What would make a Meteor app stop scrolling? - meteor

Question

Any browser. All other functions operate as normal. I can traverse routes, open modals, dropdowns, manipulate collections... everything works.
But at some point, the browser will no longer scroll. In any view. Unless I refresh the browser window. Then scrolling goes back to normal.
What might cause this? Why does refreshing the page fix the issue? Is there a method to smack reactivity upside the head?

Answer 1

This is likely due to navigating away from a (Bootstrap ?) modal without properly closing it.
When you show up a modal in HTML5 frameworks, they usualy display a backdrop (some kind of fullscreen grayed out component) and disable scrolling to simulate desktop experience.
You can solve this problem using a simple iron:router pattern, if you're not using this package, be sure to execute the corresponding code whenever you navigate away from a page where a modal might get shown.
client/views/modal/modal.html
<template name="modal">
<div id="modal" class="modal fade">
...
</div>
</template>
<template name="main">
{{> modal}}
<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#modal">
Show Modal
</button>
</template>
client/config/router.js :
// define the plugin
Iron.Router.plugins.hideBootstrapModalOnStop=function(router,options){
router.onStop(function(){
// hide modal backdrop on route change
$(".modal-backdrop").remove();
// remove modal-open state on body
$("body").removeClass("modal-open");
});
};
// activate the plugin
Router.plugin("hideBootstrapModalOnStop");
The .modal-open class set on the HTML body tag is the one disabling scrolling when it is set, so by making sure that we remove that class whenever we navigate away from a page when a modal is possibly shown, we prevent this weird unexpected behavior to happen.