/*!
    \page editor-type.html
    \title 10. Adding editor type
    
    At the very basic level Qt Creator is a text editor. On top of supporting editing of text files, Qt Creator also allows users
    to edit UI (Qt Designer) files, QRC (Resource) files, PRO/PRI (Project) files and EXE/DLL/SO (Binary) files.
    
    \inlineimage qtc-editor-10.png 
    
    
    In this chapter we will understand how to provide editors for custom file formats, specifically the HTML file format.
    When we are done, we will be able to load HTML files from the local file system and view/edit them.
    
    \inlineimage  qtc-fileformat-10.png
    
    \section1 10.1 Core Classes and Interfaces
    
    To support a new editor type, we need to
    \list
    \o Implement a plugin \bold {(Core::IPlugin} implementation) class that exposes an "editor factory". Chapter 2 in this
       document provides a detailed description on creating plugins by implementing the \bold {Core::IPlugin interface}.
    
    \o Implement the editor factory, \bold {Core::IEditorFactory}, interface. This interface implementation provides
       methods to help create instances of "editor" object for a specified mime-type.
    \o Implement the editor, \bold {Core::IEditor}, interface. This interface implementation provides a widget that helps
       edit a file type (for example: HTML, ODF etc). Editors must provide access to the "file" that it is currently being
       shown or edited.
    \o Implement the file, \bold{Core::IFile}, interface to help customize the loading and saving of data into disk files.
    
    \endlist
    
    In the following subsections, we will take a look at each of the above mentioned core interfaces.
    
    \section2  10.1.1 The Core::IFile interface
    
    This interface abstracts file operations from the user-interface point of view. It provides virtual methods to load and
    save files, given a file name. It also helps in understanding the mime-type of file and value of certain flags like "modified"
    and "read-only". The \bold{Core::IFile} interface is declared as follows in src/plugins/coreplugin/ifile.h
    
   \code
    namespace Core 
    {
        class IFile : public QObject
        {
            Q_OBJECT

        public:
            enum ReloadBehavior { AskForReload, ReloadAll, ReloadPermissions, ReloadNone };
            IFile(QObject *parent = 0) : QObject(parent) {}
            virtual ~IFile() {}
            virtual bool save(const QString &fileName = QString()) = 0;
            virtual QString fileName() const = 0;
            virtual QString defaultPath() const = 0;
            virtual QString suggestedFileName() const = 0;
            virtual QString mimeType() const = 0;
            virtual bool isModified() const = 0;
            virtual bool isReadOnly() const = 0;
            virtual bool isSaveAsAllowed() const = 0;
            virtual void modified(ReloadBehavior *behavior) = 0;
            virtual void checkPermissions() {}

        signals:
            void changed();
        };
    } // namespace Core   
        
    \endcode
    
    You may be wondering: "Why go for another interface called \bold {IFile} when we already have a class called \bold {QFile} that
    provides the exact same functionality?" Good point. The responses to this question are listed below
    
    \list
    \o  \bold {IFile} has to take care of loading contents of a filename into an editor \bold {(Core::IEditor} interface discussed
        next). \bold {QFile} on the other hand simply loads contents into a \bold {QByteArray}.
        
    \o  \bold {IFile} has to emit the \bold {modified()} signal when the user edits the contents of the file in the editor, but the
        actual disk-file contents have not been modified. \bold {QFile} emits the \bold {bytesWritten()} signal only when the
        disk-file contents have been modified.
        
    \o  \bold {IFile} has to handle how a modified file, on the disk, is reloaded. \bold {QFile} on the other-hand doesn't need to
        handle this.    
    \endlist

    We will learn more about implementing the \bold {Core::IFile} interface in a future section.
    
    \section2 10.1.2 The Core::IEditor interface
    Implementations of the \bold {Core::IEditor} interface provide editors for different types of files. It is declared as follows
    in src/plugins/coreplugin/editormanager/ieditor.h.
    
    \code
    namespace Core 
    {
        class IContext : public QObject
        {
            Q_OBJECT
            
        public:
            IContext(QObject *parent = 0) : QObject(parent) {}
            virtual ~IContext() {}
            virtual QList<int> context() const = 0;
            virtual QWidget *widget() = 0;
            virtual QString contextHelpId() const { return QString(); }
        };

        class IEditor : public IContext
        {
            Q_OBJECT

        public:
            IEditor(QObject *parent = 0) : IContext(parent) {}
            virtual ~IEditor() {}
            virtual bool createNew(const QString &contents = QString()) = 0;
            virtual bool open(const QString &fileName = QString()) = 0;
            virtual IFile *file() = 0;
            virtual const char *kind() const = 0;
            virtual QString displayName() const = 0;
            virtual void setDisplayName(const QString &title) = 0;
            virtual bool duplicateSupported() const = 0;
            virtual IEditor *duplicate(QWidget *parent) = 0;
            virtual QByteArray saveState() const = 0;
            virtual bool restoreState(const QByteArray &state) = 0;
            virtual int currentLine() const { return 0; }
            virtual int currentColumn() const { return 0; }
            virtual bool isTemporary() const = 0;
            virtual QToolBar *toolBar() = 0;

        signals:
            void changed();
        };
    } // namespace Core
    
    \endcode
    
    The \bold {Core::IEditor} interface primary provides access to
    \list
    \o An \underline{editor widget}\bold{ (Core::IEditor::widget()} method) that Qt Creator can use to display contents of the
       file being edited.
       
    \o The file \bold {(Core::IEditor::file() } method), which is a \bold {Core::IFile} implementation, that Qt Creator
       can use to trigger the loading and saving of data from disk-files.
       
    \o An optional custom toolbar that Qt Creator can show whenever the editor becomes active.
    
    \o The current position of the edit-cursor within the file \bold {(Core::IEditor::currentLine()} and
       \bold {Core::IEditor::currentColumn())}
       
    \o The name that needs to be displayed in the \underline{open-files combo box}.
    \endlist
    
    Take a look at the following screenshot to get a better understanding.
    
    \inlineimage qtc-ieditor-10.png 
    
    
    We will understand more about implementing the \bold {Core::IEditor} interface in a future section.
    
    
    \section2 10.1.3 The Core::IEditorFactory interface
    
    Implementations of \bold {Core::IEditorFactory} interface provide methods to create instances of Core::IEditor
    for a supported mime-type. It is declared as follows in src/plugins/coreplugin/editormanager/ieditorfactory.h.
    
    \code
    namespace Core
    {
        class IFileFactory : public QObject
        {
            Q_OBJECT
            
        public:
            IFileFactory(QObject *parent = 0) : QObject(parent) {}
            virtual ~IFileFactory() {}
            virtual QStringList mimeTypes() const = 0;
            virtual QString kind() const = 0;
            virtual Core::IFile *open(const QString &fileName) = 0;
        };
        
        class IEditorFactory : public Core::IFileFactory
        {
            Q_OBJECT
            
        public:
            IEditorFactory(QObject *parent = 0) : IFileFactory(parent) {}
            virtual ~IEditorFactory() {}
            virtual IEditor *createEditor(QWidget *parent) = 0;
        };
    } // namespace Core
    
    \endcode
    
    The \bold {IEditorFactory::mimeType()} method should be implemented to return the mime-type supported by the
    editor for which the factory is implemented. The \bold {IEditorFactory::createEditor()} method should be
    implemented to actually create a concrete editor and return the same.
    
    \section2 10.1.4 The Core::MimeDatabase class
    
    The \bold {Core::MimeDatabase} class keeps track of all the mime-types supported by Qt Creator. It also helps figure out
    the mime-type of a given file. Take the following code for example:
    
    \code
    #include <coreplugin/mimedatabase.h>
    Core::ICore* core = Core::ICore::instance();
    Core::MimeDatabase* mdb = core->mimeDatabase();
    Core::MimeType type1 = mdb->findByFile( QFileInfo("C:/Temp/sample.html") );
    
    qDebug("File Type for sample.html = %s", qPrintable(type1.type()));
    Core::MimeType type2 = mdb->findByFile( QFileInfo("C:/Temp/TextEdit/Main.cpp") );
    
    qDebug("File Type for Main.cpp = %s", qPrintable(type2.type()));
    Core::MimeType type3 = mdb->findByFile( QFileInfo("C:/Temp/TextEdit/TextEdit.pro") );
    
    qDebug("File Type for TextEdit.pro = %s", qPrintable(type3.type()));
    \endcode
    
    When the above code is compiled and executed, we get the following as output.
    \code
    File Type for sample.html = text/plain
    File Type for Main.cpp = text/x-c++src
    File Type for TextEdit.pro = text/plain
    \endcode
    
    The \bold { Core::MimeDatabase } uses filename suffix, glob patterns and "magic" matchers to figure out the mime-type of
    a given filename. At this point however, lets not dig into how the mime-database manages to figure out the mime-type
    from a filename; it is enough if we know that mime-type discovery is possible.
    
    The \bold Core::IEditorFactory interface, as described in the previous section, provides an editor \bold{(Core::IEditor}
    implementation) for a specific mime-type. The following points help us understand how Qt Creator manages to pick the
    appropriate \bold {Core::IEditorFactory} for a given filename.
    
    \list 1
    \o User selects File -> Open and chooses a file to open
    
    \o Qt Creator uses \bold {Core::MimeDatabase} to figure out the mime-type of the selected file
    
    \o Qt Creator runs through all \bold {Core::IEditorFactory} implementations and picks the editor-factory that
       supports the mime-type evaluated in step 2
    
    \o Qt Creator asks the selected editor factory to create an editor (Core::IEditor implementation)
    
    \o The widget returned by \bold {Core::IEditor::widget()} is then shown in the workspace area of the mainwindow
    
    \o The \bold {Core::IEditor::open()} method is then called to open the file selected in step 1.
    
    \endlist
    
    \section2 10.1.5 Adding a new mime-type
    
    If we wanted to support a new editor type, then we need to register the mime-type supported by the new editor with
    the \bold {Core::MimeDatabase}. Several mechanisms can be used to register a new mime-type. In this chapter we will
    learn the simplest way to register a new mime-type from an XML file.
    Suppose that we wanted to register the \bold {text/html} mime-type and associate it with \bold {*.html} filenames. We create an XML
    file as and save it as \bold {text-html-mimetype.xml}.
    
    \code
    <?xml version="1.0" encoding="UTF-8"?>
    <mime-info xmlns='http://www.freedesktop.org/standards/shared-mime-info'>
    <mime-type type="text/html">
    <sub-class-of type="text/plain"/>
    <comment>HTML File</comment>
    <glob pattern="*.html"/>
    </mime-type>
    </mime-info>
    \endcode
    
    We then register the mime-type described in the XML file (above) using the
    \bold {Core::MimeDatabase::addMimeTypes()} method. Take a look at the code snippet below
    
    \code
    Core::ICore* core = Core::ICore::instance();
    Core::MimeDatabase* mdb = core->mimeDatabase();
    QString errMsg;
    bool success = mdb->addMimeTypes("text-html-mimetype.xml", errMsg);
    \endcode
    
    Once registered, Qt Creator will begin to map all *.html filenames to text/plain mime-type.
    
    \section1 10.2 Providing a HTML Editor in Qt Creator
    
    Let's implement a plugin for Qt Creator that provides support for viewing and editing HTML files. The following
    screenshots show the expected results.
    
    The user select a HTML file to open using the standard File -> Open menuitem.
    
    \inlineimage qtc-menuitem-10.png
    
    
    Upon selecting a HTML file, Qt Creator will show a custom editor as shown below.
    
    
    \inlineimage qtc-customeditor-10.png
    
    
    Notice that the editor has two tabs called "Preview" and "Source" at the bottom edge.
    
    
    \inlineimage qtc-editortabs-10.png
    
    
    Clicking on the "Source" tab shows the HTML code in a \bold { QPlainTextEdit}  widget.
    
    \inlineimage qtc-plaintextedit-10.png
    
    
    Users can edit the HTML in this tab, and when he moves back to the "preview" tab the changes are reflected. Users can
    continue to make use of File -> Save menu item to save changes to the HTML file.
    
    For achieving the above we implement the following classes
    
    \table
    \header
    \o Class
    \o Interface\\Baseclass
    \o Description
     
      \row
      \o \c{HtmlEditorWidget}
      \o \bold {QTabWidget}
      \o Provides a tab widget with two tabs, one for showing the
         HTML preview and other for showing the HTML code.
         
      \row
      \o \c{HtmlFile}
      \o \bold {Core::IFile}
      \o Implements the \bold {IFile} interface for the file shown in
         \bold {HtmlEditorWidget}.
      \row
      \o \c {HtmlEditor}
      \o \bold {Core::IEditor}
      \o Implements the \bold{IEditor} interface for managing the
         \bold{HtmlEditorWidget} and hooking up an \bold{IFile} with it.
      \row
      \o \c {HtmlEditorFactory}
      \o \bold {Core::IEditorFactory}
      \o Implements the \bold{IEditorFactory} interface for creating
         instances of \bold{IEditor} for the "text/html" mime-type.
      
      \row
      \o \c {HtmlEditorPlugin}
      \o \bold {Core::IPlugin }
      \o Implements the \bold{IPlugin} interface for hooking all of the
         above into Qt Creator.   
    \endtable    
    
    For every html file there is an instance each of \bold{HtmlEditorWidget},\bold{HtmlFile} and \bold{HtmlEditor} handling the
    loading, editing and saving functionality. In our implementation we provide mechanisms to help establish association
    between instances of the above classes that handle the same file.
    
    \section2 10.2.1 Implementing the HTML Editor Widget
    By default, Qt Creator uses a plain-text editor widget to display the contents of the HTML file being edited. We would
    like to offer a tabbed widget as editor. One of the tabs shows the HTML preview, the other shows the HTML code. The
    class \bold {HtmlEditorWidget} is our editor; and it is declared as follows.
    
    \code
    struct HtmlEditorWidgetData;
    class HtmlEditorWidget : public QTabWidget
    {
        Q_OBJECT

    public:
        HtmlEditorWidget(QWidget* parent = 0);
        ~HtmlEditorWidget();
        void setContent(const QByteArray& ba, const QString& path=QString());
        QByteArray content() const;
        QString title() const;

    protected slots:
        void slotCurrentTabChanged(int tab);
        void slotContentModified();

    signals:
        void contentModified();
        void titleChanged(const QString&);

    private:
        HtmlEditorWidgetData* d;
    };
    \endcode
    
    The constructor basically creates two different views from \bold{QWebView} and \bold {QPlainTextEdit} and adds them as tabs
    at the bottom position of the tab widget. We will learn about the signal-slot connections later.
        
    \code
    HtmlEditorWidget::HtmlEditorWidget(QWidget* parent):QTabWidget(parent)
    {
        d = new HtmlEditorWidgetData;
        d->webView = new QWebView;
        d->textEdit = new QPlainTextEdit;

        addTab(d->webView, "Preview");
        addTab(d->textEdit, "Source");

        setTabPosition(QTabWidget::South);
        setTabShape(QTabWidget::Triangular);

        d->textEdit->setFont( QFont("Courier", 12) );
        connect(this, SIGNAL(currentChanged(int)),this, SLOT(slotCurrentTabChanged(int)));
        connect(d->textEdit, SIGNAL(textChanged()),this, SLOT(slotContentModified()));
        connect(d->webView, SIGNAL(titleChanged(QString)),this, SIGNAL(titleChanged(QString)));
        d->modified = false;
    }
    \endcode
    
    
    The destructor does nothing other than deleting the private \bold{"d"} object.
    
    \code
    HtmlEditorWidget::~HtmlEditorWidget()
    {
        delete d;
    }
    \endcode
    
    The setContent method simply sets the contents of html file to \bold{webView} and \bold {textEdit}.
    
    \code
    void HtmlEditorWidget::setContent(const QByteArray& ba, const QString& path)
    {
        if(path.isEmpty())
            d->webView->setHtml(ba);
        else
            d->webView->setHtml(ba, "file:///" + path);
            d->textEdit->setPlainText(ba);
            d->modified = false;
            d->path = path;
    }
    \endcode
    
    The \bold {content} method returns the contents of the \bold {textEdit}.
    
    \code
    QByteArray HtmlEditorWidget::content() const
    {
        QString htmlText = d->textEdit->toPlainText();
        return htmlText.toAscii();
    }
    \endcode
    
    The \bold {title()} method returns the title from the webView. The string returned from this method will be used in the
    open-file combo box.
    
    \inlineimage qtc-title-10.png
    
    \code
    QString HtmlEditorWidget::title() const
    {
        return d->webView->title();
    }
    \endcode
    
    The following connection made in the constructor of \bold {HtmlEditorWidget} makes sure that when the user moves from
    "source" to "preview" tab, the HTML content viewed in the preview tab is updated.
    
    \code
    connect(this, SIGNAL(currentChanged(int)),this, SLOT(slotCurrentTabChanged(int)));
    
    void HtmlEditorWidget::slotCurrentTabChanged(int tab)
    {
        if(tab == 0 && d->modified)
        setContent( content(), d->path );
    }
    \endcode
    
    
    Following connection makes sure that \bold {setContentModified()} slot is called whenever user edits the html source.
    The slot \bold {setContentModified()} simply sets modified to true and emits the signal "contentModified" We will
    know the usability of this signal later in the section while understanding \bold {HtmlFile} class.
    
    \code
    connect(d->textEdit, SIGNAL(textChanged()), this, SLOT(slotContentModified()));

    void HtmlEditorWidget::slotContentModified()
    {
        d->modified = true;
        emit contentModified();
    }
    \endcode
    
    Following connection simply emits \bold {titleChanged()} signal on title change of \bold {webView}. We will know more about
    this signal later.
    
    \code
    connect(d->webView, SIGNAL(titleChanged(QString)),this, SIGNAL(titleChanged(QString)));
    \endcode
    
    \section2 10.2.2 Implementing the Core::IFile interface
    
    We implement the \bold {Core::IFile} interface in the \bold {HtmlFile} class. Apart from implementing the pure virtual
    functions from \bold {IFile} (introduced in section 5.1.1); the \bold {HtmlFile} class has methods to get/set the modified flag
    which indicates the modification status of the file contents.
    
    \code
    struct HtmlFileData;
    class HtmlFile : public Core::IFile
    {
        Q_OBJECT
        
    public:
        HtmlFile(HtmlEditor* editor, HtmlEditorWidget* editorWidget);
        ~HtmlFile();
        void setModified(bool val=true);
        // Declare all the virtual functions from IFile here..
    protected slots:
        void modified() { setModified(true); }
    private:
        HtmlFileData* d;
    };
    
    struct HtmlFileData
    {
        HtmlFileData(): mimeType(HtmlEditorConstants::C_HTMLEDITOR_MIMETYPE),editorWidget(0), editor(0), modified(false) { }
        const QString mimeType;
        HtmlEditorWidget* editorWidget;
        HtmlEditor* editor;
        QString fileName;
        bool modified;
    };
    
    \endcode
    
    In the constructor implementation is simple. It establishes the association between an instance of \bold {HtmlFile} with the
    corresponding \bold {HtmlEditor} and the \bold {HtmlEditorWidget} instances.
    
    \code
    
    HtmlFile::HtmlFile(HtmlEditor* editor, HtmlEditorWidget* editorWidget): Core::IFile(editor)
    {
        d = new HtmlFileData;
        d->editor = editor;
        d->editorWidget = editorWidget;
    }
    \endcode
    
    The destructor does nothing other than deleting the private \bold {"d"} object.
    
    \code
    HtmlFile::~HtmlFile()
    {
        delete d;
    }
    \endcode
    
    The \bold {setModified()} function stores the modification flag and emits the \bold {changed()} signal.
    
    \code
    
    void HtmlFile::setModified(bool val)
    {
        if(d->modified == val)
            return;
        d->modified = val;
        emit changed();
    }
    
    bool HtmlFile::isModified() const
    {
        return d->modified;
    }
    
    \endcode
    
    Returns the mime-type handled by this class.
    
    \code
    
    QString HtmlFile::mimeType() const
    {
        return d->mimeType;
    }
    \endcode
    
    The save method is called when file->save action (Ctrl+s) is triggered. This saves the contents of \bold {HtmlEditorWidget}
    (the contents shown by plain text editor) in the file as shown below. The modified flag is set to false after the contents
    are saved into the file.
    
    
    \code
    bool HtmlFile::save(const QString &fileName)
    {
    QFile file(fileName);
        if(file.open(QFile::WriteOnly))
        {
            d->fileName = fileName;
            QByteArray content = d->editorWidget->content();
            file.write(content);
            setModified(false);
            return true;
        }
        return false;
    }
    \endcode
    
    The \bold {open} method is called when file->open action is triggered. This opens the file and calls the setContent()
    method of \bold {HtmlEditorWidget}. The display name is set to the title of the html file.
    
    \code
    bool HtmlFile::open(const QString &fileName)
    {
        QFile file(fileName);
        if(file.open(QFile::ReadOnly))
        {
            d->fileName = fileName;
            QString path = QFileInfo(fileName).absolutePath();
            d->editorWidget->setContent(file.readAll(), path);
            d->editor->setDisplayName(d->editorWidget->title());
            return true;
        }
        return false;
    }
    
    \endcode
    
    The following methods implement the "filename" property.
    
    \code
    void HtmlFile::setFilename(const QString& filename)
    {
        d->fileName = filename;
    }
    
    QString HtmlFile::fileName() const
    {
        return d->fileName;
    }
    \endcode
    
    We implement the \bold {defaultPath()},\bold { suggestedFileName()},\bold {fileFilter()} and fileExtension()
    methods to do nothing at the moment.
    
    \code
    QString HtmlFile::defaultPath() const
    {
        return QString();
    }

    QString HtmlFile::suggestedFileName() const
    {
        return QString();
    }

    QString HtmlFile::fileFilter() const
    {
        return QString();
    }

    QString HtmlFile::fileExtension() const
    {
        return QString();
    }
    \endcode
    
    Since we want to edit the file, we return false in \bold {isReadOnly()} method and true from \bold {isSaveAsAllowed()}
    method.
    
    \code
    bool HtmlFile::isReadOnly() const
    {
        return false;
    }

    bool HtmlFile::isSaveAsAllowed() const
    {
        return true;
    }
    \endcode
    
    The \bold {modified()} function has to be implemented to customize the way in which the Html editor should handle
    reloading of a modified file. This function is called if a html-file was modified outside of Qt Creator, while it is being
    edited. For now we do nothing.
    
    \code
    void HtmlFile::modified(ReloadBehavior* behavior)
    {
        Q_UNUSED(behavior);
    }
    \endcode
    
    \section2 10.2.3 Implementing the Core::IEditor interface
    
    The \bold {HtmlEditor} class implements \bold {IEditor} interface to provide an editor widget for html (*.html) files and
    associate a \bold {HtmlFile} instance with it.
    
    
    \code
    #include <coreplugin/editormanager/ieditor.h>
    struct HtmlEditorData;
    class HtmlEditor : public Core::IEditor
    {
        Q_OBJECT

    public:
        HtmlEditor(HtmlEditorWidget* editorWidget);
        ~HtmlEditor();

        bool createNew(const QString& contents = QString());
        QString displayName() const;

        IEditor* duplicate(QWidget* parent);
        bool duplicateSupported() const;
        Core::IFile* file();


        bool isTemporary() const;
        const char* kind() const;
        bool open(const QString& fileName = QString()) ;
        bool restoreState(const QByteArray& state);
        QByteArray saveState() const;
        void setDisplayName(const QString &title);
        QToolBar* toolBar();

        // From Core::IContext
        QWidget* widget();
        QList<int> context() const;

    protected slots:
        void slotTitleChanged(const QString& title)
        { setDisplayName(title); }

    private:
        HtmlEditorData* d;
    };
    
    \endcode    
    
    \bold {HtmlEditorData} holds object of \bold {HtmlEditorWidget} and \bold {HtmlFile}. displayName is used as visual
    description of the document.
    
    \code
    struct HtmlEditorData
    {
        HtmlEditorData() : editorWidget(0), file(0) { }
        HtmlEditorWidget* editorWidget;
        QString displayName;
        HtmlFile* file;
        QList<int> context;
    };
    \endcode
    
    The constructor creates initializes itself on an \bold {HtmlEditorWidget}. It creates an \bold {HtmlFile} instance so that its
    association with \bold {HtmlEditor} and widget is set.
    
    \code
    HtmlEditor::HtmlEditor(HtmlEditorWidget* editorWidget): Core::IEditor(editorWidget)
    {
        d = new HtmlEditorData;
        d->editorWidget = editorWidget;
        d->file = new HtmlFile(this, editorWidget);
        Core::UniqueIDManager* uidm = Core::UniqueIDManager::instance();
        d->context << uidm->uniqueIdentifier(HtmlEditorConstants::C_HTMLEDITOR);

        connect(d->editorWidget, SIGNAL(contentModified()),d->file,SLOT(modified()));
        connect(d->editorWidget, SIGNAL(titleChanged(QString)),this,SLOT(slotTitleChanged(QString)));
        connect(d->editorWidget, SIGNAL(contentModified()),this,SIGNAL(changed()));
    }
    \endcode
    
    The destructor does nothing other than deleting the private \bold {'d'} object.
    
    \code
    HtmlEditor::~HtmlEditor()
    {
        delete d;
    }
    \endcode
    
    The following functions are self explanatory.
    
    \code
    QWidget* HtmlEditor::widget()
    {
        return d->editorWidget;
    }

    QList<int> HtmlEditor::context() const
    {
        return d->context;
    }

    Core::IFile* HtmlEditor::file()
    {
        return d->file;
    }
    \endcode    
    
    The \bold {createNew()} method is implemented to reset the contents of the \bold {HtmlEditorWidget} and \bold {HtmlFile}
    objects. For now we ignore the contents parameter.
    
    \code
    bool HtmlEditor::createNew(const QString& contents)
    {
        Q_UNUSED(contents);
        d->editorWidget->setContent(QByteArray());
        d->file->setFilename(QString());
        return true;
    }
    \endcode
    
    The \bold {open()} method causes the \bold {HtmlFile} to open a given filename. It is assumed that the filename is a HTML
    filename.
    
    \code
    bool HtmlEditor::open(const QString &fileName)
    {
        return d->file->open(fileName);
    }
    
    \endcode
    
    The following method returns the \bold {'kind'} of the editor.
    
    \code
    namespace HtmlEditorConstants
    {
        const char* const C_HTMLEDITOR_MIMETYPE = "text/html";
        const char* const C_HTMLEDITOR = "HTML Editor";
    }

    const char* HtmlEditor::kind() const
    {
        return HtmlEditorConstants::C_HTMLEDITOR;
    }
        
    \endcode
    
    The string returned by \bold {displayName} is used in the open-file combobox. The following methods help set and fetch the
    display name.
    
    \code
    QString HtmlEditor::displayName() const
    {
        return d->displayName;
    }

    void HtmlEditor::setDisplayName(const QString& title)
    {
        if(d->displayName == title)
            return;
        d->displayName = title;
        emit changed();
    }
    \endcode
    
    We implement the following methods to do nothing in this example.
    
    \code
    bool HtmlEditor::duplicateSupported() const
    {
        return false;
    }
    
    Core::IEditor* HtmlEditor::duplicate(QWidget* parent)
    {
        Q_UNUSED(parent);
        return 0;
    }
    
    QByteArray HtmlEditor::saveState() const
    {
        return QByteArray();
    }

    bool HtmlEditor::restoreState(const QByteArray& state)
    {
        Q_UNUSED(state);
        return false;
    }

    QToolBar* HtmlEditor::toolBar()
    {
        return 0;
    }

    bool HtmlEditor::isTemporary() const
    {
        return false;
    }
    \endcode
    
    \section2 10.2.4 Implementing the Core::IEditorFactory interface
    
    The \bold HtmlEditorFactory class implements the \bold Core::IEditorFactory interface; and is declared as follows.
    
    \code
    #include <coreplugin/editormanager/ieditorfactory.h>

    struct HtmlEditorFactoryData;

    class HtmlEditorFactory : public Core::IEditorFactory
    {
        Q_OBJECT

    public:
        HtmlEditorFactory(HtmlEditorPlugin* owner);
        ~HtmlEditorFactory();
        QStringList mimeTypes() const;
        QString kind() const;
        Core::IEditor* createEditor(QWidget* parent);
        Core::IFile* open(const QString &fileName);

    private:
        HtmlEditorFactoryData* d;
    };
    \endcode
        
    \bold {HtmlEditorFactoryData} structure holds the private data of the \bold {HtmlEditorFactory} class. Notice that the
    constructor initializes the mime-types to \bold {HtmlEditorConstants::C_HTMLEDITOR_MYMETYPE}. It also
    initializes the \bold {kind} of the editor. This kind should be same as \bold{kind} of \bold {HtmlEditor}.  
    
    \code
    namespace HtmlEditorConstants
    {
        const char* const C_HTMLEDITOR_MIMETYPE = "text/html";
        const char* const C_HTMLEDITOR = "HTML Editor";
    }
    
    struct HtmlEditorFactoryData
    {
        HtmlEditorFactoryData(): kind(HtmlEditorConstants::C_HTMLEDITOR)
        {
            mimeTypes << QString(HtmlEditorConstants::C_HTMLEDITOR_MIMETYPE);
        }

        QString kind;
        QStringList mimeTypes;
    };
    \endcode
    
    The following methods are self-explanatory.
    
    \code
    HtmlEditorFactory::HtmlEditorFactory(HtmlEditorPlugin* owner):Core::IEditorFactory(owner)
    {
        d = new HtmlEditorFactoryData;
    }

    HtmlEditorFactory::~HtmlEditorFactory()
    {
        delete d;
    }

    QStringList HtmlEditorFactory::mimeTypes() const
    {
        return d->mimeTypes;
    }

    QString HtmlEditorFactory::kind() const
    {
        return d->kind;
    }
    \endcode
    
    
    The \bold {open()} method should be implemented to return the IFile that is currently handling the given filename. If there
    are none, then a new editor for the file is created and it's IFile is returned. To fully understand this process take a
    look at the implementation of \bold {Core::EditorManager::openEditor()} method.
    
    \code
    Core::IFile* HtmlEditorFactory::open(const QString& fileName)
    {
        Core::EditorManager* em = Core::EditorManager::instance();
        Core::IEditor* iface = em->openEditor(fileName, d->kind);
        return iface ? iface->file() : 0;
    }
    \endcode    

    This method creates and returns an instance of the \bold {HtmlEditor} class.

    \code
    Core::IEditor* HtmlEditorFactory::createEditor(QWidget* parent)
    {
        HtmlEditorWidget* editorWidget = new HtmlEditorWidget(parent);
        return new HtmlEditor(editorWidget);
    }
    \endcode

    \section2 10.2.5 Implementing the plugin
    
    We implement the \bold {HtmlEditorPlugin} plugin class using the same means described in Chapter 2. The only change is
    the \bold {initialize()} method implementation.
    
    \code
    bool HtmlEditorPlugin::initialize(const QStringList &arguments, QString* errMsg)
    {
        Q_UNUSED(arguments);
        Core::ICore* core = Core::ICore::instance();
        Core::MimeDatabase* mdb = core->mimeDatabase();
        if(!mdb->addMimeTypes("text-html-mimetype.xml", errMsg))
        return false;
        addAutoReleasedObject(new HtmlEditorFactory(this));
        return true;
    }
    \endcode
    
    When the plugin is compiled and Qt Creator is (re)started; we will be able to load HTML files using the newly
    implemented editor plugin.
    
    \inlineimage qtc-htmleditor-10.png
        
*/