renderergl_utils: Require explicit location qualifier for OpenGLES3

src/compiler/translator/TranslatorGLSL.cpp

@@ -177,6 +177,12 @@ void TranslatorGLSL::writeExtensionBehavior(TIntermNode *root)
         }
     }
 
+    // GLSL ES 3 explicit location qualifiers need to use an extension before GLSL 330
+    if (getShaderVersion() >= 300 && getOutputType() < SH_GLSL_330_CORE_OUTPUT)
+    {
+        sink << "#extension GL_ARB_explicit_attrib_location : require\n";
+    }
+
     TExtensionGLSL extensionGLSL(getOutputType());
     root->traverse(&extensionGLSL);
 

src/libANGLE/renderer/gl/renderergl_utils.cpp

@@ -539,6 +539,15 @@ void GenerateCaps(const FunctionsGL *functions, gl::Caps *caps, gl::TextureCapsM
         LimitVersion(maxSupportedESVersion, gl::Version(2, 0));
     }
 
+    // ES3 needs to support explicit layout location qualifiers, while it might be possible to
+    // fake them in our side, we currently don't support that.
+    if (!functions->isAtLeastGL(gl::Version(3, 3)) &&
+        !functions->hasGLExtension("GL_ARB_explicit_attrib_location") &&
+        !functions->isAtLeastGLES(gl::Version(3, 0)))
+    {
+        LimitVersion(maxSupportedESVersion, gl::Version(2, 0));
+    }
+
     // Extension support
     extensions->setTextureExtensionSupport(*textureCapsMap);
     extensions->elementIndexUint = functions->standard == STANDARD_GL_DESKTOP ||