Replace XPP with Gtk print dialog and dependencies

Note: system-wide dependencies made available from
securedrop-export venv due to the need to access python3-gi.
Otherwise it would require too many build dependencies and complexity.
Given that python3-gi is already required by some Qubes components,
it does not add too many new dependencies.

export/securedrop_export/print/print_dialog.py

@@ -0,0 +1,48 @@
+import gi
+gi.require_version("Gtk", "4.0")
+from gi.repository import Gtk
+
+import logging
+from securedrop_export.print.status import Status
+from securedrop_export.exceptions import ExportException
+
+logger = logging.getLogger(__name__)
+
+def open_print_dialog(file_to_print):
+    app = PrintDialog(file_to_print)
+    app.run()
+
+
+class PrintDialog(Gtk.Application):
+    def __init__(self, file_to_print):
+        super().__init__(application_id="org.securedrop.PrintDialog")
+        self.file_to_print = file_to_print
+        self.connect("activate", self.on_activate)
+
+    def on_activate(self, app):
+        window = Gtk.Window(application=app)
+        self.dialog = Gtk.PrintUnixDialog.new("Print Document", window)
+        self.dialog.connect("response", self.on_response)
+        self.dialog.show()
+        window.hide()
+
+    def on_response(self, parent_widget, response_id):
+        if response_id == Gtk.ResponseType.OK:
+            print(f"OK")
+            self.dialog.hide()
+            settings = self.dialog.get_settings()
+            printer = self.dialog.get_selected_printer()
+            page_setup = self.dialog.get_page_setup()
+            job = Gtk.PrintJob.new("print job", printer, settings, page_setup)
+            job.set_source_file(self.file_to_print)
+            job.send(self.on_job_complete, user_data=None)
+        elif response_id == Gtk.ResponseType.APPLY: # Preview (if available)
+            pass
+        elif response_id == Gtk.ResponseType.CANCEL:
+            # FIXME should this exist or should it simply cancel and not report errors
+            raise ExportException(sdstatus=Status.ERROR_PRINT, sderror="User canceled dialog")
+
+    def on_job_complete(self, print_job, user_data, error):
+        if error:
+            self.quit()
+            raise ExportException(sdstatus=Status.ERROR_PRINT, sderror=error.message)

export/securedrop_export/print/service.py

@@ -113,31 +113,6 @@ def printer_test(self) -> Status:
         # a success status here
         return Status.PRINT_TEST_PAGE_SUCCESS
 
-    def _wait_for_print(self):
-        """
-        Use lpstat to ensure the job was fully transfered to the printer
-        Return True if print was successful, otherwise throw ExportException.
-        Currently, the handler `handler` is defined in `exceptions.py`.
-        """
-        signal.signal(signal.SIGALRM, handler)
-        signal.alarm(self.printer_wait_timeout)
-        printer_idle_string = f"printer {self.printer_name} is idle"
-        while True:
-            try:
-                logger.info(f"Running lpstat waiting for printer {self.printer_name}")
-                output = subprocess.check_output(["lpstat", "-p", self.printer_name])
-                if printer_idle_string in output.decode("utf-8"):
-                    logger.info("Print completed")
-                    return True
-                else:
-                    time.sleep(5)
-            except subprocess.CalledProcessError:
-                raise ExportException(sdstatus=Status.ERROR_PRINT)
-            except TimeoutException:
-                logger.error(f"Timeout waiting for printer {self.printer_name}")
-                raise ExportException(sdstatus=Status.ERROR_PRINT)
-        return True
-
     def _check_printer_setup(self) -> None:
         """
         Check printer setup.
@@ -420,20 +395,8 @@ def _print_file(self, file_to_print: Path):
             logger.error(f"Something went wrong: {file_to_print} not found")
             raise ExportException(sdstatus=Status.ERROR_PRINT)
 
-        logger.info(f"Sending file to printer {self.printer_name}")
-        try:
-            # We can switch to using libreoffice --pt $printer_cups_name
-            # here, and either print directly (headless) or use the GUI
-            subprocess.check_call(
-                ["xpp", "-P", self.printer_name, file_to_print],
-            )
-        except subprocess.CalledProcessError as e:
-            raise ExportException(sdstatus=Status.ERROR_PRINT, sderror=e.output)
-
-        # This is an addition to ensure that the entire print job is transferred over.
-        # If the job is not fully transferred within the timeout window, the user
-        # will see an error message.
-        self._wait_for_print()
+        logger.info("Opening print dialog")
+        open_print_dialog(str(file_to_print))
 
     def check_output_and_stderr(
         self, command: str, error_status: Status, ignore_stderr_startswith=None