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 = Qt.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 { leftPadding: 8 Flow { id: 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.
There is a context menu; we use a TapHandler to detect a right-click and open it:
TapHandler { acceptedButtons: Qt.RightButton onTapped: contextMenu.popup() }
The context Menu contains MenuItems that reuse the same Action objects as the main MenuBar and ToolBar are using. As before, it's enough to bind action to the reusable Action that represents the operation to be performed. However, we override each menu item's text to omit the underlined mnemonics on the context menu.
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: "black" 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, visit Building and Running an Example.
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