slider impl (no auto activate)

static/lazyload.js

@@ -111,3 +111,96 @@ ms = document.getElementById("main_scrollable")
 window.addEventListener('scroll', refresh_handler);
 window.addEventListener('resize', refresh_handler);
 window.addEventListener('load', refresh_handler);
+
+function initComparisons() {
+  var x, i;
+  /* Find all elements with an "overlay" class: */
+  var containers = document.getElementsByClassName("slider-container");
+  x = document.getElementsByClassName("img-comp-overlay");
+  console.log(x)
+  for (i = 0; i < containers.length; i++) {
+    /* Once for each "overlay" element:
+    pass the "overlay" element as a parameter when executing the compareImages function: */
+
+    var refImage = containers[i].children[2]
+    var testw = refImage.width
+    var testh = refImage.height
+
+    containers[i].children[0].children[0].width = testw
+    containers[i].children[1].children[0].width = testw
+    containers[i].children[0].children[0].height = testh
+    containers[i].children[1].children[0].height = testh
+
+    containers[i].children[0].style.opacity = 1
+    containers[i].children[1].style.opacity = 1
+
+    compareImages(x[i], refImage);
+  }
+  function compareImages(img, refImage) {
+    var slider = null;
+    var clicked = 0;
+    /* Get the width and height of the img element */
+    var w = img.offsetWidth;
+    var h = img.offsetHeight;
+    /* Set the width of the img element to 50%: */
+    img.style.width = (w / 2) + "px";
+    /* Create slider: */
+    slider = document.createElement("DIV");
+    slider.setAttribute("class", "img-comp-slider");
+    /* Insert slider */
+    img.parentElement.insertBefore(slider, img);
+    /* Position the slider in the middle: */
+    slider.style.top = (h / 2) - (slider.offsetHeight / 2) + "px";
+    slider.style.left = (w / 2) - (slider.offsetWidth / 2) + "px";
+    /* Execute a function when the mouse button is pressed: */
+    slider.addEventListener("mousedown", slideReady);
+    /* And another function when the mouse button is released: */
+    window.addEventListener("mouseup", slideFinish);
+    /* Or touched (for touch screens: */
+    slider.addEventListener("touchstart", slideReady);
+     /* And released (for touch screens: */
+    window.addEventListener("touchend", slideFinish);
+    function slideReady(e) {
+      /* Prevent any other actions that may occur when moving over the image: */
+      e.preventDefault();
+      /* The slider is now clicked and ready to move: */
+      clicked = 1;
+      /* Execute a function when the slider is moved: */
+      window.addEventListener("mousemove", slideMove);
+      window.addEventListener("touchmove", slideMove);
+    }
+    function slideFinish() {
+      /* The slider is no longer clicked: */
+      clicked = 0;
+    }
+    function slideMove(e) {
+      var pos;
+      /* If the slider is no longer clicked, exit this function: */
+      if (clicked == 0) return false;
+      /* Get the cursor's x position: */
+      pos = getCursorPos(e)
+      /* Prevent the slider from being positioned outside the image: */
+      if (pos < 0) pos = 0;
+      if (pos > w) pos = w;
+      /* Execute a function that will resize the overlay image according to the cursor: */
+      slide(pos);
+    }
+    function getCursorPos(e) {
+      var a, x = 0;
+      e = e || window.event;
+      /* Get the x positions of the image: */
+      a = img.getBoundingClientRect();
+      /* Calculate the cursor's x coordinate, relative to the image: */
+      x = e.pageX - a.left;
+      /* Consider any page scrolling: */
+      x = x - window.pageXOffset;
+      return x;
+    }
+    function slide(x) {
+      /* Resize the image: */
+      img.style.width = x + "px";
+      /* Position the slider: */
+      slider.style.left = img.offsetWidth - (slider.offsetWidth / 2) + "px";
+    }
+  }
+}