You can control the bar width and other properties using CSS. The bar is built using two nested divs with the following CSS classes (applies to the default "calendar_default" theme):
calendar_default_event_bar
calendar_default_event_bar_inner
You can override the styles directly or you can add a custom CSS class and use it to target the event:
dp.onBeforeEventRender = args => {
args.data.cssClass = "my_class";
};
CSS:
.calendar_default_event_bar.my_class .calendar_default_event_bar_inner {
width: 10px;
}