qt-everywhere-src-5.15.1/qtdoc/doc/src/getting-started/controls-texteditor.qdoc

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/*!
\page qtquickcontrols-texteditor.html
\title Qt Quick Text Editor Guide
\nextpage Qt Quick Text Editor Guide - UI
\brief Walkthrough of an application built with Qt Quick Controls.

\section1 Application Design

The \e{Text Editor} example is a simple example of creating an application
with Qt. Specifically, the example uses QML to set up the user interface,
C++ to implement the file operations, and the Qt tools to manage the project
files and build environment.

We will use Qt Quick Designer to add QML controls onto our application and set
up the controls and resources. We will also implement the logic and connect
the user interface to a C++ backend that will handle the saving and loading of
text files.

This guide assumes that you have downloaded Qt and are able to install, open,
and run the basic examples found in Qt Creator's \uicontrol{Welcome Mode}. If
not, here are the pages that will help you:

\list
\li \l{Getting Started with Qt}
\endlist

The guide attempts to be self-contained but will refer to topics in the Qt
reference documentation. Feel free to click on the links, but it is not
necessary to leave the guide to find the information necessary to develop
the application.

The files are part of the Qt package and are available when searched for
\uicontrol{Qt Quick Text Editor} in Qt Creator's \uicontrol{Welcome mode}.
All files used in the application are listed for viewing in the
\l{Qt Quick Controls 1 - Text Editor Example} page.

\section1 Setting Up the Environment and Project

We can start by creating the project in Qt Creator. Our application has the
name \e{Text Editor} and it is a Qt Quick Application. Qt Creator has a wizard
that can create the project for you.

\list 1
    \li Select \uicontrol File > \uicontrol {New File or Project} > \uicontrol Applications >
        \uicontrol {Qt Quick Application} > \uicontrol Choose.
    \li In the \uicontrol Name field, enter \uicontrol TextEditor and select \uicontrol Next.
    \li In the \uicontrol {Qt Quick component set} field, select
        \uicontrol{Qt Quick Controls 1.2} > \uicontrol Next.
    \li In the \uicontrol{Kit Selection} page, select \uicontrol Next.
    \li In the \uicontrol{Summary} page, select \uicontrol Finish.
\endlist

The wizard creates the project and you can run it by clicking on the run button,
\inlineimage{qtcreator/qtcreator-run.png}
. The application is an empty shell but it contains the basic window and layout
on which we can build. Make sure that you can run the basic application and if
not, make sure that your build environment and Qt version are configured.

\section2 Project Files

The wizard creates the project files used to build the project. To view them,
select the \uicontrol{Edit mode}. The following project files are modified
later in the guide:

\list
\li \uicontrol TextEdit.pro - the project file used to create the build files.
    Also sets the paths that are visible to the project.
\li \uicontrol Sources - contains the C++ implementation files (\c{.cpp}).
\li \uicontrol Resources - contains a resource file that configures the application
    assets and how the application resolves the location of the assets. The QML
    file is also found here.
\li \uicontrol Headers - contains the C++ header files (\c{.h}). The default
    project does not have any header files, therefore this is not visible.
\endlist

\section2 Resource Files

The text editor uses several icons to represent various actions. The icons are
in the \e images directory which is directly under the \e TextEditor project
directory. The images as well as the project files are also listed in the
reference documentation on the \l{Qt Quick Controls 1 - Text Editor Example} page.

We first need to register the image files into the project's resource file,
\e qml.qrc. The resource files compact the images into the binary packages.
The resource files provide a streamlined directory structure, which is
cross-platform. It is beneficial especially on mobile platforms, where each
platform manages the application resources differently.

\list
\li To register the image files, in the \uicontrol Edit mode, right-click the
    \e qml.qrc file and select \uicontrol{Open in Editor}.
\li Click the \uicontrol Add button and select \uicontrol{Add Files}.
\li In the file manager, select the files to be added. You can select
    all the images in the \e images directory at once.
\endlist

You can refer to the images from QML by referring directly to the filename.
For example, \c{images/editcopy.png} is the name of the \e editcopy.png file.
We will use these images later in the guide.

Qt Creator then packages the images alongside your application in a single
binary. For more information about resource files, see the
\l{Managing Resource Files with the Qt Resource System} and the
\l{The Qt Resource System} pages.

\section1 Example Files

The accompanying examples files are listed in the following page:
\list
\li \l{Qt Quick Controls 1 - Text Editor Example}
\endlist

*/

/*!
\page qtquickcontrols-texteditor-ui.html
\title Qt Quick Text Editor Guide - UI
\previouspage Qt Quick Text Editor Guide
\nextpage Qt Quick Text Editor Guide - Logic
\brief Walkthrough of an application built with Qt Quick Controls.

Qt Quick Designer is integrated into Qt Creator, allowing you to switch between
\uicontrol Edit and \uicontrol Design modes. To start using Qt Quick Designer,
select the QML file, \e main.qml, and click the \uicontrol Design button on the
left panel.

It is important to familiarize yourself with the windows in Qt Quick Designer.
This guide uses Qt Quick Designer to add and set up the layout.

\image controlstexteditor/controlstexteditor_designer.png

\note The default kit for the project must be a Desktop kit, as Qt Quick
Designer cannot yet emulate the styles for a mobile platform.

To start, we can customize the default application created by the wizard. You
can delete the \uicontrol MainForm.ui.qml file and remove the following lines
from the \uicontrol main.qml file:
\qml
    MainForm {
        anchors.fill: parent
        button1.onClicked: messageDialog.show(qsTr("Button 1 pressed"))
        button2.onClicked: messageDialog.show(qsTr("Button 2 pressed"))
        button3.onClicked: messageDialog.show(qsTr("Button 3 pressed"))
    }

    MessageDialog {
        id: messageDialog
        title: qsTr("May I have your attention, please?")

        function show(caption) {
            messageDialog.text = caption;
            messageDialog.open();
        }
    }
\endqml

The default dimension of the \c ApplicationWindow may remain but
you can change the \c title property to a relevant name such as:

\qml
title: qsTr("Text Editor Example")
\endqml

\note The example uses the \c qsTr() function to facilitate translation. For
more information, visit the \l{Internationalization and Localization with Qt Quick}
page.

Make sure that \uicontrol Resources tab contains the images from the
\l{Resource Files}{previous page}.

\section1 Defining the Application Layout

Our application has a simple layout, which consists of a \e{tool bar} and a
\e{text area}. The tool bar contains the \e{tool buttons} that the user can
choose to manipulate the text area contents. At the top, there are menus, which
perform actions such as saving and opening files to edit.

\section1 Adding the Controls

To add a control, you have the following options:

\list 1
\li Drag and drop a control from the \uicontrol{QML Types} window onto the
    main design window. This allows you to drop the control onto a specific
    area of the layout.
\li Drag and drop a control from the \uicontrol{QML Types} window onto the
    \uicontrol Navigator window. This allows you to set the layout hierarchy.
\endlist

Both these actions give you several options to quickly set up the layout.
Whichever method you use, designer gives you a more direct way of setting up a
particular aspect of the control, such as the scene hierarchy or the position
of the control.

Afterwards, the various properties are set from within the
\uicontrol Properties window on the right side of Qt Creator window.

\section1 Setting Up the Tool Bar

First, we need to add the tool bar. We can do this in the
\e Edit mode and typing in a \l ToolBar type inside the ApplicationWindow type.
This configures the ApplicationWindow object as the tool bar's parent.

\badcode
ApplicationWindow {

    ToolBar {
        id: toolBar
    }
}
\endcode

In the \uicontrol Design mode, the \uicontrol Properties window lets us set the
tool bar \uicontrol id to \c toolbar.

In the \uicontrol Navigator window, make sure that the tool bar is a child of the
application window. To make the tool bar a child of the window, simply drag the tool bar
underneath the application window.

Within the tool bar, we need a \e{row} layout. Drag the \e{row} layout into the
\uicontrol Navigator window and set it to be a child of the tool bar.

Similarly, set these layout properties:
\list
\li \uicontrol id - set it to \c rowToolbar
\li click on the fill area button to set the fill area to \e parent. The parent should
    be the tool bar.
\endlist

\image controlstexteditor/controlstexteditor_rowproperties.png

\section2 Adding the Tool Buttons

\e{Tool buttons} exist within a tool bar and specifically use the layout within the tool bar.
\e{Text Editor} has six tool buttons, each performing a specific action, such as
\e copy and \e paste to and from the clipboard.

The steps for adding the six tool buttons are mainly the same:
\list
\li Drag and drop the \uicontrol{Tool Button} type as a child of the row layout.
\li The \uicontrol id should be set to a unique name that is related to the
    tool button's action.
    The parent is set to \uicontrol parent and set the \uicontrol margin to \c 0.

    \image controlstexteditor/controlstexteditor_newproperties.png
\li The first tool button, for example \uicontrol New, should have the left anchor
    set to the row layout.
\li The subsequent tool buttons should have the left anchor set to their previous
    sibling and the \uicontrol margin to \c 0. These settings makes sure that
    the tool buttons are adjacent to each other.
\li Set the \uicontrol iconName and \uicontrol iconSource properties in the
    \uicontrol ToolButton tab. The \uicontrol iconName should be set to a unique name
    identifying the icon name while the \uicontrol iconSource property should
    be set to the name of the icon for the tool button.
\endlist

For example, the \uicontrol New tool button has \c newIcon set as its \uicontrol iconName and
\c images/filenew.png set to the \uicontrol iconSource property. The icons are also viewable in the
\uicontrol Resources inside the \uicontrol Library window.

Similarly for the \uicontrol Open tool button, the margins are set to \c 0
but the left anchor is set to the \uicontrol New tool button.

\image controlstexteditor/controlstexteditor_openproperties.png

\note Dragging and dropping the images from the \uicontrol Resources onto
the scene adds the image into the scene as an \l Image object, instead
of setting the iconSource property.

\section1 Setting Up the Text Area

Next, add a \uicontrol{Text Area} onto the scene as a child of the application
window and a sibling of \c toolBar. The tool bar should be above the text area.
Similarly, set the following text area properties:

\list
\li \uicontrol id - set it to \c textArea
\li set the left, right, and bottom margin to the parent and the top margin
    to \c toolBar.bottom and set the margins to \c 0.
    \qml
    anchors.top: toolBar.bottom
    anchors.right: parent.right
    anchors.bottom: parent.bottom
    anchors.left: parent.left
    \endqml
\endlist

Verify that you have the parent, margins, and icons set up. Your
\uicontrol Navigator should look similar to:

\image controlstexteditor/controlstexteditor_navigator.png

Running the application should result in this layout:
\image controlstexteditor/controlstexteditor_main.png

We are now ready to go back to \uicontrol Edit and set the handlers and
actions. A QML \e handler is called when the buttons are pressed and
triggers the necessary action associated with the tool buttons. An
\e action collects various QML logic into one code block so it may be
reused by several handlers. For more information, visit the \l Action
QML type and \l{Signal and Handler Event System}.

\section1 Example Files

The accompanying examples files are found in the following page:
\list
\li \l{Qt Quick Controls 1 - Text Editor Example}
\endlist

*/

/*!
\page qtquickcontrols-texteditor-logic.html
\title Qt Quick Text Editor Guide - Logic
\previouspage Qt Quick Text Editor Guide - UI
\nextpage qtquickcontrols-texteditor-action.html
\brief Walkthrough of an application built with Qt Quick Controls.

This part of the guide is about adding logic and backend to the
text editor example. At this stage, the user interface is
set up from the \l{Qt Quick Text Editor Guide - Logic}{previous} stage.

\section1 Implementing the Logic and C++ Backend

\e{Text Editor} has a QML user interface and a C++ backend to
implement the document handling. To connect QML and C++,
we need to create \e actions associated to the tool buttons,
which will call the document handling logic in C++.

\section1 Creating the Document Handler

The document handler implements the file loading and file
saving logic with Qt's C++ APIs. First, we need to create the
header file and the implementation file in Qt Creator's
\uicontrol Edit mode.

\list
\li Right-click a folder, and select \uicontrol{Add New}.
\li Follow the wizard and create a new \uicontrol{C++ Class}.
\li Create a class called \uicontrol DocumentHandler and select
\uicontrol{Inherits QObject} in the \uicontrol{Type information}.
\li You can use default values for the rest and finish the wizard.
\endlist

The wizard creates a \uicontrol DocumentHandler class in two files,
\e documenthandler.h and \e documenthandler.cpp.

There are two functionalities we can expose to QML, the file loading and
saving. We can do this by creating \e properties and binding them to C++
functions through the \l{The Property System}{Qt Property System}.

In the \e documenthandler.h header file, add the following functions with their
respective access modifier:

\code
    Q_PROPERTY(QUrl fileUrl READ fileUrl WRITE setFileUrl NOTIFY fileUrlChanged)
    Q_PROPERTY(QString text READ text WRITE setText NOTIFY textChanged)
    Q_PROPERTY(QString documentTitle READ documentTitle WRITE setDocumentTitle NOTIFY documentTitleChanged)

public:
    QUrl fileUrl() const;
    QString text() const;
    QString documentTitle() const;

public slots:
    void setFileUrl(const QUrl &arg);
    void setText(const QString &arg);
    void setDocumentTitle(QString arg);

signals:
    void fileUrlChanged();
    void textChanged();
    void documentTitleChanged();
\endcode

The lines with \c Q_PROPERTY() macro declares the \e property and its \e write
and \e read methods as well as its \e notify signal. For example, setting the
\c fileUrl property calls \c setFileUrl() and reading the property calls the
\c fileUrl() function. Similarly, when the value of fileUrl changes the
\c fileUrlChanged() function is called.

Internally, the properties are represented by private member variables. For our
needs, here are the three variables in \e documenthandler.h which correspond to the properties:
\code
private:
    QUrl m_fileUrl;
    QString m_text;
    QString m_documentTitle;
\endcode

Implementing the read functions is straightforward. They simply return
the private member variables. For example, the implementation of
\c documentTitle() in \e documenthandler.cpp is:
\code
QString DocumentHandler::documentTitle() const
{
    return m_documentTitle;
}
\endcode

Implementing the write (\c setText(), for example) functions is also straightforward as they simply
assign a value to a private member variable. They also handle basic error handling
and they emit their respective notify signals. For example, the \c setDocumentTitle() function
is implemented in \e documenthandler.cpp as:

\code
void DocumentHandler::setDocumentTitle(QString arg)
{
    if (m_documentTitle != arg) {
        m_documentTitle = arg;
        emit documentTitleChanged();
    }
}
\endcode

The opening of the file is done in the \c setFileUrl() function:
\code
void DocumentHandler::setFileUrl(const QUrl &arg)
{
    if (m_fileUrl != arg) {
        m_fileUrl = arg;
        QString fileName = arg.fileName();
        QFile file(arg.toLocalFile());
        if (file.open(QFile::ReadOnly)) {
            setText(QString(file.readAll()));
            if (fileName.isEmpty())
                m_documentTitle = QStringLiteral("untitled");
            else
                m_documentTitle = fileName;
            emit textChanged();
            emit documentTitleChanged();
        }
        emit fileUrlChanged();
    }
}
\endcode

Note how the function emits the notify signals with the \c emit keyword.

Similarly, we use QFile and text streams to save files. The function signature in
\e documenthandler.h is placed under \c{public slots} because that is one
way to expose functions to the QML engine. \c saveFile() is called from the
QML file during saving.
\code
public slots:

    Q_INVOKABLE void saveFile(const QUrl &arg) const;
\endcode

The implementation of \c saveFile() is in documenthandler.cpp:
\code
void DocumentHandler::saveFile(const QUrl &arg) const
{
    QFile file(arg.toLocalFile());
    if (file.open(QFile::WriteOnly | QFile::Truncate)) {
        QTextStream out(&file);
        out << text();
    }
}
\endcode

For information about reading files and data storage, visit the QFile
and the \l{Data Storage} documentation.

\section1 Registering the DocumentHandler Class

We now need to let the QML engine know about the \c DocumentHandler and its
type. The \c qmlRegisterType() function is called in the application's \c main()
function in \e main.cpp:

\code
    qmlRegisterType<DocumentHandler>("org.qtproject.example", 1, 0, "DocumentHandler");
\endcode

The \c org.qtproject.example is the library with the version \c 1.0 and the
QML type registered is \c DocumentHandler. The import statement for the
DocumentHandler QML type is then
\code
import org.qtproject.example 1.0
\endcode

\note The \c qmlRegisterType() function should be called before the engine loads the QML file.

\section1 Using the DocumentHandler QML type

With the basic loading implemented, we can use the functionalities in the
QML file by creating an instance of the DocumentHandler class and by accessing
its properties.

The \l{Qt Quick Text Editor - Connecting Actions}{next page} is about using
these C++ functions in QML files.

\section1 Example Files

The accompanying examples files are found in the following page:
\list
\li \l{Qt Quick Controls 1 - Text Editor Example}
\endlist

*/

/*!
\page qtquickcontrols-texteditor-action.html
\title Qt Quick Text Editor - Connecting Actions
\previouspage Qt Quick Text Editor Guide - Logic

Earlier in the \l{Qt Quick Text Editor Guide}, we created a \e main.qml file
containing the description of our user interface in QML. The user interface
contains tool buttons in a tool bar on top of a text area. Afterwards, we
created a DocumentHandler class in C++ that will handle the file loading
and saving.

Now we shall use the DocumentHandler in the QML file through \e actions. There
is an \l Action QML type that we can connect to the tool buttons which in turn
calls the DocumentHandler functions.

\section1 Importing the DocumentHandler QML Type

With the \c qmlRegisterType() function, we declared that the DocumentHandler
QML type is imported from the \c org.qtproject.example library.

The following code is taken from the \e main.cpp file from the previous stage.
\code
    qmlRegisterType<DocumentHandler>("org.qtproject.example", 1, 0, "DocumentHandler");
\endcode

In the \e main.qml file, enter the following import statement:
\qml
import org.qtproject.example 1.0
\endqml
The DocumentHandler type is then available and we can create an object directly by adding it at
the bottom of the application window.
\qml
    DocumentHandler {
        id: document
    }
\endqml

\section1 Assigning Actions

As mentioned, the tool buttons are associated with an \e action, for example, the cut button
is associated with the cut action. The cut action embodies the events that define the action,
for example, the calling of the appropriate function in the text area.

For our application, we have six actions, which may be placed inside the application window.

\qml
    Action {
        id: cutaction
        text: "Cut"
        shortcut: "ctrl+x"
        iconSource: "images/editcut.png"
        iconName: "edit-cut"
        onTriggered: textarea.cut()
    }

    Action {
        id: copyaction
        text: "Copy"
        shortcut: "Ctrl+C"
        iconSource: "images/editcopy.png"
        iconName: "edit-copy"
        onTriggered: textarea.copy()
    }

    Action {
        id: pasteaction
        text: "Paste"
        shortcut: "ctrl+v"
        iconSource: "qrc:images/editpaste.png"
        iconName: "edit-paste"
        onTriggered: textarea.paste()
    }

    Action {
        id: fileopenaction
        iconSource: "images/fileopen.png"
        iconName: "document-open"
        text: "Open"
        onTriggered: fileDialog.open()
    }
\endqml

These actions call the appropriate function and assign a specific icon and name to the
action. To connect the \c cutaction to the cut tool button, add the following to the
tool button

\qml
ToolButton {
            id: cut_toolbutton
            iconSource: "images/editcut.png"
            iconName: "cut_icon"
            anchors.left: save_toolbutton.right
            action: cutaction;
}
\endqml

For the open and save actions, we require that the user choose an existing file
or create a new file. To do this, we can pop up a file dialog and ask the user
to select the file to open from or save onto. We can create two file dialogs,
one for opening a file and one for saving the file, each setting their own
titles.

\qml
    FileDialog {
        id: fileOpenDialog
        title: "Please choose a file to open"
        nameFilters: ["Text files (*.txt)"]
        onAccepted: document.fileUrl = fileUrl
    }

    FileDialog {
        id: fileSaveDialog
        title: "Please enter the file to save"
        nameFilters: ["Text files (*.txt)"]
        selectExisting: false
        onAccepted: document.saveFile(fileUrl)
    }
\endqml

Setting the FileDialog's \c selectExisting property to \c false allows us to
save new files.

The \l FileDialog type is from the \l{Qt Quick Dialogs} and is imported with
\qml
import QtQuick.Dialogs 1.2
\endqml

\section1 Deploying TextEditor

Deploying the TextEditor depends on the platform on which the application is run. The process is simple
and Qt provides several tools for packaging applications for a given platform. The
\l{Deploying Qt Applications} page lists the instructions for the supported platforms.
For this guide, we will deploy on Windows desktop platform with the
\c windeploytool to create a directory with the required dependent libraries.

To package TextEditor,
\list 1
\li Copy the \e texteditor.exe file from the release directory to another directory which
    serves as the destination folder.
\li Run the \e windeployqt.exe file which resolves and copies the Qt libraries into
    the destination folder. \e windeployqt.exe is found in the \e bin directory of the installation.
    \code
    C:\Qt\5.3\msvc2012_opengl\bin>windeployqt.exe <path to destination folder>
    \endcode
\endlist

The destination folder can now be packaged and the binary file is executable. The images
and QML file are already packaged into the binary file.

\section1 Example Files

The accompanying examples files are found in the following page:
\list
\li \l{Qt Quick Controls 1 - Text Editor Example}
\endlist

*/