v0.1.0 initial commit

internal/ui/layout.go

@@ -0,0 +1,111 @@
+package ui
+
+import "github.com/lixenwraith/terminal/tui"
+
+// Pane identifies a region of the frame.
+type Pane uint8
+
+const (
+	PaneNone Pane = iota
+	PaneHeader
+	PaneList
+	PaneDetail
+	PaneStatus
+	PaneFooter
+)
+
+// Dir is the split axis of a container node.
+type Dir uint8
+
+const (
+	Vertical   Dir = iota // children stacked top to bottom
+	Horizontal            // children placed left to right
+)
+
+// Node is either a leaf bound to a Pane or a container. Layout is data:
+// changing pane count or arrangement edits this tree only.
+type Node struct {
+	Pane     Pane
+	Dir      Dir
+	Fixed    int // size along the parent axis, 0 = share by Weight
+	Weight   float64
+	Children []Node
+}
+
+// Layout is the root of the pane tree.
+type Layout struct{ Root Node }
+
+// DefaultLayout is the phase-1 layout: header, list|detail body, status, footer.
+func DefaultLayout() Layout {
+	return Layout{Root: Node{Dir: Vertical, Children: []Node{
+		{Pane: PaneHeader, Fixed: 1},
+		{Dir: Horizontal, Weight: 1, Children: []Node{
+			{Pane: PaneList, Weight: 0.62},
+			{Pane: PaneDetail, Weight: 0.38},
+		}},
+		{Pane: PaneStatus, Fixed: 1},
+		{Pane: PaneFooter, Fixed: 1},
+	}}}
+}
+
+// Resolve assigns a region to every leaf pane.
+func (l Layout) Resolve(r tui.Region) map[Pane]tui.Region {
+	out := make(map[Pane]tui.Region, 8)
+	place(l.Root, r, out)
+	return out
+}
+
+func place(n Node, r tui.Region, out map[Pane]tui.Region) {
+	if len(n.Children) == 0 {
+		if n.Pane != PaneNone {
+			out[n.Pane] = r
+		}
+		return
+	}
+	total := r.H
+	if n.Dir == Horizontal {
+		total = r.W
+	}
+	sizes := share(n.Children, total)
+	pos := 0
+	for i, c := range n.Children {
+		var sub tui.Region
+		if n.Dir == Horizontal {
+			sub = r.Sub(pos, 0, sizes[i], r.H)
+		} else {
+			sub = r.Sub(0, pos, r.W, sizes[i])
+		}
+		place(c, sub, out)
+		pos += sizes[i]
+	}
+}
+
+// share splits total between fixed and weighted children; the rounding
+// remainder goes to the last weighted child.
+func share(cs []Node, total int) []int {
+	sizes := make([]int, len(cs))
+	rest, sum := total, 0.0
+	for i, c := range cs {
+		if c.Fixed > 0 {
+			s := min(c.Fixed, max(rest, 0))
+			sizes[i], rest = s, rest-s
+		} else {
+			sum += c.Weight
+		}
+	}
+	if sum <= 0 {
+		sum = 1
+	}
+	lastW, acc := -1, 0
+	for i, c := range cs {
+		if c.Fixed > 0 {
+			continue
+		}
+		s := int(float64(rest) * c.Weight / sum)
+		sizes[i], acc, lastW = s, acc+s, i
+	}
+	if lastW >= 0 {
+		sizes[lastW] += rest - acc
+	}
+	return sizes
+}