1 files changed, 150 insertions, 0 deletions
diff --git a/layout/mux.go b/layout/mux.go
new file mode 100644
index 0000000..abae087
--- /dev/null
+++ b/layout/mux.go
@@ -0,0 +1,150 @@
+package layout
+
+import (
+	"image"
+	"image/draw"
+	"sync"
+
+	"github.com/faiface/gui"
+)
+
+type Mux struct {
+	masterEnv *muxEnv
+	inEvent   chan<- gui.Event
+
+	mu         sync.Mutex
+	lastResize gui.Event
+	eventsIns  []chan<- gui.Event
+	draw       chan<- func(draw.Image) image.Rectangle
+
+	Layout
+}
+
+func NewMux(env gui.Env, l Layout) (mux *Mux) {
+	drawChan := make(chan func(draw.Image) image.Rectangle)
+	mux = &Mux{
+		Layout: l,
+		draw:   drawChan,
+	}
+	mux.masterEnv, mux.inEvent = mux.makeEnv(true)
+	mux.eventsIns = make([]chan<- gui.Event, 0)
+
+	go func() {
+		for d := range drawChan {
+			env.Draw() <- d
+		}
+		close(env.Draw())
+	}()
+
+	go func() {
+		for e := range env.Events() {
+			mux.mu.Lock()
+			if resize, ok := e.(gui.Resize); ok {
+				mux.lastResize = resize
+				rect := resize.Rectangle
+
+				// Redraw self
+				mux.draw <- func(drw draw.Image) image.Rectangle {
+					mux.Redraw(drw, rect)
+					return rect
+				}
+
+				// Send appropriate resize Events to childs
+				lay := mux.Lay(rect)
+				for i, eventsIn := range mux.eventsIns {
+					resize.Rectangle = lay[i]
+					eventsIn <- resize
+				}
+			} else {
+				for _, eventsIn := range mux.eventsIns {
+					eventsIn <- e
+				}
+			}
+			mux.mu.Unlock()
+		}
+		mux.mu.Lock()
+		for _, eventsIn := range mux.eventsIns {
+			close(eventsIn)
+		}
+		mux.mu.Unlock()
+	}()
+
+	return mux
+}
+
+type muxEnv struct {
+	events <-chan gui.Event
+	draw   chan<- func(draw.Image) image.Rectangle
+}
+
+func (m *muxEnv) Events() <-chan gui.Event                      { return m.events }
+func (m *muxEnv) Draw() chan<- func(draw.Image) image.Rectangle { return m.draw }
+
+// We do not store master env
+func (mux *Mux) makeEnv(master bool) (*muxEnv, chan<- gui.Event) {
+	eventsOut, eventsIn := gui.MakeEventsChan()
+	drawChan := make(chan func(draw.Image) image.Rectangle)
+	env := &muxEnv{eventsOut, drawChan}
+
+	mux.mu.Lock()
+	mux.eventsIns = append(mux.eventsIns, eventsIn)
+	// make sure to always send a resize event to a new Env if we got the size already
+	// that means it missed the resize event by the root Env
+	if mux.lastResize != nil {
+		eventsIn <- mux.lastResize
+	}
+	mux.mu.Unlock()
+
+	go func() {
+		func() {
+			// When the master Env gets its Draw() channel closed, it closes all the Events()
+			// channels of all the children Envs, and it also closes the internal draw channel
+			// of the Mux. Otherwise, closing the Draw() channel of the master Env wouldn't
+			// close the Env the Mux is muxing. However, some child Envs of the Mux may still
+			// send some drawing commmands before they realize that their Events() channel got
+			// closed.
+			//
+			// That is perfectly fine if their drawing commands simply get ignored. This down here
+			// is a little hacky, but (I hope) perfectly fine solution to the problem.
+			//
+			// When the internal draw channel of the Mux gets closed, the line marked with ! will
+			// cause panic. We recover this panic, then we receive, but ignore all furhter draw
+			// commands, correctly draining the Env until it closes itself.
+			defer func() {
+				if recover() != nil {
+					for range drawChan {
+					}
+				}
+			}()
+			for d := range drawChan {
+				mux.draw <- d // !
+			}
+		}()
+		if master {
+			mux.mu.Lock()
+			for _, eventsIn := range mux.eventsIns {
+				close(eventsIn)
+			}
+			mux.eventsIns = nil
+			close(mux.draw)
+			mux.mu.Unlock()
+		} else {
+			mux.mu.Lock()
+			i := -1
+			for i = range mux.eventsIns {
+				if mux.eventsIns[i] == eventsIn {
+					break
+				}
+			}
+			if i != -1 {
+				mux.eventsIns = append(mux.eventsIns[:i], mux.eventsIns[i+1:]...)
+			}
+			mux.mu.Unlock()
+		}
+		if mux.lastResize != nil {
+			mux.inEvent <- mux.lastResize
+		}
+	}()
+
+	return env, eventsIn
+}