I am working on writing a for loop that updates the parameters of an OpenLayers map during each iteration. Once the map is fully rendered, I need to extract the context of the map canvas and add it to a GIF object. It is important that these actions occur synchronously to ensure proper rendering of the map and layers before adding the context. Currently, I have been using a setInterval workaround, but after reading through this informative post, I understand that utilizing async/await/Promises would be a better approach. My main concern is how to wrap my functions in a Promise to guarantee sequential execution while still maintaining access to the Vue app context (this).
The structure of my for loop would resemble:
for(let i = 0 ; i < this.dateArraySurface10.length - 1 ; i++)
{
waterfall([
this.setTimeSurface10(),
this.map.renderSync(),
this.myCallback(),
],
function(err){
console.log("Waterfall error : ",err);
});
}
The functions used in the loop are as follows:
setTimeSurface10: function () {
if (this.currentTimeSurface10 === null) {
this.currentTimeSurface10 = this.startTimeSurface10;
} else if (this.currentTimeSurface10 >= this.endTimeSurface10) {
this.currentTimeSurface10 = this.startTimeSurface10;
} else {
this.currentTimeSurface10 = new Date(
this.currentTimeSurface10.setMinutes(this.currentTimeSurface10.getMinutes() + 60)
);
}
this.surface10.getSource().updateParams({ TIME: this.currentTimeSurface10.toISOString().split(".")[0] + "Z" });
},
myCallback: function () {
const mapCanvas = document.createElement('canvas');
const divElement = document.querySelector(".map");
mapCanvas.width = divElement.offsetWidth;//size[0];
mapCanvas.height = divElement.offsetHeight;//size[1];
const mapContext = mapCanvas.getContext('2d');
Array.prototype.forEach.call(
document.querySelectorAll('.ol-layer canvas'),
function (canvas) {
if (canvas.width > 0) {
const opacity = canvas.parentNode.style.opacity;
mapContext.globalAlpha = opacity === '' ? 1 : Number(opacity);
const transform = canvas.style.transform;
const matrix = transform
.match(/^matrix\(([^\(]*)\)$/)[1]
.split(',')
.map(Number);
CanvasRenderingContext2D.prototype.setTransform.apply(mapContext,matrix);
mapContext.drawImage(canvas, 0, 0);
}
}
);
this.gif.addFrame(mapCanvas, {copy:true, delay: 200});
}