- Qt 6.12
- Qt Quick Controls
- Qt Quick Controls Examples
- Qt Quick Controls - Text Editor
- Qt 6.12.0 Reference Documentation

# Qt Quick Controls - Text Editor

A rich-text editor app using Qt Quick Controls.

The Text Editor Example allows WYSIWYG editing of an HTML, Markdown or plain text file. The application comes with two user interfaces: one for larger screens, and a simplified UI for small touch-based devices. Both are "pure" QML. `texteditor.cpp` contains the `main()` function, which calls QFontDatabase::addApplicationFont() to add an icon font. (FontLoader would be an alternative way to achieve the same result.)

#### Desktop User Interface

The desktop version is a complete text editor with capabilities for formatting text, and opening and saving HTML, Markdown and plain text files.

In the model-view-control (MVC) design pattern, the control layer includes the set of operations that can be performed. In Qt Quick Controls, the Action type is used to encapsulate a single operation or command. Accordingly, we begin with a set of Action objects:

         Action {
             id: openAction
             text: qsTr("&Open")
             shortcut: StandardKey.Open
             onTriggered: {
                 if (textArea.textDocument.modified)
                     discardDialog.open()
                 else
                     openDialog.open()
             }
         }

The Action for opening a file must first prompt the user if the existing document has been changed, to avoid losing the user's changes. Otherwise it simply opens the FileDialog which is declared further below.

The Action for saving the file is enabled only if there are changes to save:

         Action {
             id: saveAction
             text: qsTr("&Save…")
             shortcut: StandardKey.Save
             enabled: textArea.textDocument.modified
             onTriggered: textArea.textDocument.save()
         }

The Action for copying selected text is enabled only if some text is selected:

         Action {
             id: copyAction
             text: qsTr("&Copy")
             shortcut: StandardKey.Copy
             enabled: textArea.selectedText
             onTriggered: textArea.copy()
         }

Each Action to change text formatting (such as bold, italic and alignment) is checkable, and its boolean `checked` state is in sync with the relevant property in the selected text. Since declarative bidirectional synchronization is difficult, we use an `onTriggered` script to change the property when the Action is activated. The cursorSelection property is new in Qt 6.7 and makes this much easier than it was.

         Action {
             id: boldAction
             text: qsTr("&Bold")
             shortcut: StandardKey.Bold
             checkable: true
             checked: textArea.cursorSelection.font.bold
             onTriggered: textArea.cursorSelection.font.bold = checked
         }

         Action {
             id: alignCenterAction
             text: qsTr("&Center")
             shortcut: "Ctrl+|"
             checkable: true
             checked: textArea.cursorSelection.alignment === Qt.AlignCenter
             onTriggered: textArea.cursorSelection.alignment = Qt.AlignCenter
         }

We have a MenuBar containing the hierarchy of Menus and MenuItems. Each MenuItem merely needs to bind the relevant action, which encapsulates the UI representation and the implementation.

         menuBar: MenuBar {
             Menu {
                 title: qsTr("&File")

                 MenuItem {
                     action: openAction
                 }
                 MenuItem {
                     action: saveAction
                 }
                 MenuItem {
                     action: saveAsAction
                 }
                 MenuItem {
                     action: quitAction
                 }
             }

             Menu {
                 title: qsTr("&Edit")

                 MenuItem {
                     action: copyAction
                 }
             ...

The same Action objects are reused in the ToolBar; but here we override each Action's text property to choose a textual icon from our icon font:

         header: ToolBar {
             Flow {
                 width: parent.width

                 Row {
                     id: fileRow
                     ToolButton {
                         id: openButton
                         text: "\uF115" // icon-folder-open-empty
                         font.family: "fontello"
                         action: openAction
                         focusPolicy: Qt.TabFocus
                     }
                     ToolButton {
                         id: saveButton
                         text: "\uE80A" // icon-floppy-disk
                         font.family: "fontello"
                         action: saveAction
                         focusPolicy: Qt.TabFocus
                     }
                     ToolSeparator {
                         contentItem.visible: fileRow.y === editRow.y
                     }
                 }

                 Row {
                     id: editRow
                     ToolButton {
                         id: copyButton
                         text: "\uF0C5" // icon-docs
                         font.family: "fontello"
                         focusPolicy: Qt.TabFocus
                         action: copyAction
                     }
                 ...

The main part of the text editor is a TextArea inside a Flickable:

         Flickable {
             id: flickable
             flickableDirection: Flickable.VerticalFlick
             anchors.fill: parent

             ScrollBar.vertical: ScrollBar {}

             TextArea.flickable: TextArea {
                 id: textArea
                 textFormat: Qt.AutoText
                 wrapMode: TextArea.Wrap
                 focus: true
                 selectByMouse: true
                 persistentSelection: true
                 ...

A ScrollBar is attached to the vertical axis. Since word-wrapping is enabled via wrapMode, we don't need a horizontal ScrollBar.

The TextArea.flickable attached property is used so that when the text cursor is moved out of the viewport (for example via arrow keys, or by typing a lot of text), TextArea scrolls the Flickable to keep the cursor visible.

We take the same actions that we declared in the MenuBar and ToolBar and append them to the existing items in the standard context menu provided by `TextArea`:

                     const menu = textArea.ContextMenu.menu
                     menu.addItem(menuSeparatorComponent.createObject(menu.contentItem))
                     menu.addAction(fontDialogAction)
                     menu.addAction(colorDialogAction)

We consistently use the qsTr() function to enable translation of UI text, so that the application will make sense regardless of the end user's native language.

We use several kinds of dialogs:

         FileDialog {
             id: openDialog
             fileMode: FileDialog.OpenFile
             selectedNameFilter.index: 1
             nameFilters: ["Text files (*.txt)", "HTML files (*.html *.htm)", "Markdown files (*.md *.markdown)"]
             currentFolder: StandardPaths.writableLocation(StandardPaths.DocumentsLocation)
             onAccepted: {
                 textArea.textDocument.modified = false // we asked earlier, if necessary
                 textArea.textDocument.source = selectedFile
             }
         }

         FileDialog {
             id: saveDialog
             fileMode: FileDialog.SaveFile
             nameFilters: openDialog.nameFilters
             currentFolder: StandardPaths.writableLocation(StandardPaths.DocumentsLocation)
             onAccepted: textArea.textDocument.saveAs(selectedFile)
         }

         FontDialog {
             id: fontDialog
             onAccepted: textArea.cursorSelection.font = selectedFont
         }

         ColorDialog {
             id: colorDialog
             selectedColor: textArea.cursorSelection.color
             onAccepted: textArea.cursorSelection.color = selectedColor
         }

         MessageDialog {
             title: qsTr("Error")
             id: errorDialog
         }

         MessageDialog {
             id : quitDialog
             title: qsTr("Quit?")
             text: qsTr("The file has been modified. Quit anyway?")
             buttons: MessageDialog.Yes | MessageDialog.No
             onButtonClicked: function (button, role) {
                 if (role === MessageDialog.YesRole) {
                     textArea.textDocument.modified = false
                     Qt.quit()
                 }
             }
         }

         MessageDialog {
             id : discardDialog
             title: qsTr("Discard changes?")
             text: qsTr("The file has been modified. Open a new file anyway?")
             buttons: MessageDialog.Yes | MessageDialog.No
             onButtonClicked: function (button, role) {
                 if (role === MessageDialog.YesRole)
                     openDialog.open()
             }
         }

It's generally easier to declare separate instances for each purpose. We have two instances of FileDialog, for opening and saving files respectively. This became easier in Qt 6.7, with new features in TextDocument.

A FontDialog and a ColorDialog allow changing text formatting. (In Markdown format, there's no syntax to represent specific font and color choices; but font characteristics such as bold, italic and monospace are saved. In HTML format, all formatting is saved.)

We have a MessageDialog to show error messages, and two more for prompting the user what to do when a file has been modified.

#### Touch User Interface

The touch user interface is a simplified version of the text editor. It is suitable for touch devices with limited screen size. The example uses file selectors to load the appropriate user interface automatically.

#### Running the Example

To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, see Qt Creator: Tutorial: Build and run.

Example project @ code.qt.io