split off dependencies for optional installation (#546)

* add inheritance diagrams to all printers and exceptions
* split off printer implementations into separate files
* add wrapper that thros RuntimeError if not importable
* add dependency check for lp
* add dependency check for pyserial
* added check for usability
* import Win32Raw
* include WIn32Raw in documentation
* enable all extras on tox
* update github workflow

src/escpos/printer/win32raw.py

@@ -0,0 +1,115 @@
+#!/usr/bin/python
+#  -*- coding: utf-8 -*-
+"""This module contains the implementation of the CupsPrinter printer driver.
+
+:author: python-escpos developers
+:organization: `python-escpos <https://github.com/python-escpos>`_
+:copyright: Copyright (c) 2012-2023 Bashlinux and python-escpos
+:license: MIT
+"""
+
+import functools
+
+from ..escpos import Escpos
+
+#: keeps track if the win32print dependency could be loaded (:py:class:`escpos.printer.Win32Raw`)
+_DEP_WIN32PRINT = False
+
+try:
+    import win32print
+
+    _DEP_WIN32PRINT = True
+except ImportError:
+    pass
+
+
+def is_usable() -> bool:
+    """Indicate whether this component can be used due to dependencies."""
+    usable = False
+    if _DEP_WIN32PRINT:
+        usable = True
+    return usable
+
+
+def dependency_win32print(func):
+    """Indicate dependency on win32print."""
+
+    @functools.wraps(func)
+    def wrapper(*args, **kwargs):
+        """Throw a RuntimeError if win32print not installed."""
+        if not is_usable():
+            raise RuntimeError(
+                "Printing with Win32Raw requires a win32print library to"
+                "be installed. Please refer to the documentation on"
+                "what to install and install the dependencies for win32print."
+            )
+        return func(*args, **kwargs)
+
+    return wrapper
+
+
+class Win32Raw(Escpos):
+    """Printer binding for win32 API.
+
+    Uses the module pywin32 for printing.
+
+    inheritance:
+
+    .. inheritance-diagram:: escpos.printer.Win32Raw
+        :parts: 1
+
+    """
+
+    @staticmethod
+    def is_usable() -> bool:
+        """Indicate whether this printer class is usable.
+
+        Will return True if dependencies are available.
+        Will return False if not.
+        """
+        return is_usable()
+
+    @dependency_win32print
+    def __init__(self, printer_name=None, *args, **kwargs):
+        """Initialize default printer."""
+        Escpos.__init__(self, *args, **kwargs)
+        if printer_name is not None:
+            self.printer_name = printer_name
+        else:
+            self.printer_name = win32print.GetDefaultPrinter()
+        self.hPrinter = None
+        self.open()
+
+    @dependency_win32print
+    def open(self, job_name="python-escpos"):
+        """Open connection to default printer."""
+        if self.printer_name is None:
+            raise Exception("Printer not found")
+        self.hPrinter = win32print.OpenPrinter(self.printer_name)
+        self.current_job = win32print.StartDocPrinter(
+            self.hPrinter, 1, (job_name, None, "RAW")
+        )
+        win32print.StartPagePrinter(self.hPrinter)
+
+    @dependency_win32print
+    def close(self):
+        """Close connection to default printer."""
+        if not self.hPrinter:
+            return
+        win32print.EndPagePrinter(self.hPrinter)
+        win32print.EndDocPrinter(self.hPrinter)
+        win32print.ClosePrinter(self.hPrinter)
+        self.hPrinter = None
+
+    @dependency_win32print
+    def _raw(self, msg):
+        """Print any command sent in raw format.
+
+        :param msg: arbitrary code to be printed
+        :type msg: bytes
+        """
+        if self.printer_name is None:
+            raise Exception("Printer not found")
+        if self.hPrinter is None:
+            raise Exception("Printer job not opened")
+        win32print.WritePrinter(self.hPrinter, msg)