1. How can you position the modal vertically in the center when you don't know the exact height of the modal?
To absolute center the Bootstrap 3 Modal without declaring a height, you will first need to overwrite the Bootstrap CSS by adding this to your style sheet:
.modal-dialog-center { /* Edited classname 10/03/2014 */
margin: 0;
position: absolute;
top: 50%;
left: 50%;
}
This will position the modal-dialogs top-left corner in the center of the window.
We have to add this media query or else the modal margin-left is wrong on small devices:
@media (max-width: 767px) {
.modal-dialog-center { /* Edited classname 10/03/2014 */
width: 100%;
}
}
Now we will need to adjust its position with JavaScript. To do that we give the element a negative top and left margin equal to half of its height and width. In this example we will be using jQuery since it is available with Bootstrap.
$('.modal').on('shown.bs.modal', function() {
$(this).find('.modal-dialog').css({
'margin-top': function () {
return -($(this).outerHeight() / 2);
},
'margin-left': function () {
return -($(this).outerWidth() / 2);
}
});
});
Update (01/10/2015):
Adding on Finik's answer. Credits to Centering in the Unknown.
.modal {
text-align: center;
padding: 0!important;
}
.modal:before {
content: '';
display: inline-block;
height: 100%;
vertical-align: middle;
margin-right: -4px; /* Adjusts for spacing */
}
.modal-dialog {
display: inline-block;
text-align: left;
vertical-align: middle;
}
Notice the negative margin-right? This removes the space added by inline-block. That space causes the modal to jump to the bottom of the page @media width < 768px.
2. Is it possible to have the modal centered and have overflow:auto in the modal-body, but only if the modal exceeds the screen height?
This is possible by giving the modal-body an overflow-y:auto and a max-height. This takes a bit more work to get it working properly. Start with adding this to your style sheet:
.modal-body {
overflow-y: auto;
}
.modal-footer {
margin-top: 0;
}
We will use jQuery again to get the window height and set the max-height of the modal-content first. Then we have to set the max-height of the modal-body, by subtracting the modal-content with the modal-header and modal-footer:
$('.modal').on('shown.bs.modal', function() {
var contentHeight = $(window).height() - 60;
var headerHeight = $(this).find('.modal-header').outerHeight() || 2;
var footerHeight = $(this).find('.modal-footer').outerHeight() || 2;
$(this).find('.modal-content').css({
'max-height': function () {
return contentHeight;
}
});
$(this).find('.modal-body').css({
'max-height': function () {
return (contentHeight - (headerHeight + footerHeight));
}
});
$(this).find('.modal-dialog').css({
'margin-top': function () {
return -($(this).outerHeight() / 2);
},
'margin-left': function () {
return -($(this).outerWidth() / 2);
}
});
});
You can find a working demo here with Bootstrap 3.0.3: http://cdpn.io/GwvrJ
EDIT: I recommend using the updated version instead for a more responsive solution: http://cdpn.io/mKfCc
Update (30/11/2015):
function setModalMaxHeight(element) {
this.$element = $(element);
this.$content = this.$element.find('.modal-content');
var borderWidth = this.$content.outerHeight() - this.$content.innerHeight();
var dialogMargin = $(window).width() < 768 ? 20 : 60;
var contentHeight = $(window).height() - (dialogMargin + borderWidth);
var headerHeight = this.$element.find('.modal-header').outerHeight() || 0;
var footerHeight = this.$element.find('.modal-footer').outerHeight() || 0;
var maxHeight = contentHeight - (headerHeight + footerHeight);
this.$content.css({
'overflow': 'hidden'
});
this.$element
.find('.modal-body').css({
'max-height': maxHeight,
'overflow-y': 'auto'
});
}
$('.modal').on('show.bs.modal', function() {
$(this).show();
setModalMaxHeight(this);
});
$(window).resize(function() {
if ($('.modal.in').length != 0) {
setModalMaxHeight($('.modal.in'));
}
});
(Updated 30/11/2015 http://cdpn.io/mKfCc with above edit)
