We try to make things as WYSIWYG as we can, given that the application may well be, and often is, deployed at different resolutions, with Sesame open at differing sizes.

One of the early beta versions of Sesame opened the form with the same extents as set in SDesigner, but that was met with both confusion and dislike - in that designers could not predict the size that would be needed as deployed. To compensate, Sesame colors the background around the form (the background can grow as Sesame is maximized or stretched, but not the form) with the background color of the form. About an equal number of people then argued that they wanted the form centered, as argued that they wanted it in the top left corner. It was left in the top left corner in that that is simpler.

Having the form have an edge in designer remained, though, because it serves a practical non-aesthetic purpose. Elements can be dragged off the edge of the form to temporarily disable them in runtime, without deleting them. We call that "ghosting" an element.

To create an edge for your form can be done and retained in runtime by using a filled box type that is nearly the same size as the form  and a different color from the form. Then drag and drop elements on top of this unlabelled box. Using an "unfilled" box type will also create a nice border to simply mark the edge of the form.

The default box style is an unfilled border. If you select the box and go to the properties editor on the "Look" tab you will find a small pulldown menu: "Box Fill". Select "Filled" from the pulldown and your box will fill with the color selected on the "Color" tab for "Back/Fill".