Added cpp style mechanisme to queue callables on window thread.

mainwindow.cpp

@@ -5,6 +5,7 @@
 #include "QueryExplainModel.h"
 #include "sqlhighlighter.h"
 #include <QTextTable>
+#include <QTimer>
 #include <windows.h>
 #include "json/json.h"
 #include "explaintreemodelitem.h"
@@ -59,6 +60,34 @@ MainWindow::MainWindow(QWidget *parent) :
 MainWindow::~MainWindow()
 {}
 
+void MainWindow::QueueTask(callable c)
+{
+	std::lock_guard<std::mutex> lg(m_mutexCallableQueue);
+	m_callableQueue.emplace_back(std::move(c));
+	// Theoretically this needs to be only called if the queue was empty because otherwise it already would
+	// be busy emptying the queue. For now however I think it is safer to call it just to make sure.
+	QMetaObject::invokeMethod(this, "processCallableQueue",	Qt::QueuedConnection); // queues on main thread
+}
+
+void MainWindow::processCallableQueue()
+{
+	bool empty;
+	callable c;
+	{ // narrow scope for lock guard
+		std::lock_guard<std::mutex> lg(m_mutexCallableQueue);
+		c = m_callableQueue.back();
+		m_callableQueue.pop_back();
+		empty = m_callableQueue.empty();
+	}
+
+	c();
+
+	if (!empty) {
+		// This gives other events a chance to be processed to keep the UI snappy.
+		QTimer::singleShot(0, this, SLOT(processCallableQueue()));
+	}
+}
+
 void MainWindow::startConnect()
 {
 	if (connection == nullptr) {
@@ -125,6 +154,7 @@ void MainWindow::performQuery()
 			QMetaObject::invokeMethod(this, "query_ready",	 Qt::QueuedConnection); // queues on main thread
 			return res;
 		});
+
 }
 
 void MainWindow::query_ready()