I think it's referring to containers in the layout. One column container, a full row container, or two row containers.
If your widget doesn't fill up two row containers in CSS it will appear as a single row for responsiveness.
Correct me if I'm wrong, but that's been my understanding. I'd like further clarification if I am wrong, also.
That's correct. The height of a widget is determined solely by how much content it displays. The settings only control the width. If you want it taller, you could throw in some
tags. I think you could also use CSS to set wide margins and/or padding.
Thanks for your replies. I am putting in an iframe with an 800 pixel height using CSS. It starts scrolling vertically after approximately 400 pixels are shown no matter if using full or double.
I figured it out, sort of. The index.css template file has a .dashboard-block .body style in it that sets the maximum height of all dashboard blocks to 300px even though the double block is supposed to be a minimum of 400px. I commented it out and it works (at least until the next update). I have a github issue opened on this.
You should be able to override that in your own CSS file. If the widget uses PHP, the CSS can be loaded by the widget with $modx->regClientCss(). That will load it after all the Manager CSS.