docs: function onMouseDown(event, env, isSideEffectsDisabled) {
      mouse.down(event, env ? env.camera : null);
  
      if (!env || isSideEffectsDisabled) {
          return;
      }
  
      if (mouse.keys[1] && !mouse.keys[3]) {
          let focusedObject = focusObject(env.library, env.camera, env.selector);
  
          if (env.selector.selectFocused()) {
              events.triggerSelect(focusedObject);
          }   
      }
  }