Build in single-threaded mode as well.

mandelbrot/main.cpp

@@ -51,16 +51,21 @@
 #include "mandelbrotwidget.h"
 
 #include <QApplication>
+
+#if QT_CONFIG(thread)
 #include <QThreadPool>
+#endif
 
 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
-    
-    // We're managing the number of threads elsewhere; set the global
+
+#if QT_CONFIG(thread)
+    // We're managing the number of threads elsewhere; set the globalw
     // thread limit to a large value so it won't interfere.
     QThreadPool::globalInstance()->setMaxThreadCount(1024);
-    
+#endif    
+
     MandelbrotWidget widget;
     widget.show();
     return app.exec();

mandelbrot/renderthread.cpp

@@ -52,13 +52,17 @@
 
 #include <QImage>
 #include <QDebug>
+#if QT_CONFIG(thread)
 #include <QThreadPool>
+#endif
 #include <cmath>
 
 #ifdef Q_OS_WASM
 #include <emscripten.h>
 #endif
 
+
+#if QT_CONFIG(thread)
 // runs function on a thread from the global QThreadPool, returns a
 // function that can be called to vait for the function to finish.
 std::function<void()> runOnThread(std::function<void()> fn)
@@ -103,6 +107,15 @@ std::function<void()> runOnThread(std::function<void()> fn)
 
     return waitFn;
 }
+#else
+
+std::function<void()> runOnThread(std::function<void()> fn)
+{
+    fn(); // run function right away
+    return [](){}; // return a no-op wait function
+}
+
+#endif // QT_CONFIG(thread)
 
 // calls the provided \a function  \a iterationCount times, using at maximum \a maxThreads thrads.
 void runOnThreads(std::function<void(int i)> fn, int iterationCount,