Tree Model Completer Example: tree model is broken due to bugs in MainWindow::modelFromFile

-        QString line = file.readLine();
+        const QString line = QString::fromUtf8(file.readLine()).trimmed();

QRegularExpression re("^\\s+");
const QRegularExpressionMatch match = re.match(line);
-            if (line.startsWith("\t")) {
-                level = match.capturedLength();
-            } else {
-                level = match.capturedLength()/4;
-            }
+            const int capLen = match.capturedLength();
+            level = line.startsWith(QLatin1Char('\t')) ? capLen / 4 : capLen;

level = line.startsWith(QLatin1Char('\t')) ? capLen : capLen / 4;

level = capLen / 4;