perf!: move from polling to event-driven model

BREAKING CHANGE: requires wl-clipboard >= 2.0

Closes #1.

README.md

@@ -7,7 +7,7 @@ A basic clipboard manager for Wayland, with support for persisting copy buffers
 Requirements:
 
 - a windows manager that uses `wlr-data-control`, like Sway and other wlroots-based WMs.
-- wl-clipboard from latest master (NOT v1.0)
+- wl-clipboard >= 2.0
 - dmenu or rofi
 
 [Install go](https://golang.org/doc/install), add `$GOPATH/bin` to your path, then run `go get github.com/yory8/clipman` OR run `go install` inside this folder.

demon.go

@@ -4,10 +4,22 @@ import (
 	"encoding/json"
 	"io/ioutil"
 	"log"
+	"os"
 	"os/exec"
-	"time"
 )
 
+type historyBuf struct {
+	buf      []string // field name as required by io.Writer, don't change
+	histfile string
+	max      int
+	persist  bool
+}
+
+func (hb *historyBuf) Write(p []byte) (n int, err error) {
+	hb.buf = store(string(p), hb.buf, hb.histfile, hb.max, hb.persist)
+	return len(p), err // signature as required by io.Writer, don't change
+}
+
 func write(history []string, histfile string) error {
 	histlog, err := json.Marshal(history)
 	if err != nil {
@@ -41,58 +53,50 @@ func filter(history []string, text string) []string {
 	return history
 }
 
-func listen(history []string, histfile string, persist bool, max int) {
-	for {
-		t, err := exec.Command("wl-paste", "-n", "-t", "text").CombinedOutput()
-		if err != nil {
-			// wl-paste exits 1 if there's no selection (e.g., when running it at OS startup)
-			if string(t) != "No selection\n" {
-				log.Printf("Error running wl-paste: %s", t)
-			}
-			time.Sleep(1 * time.Second)
-			continue
+func store(text string, history []string, histfile string, max int, persist bool) []string {
+	l := len(history)
+	if l > 0 {
+		if history[l-1] == text {
+			return history
 		}
 
-		text := string(t)
-
-		if text == "" {
-			// there's nothing to select, so we sleep.
-			time.Sleep(1 * time.Second)
-			continue
+		if l >= max {
+			// usually just one item, but more if we reduce our --max-items value
+			history = history[l-max+1:]
 		}
 
-		l := len(history)
+		// remove duplicates
+		history = filter(history, text)
+	}
 
-		if l > 0 {
-			// wl-paste will always give back the last copied text
-			// (as long as the place we copied from is still running)
-			if history[l-1] == text {
-				time.Sleep(1 * time.Second)
-				continue
-			}
+	history = append(history, text)
 
-			if l >= max {
-				// usually just one item, but more if we reduce our --max-items value
-				history = history[l-max+1:]
-			}
+	// dump history to file so that other apps can query it
+	if err := write(history, histfile); err != nil {
+		log.Fatalf("Fatal error writing history: %s", err)
+	}
 
-			// remove duplicates
-			history = filter(history, text)
-		}
-
-		history = append(history, text)
-
-		// dump history to file so that other apps can query it
-		if err := write(history, histfile); err != nil {
-			log.Fatalf("Fatal error writing history: %s", err)
-		}
-
-		if persist {
-			// make the copy buffer available to all applications,
-			// even when the source has disappeared
-			if err := exec.Command("wl-copy", []string{"--", text}...).Run(); err != nil {
-				log.Printf("Error running wl-copy: %s", err)
-			}
+	if persist {
+		// make the copy buffer available to all applications,
+		// even when the source has disappeared
+		if err := exec.Command("wl-copy", []string{"--", text}...).Run(); err != nil {
+			log.Printf("Error running wl-copy: %s", err)
 		}
 	}
+
+	return history
+}
+
+func listen(history []string, histfile string, persist bool, max int) {
+	cmd := exec.Command("wl-paste", "-t", "text", "--watch", "cat")
+	cmd.Stdout = &historyBuf{history, histfile, max, persist}
+	cmd.Stderr = os.Stderr
+
+	if err := cmd.Start(); err != nil {
+		log.Fatalf("Error running wl-paste (cmd.Start): %s", err)
+	}
+
+	if err := cmd.Wait(); err != nil {
+		log.Fatalf("Error running wl-paste (cmd.Wait): %s", err)
+	}
 }