What is the standard calculation for form size based on screen resolution or size?

www.codemine.com offers what they call a 'stretchy control' which is free and stable. Their description:

"Simply drop this control on any VFP form and call it from the Resize() event to stretch the form to any size. Control and font sizes are proportionally resized to match the current form size"

In addition, you can emulate a corner image that implies that a form has resize capabilities with a image whose properties are FontName: Martlett,
Caption p.