Using CSS transitions in CSS Grid Layout

I am trying to get my sticky header to have a transition effect so it eases in rather than just a snap movement.

What am I doing wrong?

Here's my a working version:

Basically the following code adds the class tiny to my wrapper class, this works fine.

$(window).on('load', function() {
    $(window).on("scroll touchmove", function () {
        $('.wrapper').toggleClass('tiny', $(document).scrollTop() > 0);
    });
});

Here's the CSS part:

.wrapper {
    grid-template-rows: 80px calc(75vh - 80px) 25vh 80px;
    -o-transition: all 0.5s;
    -moz-transition: all 0.5s;
    -webkit-transition: all 0.5s;
    transition: all 0.5s;
}
.tiny {
    grid-template-rows: 40px calc(75vh - 40px) 25vh 80px;
}

So the header does shrink as it should but there is no animation, have I missed something or does transitions simply not work with grid?

Here's a link to the css-grid docs.

https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Grid_Layout

$(window).on('load', function() {
  $(window).on("scroll touchmove", function() {
    $('.wrapper').toggleClass('tiny', $(document).scrollTop() > 0);
  });
});

* {
	margin:0;
	padding:0;
}

.wrapper {
	display: grid;
	grid-gap: 0px;
	grid-template-columns: 1fr 1fr 1fr 1fr;
	grid-template-rows: 80px calc(75vh - 80px) 25vh 80px;
	grid-template-areas:
		"head head head head"
		"main main main main"
		"leader leader leader leader"
		"foot foot foot foot";
	background-color: #fff;
	color: #444;
}
.tiny {
	grid-template-rows: 40px calc(75vh - 40px) 25vh 80px;
}
.box {
	background-color: #444;
	color: #fff;
	border-radius: 5px;
	font-size: 150%;
}
.box .box {
	background-color: lightcoral;
}

.head {
	grid-area: head;
	background-color: #999;
	z-index: 2;
	display: grid;
	grid-gap: 0px;
	grid-template-columns: 20% 1fr;
	-o-transition: all 0.5s;
	-moz-transition: all 0.5s;
	-webkit-transition: all 0.5s;
	transition: all 0.5s;
	position: sticky;
	top: 0;
}

.logo{
        height: inherit;
        grid-column: 1;
        grid-row: 1;
        background-color:red;
        position: relative;
        overflow: hidden;
    }
.logo img {
        position: absolute;
        top: 50%;
        left: 50%;
        transform: translate(-50%, -50%);
        display: block;
        max-width: 100%;
        height: auto;
    }
.main {
	grid-area: main;
	/* CSS Grid */
	z-index: 1;
	grid-column: head-start / head-end;
	grid-row: head-start / leader-start;
	background-color: red;
}
.leader {
	grid-area: leader;
	z-index:1;
	display: grid;
	grid-gap: 0px;
	grid-template-columns: repeat(4, 1fr  );
}
.foot {
	grid-area: foot;
	z-index:1;
}

<div class="wrapper">
  <div class="box head">
    <div class="box logo">
      <a href="#"><img src="https://unsplash.it/200/300/?random" /></a>
    </div>
    <div class="box nav">nav</div>
  </div>
  <div class="box main">main</div>
  <div class="box leader">
    <div class="box leader-1">1</div>
    <div class="box leader-2">2</div>
    <div class="box leader-3">3</div>
    <div class="box leader-4">4</div>
  </div>
  <div class="box foot">foot</div>
</div>

Solution

According to the spec, transitions should work on grid-template-columns and grid-template-rows.

7.2. Explicit Track Sizing: the grid-template-rows and grid-template-columns properties

Animatable: as a simple list of length, percentage, or calc, provided the only differences are the values of the length, percentage, or calc components in the list

So, if my interpretation is correct, as long as the only changes are to the values of the properties, with no changes to the structure of the rule, transitions should work. But they don't.

UPDATE

This does work but is so far only implemented in Firefox. Follow here for other browser updates. https://codepen.io/matuzo/post/animating-css-grid-layout-properties

~ a contribution in the comments by @bcbrian

Here's a test I created:

grid-container {
  display: inline-grid;
  grid-template-columns: 100px 20vw 200px;
  grid-template-rows: repeat(2, 100px);
  background-color: black;
  height: 230px;
  transition: 2s;
  
  /* non-essential */
  grid-gap: 10px;
  padding: 10px;
  box-sizing: border-box;
}

grid-container:hover {
  grid-template-columns: 50px 10vw 100px;
  grid-template-rows: repeat(2, 50px);
  background-color: red;
  height: 130px;
  transition: 2s;
}

grid-item {
  background-color: lightgreen;
}

<grid-container>
  <grid-item></grid-item>
  <grid-item></grid-item>
  <grid-item></grid-item>
  <grid-item></grid-item>
  <grid-item></grid-item>
  <grid-item></grid-item>
</grid-container>

jsFiddle demo

In the test, the transition works on the height and background color, but not on grid-template-rows or grid-template-columns.