leaflet map does not appear correctly until resize - scala

Question

I am using Leaflet with scalajs-leaflet facade on Binding.scala, and the map initializes/appears incorrectly.
In order to reproduce the issue, i have prepared a lihaoyi/workbench page similar to that in scalajs-leaflet.
First, download the forked scalajs-leaflet from https://github.com/mcku/scalajs-leaflet
Run sbt in scalajs-leaflet directory.
Enter ~ example/fastOptJS in sbt. Now, a web server started at port 12345.
Open
http://localhost:12345/example/target/scala-2.12/classes/leaflet2binding-dev.html in a browser
The problem is the map container appears but the content (tiles, etc) is not correct. Map becomes fine after a small resize on window, which triggers _onResize handler of leaflet.
The container is in the Leaflet2Binding.scala file and has its size already specified prior to initialization:
val mapElement = <div id="mapid" style="width: 1000px; height: 600px;
position: relative; outline: currentcolor none medium;"
class="leaflet-container leaflet-touch leaflet-fade-anim
leaflet-grab leaflet-touch-drag leaflet-touch-zoom"
data:tabindex="0"></div>.asInstanceOf[HTMLElement]
It is possible to insert a line lmap.invalidateSize(true) in the following line before returning the element
https://github.com/mcku/scalajs-leaflet/blob/83b770bc76de450567ababf6c7d2af0700dd58c9/example/src/main/scala/example/Leaflet2Binding.scala#L39, but did not help in this case. Namely here:
#dom def renderMap = {
val mapElement = ... (same element as above)
.. some other initializations ..
lmap.invalidateSize(true) // true means, use animation
println("mapElement._leaflet_id " +mapElement.asInstanceOf[js.Dynamic]._leaflet_id) // prints non-null value, makes me think the container is initialized
mapElement
}
Any ideas? This is binding.scala specific, but it may be a leaflet issue as well.
EDIT Possible workaround
It looks like, the map element has its clientWidth property not available during the process. Which is understandable as the document is not "ready" yet. However, the css style.width is available and could be defined in px. In that case it is possible to patch leaflet to take css style width into account during computation.
it works if the style width is specified in px.
diff --git a/src/map/Map.js b/src/map/Map.js
index b94dd443..6544d7b7 100644
--- a/src/map/Map.js
+++ b/src/map/Map.js
## -903,8 +903,9 ## export var Map = Evented.extend({
getSize: function () {
if (!this._size || this._sizeChanged) {
this._size = new Point(
- this._container.clientWidth || 0,
- this._container.clientHeight || 0);
+
+ this._container.clientWidth || parseInt(this._container.style.width.replace("px",""),10) || 0,^M
+ this._container.clientHeight || parseInt(this._container.style.height.replace("px",""),10) || 0);;^M
this._sizeChanged = false;
}

Answer 1

Maybe lmap.invalidateSize(true) is called too early (DOM is not ready or repainted).
Make sure this does not happen. To prevent that I wrap this code like:
setTimeout(function () {
mapid.invalidateSize(true);
}, 100);
This must be done after every DOM repaint.

Answer 2

People that are still facing this issue for react-leaflet, making the component only render when zoom and center are initiated, and removed when the Map is not displaying:
useEffect(() => {
setCenter([50.5, 30.5]);
setZoom(14);
}, []);
And then in the JSX
{zoom && center.length > 0 && (
<div className={styles.map}>
<Map center={center} zoom={zoom} />
</div>
)}