checkgl uncleared error support, all aliased away in non-debug

glamour/util.d

@@ -39,21 +39,35 @@ debug {
 
 /// checkgl checks in a debug build after every opengl call glGetError
 /// and calls an error-callback which can be set with set_error_callback
-/// a default is provided
-ReturnType!func checkgl(alias func, Args...)(Args args) {
-    debug scope(success) {
+/// a default is provided.
+/// Example:
+/// checkgl!glDrawArrays(GL_POINTS, 0, 10);
+template checkgl(alias func)
+{
+    debug ReturnType!func checkgl(Args...)(Args args) {
+        //get and clear previous error, if any.
         GLenum error_code = glGetError();
 
         if(error_code != GL_NO_ERROR) {
-            _error_callback(error_code, func.stringof, format("%s".repeat(Args.length).join(", "), args));
+            _error_callback(error_code, "<unknown>", "<unknown>");
         }
-    }
+
+        scope(success) {
+            error_code = glGetError();
 
-    debug if(func is null) {
-        throw new Error("%s is null! OpenGL loaded? Required OpenGL version not supported?".format(func.stringof));
-    }
+            if(error_code != GL_NO_ERROR) {
+                _error_callback(error_code, func.stringof, format("%s".repeat(Args.length).join(", "), args));
+            }
+        }
 
-    return func(args);
+        if(func is null) {
+            throw new Error("%s is null! OpenGL loaded? Required OpenGL version not supported?".format(func.stringof));
+        }
+
+        return func(args);
+    } else {
+        alias checkgl = func;
+    }
 }
 
 /// Converts an OpenGL errorenum to a string
@@ -174,4 +188,4 @@ int glenum2size(GLenum t) {
         case GL_DOUBLE: return glenum2sizect!GL_DOUBLE;
         default: throw new Exception("Unknown GLenum");
     }
-}
+}