Fast scroll zoom results in out of memory error #7021

See https://codepen.io/arnog/pen/YgZdEZ

1. Create a heatmap plot with about 500 x 500 elements
2. Configure the plot with scrollZoom = true and zsmooth = 'fast'
3. Use the mouse wheel to zoom in rapidly into the plot

Result:

• the plot is not zoomed in and the console displays "Uncaught RangeError: Invalid array length"

The array being created is the pixel array in which to draw the interpolated heatmap at traces/heatmap/plot.js:238

The problem seems to be that imageWidth and imageHeight are used here and later in the function, perhaps instead of canvasW and canvasH.

(refiled #3615 as per request)

I have seen this on Chrome on macOS. The error happens here:

        if(zsmooth) { // best or fast, works fastest with imageData
            var pxIndex = 0;
            var pixels;

            try {
                pixels = new Uint8Array(imageWidth * imageHeight * 4);
            } catch(e) {
                pixels = new Array(imageWidth * imageHeight * 4);
            }

when executing the new Array in the catch statement. When it happens, imageWidth was 63775964 and imageHeight was 63442058.