var preloadedImages = new Array();

var showFrameNum = -1;  /* Will get incr'd to 0 */


// Preload animation images
function loadAnims() {
   // Following trick from NCWF page @ http://cdm.aviationweather.gov/ncwf/
   // G. M. Cunning NCAR,RAP March 2000
   //
   // get new images from server, regardless of contents of cache.
   // this is done by apending uniq to rhs of document.<NAME>.src
   //
   uniq = new Date();
   uniq = "?" + uniq.getTime();
   
   for (var currAnim = 0; currAnim < numAnims; currAnim++) {
      preloadedImages[currAnim] = new Array();
      for (var currFrame = 0; currFrame < numFrames; currFrame++) {
         preloadedImages[currAnim][currFrame] = new Image();
         preloadedImages[currAnim][currFrame].src = sourceUris[currAnim][currFrame] + uniq;
      }
   }
   showFrameNum = -1;
   startAnim();  /* Will get incr'd to 0 */
}


// Time to advance to next frame
function animate() {
   if (interframeInterval <= 0) {
      // stopped
      return;
   }
   
   forwardAnim();
   
   var delay = interframeInterval;
   if (showFrameNum == 0) {
      delay = interframeInterval * initialFrameMultipler;
   }
   if (showFrameNum == numFrames - 1) {
      delay = interframeInterval * finalFrameMultipler;
   }
   
   setTimeout("animate()", delay);
}

function stopAnim() {
   if (interframeInterval > 0) {
      interframeInterval = -interframeInterval;
   }

   document.buttonForm.startButton.disabled = false;
   document.buttonForm.stopButton.disabled = true;
   document.buttonForm.fasterButton.disabled = true;
   document.buttonForm.slowerButton.disabled = true;
   document.buttonForm.forwardButton.disabled = false;
   document.buttonForm.backButton.disabled = false;
}

function startAnim() {
   if (interframeInterval < 0) {
      interframeInterval = -interframeInterval;
   }
   if (interframeInterval == 0) {
      interframeInterval = 50;
   }

   document.buttonForm.startButton.disabled = true;
   document.buttonForm.stopButton.disabled = false;
   document.buttonForm.fasterButton.disabled = false;
   document.buttonForm.slowerButton.disabled = false;
   document.buttonForm.forwardButton.disabled = true;
   document.buttonForm.backButton.disabled = true;
   
   animate();
}

function fasterAnim() {
   if (interframeInterval <= 0) {
      // stopped
      return;
   }
   
   interframeInterval = interframeInterval - 50;
   
   if (interframeInterval <= 0) {
      interframeInterval = 50;
   }
}

function slowerAnim() {
   if (interframeInterval <= 0) {
      // stopped
      return;
   }
   
   interframeInterval = interframeInterval + 50;
}

function forwardAnim() {
   showFrameNum++;
   if (showFrameNum >= numFrames) {
      showFrameNum = 0;
   }
   
   for (var currAnim = 0; currAnim < numAnims; currAnim++) {
      document.images[imageNames[currAnim]].src = preloadedImages[currAnim][showFrameNum].src;
   }
}

function backAnim() {
   showFrameNum--;
   if (showFrameNum < 0) {
      showFrameNum = numFrames - 1;
   }
   
   for (var currAnim = 0; currAnim < numAnims; currAnim++) {
      document.images[imageNames[currAnim]].src = preloadedImages[currAnim][showFrameNum].src;
   }
}