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|
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
}
|