Collapsible

Single-child container with a clickable header that expands and collapses the body. When collapsed only the header row is visible; the parent layout reclaims the freed space automatically.

Constructor: NewCollapsible(id, class, title string, expanded bool) *Collapsible

Methods

• Add(widget Widget) — sets the body widget; replaces any previous child
• Children() []Widget — returns the body widget (empty slice when none)
• Collapse() — hides the body; moves focus to the collapsible if the body had it
• Expand() — shows the body
• Expanded() bool — reports whether the body is currently visible
• Hint() (int, int) — collapsed: (childW, 1); expanded: (childW, 1+childH); expanded with no child height hint: (childW, -1) (fractional)
• Layout() — positions the child below the header row
• Toggle() — switches between expanded and collapsed

Events

Event	Data	Description
"change"	bool	Expansion state changed; true = expanded

Notes

Flags: "focusable"

Keyboard: Enter / Space toggle; → expands; ← collapses.

Mouse: clicking the header row toggles.

Style selectors: "collapsible", "collapsible/header" — with :focused and :hovered states.

Theme strings: "collapsible.expanded" and "collapsible.collapsed" set the indicator character (defaults ▼ / ▶ ).