code: function press(keyName, keyElement) {
  
          // Press key if not yet pressed
          if (!pressed[keyName]) {
  
              addClass(keyElement, "guac-keyboard-pressed");
  
              // Get current key based on modifier state
              var key = getActiveKey(keyName);
  
              // Update modifier state
              if (key.modifier) {
  
                  // Construct classname for modifier
                  var modifierClass = "guac-keyboard-modifier-" + getCSSName(key.modifier);
  
                  // Retrieve originally-pressed keysym, if modifier was already pressed
                  var originalKeysym = modifierKeysyms[key.modifier];
  
                  // Activate modifier if not pressed
                  if (!originalKeysym) {
                      
                      addClass(keyboard, modifierClass);
                      modifierKeysyms[key.modifier] = key.keysym;
                      
                      // Send key event
                      if (osk.onkeydown)
                          osk.onkeydown(key.keysym);
  
                  }
  
                  // Deactivate if not pressed
                  else {
  
                      removeClass(keyboard, modifierClass);
                      delete modifierKeysyms[key.modifier];
                      
                      // Send key event
                      if (osk.onkeyup)
                          osk.onkeyup(originalKeysym);
  
                  }
  
              }
  
              // If not modifier, send key event now
              else if (osk.onkeydown)
                  osk.onkeydown(key.keysym);
  
              // Mark key as pressed
              pressed[keyName] = true;
  
          }
  
      }
docs: Presses the key having the given name, updating the associated key
  element with the "guac-keyboard-pressed" CSS class. If the key is
  already pressed, this function has no effect.
  
  @private
  @param {String} keyName
  The name of the key to press.
  
  @param {String} keyElement
  The element associated with the given key.