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package gui
import (
"image"
"image/draw"
"sync"
)
type Mux struct {
mu sync.Mutex
eventsIns []chan<- Event
draw chan<- func(draw.Image) image.Rectangle
}
func NewMux(env Env) (mux *Mux, master Env) {
drawChan := make(chan func(draw.Image) image.Rectangle)
mux = &Mux{draw: drawChan}
master = mux.makeEnv(true)
go func() {
for d := range drawChan {
env.Draw() <- d
}
close(env.Draw())
}()
go func() {
for e := range env.Events() {
mux.mu.Lock()
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, master
}
func (mux *Mux) MakeEnv() Env {
return mux.makeEnv(false)
}
type muxEnv struct {
events <-chan Event
draw chan<- func(draw.Image) image.Rectangle
}
func (m *muxEnv) Events() <-chan Event { return m.events }
func (m *muxEnv) Draw() chan<- func(draw.Image) image.Rectangle { return m.draw }
func (mux *Mux) makeEnv(master bool) Env {
eventsOut, eventsIn := MakeEventsChan()
drawChan := make(chan func(draw.Image) image.Rectangle)
env := &muxEnv{eventsOut, drawChan}
mux.mu.Lock()
mux.eventsIns = append(mux.eventsIns, eventsIn)
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
}
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