added layout basics

1 files changed, 165 insertions, 0 deletions

diff --git a/layout/layout.go b/layout/layout.go
new file mode 100644
index 0000000..3601629
--- /dev/null
+++ b/layout/layout.go
@@ -0,0 +1,165 @@
+package layout
+
+import (
+	"image"
+	"image/draw"
+	"sync"
+
+	"github.com/faiface/gui"
+)
+
+type Layout struct {
+	masterEnv *MuxEnv
+	inEvent   chan<- gui.Event
+
+	mu         sync.Mutex
+	lastResize gui.Event
+	eventsIns  map[string]chan<- gui.Event
+	draw       chan<- func(draw.Image) image.Rectangle
+
+	Lay    func(image.Rectangle) map[string]image.Rectangle
+	Redraw func(draw.Image, image.Rectangle)
+}
+
+func New(
+	env gui.Env,
+	lay func(image.Rectangle) map[string]image.Rectangle,
+	redraw func(draw.Image, image.Rectangle),
+) *Layout {
+
+	mux := &Layout{
+		Lay:    lay,
+		Redraw: redraw,
+	}
+	drawChan := make(chan func(draw.Image) image.Rectangle)
+	mux.draw = drawChan
+	mux.masterEnv = mux.makeEnv("master", true)
+	mux.inEvent = mux.masterEnv.In
+	mux.eventsIns = make(map[string]chan<- gui.Event)
+	go func() {
+		for d := range drawChan {
+			env.Draw() <- d
+		}
+		close(env.Draw())
+	}()
+
+	go func() {
+		for e := range env.Events() {
+			mux.inEvent <- e
+		}
+	}()
+
+	go func() {
+		for e := range mux.masterEnv.Events() {
+			mux.mu.Lock()
+			if resize, ok := e.(gui.Resize); ok {
+				mux.lastResize = resize
+				rect := resize.Rectangle
+
+				mux.draw <- func(drw draw.Image) image.Rectangle {
+					mux.Redraw(drw, rect)
+					return rect
+				}
+				l := mux.Lay(rect)
+
+				for key, eventsIn := range mux.eventsIns {
+					func(rz gui.Resize) {
+						rz.Rectangle = l[key]
+						eventsIn <- rz
+					}(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
+}
+
+func (mux *Layout) GetEnv(name string) gui.Env {
+	return mux.makeEnv(name, false)
+}
+
+type MuxEnv struct {
+	In     chan<- gui.Event
+	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 *Layout) makeEnv(envName string, master bool) *MuxEnv {
+	eventsOut, eventsIn := gui.MakeEventsChan()
+	drawChan := make(chan func(draw.Image) image.Rectangle)
+	env := &MuxEnv{eventsIn, eventsOut, drawChan}
+
+	mux.mu.Lock()
+	if !master {
+		mux.eventsIns[envName] = 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()
+			delete(mux.eventsIns, envName)
+
+			close(eventsIn)
+			mux.mu.Unlock()
+		}
+		if mux.lastResize != nil {
+			mux.inEvent <- mux.lastResize
+		}
+	}()
+
+	return env
+}