--- /dev/null
+#include <stdexcept>
+#include <cstdlib>
+#include <msp/strings/lexicalcast.h>
+#include <msp/strings/utils.h>
+#include "backend.h"
+#include "gl.h"
+
+using namespace std;
+
+namespace Msp {
+namespace GL {
+
+Version::Version()
+{
+ major = 0;
+ minor = 0;
+}
+
+Version::Version(unsigned short a, unsigned short i)
+{
+ major = a;
+ minor = i;
+}
+
+Version::Version(const string &s)
+{
+ vector<string> parts = split(s, '.');
+ major = lexical_cast<unsigned>(parts[0]);
+ minor = lexical_cast<unsigned>(parts[1]);
+}
+
+bool Version::operator>=(const Version &other) const
+{
+ return major>other.major || (major==other.major && minor>=other.minor);
+}
+
+
+GraphicsApi get_backend_api()
+{
+#ifdef GL_ES_VERSION_2_0
+ return OPENGL_ES;
+#else
+ return OPENGL;
+#endif
+}
+
+inline Version get_gl_version()
+{
+ const char *gl_ver_ptr = reinterpret_cast<const char *>(glGetString(GL_VERSION));
+ if(!gl_ver_ptr)
+ throw runtime_error("OpenGL version not available");
+
+ string gl_ver = gl_ver_ptr;
+ if(!gl_ver.compare(0, 10, "OpenGL ES "))
+ gl_ver.erase(0, 10);
+
+ Version ver(gl_ver.substr(0, gl_ver.find(' ')));
+
+ if(const char *force_ver_ptr = getenv("MSPGL_FORCE_VERSION"))
+ {
+ Version force_ver(force_ver_ptr);
+ if(force_ver<ver)
+ ver = force_ver;
+ }
+
+ return ver;
+}
+
+const Version &get_backend_version()
+{
+ static Version version = get_gl_version();
+ return version;
+}
+
+} // namespace GL
+} // namespace Msp