init layout, notifications, tabs & more

Signed-off-by: Hadi <112569860+anotherhadi@users.noreply.github.com>

layout/geometry.go

@@ -0,0 +1,64 @@
+package layout
+
+import "math"
+
+// Rect is an axis-aligned screen region in terminal cells, origin top-left.
+type Rect struct {
+	X, Y, W, H int
+}
+
+// LeafRect pairs a Leaf's id with the Rect it was allocated by the most
+// recent layout pass.
+type LeafRect struct {
+	ID   string
+	Rect Rect
+}
+
+// computeLayout descends the tree rooted at n, allocating r between its
+// leaves according to each Split's ratio/min/max, and returns a flat
+// registry of every leaf's resolved Rect. Order is deterministic (a
+// depth-first walk, first child before second), which is what makes it safe
+// to use directly as a stable iteration order elsewhere (Init, routing).
+func computeLayout(n *Node, r Rect) []LeafRect {
+	if n == nil {
+		return nil
+	}
+	if n.leaf {
+		return []LeafRect{{ID: n.id, Rect: r}}
+	}
+
+	var firstRect, secondRect Rect
+	if n.dir == Horizontal {
+		w1 := resolveSize(n, r.W)
+		firstRect = Rect{X: r.X, Y: r.Y, W: w1, H: r.H}
+		secondRect = Rect{X: r.X + w1, Y: r.Y, W: r.W - w1, H: r.H}
+	} else {
+		h1 := resolveSize(n, r.H)
+		firstRect = Rect{X: r.X, Y: r.Y, W: r.W, H: h1}
+		secondRect = Rect{X: r.X, Y: r.Y + h1, W: r.W, H: r.H - h1}
+	}
+
+	leaves := computeLayout(n.first, firstRect)
+	return append(leaves, computeLayout(n.second, secondRect)...)
+}
+
+// resolveSize returns the cell size a Split's first child gets out of total,
+// starting from n.ratio and then clamped to [n.min, n.max] (0 on either side
+// means that bound is unset). n.min == n.max fixes the size outright,
+// regardless of ratio.
+func resolveSize(n *Node, total int) int {
+	size := int(math.Round(n.ratio * float64(total)))
+	if n.min > 0 && size < n.min {
+		size = n.min
+	}
+	if n.max > 0 && size > n.max {
+		size = n.max
+	}
+	if size < 0 {
+		size = 0
+	}
+	if size > total {
+		size = total
+	}
+	return size
+}