Programming Page Watermarks

We explained page watermarks in Column 29, DOCJSLIB Version 3.0: Page Watermarks. We create the watermark in the function makeLinkedObject(). We every so often compute its position by the function waterMark(), which we call every 100 milliseconds via DOCJSLIB 3.1's function:

myBrowserAPIObj.doThisCommandEveryIntervalMS
  ("waterMark()", 100);

We use DOCJSLIB 3.1 a lot inside the function waterMark(), to set and get the watermark position on the page. We also compute the highest Z index in DOCJSLIB 3.1 as well as set it to the desired value:

function waterMark(){
    oldWindowWidth= windowWidth;
    oldWindowHeight= windowHeight;
    oldPageScrollLeft= pageScrollLeft;
    oldPageScrollTop= pageScrollTop;
    windowWidth = myBrowserAPIObj.getWindowWidth();
    windowHeight = myBrowserAPIObj.getWindowHeight();
    pageScrollLeft = myBrowserAPIObj.getPageScrollLeft();
    pageScrollTop = myBrowserAPIObj.getPageScrollTop();
    if ((windowHeight != oldWindowHeight)||(windowWidth !=
      oldWindowWidth)||(pageScrollLeft !=
      oldPageScrollLeft)|| (pageScrollTop !=
      oldPageScrollTop)){

      myBrowserAPIObj.setPosFromTop("docjslib", windowHeight
        + pageScrollTop - (imageHeight + bottomSpacer));
      myBrowserAPIObj.setPosFromLeft("docjslib", windowWidth
        + pageScrollLeft - (imageWidth + rightSpacer));
      var topZ = myBrowserAPIObj.findHighestZ();
      myBrowserAPIObj.setZposition("docjslib", topZ);
    }
}

Next: Tic-Tac-Toe, popout elements, and watermarks application listing