fix(linux): use CUPS cache for pre-driver capture handoff

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@fieldlens/print",
-  "version": "0.1.10",
+  "version": "0.1.11",
   "private": true,
   "type": "module",
   "scripts": {

src-tauri/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "fieldlens-print"
-version = "0.1.10"
+version = "0.1.11"
 description = "FieldLens print-stream barcode capture companion"
 authors = ["Arrowstack"]
 edition = "2021"

src-tauri/src/capture.rs

@@ -28,10 +28,6 @@ use crate::{
 const SYSTEM_CUPS_SPOOL_DIR: &str = "/var/cache/cups/fieldlens-print";
 #[cfg(target_os = "linux")]
 const TEST_CAPTURE_SINK_ADDR: &str = "127.0.0.1:9101";
-#[cfg(target_os = "linux")]
-const CUPS_ORIGINAL_CAPTURE_ADDR: &str = "127.0.0.1:9102";
-#[cfg(target_os = "linux")]
-const CUPS_TEST_CAPTURE_ADDR: &str = "127.0.0.1:9103";
 
 pub struct CaptureRuntime {
     stop: Arc<AtomicBool>,
@@ -90,46 +86,22 @@ pub fn start(config: AppConfig, state: SharedState, app: AppHandle) -> Result<Ca
     #[cfg(target_os = "linux")]
     {
         let system_spool = PathBuf::from(SYSTEM_CUPS_SPOOL_DIR);
-        if system_spool.is_dir() && system_spool != PathBuf::from(&config.spool_dir) {
+        if system_spool != PathBuf::from(&config.spool_dir) {
             let worker_stop = stop.clone();
             let worker_state = state.clone();
             let worker_app = app.clone();
             let worker_config = config.clone();
             handles.push(thread::spawn(move || {
-                spool_folder_loop(
+                cups_cache_folder_loop(
+                    system_spool,
                     worker_config,
                     worker_state,
                     worker_app,
                     worker_stop,
-                    Some(system_spool),
-                    "cups-original",
-                    true,
                 )
             }));
         }
 
-        for (address, source, forwarded) in [
-            (CUPS_ORIGINAL_CAPTURE_ADDR, "cups-original", true),
-            (CUPS_TEST_CAPTURE_ADDR, "cups-test", false),
-        ] {
-            if let Ok(listener) = TcpListener::bind(address) {
-                let _ = listener.set_nonblocking(true);
-                let worker_stop = stop.clone();
-                let worker_state = state.clone();
-                let worker_app = app.clone();
-                handles.push(thread::spawn(move || {
-                    cups_document_capture_loop(
-                        listener,
-                        worker_state,
-                        worker_app,
-                        worker_stop,
-                        source,
-                        forwarded,
-                    )
-                }));
-            }
-        }
-
         let sink = TcpListener::bind(TEST_CAPTURE_SINK_ADDR)
             .with_context(|| format!("bind test-capture sink {TEST_CAPTURE_SINK_ADDR}"))?;
         sink.set_nonblocking(true)?;
@@ -144,91 +116,6 @@ pub fn start(config: AppConfig, state: SharedState, app: AppHandle) -> Result<Ca
     Ok(CaptureRuntime { stop, handles })
 }
 
-#[cfg(target_os = "linux")]
-fn cups_document_capture_loop(
-    listener: TcpListener,
-    state: SharedState,
-    app: AppHandle,
-    stop: Arc<AtomicBool>,
-    source: &'static str,
-    forwarded: bool,
-) {
-    while !stop.load(Ordering::SeqCst) {
-        match listener.accept() {
-            Ok((stream, _)) => {
-                let worker_state = state.clone();
-                let worker_app = app.clone();
-                thread::spawn(move || {
-                    handle_cups_document_connection(
-                        stream,
-                        worker_state,
-                        worker_app,
-                        source,
-                        forwarded,
-                    )
-                });
-            }
-            Err(error) if error.kind() == ErrorKind::WouldBlock => {
-                thread::sleep(Duration::from_millis(80));
-            }
-            Err(_) => {
-                thread::sleep(Duration::from_millis(250));
-            }
-        }
-    }
-}
-
-#[cfg(target_os = "linux")]
-fn handle_cups_document_connection(
-    mut stream: TcpStream,
-    state: SharedState,
-    app: AppHandle,
-    source: &'static str,
-    forwarded: bool,
-) {
-    let _ = stream.set_read_timeout(Some(Duration::from_secs(4)));
-    let mut bytes = Vec::new();
-    let mut buffer = [0u8; 32 * 1024];
-
-    loop {
-        match stream.read(&mut buffer) {
-            Ok(0) => break,
-            Ok(read) => bytes.extend_from_slice(&buffer[..read]),
-            Err(error) if matches!(error.kind(), ErrorKind::WouldBlock | ErrorKind::TimedOut) => {
-                if !bytes.is_empty() {
-                    break;
-                }
-            }
-            Err(error) => {
-                process_payload(
-                    &state,
-                    &app,
-                    source,
-                    "cups-live-capture".into(),
-                    bytes,
-                    forwarded,
-                    Some(format!("CUPS live capture read failed: {error}")),
-                );
-                return;
-            }
-        }
-    }
-
-    if bytes.is_empty() {
-        return;
-    }
-
-    process_payload(
-        &state,
-        &app,
-        source,
-        format!("cups-live-{}.pdf", Uuid::new_v4()),
-        bytes,
-        forwarded,
-        None,
-    );
-}
-
 #[cfg(target_os = "linux")]
 fn test_capture_sink_loop(listener: TcpListener, stop: Arc<AtomicBool>) {
     while !stop.load(Ordering::SeqCst) {
@@ -378,6 +265,33 @@ fn handle_raw_connection(
     );
 }
 
+#[cfg(target_os = "linux")]
+fn cups_cache_folder_loop(
+    spool_dir: PathBuf,
+    config: AppConfig,
+    state: SharedState,
+    app: AppHandle,
+    stop: Arc<AtomicBool>,
+) {
+    while !stop.load(Ordering::SeqCst) && !spool_dir.is_dir() {
+        thread::sleep(Duration::from_millis(500));
+    }
+
+    if stop.load(Ordering::SeqCst) {
+        return;
+    }
+
+    spool_folder_loop(
+        config,
+        state,
+        app,
+        stop,
+        Some(spool_dir),
+        "cups-original",
+        true,
+    );
+}
+
 fn spool_folder_loop(
     config: AppConfig,
     state: SharedState,

src-tauri/src/printers.rs

@@ -25,9 +25,7 @@ const FIELDLENS_CUPS_SPOOL_DIR: &str = "/var/cache/cups/fieldlens-print";
 const FIELDLENS_CUPS_FILTER: &str = r#"#!/usr/bin/python3
 import os
 import re
-import socket
 import sys
-import uuid
 
 SPOOL = os.path.join(os.environ.get("CUPS_CACHEDIR", "/var/cache/cups"), "fieldlens-print")
 
@@ -39,39 +37,33 @@ job_id = safe(sys.argv[1] if len(sys.argv) > 1 else "job")
 title = safe(sys.argv[3] if len(sys.argv) > 3 else "print")
 printer = safe(os.environ.get("PRINTER", "printer"))
 content_type = os.environ.get("CONTENT_TYPE", "application/pdf")
-ext = {
+is_test = printer.lower() == "fieldlens-test-capture"
-    "application/pdf": "pdf",
+prefix = "test-" if is_test else "print-"
-    "application/postscript": "ps",
+ext = "pdf" if "pdf" in content_type else "dat"
-    "image/png": "png",
+
-    "image/jpeg": "jpg",
+# Use a deterministic name so multiple PDF pre-filter stages for the same
-}.get(content_type, "dat")
+# CUPS job do not create duplicate FieldLens jobs.
-prefix = "test-" if printer.lower() == "fieldlens-test-capture" else "print-"
+name = f"{prefix}{printer}-{job_id}-{title}.{ext}"
-name = f"{prefix}{printer}-{job_id}-{title}-{uuid.uuid4().hex}.{ext}"
 final_path = os.path.join(SPOOL, name)
 part_path = final_path + ".part"
 
 source = None
-live = None
 capture = None
 captured_ok = False
-live_ok = False
 try:
     if len(sys.argv) > 6 and sys.argv[6]:
         source = open(sys.argv[6], "rb")
     else:
         source = sys.stdin.buffer
 
-    live_port = 9103 if printer.lower() == "fieldlens-test-capture" else 9102
+    # If an earlier pre-filter stage already captured this job, only pass the
-    try:
+    # bytes onward. Otherwise tee the pre-driver document into CUPS_CACHEDIR.
-        live = socket.create_connection(("127.0.0.1", live_port), timeout=0.35)
+    if not os.path.exists(final_path):
-        live.settimeout(None)
-    except OSError:
-        live = None
-
         try:
             os.makedirs(SPOOL, exist_ok=True)
             capture = open(part_path, "wb")
-    except OSError:
+        except OSError as error:
+            print(f"WARNING: FieldLens capture cache unavailable: {error}", file=sys.stderr)
             capture = None
 
     while True:
@@ -79,20 +71,11 @@ try:
         if not chunk:
             break
 
-        if live is not None:
-            try:
-                live.sendall(chunk)
-            except OSError:
-                try:
-                    live.close()
-                except OSError:
-                    pass
-                live = None
-
         if capture is not None:
             try:
                 capture.write(chunk)
-            except OSError:
+            except OSError as error:
+                print(f"WARNING: FieldLens capture write failed: {error}", file=sys.stderr)
                 try:
                     capture.close()
                 except OSError:
@@ -103,39 +86,20 @@ try:
 
     sys.stdout.buffer.flush()
 
-    if live is not None:
-        try:
-            live.shutdown(socket.SHUT_WR)
-        except OSError:
-            pass
-        live.close()
-        live = None
-        live_ok = True
-
     if capture is not None:
         capture.flush()
         capture.close()
         capture = None
-        if live_ok:
-            try:
-                os.unlink(part_path)
-            except OSError:
-                pass
-        else:
         os.chmod(part_path, 0o644)
         os.replace(part_path, final_path)
         captured_ok = True
+        print(f"INFO: FieldLens captured {name}", file=sys.stderr)
 finally:
     if source is not None and source is not sys.stdin.buffer:
         source.close()
-    if live is not None:
-        try:
-            live.close()
-        except OSError:
-            pass
     if capture is not None:
         capture.close()
-    if not live_ok and not captured_ok:
+    if not captured_ok:
         try:
             os.unlink(part_path)
         except OSError:
@@ -620,7 +584,8 @@ fn build_fieldlens_ppd(target_printer: &str) -> Result<PathBuf> {
 
     let prefilter = concat!(
         "*% FieldLens original-document capture before printer rendering\n",
-        "*cupsPreFilter: \"application/pdf 0 fieldlens-capture\"\n"
+        "*cupsPreFilter: \"application/pdf 0 fieldlens-capture\"\n",
+        "*cupsPreFilter: \"application/vnd.cups-pdf 0 fieldlens-capture\"\n"
     );
     if let Some(index) = cleaned.rfind("*% End") {
         cleaned.insert_str(index, prefilter);

src-tauri/tauri.conf.json

@@ -1,7 +1,7 @@
 {
   "$schema": "https://schema.tauri.app/config/2",
   "productName": "FieldLens Print",
-  "version": "0.1.10",
+  "version": "0.1.11",
   "identifier": "dev.arrowstack.fieldlens.print",
   "build": {
     "beforeDevCommand": "npm run dev",

src/main.ts

@@ -85,7 +85,7 @@ let config: AppConfig
 let jobs: Job[] = []
 let status: Status
 let loginTimer: number | undefined
-let currentVersion = '0.1.10'
+let currentVersion = '0.1.11'
 let bundleType: BundleType | null = null
 let availableUpdate: Update | null = null
 let availableManualUpdate: ManualUpdate | null = null