Composite Pattern

Compose objects into tree structures. Individual objects and compositions treated uniformly through common interface.

ikigai Application

Layer system: Layers (scrollback, separator, input, spinner) compose into layer stack. Each implements same render interface:

typedef struct {
    void (*render)(void *layer, ik_render_ctx_t *render);
    void (*resize)(void *layer, int width, int height);
} ik_layer_vtable_t;

Rendering: REPL iterates layers, calls render on each. Doesn't care if layer is simple or composite.

Future uses:

• Nested UI components
• Tool result trees
• Message threading/nesting

Benefit: Add new layer types without changing render loop.