Forward declarations are your friends

Why leak gl headers into most of kicad

common/singleton.cpp

@@ -0,0 +1,43 @@
+/*
+ * This program source code file is part of KiCad, a free EDA CAD application.
+ *
+ * Copyright The KiCad Developers, see AUTHORS.txt for contributors.
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <singleton.h>
+#include <bs_thread_pool.hpp>
+#include <gal/opengl/gl_context_mgr.h>
+
+
+KICAD_SINGLETON::~KICAD_SINGLETON()
+{
+    // This will wait for all threads to finish and then join them to the main thread
+    delete m_ThreadPool;
+
+    m_ThreadPool = nullptr;
+
+    m_GLContextManager->DeleteAll();
+    delete m_GLContextManager;
+    m_GLContextManager = nullptr;
+}
+
+
+void KICAD_SINGLETON::Init()
+{
+    int num_threads = std::max( 0, ADVANCED_CFG::GetCfg().m_MaximumThreads );
+    m_ThreadPool = new BS::thread_pool( num_threads );
+    m_GLContextManager = new GL_CONTEXT_MANAGER();
+}