute set is replaced. The function returns true if the operation succeeded, otherwise it returns false.

See also customFilters() and removeCustomFilter().

### bool QHelpEngineCore.autoSaveFilter (self)

### QString QHelpEngineCore.collectionFile (self)

### bool QHelpEngineCore.copyCollectionFile (self, QString fileName)

Creates the file fileName and copies all contents from the current collection file into the newly created file, and returns true if successful; otherwise returns false.

The copying process makes sure that file references to Qt Collection files (`.qch`) files are updated accordingly.

### QString QHelpEngineCore.currentFilter (self)

### QStringList QHelpEngineCore.customFilters (self)

Returns a list of custom filters.

See also addCustomFilter() and removeCustomFilter().

### QVariant QHelpEngineCore.customValue (self, QString key, QVariant defaultValue = QVariant())

Returns the value assigned to the key. If the requested key does not exist, the specified defaultValue is returned.

See also setCustomValue() and removeCustomValue().

### QString QHelpEngineCore.documentationFileName (self, QString namespaceName)

Returns the absolute file name of the Qt compressed help file (.qch) identified by the namespaceName. If there is no Qt compressed help file with the specified namespace registered, an empty string is returned.

See also namespaceName().

### QString QHelpEngineCore.error (self)

Returns a description of the last error that occurred.

### QByteArray QHelpEngineCore.fileData (self, QUrl url)

Returns the data of the file specified by url. If the file does not exist, an empty QByteArray is returned.

See also findFile().

### list-of-QUrl QHelpEngineCore.files (self, QString namespaceName, QStringList filterAttributes, QString extensionFilter = QString())

Returns a list of files contained in the Qt compressed help file namespaceName. The files can be filtered by filterAttributes as well as by their extension extensionFilter (e.g. 'html').

### QStringList QHelpEngineCore.filterAttributes (self)

Returns a list of all defined filter attributes.

### QStringList QHelpEngineCore.filterAttributes (self, QString filterName)

Returns a list of filter attributes used by the custom filter filterName.

### list-of-QStringList QHelpEngineCore.filterAttributeSets (self, QString namespaceName)

Returns a list of filter attributes for the different filter sections defined in the Qt compressed help file with the given namespace namespaceName.

### QUrl QHelpEngineCore.findFile (self, QUrl url)

Returns an invalid URL if the file url cannot be found. If the file exists, either the same url is returned or a different url if the file is located in a different namespace which is merged via a common virtual folder.

### dict-of-QString-QUrl QHelpEngineCore.linksForIdentifier (self, QString id)

Returns a map of hits found for the id. A hit contains the title of the document and the url where the keyword is located. The result depends on the current filter, meaning only the keywords registered for the current filter will be returned.

### QVariant QHelpEngineCore.metaData (QString documentationFileName, QString name)

Returns the meta data for the Qt compressed help file documentationFileName. If there is no data available for name, an invalid QVariant() is returned. The meta data is defined when creating the Qt compressed help file and cannot be modified later. Common meta data includes e.g. the author of the documentation.

### QString QHelpEngineCore.namespaceName (QString documentationFileName)

Returns the namespace name defined for the Qt compressed help file (.qch) specified by its documentationFileName. If the file is not valid, an empty string is returned.

See also documentationFileName().

### bool QHelpEngineCore.registerDocumentation (self, QString documentationFileName)

Registers the Qt compressed help file (.qch) contained in the file documentationFileName. One compressed help file, uniquely identified by its namespace can only be registered once. True is returned if the registration was successful, otherwise false.

See also unregisterDocumentation() and error().

### QStringList QHelpEngineCore.registeredDocumentations (self)

Returns a list of all registered Qt compressed help files of the current collection file. The returned names are the namespaces of the registered Qt compressed help files (.qch).

### bool QHelpEngineCore.removeCustomFilter (self, QString filterName)

Returns true if the filter filterName was removed successfully, otherwise false.

See also addCustomFilter() and customFilters().

### bool QHelpEngineCore.removeCustomValue (self, QString key)

Removes the key from the settings section in the collection file. Returns true if the value was removed successfully, otherwise false.

See also customValue() and setCustomValue().

### QHelpEngineCore.setAutoSaveFilter (self, bool save)

### QHelpEngineCore.setCollectionFile (self, QString fileName)

### QHelpEngineCore.setCurrentFilter (self, QString filterName)

### bool QHelpEngineCore.setCustomValue (self, QString key, QVariant value)

Save the value under the key. If the key already exist, the value will be overwritten. Returns true if the value was saved successfully, otherwise false.

See also customValue() and removeCustomValue().

### bool QHelpEngineCore.setupData (self)

Sets up the help engine by processing the information found in the collection file and returns true if successful; otherwise returns false.

By calling the function, the help engine is forced to initialize itself immediately. Most of the times, this function does not have to be called explicitly because getter functions which depend on a correctly set up help engine do that themselves.

Note: `qsqlite4.dll` needs to be deployed with the application as the help system uses the sqlite driver when loading help collections.

### bool QHelpEngineCore.unregisterDocumentation (self, QString namespaceName)

Unregisters the Qt compressed help file (.qch) identified by its namespaceName from the help collection. Returns true on success, otherwise false.

See also registerDocumentation() and error().

## Qt Signal Documentation

### void currentFilterChanged (const QString&)

This is the default overload of this signal.

This signal is emitted when the current filter is changed to newFilter.

### void setupFinished ()

This is the default overload of this signal.

This signal is emitted when the setup is complete.

### void setupStarted ()

This is the default overload of this signal.

This signal is emitted when setup is started.

### void warning (const QString&)

This is the default overload of this signal.

This signal is emitted when a non critical error occurs. The warning message is stored in msg.