instantly close panes instead of waiting for process to end

src/main/java/com/gregor/jprototerm/LinuxPty.java

@@ -15,6 +15,8 @@ import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 /**
  * A Linux PTY backed by libc via the Foreign Function & Memory API.
@@ -33,6 +35,11 @@ import java.util.Map;
 public final class LinuxPty implements AutoCloseable {
     static final Linker LINKER = Linker.nativeLinker();
     private static final SymbolLookup LIBC = LINKER.defaultLookup();
+    private static final ExecutorService REAPER = Executors.newCachedThreadPool(runnable -> {
+        Thread thread = new Thread(runnable, "pty-reaper");
+        thread.setDaemon(true);
+        return thread;
+    });
 
     static final AddressLayout C_POINTER = (AddressLayout) LINKER.canonicalLayouts().get("void*");
     static final ValueLayout.OfShort C_SHORT = (ValueLayout.OfShort) LINKER.canonicalLayouts().get("short");
@@ -275,14 +282,43 @@ public final class LinuxPty implements AutoCloseable {
 
     @Override
     public void close() {
-        if (closed) {
+        if (!markClosed()) {
             return;
         }
+        closeMaster();
+        try {
+            reap();
+        } finally {
+            arena.close();
+        }
+    }
+
+    /** Send the configured close signal and close the master fd now; reap off the caller thread. */
+    public void closeDetached() {
+        if (!markClosed()) {
+            return;
+        }
+        closeMaster();
+        REAPER.submit(() -> {
+            try {
+                reap();
+            } finally {
+                arena.close();
+            }
+        });
+    }
+
+    private synchronized boolean markClosed() {
+        if (closed) {
+            return false;
+        }
         closed = true;
+        return true;
+    }
+
+    private void closeMaster() {
         callKill(pid, closeSignal);
         callInt(CLOSE, masterFd);
-        reap();
-        arena.close();
     }
 
     private void reap() {

src/main/java/com/gregor/jprototerm/ShellSession.java

@@ -180,8 +180,27 @@ public final class ShellSession implements AutoCloseable {
 
     @Override
     public void close() {
-        closed = true;
+        if (!markClosed()) {
+            return;
+        }
         reader.shutdownNow();
         pty.close();
     }
+
+    /** Signal and disconnect the pty immediately, but leave child reaping to a background thread. */
+    public void closeDetached() {
+        if (!markClosed()) {
+            return;
+        }
+        reader.shutdownNow();
+        pty.closeDetached();
+    }
+
+    private synchronized boolean markClosed() {
+        if (closed) {
+            return false;
+        }
+        closed = true;
+        return true;
+    }
 }

src/main/java/com/gregor/jprototerm/TerminalPane.java

@@ -383,7 +383,7 @@ public final class TerminalPane implements AutoCloseable, RenderTarget {
     @Override
     public void close() {
         if (session != null) {
-            session.close();
+            session.closeDetached();
             session = null;
         }
         mouseEncoder.close();

src/main/java/com/gregor/jprototerm/TerminalWindow.java

@@ -86,7 +86,7 @@ final class TerminalWindow {
 
     /**
      * Fully tears this window down (FX thread, idempotent): stops rendering, closes the compositor —
-     * which reaps the pane shells via the configured {@code close_signal} — disposes the Stage, and
+     * which signals pane shells via the configured {@code close_signal} — disposes the Stage, and
      * notifies the manager so it can drop the window (and, in standalone mode, exit the JVM). Both
      * the WM close button and the last-pane-closed hook route through here.
      */