Don't round scaling factor

Qt 5.14 introduced new feature related to HighDPI screens support,
this parameter is called "scale factor rounding policy", and it is
intended to improve fractional scale factor support (like 150%).
Qt::PassThrough value guarantee that no any rounding will applied to
scale factor, and will be used as is.

src/app/main.cpp

@@ -136,6 +136,9 @@ int main(int argc, char *argv[])
     // Attribute Qt::AA_EnableHighDpiScaling must be set before QCoreApplication is created
     if (qgetenv("QT_ENABLE_HIGHDPI_SCALING").isEmpty() && qgetenv("QT_AUTO_SCREEN_SCALE_FACTOR").isEmpty())
         Application::setAttribute(Qt::AA_EnableHighDpiScaling, true);
+    // HighDPI scale factor policy must be set before QGuiApplication is created
+    if (qgetenv("QT_SCALE_FACTOR_ROUNDING_POLICY").isEmpty())
+        Application::setHighDpiScaleFactorRoundingPolicy(Qt::HighDpiScaleFactorRoundingPolicy::PassThrough);
 #endif
 
     try {