main: directly set Xwayland scale, instead of starting a KCM to do the same

src/main.cpp

@@ -383,8 +383,15 @@ void Application::setXwaylandScale(qreal scale)
 {
     if (scale != m_xwaylandScale) {
         m_xwaylandScale = scale;
-        // rerun the fonts kcm init that does the appropriate xrdb call with the new settings
+        // change the font dpi to match
-        QProcess::startDetached("kcminit", {"kcm_fonts", "kcm_style"});
+        const int dpi = std::round(scale * 96);
+        const QByteArray input = "Xft.dpi: " + QByteArray::number(dpi);
+        QProcess p;
+        p.start(QStringLiteral("xrdb"), {QStringLiteral("-quiet"), QStringLiteral("-merge"), QStringLiteral("-nocpp")});
+        p.setProcessChannelMode(QProcess::ForwardedChannels);
+        p.write(input);
+        p.closeWriteChannel();
+        p.waitForFinished(-1);
         Q_EMIT xwaylandScaleChanged();
     }
 }