1 files changed, 161 insertions, 0 deletions
diff --git a/layout/split.go b/layout/split.go
new file mode 100644
index 0000000..0c197b3
--- /dev/null
+++ b/layout/split.go
@@ -0,0 +1,161 @@
+package layout
+
+import (
+	"image"
+
+	"github.com/faiface/gui/event"
+)
+
+type Box struct {
+	event.Dispatch
+	dst EventImageFlusher
+	sub *image.RGBA
+}
+
+func (b *Box) Image() *image.RGBA {
+	return b.sub
+}
+
+func (b *Box) Flush(r image.Rectangle) {
+	r = r.Intersect(b.dst.Image().Bounds())
+	b.dst.Flush(r)
+}
+
+type Splitter func(r image.Rectangle, i, n int) image.Rectangle
+
+func Vertical() Splitter {
+	return func(r image.Rectangle, i, n int) image.Rectangle {
+		width := r.Dx()
+		return image.Rect(
+			r.Min.X+width*i/n,
+			r.Min.Y,
+			r.Min.X+width*(i+1)/n,
+			r.Max.Y,
+		)
+	}
+}
+
+func Horizontal() Splitter {
+	return func(r image.Rectangle, i, n int) image.Rectangle {
+		height := r.Dy()
+		return image.Rect(
+			r.Min.X,
+			r.Min.Y+height*i/n,
+			r.Max.X,
+			r.Min.Y+height*(i+1)/n,
+		)
+	}
+}
+
+func FixedTop(thickness int, rest Splitter) Splitter {
+	return VariableTop(&thickness, rest)
+}
+
+func FixedBottom(thickness int, rest Splitter) Splitter {
+	return VariableBottom(&thickness, rest)
+}
+
+func FixedLeft(thickness int, rest Splitter) Splitter {
+	return VariableLeft(&thickness, rest)
+}
+
+func FixedRight(thickness int, rest Splitter) Splitter {
+	return VariableRight(&thickness, rest)
+}
+
+func VariableTop(thickness *int, rest Splitter) Splitter {
+	return func(r image.Rectangle, i, n int) image.Rectangle {
+		if i == 0 {
+			r.Max.Y = r.Min.Y + *thickness
+			return r
+		}
+		r.Min.Y += *thickness
+		return rest(r, i-1, n-1)
+	}
+}
+
+func VariableBottom(thickness *int, rest Splitter) Splitter {
+	return func(r image.Rectangle, i, n int) image.Rectangle {
+		if i == 0 {
+			r.Min.Y = r.Max.Y - *thickness
+			return r
+		}
+		r.Max.Y -= *thickness
+		return rest(r, i-1, n-1)
+	}
+}
+
+func VariableLeft(thickness *int, rest Splitter) Splitter {
+	return func(r image.Rectangle, i, n int) image.Rectangle {
+		if i == 0 {
+			r.Max.X = r.Min.X + *thickness
+			return r
+		}
+		r.Min.X += *thickness
+		return rest(r, i-1, n-1)
+	}
+}
+
+func VariableRight(thickness *int, rest Splitter) Splitter {
+	return func(r image.Rectangle, i, n int) image.Rectangle {
+		if i == 0 {
+			r.Min.X = r.Max.X - *thickness
+			return r
+		}
+		r.Max.X -= *thickness
+		return rest(r, i-1, n-1)
+	}
+}
+
+type Split struct {
+	event.Dispatch
+	dst      EventImageFlusher
+	splitter Splitter
+	boxes    []*Box
+}
+
+func NewSplit(dst EventImageFlusher, splitter Splitter) *Split {
+	s := &Split{
+		dst:      dst,
+		splitter: splitter,
+	}
+	dst.Event("", s.Happen)
+	s.Event("resize", func(evt string) bool {
+		s.Split()
+		return true
+	})
+	return s
+}
+
+func (s *Split) Happen(evt string) bool {
+	if s.Dispatch.Happen(evt) {
+		return true
+	}
+	for _, box := range s.boxes {
+		if box.Happen(evt) {
+			return true
+		}
+	}
+	return false
+}
+
+func (s *Split) Add() *Box {
+	box := &Box{
+		dst: s.dst,
+	}
+	s.boxes = append(s.boxes, box)
+	return box
+}
+
+func (s *Split) Split() {
+	r := s.dst.Image().Bounds()
+	n := len(s.boxes)
+	for i := range s.boxes {
+		subR := s.splitter(r, i, n)
+		s.boxes[i].sub = s.dst.Image().SubImage(subR).(*image.RGBA)
+	}
+	for i := range s.boxes {
+		subR := s.boxes[i].sub.Bounds()
+		s.boxes[i].Happen(event.Sprint("resize", subR.Min.X, subR.Min.Y, subR.Max.X, subR.Max.Y))
+	}
+}