Responsive Heatmaps

Question

The Problem

I've encountered a slight problem where I've written some code where I've automated a script to track the users interactions with a UI, including mousemove & click events. If I didn't have to worry about making it responsive, then I could probably call it a day & ship the work that I've done already, however my brain is seeking some wizardry knowledge, I'm struggling to make it super responsive. Here's just a quick example of the kinda thing that I'm working on, it's nothing genius, if anything I it's mostly heatmap.js that's doing the heavy lifting. Currently I'm just seeing if I can do this as a proof of concept more than anything else...

The Code

So currently, I'm tracking the event.pageX & event.pageY values to store exactly where an event took place, I'm also storing the window.innerWidth & window.innerHeight values to try & work out some function that would allow me to offset the positions based on the size(s) of other devices.

E.g. If you look at the sample image above, that's perfect for a static page, but if I were to say make the page a little more narrow, you can see here that it's doesn't line up with the image above:

Anyway, without blabbering on too much, here's some sample code:

// A lot of other code...

var setupHeatMaps = function (pages, heatMaps) {
  pages.forEach(function (page) {
    page.addEventListener("click", function (event) {
      heatMaps.push({ x: event.pageX, y: event.pageY, value: 10000 });
      onStateChange();  
    });

    // Don't collect ALL mouse movements, that'd be crazy, so collect 
    // every 1/10 mouse movements.
    var counter = 0;

    page.addEventListener("mousemove", function (event) {
      if (counter === 10) {
        heatMaps.push({ x: event.pageX, y: event.pageY, value: 20 });
        onStateChange();
        counter = 0;
      } else {
        counter ++;
      }
    });
  });
};

// A lot of other code... 

// Curried function so that it can be passed around without exposing the state...
var renderHeatMaps = function (heatMaps) {
  return function () {
    var max = heatMaps.length;
    var points = heatMaps;

    var parent = getParentElement();
    var styleObj = window.getComputedStyle(parent);
    var div = document.createElement("div");
    var body = document.querySelector("body");
    var background = document.createElement("div");

    // This element needs to sit in front of the 
    // background element, hence the higher z-index value.
    div.style.position = "absolute";
    div.style.zIndex = 9;
    div.style.left = "0px";
    div.style.top = "-80px";
    div.style.width = "100vw";

    // Even though this element will sit behind the element
    // that's created above, we will still want this element to 
    // sit in front of 99% of the content that's on the page.
    background.style.position = "fixed";
    background.style.top = "0px";
    background.style.left = "0px";
    background.style.height = "100vh";
    background.style.width = "100vw";
    background.style.zIndex = 5;
    background.style.backgroundColor = "rgba(255, 255, 255, 0.35)";
    background.setAttribute("id", "quote-customer-heat-map-background");

    var heightInPx = styleObj.getPropertyValue("height");
    var rawHeight = parseInt(heightInPx.replace("px", ""));
    var newHeight = parseInt((rawHeight + 80));

    div.style.height = newHeight + "px";
    div.setAttribute("id", "quote-customer-heat-map-foreground");
    body.style.paddingBottom = "0px";
    body.appendChild(background);
    body.appendChild(div);

    var heatMap = h337.create({
      container: div,
      radius: 45
    });
    
    heatMap.setData({ max: max, data: points });
  };
};

// A lot of other code...

As the pages elements that you can see being used in setupHeatMaps changes in width, viewing this data gets offset quite badly. I'll be honest, I've spent a lot of time yesterday thinking about this issue & I've still not thought of anything that seems reasonable.

Alternatively

I have wondered if I should somehow just store the page as an image, with the heatmap overplayed, that way I wouldn't really have to worry about the heatmap being responsive. But then I need to figure out some other things... E.g. Versioning this data, so in the event that a user views a page on their phone, it'll stored that data separately to data that was collected from a previous session where they were on a laptop or on a desktop device.

Conclusion

I'll be honest, I'm not entirely sure what the best course of action is, have any of you guys encountered anything like this before? Have you guys thought of something genius that solves an issue like this?

P.S. I would share a lot more code, however there's an immense amount of code that goes into this overall solution, so I kinda can't share all of it, I'm pretty sure the guys at Stackoverflow would hate me for that! 😅 - You can also tell that I'm doing this as a POC because normally I'd just offload the rendering of the background element & the div element to the underlying framework rather than do it programatically like this, keep that in mind, this is just a POC.

Answer 1

Perhaps you could change the setup and record what element an event is on and save the location data relative to that element, not the whole page. You record all events on the page still but you save the data relative to the elements instead of the whole page, which prevents you from mashing the data together in your heatmap afterwards when you view it over your website at various widths.

Say you you have a setup like this in pseudocode:

@1000px width
[html width 1000px, height 500px
  [div width 800px, height 400px centered
    [button1 width 100px, height 30px centered] 
  ]
]

@500px width
[html width 500px, height 1000px
  [div width 400px, height 800px centered
    [button1 width 80px, height 30px centered]
  ]
]

Your users move over some element at all times. Just capture that data like this, example data from 2 users at the two different screen sizes moving the cursor towards the button in the center:

user interaction{
  over element: html {dimensions: width 1000px, height 500px}
  user position: {x 900, y 20}
}

user interaction{
  over element: html {dimensions: width 1000px, height 500px}
  user position: {x 850, y 60}
}

user interaction{
  over element: div {width 800px, height 400px}
  user position: {x 700, y 60}
}

user interaction{
  over element: button1 {width 100px, height 30px}
  user position: {x 90, y 10}
}

user interaction{
  over element: html {dimensions: width 500, height 1000px}
  user position: {x 450, y 100}
}

user interaction{
  over element: div {width 400px, height 800px}
  user position: {x 380, y 40}
}

user interaction{
  over element: button1 {width 80px, height 30px} 
  user position: {x 60, y 10}
}

Then when you view your website draw the heat over all elements and calculate the relative position of the captured data. So when you would view your site at @500px width the heat over your button1 would be as following:

[button 1 width 80px, height 30px
heat 1, x 72px y 10
heat 2, x 60px y 10
]

And you do the same for all other elements. I don't know how useful the data is like this, but it was for the sake of weird wizardry right?

Personally I'd just exclude data based on the screen width your viewing your heatmap at. That way you can use this setup and get useful heatmap data. So you'd exclude data based on if it was captured at a specific responsive width. So you could at the very least mash all user data together at high widths cause you'd know your interesting web elements would probably be centered still and the same size.

Its common to cut up your responsive design in 2 or 3 sizes, monitor, tablet and phone. You'd be surprised how similar you can keep your design layout across those 3. The more similar the more useful it will be to mix the data from different width that will fall into the specific media query range.

As long as you use the same technique for getting the width and height for saving your data as painting it later it will be fine. Even if you'd ignore margins and borders for instance your event would still capture on the element when its in the margin and that way you could get data like this: user position: {x -10, y -1} and still use that to paint your heat just fine on the element.

You could also give the option to mix and filter the user data across different size to the user, just call it experimental data mixing or something. You could potentially still get some very useful visual information on the most clicked elements for instance if you mix all user data regardless of screen size.

Another thing you could do is soft-mix the results. If your user data differs too much in width and height from the current element's dimensions, say more then 30%, you could exclude it. You could make this dynamic by letting the user set the sensitivity (feathering) of that percentage. That way you can still view all user heat on all smaller elements while it ignores the not very relevant user events on your larger more changeable elements.

Answer 2

My understanding of the issue is that the project works well, in terms of correctly performing the events, storing the information and displaying it, yet, there is a UX problem, because the system is offsetting (in time, I assume). I would use an idea which resembles very much compression. Imagine your monitor as a grid of pixels. It's perfectly clear that there are some precision problems, because even if we use the maximum precision our computer and its components allows us to use, if we take two adjacent pixels and want to click in between the two, we quickly realize that the precision our system offers is quite limited, which is axiomatically true for digital devices, which are unable to respect the Hausdorf separation.

Now that we have explored the limitations with our little thought experiment, we can acknowledge that such limitations exist. Hence, in principle, lowering the number of pixels, but not the number of events would not introduce more problems, it would decrease spatial precision though for a certain amount (the amount that you deem to be still acceptable, off course). So, if you have x * y resolution applied for the map, then you can think about your resolution as "every 5 pixels in with and height counts". That would make a mapping between actual pixels and imaginary pixels that would form the basis of our compression, decreasing the clickable places 25x.

This would allow you to think about the monitor as a set of regions, the number of regions being significantly smaller than the actual number of pixels (25x in our example). That would allow you to avoid storing each coordination/click separately and instead, you could always store the (x, y, n), that is, the center of the region where the event occurred and the number that event was repeated.

This way if the user clicks on a pixel (x', y'), which is located in a region whose center is (x, y), then you would only have new data if a click did not occur in that region yet. Otherwise, if a click occurred there (not necessarily at the exact same pixel, but in the region), then you would just increase n. As a result, instead of a very large set of raw pixel-event data you would have a much smaller set of pixel-event-number data.

The drawback of this approach, off course is that it somewhat reduces geometrical precision, but it should contribute to the optimization of data processing.

I confess that I'm not very experienced with Heatmap.js, so I'm unsure whether it has API support for what I am suggesting. If it has, then trying to use it would make sense. If it is not optimized properly, or does not support such a feature, then I would implement the heatmap feature using a canvas or an svg, depending on the actual needs.