1 files changed, 172 insertions, 0 deletions
diff --git a/gui/layout/mux.go b/gui/layout/mux.go
new file mode 100644
index 0000000..7b193e7
--- /dev/null
+++ b/gui/layout/mux.go
@@ -0,0 +1,172 @@
+package layout
+
+import (
+	"image"
+	"image/draw"
+	"log"
+	"sync"
+
+	"volute/gui"
+)
+
+// Mux can be used to multiplex an Env, let's call it a root Env. Mux implements a way to
+// create multiple virtual Envs that all interact with the root Env. They receive the same
+// events apart from gui.Resize, and their draw functions get redirected to the root Env.
+//
+// All gui.Resize events are instead modified according to the underlying Layout.
+// The master Env gets the original gui.Resize events.
+type Mux struct {
+	mu         sync.Mutex
+	lastResize gui.Event
+	eventsIns  []chan<- gui.Event
+	draw       chan<- func(draw.Image) image.Rectangle
+
+	layout Layout
+}
+
+// Layout returns the underlying Layout of the Mux.
+func (mux *Mux) Layout() Layout {
+	return mux.layout
+}
+
+// NewMux should only be used internally by Layouts.
+// It has mostly the same behaviour as gui.Mux, except for its use of an underlying Layout
+// for modifying the gui.Resize events sent to the childs.
+func NewMux(ev gui.Env, envs []*gui.Env, l Layout) (mux *Mux, master gui.Env) {
+	env := l.Intercept(ev)
+	drawChan := make(chan func(draw.Image) image.Rectangle)
+	mux = &Mux{
+		layout: l,
+		draw:   drawChan,
+	}
+	master, masterIn := mux.makeEnv(true)
+	events := make(chan gui.Event)
+	go func() {
+		for d := range drawChan {
+			env.Draw() <- d
+		}
+		close(env.Draw())
+	}()
+
+	go func() {
+		for e := range env.Events() {
+			events <- e
+		}
+	}()
+
+	go func() {
+		for e := range events {
+			// master gets a copy of all events to the Mux
+			masterIn <- e
+			mux.mu.Lock()
+			if resize, ok := e.(gui.Resize); ok {
+				mux.lastResize = resize
+				rect := resize.Rectangle
+				lay := mux.layout.Lay(rect)
+				if len(lay) < len(envs) {
+					log.Printf("Lay of %T is not large enough (%d) for %d childs, skipping\n", l, len(lay), len(envs))
+					mux.mu.Unlock()
+					continue
+				}
+
+				// Send appropriate resize Events to childs
+				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()
+	}()
+
+	for _, en := range envs {
+		*en, _ = mux.makeEnv(false)
+	}
+	return
+}
+
+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) (env gui.Env, eventsIn chan<- gui.Event) {
+	eventsOut, eventsIn := gui.MakeEventsChan()
+	drawChan := make(chan func(draw.Image) image.Rectangle)
+	env = &muxEnv{eventsOut, drawChan}
+
+	if !master {
+		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()
+		}
+	}()
+
+	return env, eventsIn
+}