Fixed bug in InteractionMode and improved it

When using the the InteractionMode, whe noticed the following problem / bug:

in our software the user can toggle the interaction mode via a checkable action
this action calls the setOn() function of InteractionMode
if the interaction mode is on and the user presses the ALT key, then the event manager remains in NO_NAVIGATION state because of the backed up previous state:

The problem is the following code in setOn():

  if (on) {
    this->altkeydown = true;
    this->prevnavstate = eventmanager->getNavigationState();
    this->prevcursor = this->quarterwidget->cursor();
    this->quarterwidget->setCursor(this->quarterwidget->stateCursor("interact"));
    eventmanager->setNavigationState(SoEventManager::NO_NAVIGATION);
  } else {
    this->altkeydown = false;
    this->quarterwidget->setCursor(this->prevcursor);
    eventmanager->setNavigationState(this->prevnavstate);
  }

To reproduce this, do the following steps:

activate interactive mode via setOn(true) call
press and release the ALT key
deactivate interactive mode via setOn(false) call

The event manager will remain in NO_NAVIGATION state.

To fix this I use different variables to track the on, altkey and interactive state. After the change, the ALT key works as a toggle switch. If it is pressed, then the other mode is activated. That means, if the widget is in navigation mode, ALT activates the interactive mode as long as pressed and if the widget is in interactive mode, pressing the ALT key temporary activates the navigation mode.

coin3d / quarter

Fixed bug in InteractionMode and improved it #65