Layout

A frame is built top-down: you ask the terminal for the root area, split it into sub-areas, optionally take the "inner" rectangle of a bordered block, and draw widgets into those areas.

Root Area

uint root = term.RootArea;

This is the full terminal rectangle (Cols × Rows). Every layout starts here.

Splitting

Split(area, direction, constraints…) returns child area IDs in declaration order.

// Top bar (3 rows) + main content (rest)
var rows = term.Split(root, Direction.Vertical,
    Constraint.Length(3),
    Constraint.Min(0));

uint topBar = rows[0];
uint main   = rows[1];

Always guard against degenerate sizes:

if (rows.Length < 2) return;

When the terminal is too small to satisfy every constraint, Split may return fewer areas than requested.

Constraint Types

Constraint	Meaning
Constraint.Length(n)	Exactly n rows/columns
Constraint.Min(n)	At least n, grows to absorb leftover space
Constraint.Max(n)	At most n, shrinks if needed
Constraint.Percentage(p)	Percent of parent area (0–100)
Constraint.Fill(weight)	Proportional fill against other Fill siblings

Example with mixed types:

var cols = term.Split(main, Direction.Horizontal,
    Constraint.Length(20),       // fixed 20-col sidebar
    Constraint.Percentage(60),   // 60% of remaining
    Constraint.Min(10));         // at least 10, takes leftover

Borders + Inner

Block draws a bordered frame; Inner(area) returns the rectangle inside the border so children don't overdraw the frame.

term.Block(area, "Title", Borders.All);
uint inner = term.Inner(area);
term.Paragraph(inner, "Body text inside the bordered block.");

Borders is a flag enum: Borders.Top | Borders.Bottom, Borders.Left | Borders.Right, Borders.All, Borders.None.

Area Hit-Testing

Every area ID can be reverse-queried for its terminal rectangle, useful for mouse input:

if (term.TryGetAreaRect(inner, out int x, out int y, out int w, out int h))
{
    // x, y, w, h in terminal cells
}

See Input Handling for using these IDs in mouse routing.

Nested Example

protected override void BuildFrame(RatatuiTerminal term)
{
    uint root = term.RootArea;

    // Header + body
    var outerRows = term.Split(root, Direction.Vertical,
        Constraint.Length(3),
        Constraint.Min(0));
    if (outerRows.Length < 2) return;

    // Two-column body
    var bodyCols = term.Split(outerRows[1], Direction.Horizontal,
        Constraint.Percentage(30),
        Constraint.Percentage(70));
    if (bodyCols.Length < 2) return;

    term.Block(outerRows[0], "Header", Borders.All);
    term.Block(bodyCols[0],  "Sidebar", Borders.All);
    term.Block(bodyCols[1],  "Content", Borders.All);

    term.Paragraph(term.Inner(bodyCols[1]), "Hello, layout.");
}