jquery - Bootstrap 3 - set height of modal window according to screen size

Question

I am trying to create a kind of responsive megamenu using Bootstrap 3 modal dialog. I would like to set the width and height of the whole modal window to 80% of the viewport, while setting the modal-body to a max-height in order not to populate the whole screen on large viewports.

My HTML:

    <div class="modal fade">
            <div class="modal-dialog modal-megamenu">
                <div class="modal-content">
                    <div class="modal-header">
                        <button type="button" class="close" data-dismiss="modal" aria-hidden="true">x</button>
                        <h4 class="modal-title">Modal Mega Menu Test</h4>
                    </div>
                    <div class="modal-body">
                        <div class="row">
                            <div class="col-md-3"></div>
                            <div class="col-md-3"></div>
                            <div class="col-md-3"></div>
                            <div class="col-md-3"></div>
                        </div>
                    </div>
                </div>
                    <div class="modal-footer">
                        <button type="button" data-dismiss="modal" class="btn btn-primary">close</button>
                    </div>
             </div>
        </div>

My CSS:

.modal-megamenu {
    width:80%;
    height:80%;
}

.modal-body {
    max-height:500px;
    overflow:auto;
}

This works as intended for the width, but the "height" parameter doesn't give any result. Like that, the height of the modal window is always set to the max-height value. Does anybody have an idea of how to set the height dynamically according to the viewport height?

Answer 1

Pure CSS solution, using calc

.modal-body {
    max-height: calc(100vh - 200px);
    overflow-y: auto;
}

200px may be adjusted in accordance to height of header & footer