InDesign FXLs: prevent UI from displaying with touches

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If you’ve been playing around with InDesign’s FXL export, you know it allows for a huge amount of interactivity with almost no hand coding.

There’s just one thing they missed in the export option. When you tap on an element to trigger an interactive in iBooks on iOS and Kobo tablets, it often triggers the reader Chrome.

When tapped in iBooks, the iBooks UI chrome appears.

You could argue that’s expected behavior, but it creates a sub-optimal reader experience. The great news is that it’s super easy to fix. Let’s dig in.

Setup

The first thing you’ll want to do is unzip your EPUB file. Yes, we’ll need to write some code, but I promise to make it quick and painless.

Next, navigate to your EPUB folder, then navigate to “OEBPS,” then “script,” and finally the file named “idGeneratedScript.js.” Open this file in a text editor like Dreamweaver or BBEdit.

Javascript

If you’ve never written Javascript before, don’t freak out! Javascript controls all of the interactivity in ebooks, and while it looks like a crazy jumble of code the lines we’ll be adding will be very, very easy to add.

Adobe’s export actually creates Javascript that—even for a seasoned script writer like myself—is a bit murky. But the magic happens here:

function onMouseUp(element, event) {
var is_touch_device = 'ontouchstart' in document.documentElement;
if (is_touch_device) return;
removeClass(element, '_idGenStateClick');
var actions = element.getAttribute("data-releaseactions");
if(actions) {
eval(actions);
}
event.stopPropagation();
}

I won’t go into too much detail here, but this function handles all the code for when a mouse or finger move “up” on an element in your ebook. All we need to do is add one line of code to this function to fix the UI Chrome issue.

function onMouseUp(element, event) {
event.preventDefault();
var is_touch_device = 'ontouchstart' in document.documentElement;
if (is_touch_device) return;
removeClass(element, '_idGenStateClick');
var actions = element.getAttribute("data-releaseactions");
if(actions) {
eval(actions);
}
event.stopPropagation();
}

We added event.preventDefault(); right below the first line of the function. This tells the device “don’t do anything you would normally do when a screen is touched!” Really, that’s all it says. (For the more technical folks out there, you can read this for more info.)

To be safe, we should add this to every function in that js file.

Do a search for:

, event) {

and replace that with:

, event) {
event.preventDefault();

(Thanks to Anne-Marie for the better find/replace code than I had previously included here)

Note: this find and replace may not be perfect—I haven’t looked at enough InDesign script files to be sure this will work 100% of the time. If you run into issues, it may be safe to just search for “event” and make sure any function that uses an event paramater (i.e. is inside the parentheses) includes event.preventDefault();

Finally, save the file and zip your EPUB back up and test on your devices. You should no longer have the Chrome appear when you interact.

no chrome!

Caveats and Warnings

I’d like to note that this post is about fixing this particular issue, but care should be taken to overusing this—or using it in the wrong place on a page. As Naomi Kennedy and Anne-Marie point out, overusing these features or using them too close to page margins can have negative affects.

@ePubSecrets Add a warning not to apply it to things near the edge of the page or cover the whole page? could prevent page turns #eprdctn

— Naomi Kennedy (@naomikennedy) December 2, 2014

@naomikennedy @ePubSecrets best practice would be to limit touch-areas in ebooks to a safe zone (away from page turn margins) #eprdctn — AnneMarie Concepcion (@amarie) December 2, 2014

The above code samples and images come from Anne-Marie’s excellent InDesign CC Fixed Layout video series on Lynda.com. Check it out to learn even more about Fixed Layout from InDesign.