gl::query class, use of occlusion queries in glare rendering

gl/query.h

@@ -0,0 +1,36 @@
+#pragma once
+
+#include "object.h"
+
+namespace gl
+{
+class query : public object
+{
+public:
+	enum targets
+	{
+		SAMPLES_PASSED = 0,
+		ANY_SAMPLES_PASSED,
+		ANY_SAMPLES_PASSED_CONSERVATIVE,
+		PRIMITIVES_GENERATED,
+		TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN,
+		TIME_ELAPSED
+	};
+
+private:
+	targets target;
+	thread_local static query* active_queries[6];
+
+protected:
+	GLenum glenum_target(targets target);
+
+public:
+	query(targets target);
+	~query();
+
+	void begin();
+	void end();
+
+	std::optional<int64_t> result();
+};
+}