I want to show a login form at the center of my layout. I found this example:
const ui = { rows: [ {}, { cols:[ {}, login_form, {}]}, {} ] };
Is that really the “official” way of centering something with webix? 
I already found out that I actually NEED the outer {} Otherwise my form will always be as large as the containing div. But I want my form to be smaller and centered.
You can set css property of form config object like this: css: { margin:“auto” }
Snippet here: https://webix.com/snippet/45ac366b
If you want to know more about center element. See CSS Layout - Horizontal & Vertical Align
Is that really the “official” way of centering
Yes. A spacer provides the dynamic gap within the UI which supports all webix sizing properties.
For example, such structure will be useful in SPA where views are placed in a single webix.ui, which means they are not divided by HTML containers.
CSS will be valid for the container of the UI.
But please note that custom CSS sizing/positioning for the views within the Webix layout may be eliminated or cause conflict with the inner sizing logic of Webix.
@Doogie: yes, it may sound strange, but there’s no attribute to “center” a UI element in its parent. Webix uses those spacers { }.
Here’s a sample showing how to center horizontally a Datatable. The key is to make sure the centered element defines its own width. In the case of the Datatable, that meant setting widths for the columns, instead of using fillspace: true.
https://snippet.webix.com/1f1mqzj5
trying center horizontally and vertically