The calendar component doesn’t re-render events when the width changes. The resizing itself is fully handled by the browser (so there is nothing to optimize). Generally, it will take longer if the resized content is bigger.
However, the calendar watches for dimension and visibility changes. It updates measurements required for calculating proper position of some UI elements (especially when the scrollbar visibility changes as a result) and re-renders these elements when necessary. You can turn this auto-adjustment off using the watchWidthChanges property:
{
watchWidthChanges: false,
// ...
}
In React, you will need the latest sandbox build (version 2023.4.5810+) to change the value. This build also debounces the calculations and updates by 100ms so you may also see an improvement without turning it off.
To manually recalculate the necessary internal values after the resizing is complete, you can call the show() method.