Layer render buffer

[phil]

I'm using openlayers 4 and have some ol.layer.Tile Layers.

I'm loading WMS-Tiles from my Server with a Size of 256x256px.

Everything works fine so far.

Right now I have a use case, where I would like to load more Tiles than it needs to fill the current ViewPort. I would like to define a buffer, say 500m around the current ViewPort. Therefore, the user can drag around this extended area, without the need of loading this tiles (better user experience if working on a small area and same zoom level).

Is there some PreRender or PreCompose hook, where I can buffer the frameState.extent?

Something like following:

layer.addPreComposeFunction(frameState => {

  var extent = frameState.extent;

  extent = ol.extent.buffer(extent, 500);

  famreState.extent = extent;

});

Or is there another way to accomplish this?