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package layout
import (
"image"
"image/draw"
"log"
"git.samanthony.xyz/share"
"github.com/faiface/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.
type Mux struct {
// Sending any value to Kill will terminate the Mux.
Kill chan<- any
bounds share.Val[image.Rectangle]
draw chan<- func(draw.Image) image.Rectangle
eventsIns share.ConstSlice[chan<- gui.Event]
layout Layout
}
// Layout returns the underlying Layout of the Mux.
func (mux *Mux) Layout() Layout {
return mux.layout
}
func NewMux(parent gui.Env, children []*gui.Env, layout Layout) Mux {
parent = layout.Intercept(parent)
kill := make(chan any)
bounds := share.NewVal[image.Rectangle]()
drawChan := make(chan func(draw.Image) image.Rectangle)
eventsIns := func() share.ConstSlice[chan<- gui.Event] { // create child Env's
evIns := make([]chan<- gui.Event, len(children))
for i, child := range children {
*child, evIns[i] = makeEnv(drawChan)
}
return share.NewConstSlice(evIns)
}()
mux := Mux{
kill,
bounds,
drawChan,
eventsIns,
layout,
}
go func() {
defer close(parent.Draw())
defer close(kill)
defer bounds.Close()
defer close(drawChan)
defer func() {
for eventsIn := range eventsIns.Elems() {
close(eventsIn)
}
eventsIns.Close()
}()
for {
select {
case <-kill:
return
case d := <-drawChan:
parent.Draw() <- d
case e := <-parent.Events():
if resize, ok := e.(gui.Resize); ok {
bounds.Set <- resize.Rectangle
mux.resizeChildren()
} else {
for eventsIn := range eventsIns.Elems() {
eventsIn <- e
}
}
}
}
}()
// First event of a new Env must be Resize.
mux.resizeChildren()
return mux
}
func (mux *Mux) resizeChildren() {
rect := mux.bounds.Get()
lay := mux.layout.Lay(rect)
i := 0
for eventsIn := range mux.eventsIns.Elems() {
if i > len(lay) {
log.Printf("Lay of %T is not large enough (%d) for the number of children, skipping\n",
mux.layout, len(lay))
break
}
eventsIn <- gui.Resize{lay[i]}
i++
}
}
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 }
func makeEnv(muxDraw chan<- func(draw.Image) image.Rectangle) (env gui.Env, eventsIn chan<- gui.Event) {
eventsOut, eventsIn := gui.MakeEventsChan()
envDraw := make(chan func(draw.Image) image.Rectangle)
env = &muxEnv{eventsOut, envDraw}
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 envDraw {
}
}
}()
for d := range envDraw {
muxDraw <- d // !
}
}()
}()
return env, eventsIn
}
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