Function seed 

pub fn seed(kind: &str, rect: Rect) -> String

The smallest node of this kind that a form can actually hold, as file text.

What a designer writes when somebody drops a widget on the canvas. A rectangle is the most of it — but “a rect and nothing else” is not true of every widget, because three of them have a property the builder requires: an alert has no colour to draw itself in without a role, a slider has no range without min and max, and an image has nothing to draw without a src. A node missing one of those parses and then will not build, so a designer that wrote one would place a widget and break the form.

select and collapse were a fourth and fifth until #118, and they were the awkward ones: what they lacked was not a number but a message, so the seed had to invent a name nobody had asked for. Both have an inert constructor now, so a dropped one carries no message at all.

This lives beside the code that raises those requirements, so the two cannot drift; a test seeds every widget in all, builds the result, and fails if a new one needs something this does not give it.

use denise::Rect;

assert_eq!(
    seed("button", Rect::new(16, 24, 100, 32)),
    r#"button "button" x=16 y=24 w=100 h=32"#,
);