piframe-go/ui/slideshow.go

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package ui
import (
"context"
"io"
"log"
"os/exec"
"syscall"
"time"
"github.com/eiannone/keyboard"
"github.com/knadh/koanf"
)
const (
CMD_FIM = "/usr/local/bin/pf-fim.sh"
)
func Slideshow(config *koanf.Koanf) {
// fim placeholder so we can operate on it when a exit slideshow is received
var fim *exec.Cmd = nil
// Run slideshow
fim = exec.Command(CMD_FIM)
// Put fim into a process group so ALL processes that may be executed are exited when main process exits
fim.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
// Setup stdin for fim to control slideshow
stdin, err := fim.StdinPipe()
if err != nil {
log.Fatalf("Error getting fim stdin : %s", err)
}
// Advance slideshow every interval as defined in const()
ticker := time.NewTicker(config.Duration(CONFIG_KEY_SLIDESHOW_INTERVAL))
stop_ticker := make(chan struct{})
go func() {
for {
select {
case <-ticker.C:
_, err = io.WriteString(stdin, "n")
if err != nil {
log.Fatalf("Error advancing slides : %s", err)
}
case <-stop_ticker:
ticker.Stop()
stdin.Close()
return
}
}
}()
// Start watching for key strokes and echo them back to stdout
keysEvents, err := keyboard.GetKeys(10)
if err != nil {
log.Fatalf("Error setting up keyboard listener : %s", err)
}
// NOT deferring keyboard.close as we do that by hand further down when fim exits ahead of showing the config UI
// Goroutine for tracking which keys are pressed and controlling fim if appropriate
keyboardCtx, keyboardCancel := context.WithCancel(context.Background())
go func(keyboardCtx context.Context) {
for {
select {
case <-keyboardCtx.Done():
return
case event := <-keysEvents:
if event.Err != nil {
log.Fatalf("Error listening to key events : %s", err)
}
// Keys for fim event management (previous/next in particular)
fimKey := ""
if event.Key == keyboard.KeyArrowLeft || event.Key == keyboard.KeyArrowDown {
fimKey = "p"
}
if event.Key == keyboard.KeyArrowRight || event.Key == keyboard.KeyArrowUp {
fimKey = "n"
}
// Exit fim and move to the config UI
if event.Key == keyboard.KeyEsc || event.Key == keyboard.KeyEnter || event.Key == keyboard.KeySpace {
if fim != nil { // Just in case someone lays on exit key or similar during startup
pgid, err := syscall.Getpgid(fim.Process.Pid)
if err == nil {
if err := syscall.Kill(-pgid, 9); err != nil {
log.Fatalf("failed to kill fim : %s", err)
}
}
}
break
}
// Control fim if we received a valid key for next/previous slide
if fimKey != "" {
log.Printf("Sending key to fim : %s", fimKey)
_, err = io.WriteString(stdin, fimKey)
if err != nil {
log.Fatalf("Error controlling fim : %s", err)
}
ticker.Reset(config.Duration(CONFIG_KEY_SLIDESHOW_INTERVAL))
}
}
}
}(keyboardCtx)
// Run fim
if err := fim.Run(); err != nil {
// Unwrap the error a bit so we can find out if a signal killed fim or something else
// An exit code of -1 means the program didn't exit in time or was terminated by a signal (per the docs)
if exitError, ok := err.(*exec.ExitError); ok && exitError.ExitCode() != -1 {
log.Fatalf("Error running fim : %s", err)
}
}
// Stop fim slideshow advancing go routine
close(stop_ticker)
// Stop listening to keyboard events
keyboard.Close()
keyboardCancel()
}