Huge Java detection refactor, version dialogs on first run (no JavaPath set) and "auto detect" button

gui/mainwindow.cpp

@@ -53,6 +53,7 @@
 #include "logic/lists/MinecraftVersionList.h"
 #include "logic/lists/LwjglVersionList.h"
 #include "logic/lists/IconList.h"
+#include "logic/lists/JavaVersionList.h"
 
 #include "logic/net/LoginTask.h"
 #include "logic/BaseInstance.h"
@@ -60,6 +61,7 @@
 #include "logic/MinecraftProcess.h"
 #include "logic/OneSixAssets.h"
 #include "logic/OneSixUpdate.h"
+#include "logic/JavaUtils.h"
 
 #include "logic/LegacyInstance.h"
 
@@ -701,3 +703,31 @@ void MainWindow::instanceEnded()
 	this->show();
 	ui->actionLaunchInstance->setEnabled(m_selectedInstance);
 }
+
+void MainWindow::checkSetDefaultJava()
+{
+	QString currentJavaPath = MMC->settings()->get("JavaPath").toString();
+	if(currentJavaPath.isEmpty())
+	{
+		QLOG_DEBUG() << "Java path not set, showing Java selection dialog...";
+
+		JavaVersionPtr java;
+
+		VersionSelectDialog vselect(MMC->javalist().get(), tr("First run: select a Java version"), this, false);
+		vselect.setResizeOn(2);
+		vselect.exec();
+
+		if (!vselect.selectedVersion())
+		{
+			QMessageBox::warning(
+						this, tr("Invalid version selected"), tr("You didn't select a valid Java version, so MultiMC will select the default. "
+																 "You can change this in the settings dialog."));
+
+			JavaUtils ju;
+			java = ju.GetDefaultJava();
+		}
+
+		java = std::dynamic_pointer_cast<JavaVersion>(vselect.selectedVersion());
+		MMC->settings()->set("JavaPath", java->path);
+	}
+}