javascript - Resizing a leaflet map on container resize

Question

I have a <div> containing a leaflet map. Upon certain events the height of the <div> will be altered. I'd like for the map to resize to the new dimensions of its surrounding <div> so that the old center is centered in the resized smaller or larger map. I tried using the invalidateSize() function, but it doesn't seem to work at all. How can I resize and center the map after that map-container-resize event?

$mapContainer.on('map-container-resize', function () {
   map.invalidateSize(); // doesn't seem to do anything
});

Edit to give more context:

The map container is styled initially as

#map-container {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;

    transition: height 0.5s ease-in-out;
}

After a user clicks a certain button, another panel shows at the bottom of the page and the map-container's height will be reduced to something less than 100% (say 80%).

Upon click on this button, the map-container-resize event is triggered so that I can make the map resize and center on its old (i.e. before the resizing happened) center. The map itself should then also be resized to 80% of its initial height.

The APi doc for invalidateSize seemed to be what I wanted:

"Checks if the map container size changed and updates the map if so [...]"

But having a look with the output of the getSize function before and after the call to invalidateSize, nothing is different, the map remains at its old size.

Answer 1

The problem is that the resizing of the #map-container div is done via a css transition. The transition hasn't started yet, let alone ended, when the call to invalidateSize happens so the leaflet map cannot recognize any change of dimensions of its surrounding div.

Triggering the map-container-resize event with a delay solved the problem. This way :

setTimeout(function(){ map.invalidateSize()}, 400);