anchor.diff:    /// Fragment shader editor
     fl.TextEditor editor;
   
  +  /// Recompile button.
  +  fl.Button button;
  +
     /// Text buffer for the editor
     fl.TextBuffer buffer;
   
  
positive.code:   /// Constructor
    ShaderEditor(int _w, int _h, String l) : super(_w, _h, l) {
      color = fl.WHITE;
      final height = _h;
      final half = (_w / 2).round();
      final pad = 10;
  
      canvas = new Gl2DCanvas(0, 0, half, height);
  
      editor = new fl.TextEditor(half + pad, pad, w - half - pad, height - pad);
      editor.box = fl.FLAT_BOX;
      editor.cursorStyle = fl.TextDisplay.SIMPLE_CURSOR;
      editor.cursorColor = fl.rgbColor(64);
  
negative.code: 
  import 'package:dartgl/dartgl.dart';
  import 'package:fltk/fltk.dart' as fl;
  
  /// More generic 2D GL canvas based on opengl.dart
  class Gl2DCanvas extends fl.GlWindow {
  