Shaders: extension queries depending on GLSL version in MeshVisualizer.

The geometry shader implementation somehow expects GLSL 1.50 and is not
working on GLSL 1.40 (probably inconsistent variable naming in
extension and core specification). Added checks for that. Might fix this
properly someday when there is need for geometry shader in GL 3.1.

src/Shaders/MeshVisualizer.cpp

@@ -34,8 +34,10 @@ namespace Magnum { namespace Shaders {
 
 MeshVisualizer::MeshVisualizer(const Flags flags): flags(flags), transformationProjectionMatrixUniform(0), viewportSizeUniform(1), colorUniform(2), wireframeColorUniform(3), wireframeWidthUniform(4), smoothnessUniform(5) {
     #ifndef MAGNUM_TARGET_GLES
-    if(flags & Flag::Wireframe && !(flags & Flag::NoGeometryShader))
+    if(flags & Flag::Wireframe && !(flags & Flag::NoGeometryShader)) {
+        MAGNUM_ASSERT_VERSION_SUPPORTED(Version::GL320);
         MAGNUM_ASSERT_EXTENSION_SUPPORTED(Extensions::GL::ARB::geometry_shader4);
+    }
     #elif defined(MAGNUM_TARGET_GLES2)
     if(flags & Flag::Wireframe)
         MAGNUM_ASSERT_EXTENSION_SUPPORTED(Extensions::GL::OES::standard_derivatives);
@@ -44,12 +46,13 @@ MeshVisualizer::MeshVisualizer(const Flags flags): flags(flags), transformationP
     Utility::Resource rs("MagnumShaders");
 
     #ifndef MAGNUM_TARGET_GLES
-    const Version v = Context::current()->supportedVersion({Version::GL320, Version::GL310, Version::GL210});
+    const Version version = Context::current()->supportedVersion({Version::GL320, Version::GL310, Version::GL300, Version::GL210});
+    CORRADE_INTERNAL_ASSERT_OUTPUT(flags & Flag::NoGeometryShader || version >= Version::GL320);
     #else
-    const Version v = Context::current()->supportedVersion({Version::GLES300, Version::GLES200});
+    const Version version = Context::current()->supportedVersion({Version::GLES300, Version::GLES200});
     #endif
 
-    Shader vert(v, Shader::Type::Vertex);
+    Shader vert(version, Shader::Type::Vertex);
     vert.addSource(flags & Flag::Wireframe ? "#define WIREFRAME_RENDERING\n" : "")
         .addSource(flags & Flag::NoGeometryShader ? "#define NO_GEOMETRY_SHADER\n" : "")
         .addSource(rs.get("compatibility.glsl"))
@@ -60,7 +63,7 @@ MeshVisualizer::MeshVisualizer(const Flags flags): flags(flags), transformationP
 
     #ifndef MAGNUM_TARGET_GLES
     if(flags & Flag::Wireframe && !(flags & Flag::NoGeometryShader)) {
-        Shader geom(v, Shader::Type::Geometry);
+        Shader geom(version, Shader::Type::Geometry);
         geom.addSource(rs.get("compatibility.glsl"))
             .addSource(rs.get("MeshVisualizer.geom"));
         CORRADE_INTERNAL_ASSERT_OUTPUT(geom.compile());
@@ -69,7 +72,7 @@ MeshVisualizer::MeshVisualizer(const Flags flags): flags(flags), transformationP
     }
     #endif
 
-    Shader frag(v, Shader::Type::Fragment);
+    Shader frag(version, Shader::Type::Fragment);
     frag.addSource(flags & Flag::Wireframe ? "#define WIREFRAME_RENDERING\n" : "")
         .addSource(flags & Flag::NoGeometryShader ? "#define NO_GEOMETRY_SHADER\n" : "")
         .addSource(rs.get("compatibility.glsl"))
@@ -79,8 +82,7 @@ MeshVisualizer::MeshVisualizer(const Flags flags): flags(flags), transformationP
     attachShader(frag);
 
     #ifndef MAGNUM_TARGET_GLES
-    if(!Context::current()->isExtensionSupported<Extensions::GL::ARB::explicit_attrib_location>() ||
-        Context::current()->version() == Version::GL210)
+    if(!Context::current()->isExtensionSupported<Extensions::GL::ARB::explicit_attrib_location>(version))
     #else
     if(!Context::current()->isVersionSupported(Version::GLES300))
     #endif
@@ -99,7 +101,7 @@ MeshVisualizer::MeshVisualizer(const Flags flags): flags(flags), transformationP
     link();
 
     #ifndef MAGNUM_TARGET_GLES
-    if(!Context::current()->isExtensionSupported<Extensions::GL::ARB::explicit_uniform_location>())
+    if(!Context::current()->isExtensionSupported<Extensions::GL::ARB::explicit_uniform_location>(version))
     #endif
     {
         transformationProjectionMatrixUniform = uniformLocation("transformationProjectionMatrix");