Added Shader:getExternVariable(name).

Returns the base type name ('float', 'image', etc.), the number of components (2 for a vec2), and number of array elements (1 for a non-array variable) for the extern variable with the specified name in the shader.

Returns nil if the variable either doesn't exist or was optimized out by the driver's shader compiler.

src/modules/graphics/opengl/wrap_Shader.cpp

@@ -346,6 +346,38 @@ int w_Shader_send(lua_State *L)
 	return luaL_argerror(L, 3, "number, boolean, table, image, or canvas expected");
 }
 
+int w_Shader_getExternVariable(lua_State *L)
+{
+	Shader *shader = luax_checkshader(L, 1);
+	const char *name = luaL_checkstring(L, 2);
+
+	int components = 0;
+	int arrayelements = 0;
+	Shader::UniformType type = Shader::UNIFORM_UNKNOWN;
+
+	type = shader->getExternVariable(name, components, arrayelements);
+
+	// Check if the variable exists (function will set components to 0 if not.)
+	if (components > 0)
+	{
+		const char *tname = nullptr;
+		if (!Shader::getConstant(type, tname))
+			return luaL_error(L, "Unknown extern variable type name.");
+
+		lua_pushstring(L, tname);
+		lua_pushinteger(L, components);
+		lua_pushinteger(L, arrayelements);
+	}
+	else
+	{
+		lua_pushnil(L);
+		lua_pushnil(L);
+		lua_pushnil(L);
+	}
+
+	return 3;
+}
+
 static const luaL_Reg functions[] =
 {
 	{ "getWarnings", w_Shader_getWarnings },
@@ -355,6 +387,7 @@ static const luaL_Reg functions[] =
 	{ "sendMatrix",  w_Shader_sendMatrix },
 	{ "sendTexture", w_Shader_sendTexture },
 	{ "send",        w_Shader_send },
+	{ "getExternVariable", w_Shader_getExternVariable },
 
 	// Deprecated since 0.9.1.
 	{ "sendImage",   w_Shader_sendTexture },