Fixed OpenGL version string being parsed incorrectly on some platforms.

Fixes #1249

src/SFML/Window/GlContext.cpp

@@ -38,6 +38,7 @@
 #include <set>
 #include <cstdlib>
 #include <cstring>
+#include <cctype>
 #include <cassert>
 
 #if !defined(SFML_OPENGL_ES)
@@ -199,6 +200,26 @@ namespace
 
     // Supported OpenGL extensions
     std::vector<std::string> extensions;
+
+    // Helper to parse OpenGL version strings
+    bool parseVersionString(const char* version, const char* prefix, unsigned int &major, unsigned int &minor)
+    {
+        std::size_t versionPosition = std::strlen(prefix);
+
+        if ((std::strlen(version) >= (versionPosition + 3)) &&
+            !std::strncmp(version, prefix, std::strlen(prefix)) &&
+            std::isdigit(version[versionPosition]) &&
+            (version[versionPosition + 1] == '.') &&
+            std::isdigit(version[versionPosition + 2]))
+        {
+            major = version[versionPosition] - '0';
+            minor = version[versionPosition + 2] - '0';
+
+            return true;
+        }
+
+        return false;
+    }
 }
 
 
@@ -582,18 +603,30 @@ void GlContext::initialize(const ContextSettings& requestedSettings)
     else
     {
         // Try the old way
-        const GLubyte* version = glGetString(GL_VERSION);
+
+        // If we can't get the version number, assume 1.1
+        m_settings.majorVersion = 1;
+        m_settings.minorVersion = 1;
+
+        const char* version = reinterpret_cast<const char*>(glGetString(GL_VERSION));
         if (version)
         {
-            // The beginning of the returned string is "major.minor" (this is standard)
-            m_settings.majorVersion = version[0] - '0';
-            m_settings.minorVersion = version[2] - '0';
+            // OpenGL ES Common Lite profile: The beginning of the returned string is "OpenGL ES-CL major.minor"
+            // OpenGL ES Common profile:      The beginning of the returned string is "OpenGL ES-CM major.minor"
+            // OpenGL ES Full profile:        The beginning of the returned string is "OpenGL ES major.minor"
+            // Desktop OpenGL:                The beginning of the returned string is "major.minor"
+
+            if (!parseVersionString(version, "OpenGL ES-CL ", m_settings.majorVersion, m_settings.minorVersion) &&
+                !parseVersionString(version, "OpenGL ES-CM ", m_settings.majorVersion, m_settings.minorVersion) &&
+                !parseVersionString(version, "OpenGL ES ",    m_settings.majorVersion, m_settings.minorVersion) &&
+                !parseVersionString(version, "",              m_settings.majorVersion, m_settings.minorVersion))
+            {
+                err() << "Unable to parse OpenGL version string: \"" << version << "\", defaulting to 1.1" << std::endl;
+            }
         }
         else
         {
-            // Can't get the version number, assume 1.1
-            m_settings.majorVersion = 1;
-            m_settings.minorVersion = 1;
+            err() << "Unable to retrieve OpenGL version string, defaulting to 1.1" << std::endl;
         }
     }