Program not repainting upon JFrame height maximizing

Question

You can resize JFrame with mouse dragging in several ways:

1. You can resize it\'s height (top/bottom edge)
2. You can resize it\'s width (left/right edge)<

Answer 1

It appears to be a bug in the Windows implementation of Java. (I am also using Windows 7 and JDK7.)

When Windows decides to change the height of the window, a COMPONENT_MOVED event is received by Window, but no COMPONENT_RESIZED event is received.

Inside the Windows class, the non-public method dispatchEventImpl() will respond to COMPONENT_RESIZED events by calling invalidate() and validate(), but it will ignore COMPONENT_MOVED events.

Here is a brute-force method of making the window re-validate itself after such an event. This may occasionally make the window re-validate in other situations, but not very often since the Window class itself is doing re-validation after every COMPONENT_RESIZED event, and the reported bug only happens when the window is being actively resized by the user.

    masterWindow.addComponentListener(new ComponentAdapter() {
      private int oldWidth = 0;
      private int oldHeight = 0;

      @Override
      public void componentResized(ComponentEvent e) {
        oldWidth = masterWindow.getWidth();
        oldHeight = masterWindow.getHeight();
      }

      @Override
      public void componentMoved(ComponentEvent e) {
          if (masterWindow.getWidth() != oldWidth || masterWindow.getHeight() != oldHeight) {
            masterWindow.invalidate();
            masterWindow.validate();
          }
          oldWidth = masterWindow.getWidth();
          oldHeight = masterWindow.getHeight();
      }
    });