The PR significantly improves rendering performance of the choice drop-down by changing how we're displaying the "none" option.

Whereas before we used to add a special "none" option to the items list which we were then testing for in the template for each rendered item (using a switch/case), we're now instead adding a single "none" option statically in the template which is displayed/activated/disabled when needed, thus removing the need for expensive DOM checks in each rendered item.

The screenshots below are comparing the rendering performance of a drop-down with 366 visible items. The initial crest is when the user clicked on the drop-down menu. It ends when the drop-down is rendered on screen. Each test was done twice.

Legacy Implementation

Optimized Implementation