code: protected void setPageChanged(boolean changed, boolean unlock) {
  
          if (changed) {
              if (!m_pageChanged) {
                  m_pageChanged = changed;
                  lockContainerpage(new I_CmsSimpleCallback<Boolean>() {
  
                      public void execute(Boolean arg) {
  
                          // nothing to do
                      }
                  });
              }
          } else {
              m_pageChanged = changed;
              if (unlock) {
                  unlockContainerpage();
              }
          }
      }
docs: Sets the page changed flag and initializes the window closing handler if necessary.<p>
  
  @param changed if <code>true</code> the page has changed
  @param unlock if <code>true</code> the page will be unlocked for unchanged pages