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How to position two elements centered on top of each other?

The problem:
I have a form with a button underneath it to submit (post) from data with jQuery ajax(). I want for the button to be replaced with a spinner (animated png) for the duration of server ajax call. But such a trivial task is impossible in css to do right.
What i have tried:
I have placed button and image inside a bootstrap row. Ox ajax call I have set button display to none and img display to block. But because this two are not of the same size makes the whole page flicker, breaks the positioning of other elements and so on.
Another idea was to try to place both elements on top of each other with absolute positioning. But, stupid as css is I cannot center it on the middle of the row.
Is there a way to position both elements on top of each other so I can control their visibility?
Please bear in mind that I cannot used absolute position in pixel, because this is a web page and I do not not how wide the browser will be, image can change in the future, text in the button can change in the future, all this things affect absolute size.
If there is another solution to my problem which would prevent the page from jumping up and down it would also be great.
EDIT
Link to one of fiddle experiments:
https://jsfiddle.net/ofb2qdt8/
.button {
position: relative;
margin: auto;
height: 50px;
width: 30px;
background: blue;
z-index: 1;
display: block;
}
.spinner {
position: relative;
margin: auto;
height: 30px;
width: 50px;
background:red;
z-index: 2;
}
This renders second element underneath on screen. Not on different z layer.
Experiment 2:
https://jsfiddle.net/ofb2qdt8/
.button {
position: absolute;
margin: auto;
height: 50px;
width: 30px;
background: blue;
z-index: 1;
display: block;
}
.spinner {
position: absolute;
margin: auto;
height: 30px;
width: 50px;
background:red;
z-index: 2;
}
This does not center both elements, and they are pushed to the top of the containing div. The element with less height should be centered.

Check this working demo: https://jsfiddle.net/ofb2qdt8/3/
Add in a few lines of jquery and update your css.
Position your loading div according to button div's position, width, height using jquery.
*Click the button to see loading div, and try to play the margin of the button to any pixel.
###JQUERY
$(document).ready(function () {
$('.c2').each(function () {
$(this).css({
'width': $(this).siblings('.c1').outerWidth(),
'height': $(this).siblings('.c1').outerHeight(),
'top': $(this).siblings('.c1').offset().top,
'left': $(this).siblings('.c1').offset().left
});
});
$('.c2').on('click', function () {
$(this).hide(0);
});
});
###CSS
.c1 {
margin: 100px auto;
width: 100px;
text-align: center;
padding: 5px 10px;
background: blue;
z-index: 1;
}
.c2 {
position: fixed;
text-align: center;
background: red;
z-index: 2;
cursor: pointer;
}

Rough, ready and untested:
HTML
<div>
<input type='submit' />
<img src="spinneyIMage.gif" />
</div>
CSS
div{ text-align: center; }
div img{ display: none; }
jQuery
$('submit').click(function(e){
e.preventDefault();
$(this).hide().next().show();
});
After the Ajax call completes reverse the above jQuery.

As I haven't been able to find a working solution I have reverted to my first idea which I discarded at first. Albeit with a little twist.
HTML
<div class="row>
<div id="container-button" class="col-xs-12>
<button id="button" onclick="button_OnClick(e)">submit form via ajax</button>
<img src="img/spinner.png" sytle="display: none" />
</div>
</div>
JS
function btnContact_OnClick() {
// show the soinner and hide the button
showSpinner();
$.ajax(
{
type: 'POST',
url: "someurl.com/target",
data: $("#form").serialize(),
dataType: "json",
complete: function() { hideSpinner();},
success: onAjaxSuccess,
error : onAjaxError
});
}
function hideSpinner() {
$("#spinner").hide();
$("#button").show();
// make container height non-fixed and content adjustable again
$("#container-button").height('auto');
}
function showSpinner() {
// THis is the trick !!!
// Make the container fixed height as it was before displaying spinner, so it does not change with content (spinner is not the same height as button
$("#container-button").height($("#container-button").height());
$("#button").hide();
$("#spinner").show();
}
This is not the perfect solution but the best I could make.
Drawbacks:
it is not clean, you have to use javasript to fix what is css layout
problem
it still causes a little flicker
the height of container while displaying spinner is dependant on button, this may cause clipping if spinner is too big

CSS remove hover effect when semi-transparent div overlays another div

I have several underlaying divs with hover effect. Sometimes I need to show modal dialog and all undelaying divs should be "disabled". This is done by placing semi-transparent high z-index div on top of them, but the problem is that hover effect on underlaying div stays until I move my mouse. Is there a way to "unhover" underlaying divs when overlaying semi-transparent div becomes visible?
Simplified exanple
HTML:
<div class="somediv"></div>
<div id="modal"></div>
CSS:
#modal {
z-index: 1000;
background:#000;
position:fixed;
top:0; left:0;
width:100%;
height:100%;
display: none;
opacity: 0.3;
}
.somediv {
position: absolute;
left: 20px;
top: 20px;
width: 100px;
height: 100px;
background-color: red;
}
.somediv:hover {
background-color: blue;
}
JS:
setTimeout(function(){
$("#modal").show();
}, 5000);
Hover over square and wait 5 seconds.

It should work: http://jsfiddle.net/rjLhj/
When you open a modal (in JS), just add a class to your .somediv ('.no-hover', for example). In CSS, change your .somediv:hover to .somediv:not(.no-hover):hover.
I don't know about compatibility... So, you should test :P
JS:
setTimeout(function(){
$("#modal").show();
$('.somediv').addClass('no-hover')
}, 2000);
CSS:
.somediv:not(.no-hover):hover {
background-color: blue;
}
Update:
http://caniuse.com/#feat=css-sel3
It works on IE9+, FF3.5+ and Safari3.1+... But you can use Attribute Selectors for reach the same result.
HTML:
<div class="somediv" data-nohover="0"></div>
<div id="modal"></div>
CSS:
.somediv[data-nohover="0"]:hover {
background-color: blue;
}
JS:
setTimeout(function(){
$("#modal").show();
$('.somediv').attr('data-nohover','1')
}, 2000);
Or better, add one class to your somediv ('hashover', for example), remove it on modal open and define your css like this:
.somediv.hashover:hover {...}

Unfortunately the browser wont pick up mouse events until the mouse is moved...
The best way to deal with this is to create a new class that overrides the hover behaviour and apply this at the same time as you show the modal.

javascript window scroll issue

I am working on javascript scroll. I have following html code
JSFIDDLE
<div class="wrapper">
<div class="red div current"></div>
<div class="blue div"></div>
<div class="green div"></div>
<div class="yellow div"></div>
</div>
In above code I have four div tags red, blue, green and yellow. All of them are position in following css.
html, body {
height: 100%;
}
.wrapper {
overflow: hidden;
height: 100%;
}
.div {
position: relative;
height: 100%;
}
.red {
background: red;
}
.blue {
background: blue;
}
.green {
background: green;
}
.yellow {
background: yellow;
}
In above html and css the red div tag is the current one which means user is seeing the red div tag on the screen. Now what I am trying to do is when user scroll over window once, then the next div tag i.e. blue will be animated and moved to the top and will become visible to the user whereas the red div tag will be behind the blue one. This same process goes for both green and yellow.
The problem is that when user scroll once then the div tag should animate however my current javascript code is keep reading the scroll and animating the div tags one after another. What I want is when user scroll once then scroll should be disabled until the blue div tag is animated. Then scroll should be enabled. Again when user scroll second time, the scroll should disable until the green div tag completes its animation. Same goes for yellow.
How can I achieve above?
Here is my javascript
$(window).on("scroll", function () {
var next = $('.current').next();
var height = next.outerHeight();
next.animate({top: '-=' + height}, 500, function () {
$(this).prev().removeClass('current');
$(this).addClass('current');
});
});

Please have a look on update JsFiddle
$(window).on("scroll", function () {
var next = $('.current').next();
var height = $('.current').outerHeight();
$('.current').prevAll().each(function(){
height += $(this).outerHeight();
});
next.animate({top: '-=' + height}, 500, function () {
$(this).prev().css('top','');
$(this).prev().toggleClass('current');
$(this).toggleClass('current');
});
});

The main reason your example wasn't working as expected is because you were relatively positioning the divs, and not moving them to the correct spot.
Working JSFiddle:
http://jsfiddle.net/seanjohnson08/rVVuc/6/
.wrapper {
overflow: hidden;
height: 100%;
position: relative;
}
.div {
position: absolute;
height: 100%;
width: 100%;
top: 100%;
}
.current{
top: 0;
}
If you are looking for a way to limit the amount of scroll events fired, try throttling: http://benalman.com/projects/jquery-throttle-debounce-plugin/. My solution doesn't require this, because no matter how many times it is firing the scroll event, it only ever tells jquery to animate to top:0, there's no chance of it animating past that.

How to make divs rise up from other divs?

I know how to stack divs on top of divs by doing position:absolute for the parent and position:relative for the children, but how can I make a div "rise up" from another div? An example of what I want to achieve is here. Scroll to the bottom and hover your mouse over the artwork.

What you can do is absolute position that pop-up in a relative positioned box, for example:
<div class="featured-image">
<div class="caption">
<p>This is where your text goes</p>
</div>
</div>
Now that you have that, you'll want to make the caption invisible unless scrolled over. So, a simple way to do this with just CSS is:
.featured-image { position:relative; width:300px; height: 400px; }
.caption { position:absolute; bottom:0; display:none; }
.feature-image:hover > .caption { display:block; }
The last line makes it seen when you mouse-over the image.
Then you could animate it with jQuery easily. That appears to be what they're using.
$(document).ready(function(e) {
$(".caption").hide();
});
var show = function() {
$(".caption", this).stop(true, true).show(500)
};
var hide = function() {
$(".caption", this).stop(true, true).hide(500);
};
$(".featured-image").hover(show, hide);

HTMl
<div id="pic">
<div>
</div>
</div>
CSS
#pic {
position: relative;
background: yellow;
width: 100px;
height: 100px;
overflow: hidden;
}
#pic div {
position: absolute;
bottom: -50px;
background: black;
height: 50px;
width: 100px;
}
JQuery
$('#pic').hover(
function(){
$(this).find('div').stop(true, true).animate({
'bottom': '+=50'
}, 100);
},
function(){
$(this).find('div').stop(true, true).animate({
'bottom': '-=50'
}, 100);
}
);
jsfiddle: http://jsfiddle.net/Z6eLa/2/

Introduce yourself to jQuery and z-index.
http://api.jquery.com/slideDown/
The trick here is slidedown will make your top div slide down. The only thing that comes to my mind, is instead of expanding that bottom div up, do the opposite. Get the top div, and have it slide-up, while the other div is displayed behind it. It should give the appearance of the bottom div 'sliding-up'.
Note, sorry if this doesn't work. I'm actually not sure if you can get it to slide only halfway up instead of all the way...good luck though!

You don't need JS for that, just use css3 transitions.

jQuery fadeIn fadeOut background problem

When I fadeIn a div, and this animation finished, the background suddenly disappears (this time only in Firefox).
I have a container, with two nested elements in it. The second element has a negative margin, so it appears on top of the first.
My script:
jQuery(document).ready(function($) {
$(".second_element").hide();
$(".container").each(function () {
$(this).mouseover(function () {
$(this).children(".second_element").stop(true, true);
$(this).children(".second_element").fadeIn(250, 'linear');
});
$(this).mouseout(function () {
$(this).children(".second_element").stop(true, true);
$(this).children(".second_element").fadeOut(100, 'linear');
});
});
});
CSS:
.container{
width: 221px;
height: 202px;
display: block;
float: left;
position: relative;
}
.first_element {
height: 200px;
width: 219px;
}
.second_element {
display:none;
background: #fff !important;
margin-top: -51px;
width: 219px;
height: 50px;
}
And for clarity, this a HTML example
<td class="container">
<div id="first_element">...</div>
<div id="second_element">...</div>
</td>
My second problem is, that when my mouse is hovering above the second element, the function is executed again (so the second element fades out and in). While the second element is just IN the container

This is shorter, and also, for first run, it is better that hide target by fadeOut() instead of hide()
$(".caption").fadeOut(1);
$(".container").each(function() {
$(this).mouseover(function() {
$(".caption", this).stop().fadeIn(250);
});
$(this).mouseout(function() {
$(".caption", this).stop().fadeOut(250);
});
});

Complementing the last comments; I got it. I tried it in several ways, and also with the caption to position: absolute, but instead I had to set the first element to position: absolute... now it works (however not with fading, but this is fine). I thank you very much for all your help and support!