fix: stop printing and saving halting after 10-12 hours of runtime

docs/changelog.md

@@ -6,6 +6,14 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 ## [Unreleased]
 
+### Fixed
+- **Printing & Ticket Saving: Fix 10-12 hour runtime failure** (2026-06-02)
+  - After extended runtime (~10-12 hours) the system would silently stop printing and saving new orders. Three bugs combined to cause this.
+  - **Root cause — stale Xt input handler spin loop (`main/hardware/remote_printer.cc`):** `PrinterCB()` was closing the socket and marking the printer offline (`failure = 999`) but never calling `RemoveInputFn(p->input_id)`. The X event loop continued polling the closed file descriptor on every tick, creating an infinite error-callback spin loop. Over 10-12 hours of normal restaurant operation this CPU waste progressively starved the main event thread, causing both printing and order-saving to hang. Fix: deregister the input handler (`RemoveInputFn` + `input_id = -1`) before closing the socket in the offline-marking block.
+  - **Secondary — blocking `system()` call in `LPDPrint` (`main/hardware/printer.cc`):** `Printer::Close()` called the synchronous `LPDPrint()` (which runs `system("cat file | lpr -P...")`) on the main thread. If CUPS became unresponsive this blocked the entire event loop for the duration. Fix: `Close()` now delegates `TARGET_LPD` and `TARGET_SOCKET` to `CloseAsync()`, which already dispatches print jobs to a background thread pool.
+  - **Tertiary — silent I/O errors in archive save (`main/data/archive.cc`, `src/core/data_file.hh`):** `Archive::SavePacked()` did not check for write errors after the drawer and check write loops. A disk-full or I/O error would be silently ignored and the archive marked as successfully saved. Fix: added `OutputDataFile::HasError()` (using `ferror`/`gzerror`) and inserted checks after both write loops with appropriate `ReportError` messages and early-return on failure.
+  - Files modified: `main/hardware/remote_printer.cc`, `main/hardware/printer.cc`, `main/data/archive.cc`, `src/core/data_file.hh`.
+
 ### Removed
 - **Button Properties Dialog: Remove redundant "Menu Type" field** (2026-05-28)
   - The "Menu Type" selector (`item_type` `DialogMenu` widget in `ZoneDialog`) was redundant with the more specific zone types already present in "Button's Type" (`ZONE_ITEM_NORMAL`, `ZONE_ITEM_MODIFIER`, `ZONE_ITEM_METHOD`, `ZONE_ITEM_SUBSTITUTE`, `ZONE_ITEM_POUND`, `ZONE_ITEM_ADMISSION`). The item classification (`itype`) is now derived entirely from the selected zone type; for the legacy generic `ZONE_ITEM` type the classification defaults to `ITEM_NORMAL`. The network protocol byte is preserved unchanged.

main/data/archive.cc

@@ -644,6 +644,11 @@ int Archive::SavePacked()
         drawer->Write(df, DRAWER_VERSION);
         drawer = drawer->next;
     }
+    if (df.HasError())
+    {
+        ReportError("Archive::SavePacked(): I/O error writing drawers — archive may be corrupt");
+        return 1;
+    }
 
     // Save Checks
     count = 0;
@@ -659,6 +664,11 @@ int Archive::SavePacked()
         c->Write(df, CHECK_VERSION);
         c = c->next;
     }
+    if (df.HasError())
+    {
+        ReportError("Archive::SavePacked(): I/O error writing checks — archive may be corrupt");
+        return 1;
+    }
 
     // Save Tips
     count = 0;

main/hardware/printer.cc

@@ -258,27 +258,32 @@ int Printer::Close()
 {
     FnTrace("Printer::Close()");
 
-    // assume we're going to do something.  But only close if we're pretty
-    // sure we have a valid file handle
+    // LPD and socket printing block the calling thread (system() / connect()).
+    // Delegate to CloseAsync() which dispatches to a thread pool so the main
+    // event loop is never stalled waiting for CUPS or a network printer.
+    // CloseAsync() owns temp_fd/temp_name cleanup for these two types.
+    if (target_type == TARGET_LPD || target_type == TARGET_SOCKET)
+    {
+        CloseAsync();
+        return 0;
+    }
+
+    // For all other target types: close the file handle, dispatch, then clean up.
     if (temp_fd > 0)
         close(temp_fd);
     switch (target_type)
     {
     case TARGET_PARALLEL:
         ParallelPrint();
         break;
-    case TARGET_LPD:
-        LPDPrint();
-        break;
-    case TARGET_SOCKET:
-        SocketPrint();
-        break;
     case TARGET_FILE:
         FilePrint();
         break;
     case TARGET_EMAIL:
         EmailPrint();
         break;
+    default:
+        break;
     }
     // delete the temp file unless printing to the parallel port might still need it
     if (target_type != TARGET_PARALLEL)

main/hardware/remote_printer.cc

@@ -579,6 +579,16 @@ void PrinterCB(XtPointer client_data, int *fid, XtInputId *id)
                  p->host_name.Value(), p->port_no, p->failure);
         ReportError(errmsg.data());
 
+        // Deregister the Xt input handler BEFORE closing the socket.
+        // Without this, the event loop keeps polling the closed FD every tick,
+        // spinning in an infinite error loop that starves the main thread after
+        // ~10-12 hours of accumulated failures.
+        if (p->input_id >= 0)
+        {
+            RemoveInputFn(p->input_id);
+            p->input_id = -1;
+        }
+
         if (p->socket_no >= 0)
         {
             // close socket here instead of letting the destructor do it
@@ -587,7 +597,7 @@ void PrinterCB(XtPointer client_data, int *fid, XtInputId *id)
             p->socket_no = -1;
         }
 
-        // Critical fix: Don't kill the printer immediately, mark it for reconnection
+        // Don't kill the printer immediately, mark it for reconnection
         if (db)
         {
             // Mark printer as offline but keep it in the list for reconnection attempts

src/core/data_file.hh

@@ -131,6 +131,17 @@ public:
     int Write(Flt  *val, int bk = 0);
     int Write(Str  *val, int bk = 0);
     [[nodiscard]] const std::string &FileName() const noexcept { return filename; }
+    // Returns true if any underlying write has failed (e.g. disk full).
+    [[nodiscard]] bool HasError() const noexcept
+    {
+        if (compress && gz_fp)
+        {
+            int errnum = 0;
+            gzerror(gz_fp, &errnum);
+            return errnum != Z_OK && errnum != Z_STREAM_END;
+        }
+        return file_fp && ferror(file_fp) != 0;
+    }
 };
 
 /*********************************************************************