all: initial import

Signed-off-by: Elias Naur <mail@eliasnaur.com>

ui/layout/stack.go

@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package layout
+
+import (
+	"image"
+
+	"gioui.org/ui"
+)
+
+type Stack struct {
+	Alignment Direction
+
+	cs       Constraints
+	children []stackChild
+	maxSZ    image.Point
+	baseline int
+
+	ccache  [10]stackChild
+	opCache [10]ui.Op
+}
+
+type stackChild struct {
+	op   ui.Op
+	dims Dimens
+}
+
+type Direction uint8
+
+const (
+	NW Direction = iota
+	N
+	NE
+	E
+	SE
+	S
+	SW
+	W
+)
+
+func (s *Stack) Init(cs Constraints) *Stack {
+	if s.children == nil {
+		s.children = s.ccache[:0]
+	}
+	s.children = s.children[:0]
+	s.maxSZ = image.Point{}
+	s.baseline = 0
+	s.cs = cs
+	return s
+}
+
+func (s *Stack) Rigid(w Widget) *Stack {
+	op, dims := w.Layout(s.cs)
+	if w := dims.Size.X; w > s.maxSZ.X {
+		s.maxSZ.X = w
+	}
+	if h := dims.Size.Y; h > s.maxSZ.Y {
+		s.maxSZ.Y = h
+	}
+	s.add(op, dims)
+	return s
+}
+
+func (s *Stack) Expand(idx int, w Widget) *Stack {
+	cs := Constraints{
+		Width:  Constraint{Min: s.maxSZ.X, Max: s.maxSZ.X},
+		Height: Constraint{Min: s.maxSZ.Y, Max: s.maxSZ.Y},
+	}
+	s.add(w.Layout(cs))
+	if idx < 0 {
+		idx += len(s.children)
+	}
+	s.children[idx], s.children[len(s.children)-1] = s.children[len(s.children)-1], s.children[idx]
+	return s
+}
+
+func (s *Stack) add(op ui.Op, dims Dimens) {
+	s.children = append(s.children, stackChild{op, dims})
+	if s.baseline == 0 {
+		if b := dims.Baseline; b != dims.Size.Y {
+			s.baseline = b
+		}
+	}
+}
+
+func (s *Stack) Layout() (ui.Op, Dimens) {
+	var ops ui.Ops
+	if len(s.children) > len(s.opCache) {
+		ops = make([]ui.Op, len(s.children))
+	} else {
+		ops = s.opCache[:len(s.children)]
+	}
+	for i, ch := range s.children {
+		sz := ch.dims.Size
+		var p image.Point
+		switch s.Alignment {
+		case N, S, Center:
+			p.X = (s.maxSZ.X - sz.X) / 2
+		case NE, SE, E:
+			p.X = s.maxSZ.X - sz.X
+		}
+		switch s.Alignment {
+		case W, Center, E:
+			p.Y = (s.maxSZ.Y - sz.Y) / 2
+		case SW, S, SE:
+			p.Y = s.maxSZ.Y - sz.Y
+		}
+		ops[i] = ui.OpLayer{Op: ui.OpTransform{Transform: ui.Offset(toPointF(p)), Op: ch.op}}
+	}
+	b := s.baseline
+	if b == 0 {
+		b = s.maxSZ.Y
+	}
+	return ops, Dimens{
+		Size:     s.maxSZ,
+		Baseline: b,
+	}
+}