Detecting whether ANGLE is used as GLES2 implementation.

src/Magnum/Context.h

@@ -178,7 +178,17 @@ class MAGNUM_EXPORT Context {
         enum class DetectedDriver: UnsignedShort {
             #ifndef MAGNUM_TARGET_GLES
             /** Binary AMD desktop drivers on Windows and Linux */
-            AMD = 1 << 0
+            AMD = 1 << 0,
+            #endif
+
+            #ifdef MAGNUM_TARGET_GLES2
+            /**
+             * OpenGL ES 2.0 implementation by ANGLE (translated to D3D9), used
+             * by browsers on Windows for Native Client and WebGL. As the WebGL
+             * specification explicitly disallows exposing driver information
+             * to the application, this check cannot be done reliably.
+             */
+            ProbablyAngle = 1 << 1
             #endif
         };
 

src/Magnum/Implementation/detectedDriver.cpp

@@ -40,6 +40,17 @@ auto Context::detectedDriver() -> Context::DetectedDrivers {
         return *_detectedDrivers |= DetectedDriver::AMD;
     #endif
 
+    /* OpenGL ES 2.0 implementation using ANGLE. Taken from
+       http://stackoverflow.com/a/20149090 */
+    #ifdef MAGNUM_TARGET_GLES2
+    {
+        Range1Di range;
+        glGetIntegerv(GL_ALIASED_LINE_WIDTH_RANGE, range.data());
+        if(range.min() == 1 && range.max() == 1)
+            return *_detectedDrivers |= DetectedDriver::ProbablyAngle;
+    }
+    #endif
+
     return *_detectedDrivers;
 }