Modify a QTextDocument of a QML TextArea element - qt

Question

I'm trying to create a minimal version of the following example: https://doc.qt.io/qt-5/qtquickcontrols-texteditor-example.html
I have created a DocumentHandler class with the following method:
class DocumentHandler : public QObject {
Q_OBJECT
QML_ELEMENT
public:
Q_INVOKABLE void changeFormat(QQuickTextDocument *doc) {
QTextCursor cursor(doc->textDocument());
cursor.select(QTextCursor::Document);
QTextCharFormat format;
format.setFontItalic(true);
cursor.mergeBlockCharFormat(format);
}
}
Unfortunately, when I call this method from the following QML code
import DocumentTest 1.0
import QtQuick 2.15
import QtQuick.Controls 2.15
import QtQuick.Window 2.15
Window {
width: 640
height: 480
visible: true
title: qsTr("Document Test")
TextArea {
id: textArea
focus: true
anchors.fill: parent
wrapMode: Text.Wrap
selectByMouse: true
text: "Another day in paradise"
onReleased: {
document.changeChar(textDocument);
}
textFormat: Text.RichText
}
DocumentHandler {
id: document
}
}
I have a crash at the following line: https://github.com/qt/qtbase/blob/5.15.2/src/gui/text/qtextoption.h#L118
I read in the documentation that the QQuickTextDocument::textDocument() is read-only and that I can not modify its internal state so I wonder if using the QTextCursor is the right way to go. This is what is done in the example but I struggle finding out what is the difference with my code.

Answer 1

Looking at https://doc.qt.io/qt-5/qml-qtquick-textedit.html#textFormat-prop, i would replace textFormat: Text.RichText with textFormat: TextEdit.RichText

Answer 2

Sometime ago, I wrote a wrapper for the QSyntaxHighter classes. This achieves more than you require, but, it has the following elements:
control text color and formatting in your TextEdit
link to the TextEdit's textDocument property
Note that the example works with TextEdit not TextArea.
#include <QObject>
#include <QTextDocument>
#include <QSyntaxHighlighter>
#include <QQuickTextDocument>
class SyntaxHighlighter : public QSyntaxHighlighter
{
Q_OBJECT
Q_PROPERTY(QQuickTextDocument* textDocument READ textDocument WRITE setTextDocument NOTIFY textDocumentChanged)
public:
SyntaxHighlighter(QObject* parent = nullptr);
Q_INVOKABLE void setFormat(int start, int count, const QVariant& format);
// ...
};
You can use it like this:
TextEdit {
id: textEdit
}
SyntaxHighlighter {
textDocument: textEdit.textDocument
onHighlightBlock: {
let rx = /[A-Za-z]/g;
let m;
while ( ( m = rx.exec(text) ) !== null ) {
let keywords = [
'import', 'function', 'bool', 'var',
'int', 'string', 'let', 'const', 'property',
'if', 'continue', 'for', 'break', 'while',
];
if (keywords.includes(m[0])) {
setFormat(m.index, m[0].length, keywordFormat);
continue;
}
}
}
}
TextCharFormat {
id: keywordFormat
foreground: "#808000"
font.pointSize: 12
font.bold: true; font.italic: true
}
For full source code, refer to:
https://github.com/stephenquan/QtSyntaxHighlighterApp