ad usable static method

src/escpos/printer/cups.py

@@ -26,10 +26,11 @@ except ImportError:
 
 # TODO: dev build mode that let's the wrapper bypass?
 
-def is_usable():
+
+def is_usable() -> bool:
     """Indicate whether this component can be used due to dependencies."""
     usable = False
-    if not _DEP_PYCUPS:
+    if _DEP_PYCUPS:
         usable = True
     return usable
 
@@ -40,7 +41,7 @@ def dependency_pycups(func):
     @functools.wraps(func)
     def wrapper(*args, **kwargs):
         """Throw a RuntimeError if pycups is not imported."""
-        if is_usable():
+        if not is_usable():
             raise RuntimeError(
                 "Printing with PyCups requires the pycups library to"
                 "be installed. Please refer to the documentation on"
@@ -67,6 +68,15 @@ class CupsPrinter(Escpos):
 
     """
 
+    @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_pycups
     def __init__(self, printer_name=None, *args, **kwargs):
         """Class constructor for CupsPrinter.

src/escpos/printer/dummy.py

@@ -11,7 +11,7 @@
 from ..escpos import Escpos
 
 
-def is_usable():
+def is_usable() -> bool:
     """Indicate whether this component can be used due to dependencies."""
     return True
 
@@ -30,6 +30,15 @@ class Dummy(Escpos):
 
     """
 
+    @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()
+
     def __init__(self, *args, **kwargs):
         """Init with empty output list."""
         Escpos.__init__(self, *args, **kwargs)

src/escpos/printer/file.py

@@ -11,7 +11,7 @@
 from ..escpos import Escpos
 
 
-def is_usable():
+def is_usable() -> bool:
     """Indicate whether this component can be used due to dependencies."""
     return True
 
@@ -30,6 +30,15 @@ class File(Escpos):
 
     """
 
+    @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()
+
     def __init__(self, devfile="/dev/usb/lp0", auto_flush=True, *args, **kwargs):
         """Initialize file printer with device file.
 

src/escpos/printer/lp.py

@@ -16,10 +16,10 @@ import sys
 from ..escpos import Escpos
 
 
-def is_usable():
+def is_usable() -> bool:
     """Indicate whether this component can be used due to dependencies."""
     usable = False
-    if not sys.platform.startswith("win"):
+    if sys.platform.startswith("win"):
         usable = True
     return usable
 
@@ -30,7 +30,7 @@ def dependency_linux_lp(func):
     @functools.wraps(func)
     def wrapper(*args, **kwargs):
         """Throw a RuntimeError if not on a non-Windows system."""
-        if is_usable():
+        if not is_usable():
             raise RuntimeError(
                 "This printer driver depends on LP which is not"
                 "available on Windows systems."
@@ -52,6 +52,15 @@ class LP(Escpos):
 
     """
 
+    @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()
+
     def __init__(self, printer_name: str, *args, **kwargs):
         """LP class constructor.
 

src/escpos/printer/network.py

@@ -13,7 +13,7 @@ import socket
 from ..escpos import Escpos
 
 
-def is_usable():
+def is_usable()->bool:
     """Indicate whether this component can be used due to dependencies."""
     return True
 
@@ -40,6 +40,14 @@ class Network(Escpos):
         :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()
 
     def __init__(self, host, port=9100, timeout=60, *args, **kwargs):
         """Initialize network printer.

src/escpos/printer/serial.py

@@ -24,10 +24,10 @@ except ImportError:
     pass
 
 
-def is_usable():
+def is_usable()->bool:
     """Indicate whether this component can be used due to dependencies."""
     usable = False
-    if not _DEP_PYSERIAL:
+    if _DEP_PYSERIAL:
         usable = True
     return usable
 
@@ -38,7 +38,7 @@ def dependency_pyserial(func):
     @functools.wraps(func)
     def wrapper(*args, **kwargs):
         """Throw a RuntimeError if pyserial not installed."""
-        if is_usable():
+        if not is_usable():
             raise RuntimeError(
                 "Printing with Serial requires the pyserial library to"
                 "be installed. Please refer to the documentation on"
@@ -60,6 +60,14 @@ class Serial(Escpos):
         :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_pyserial
     def __init__(

src/escpos/printer/usb.py

@@ -24,10 +24,10 @@ except ImportError:
     pass
 
 
-def is_usable():
+def is_usable() -> bool:
     """Indicate whether this component can be used due to dependencies."""
     usable = False
-    if not _DEP_USB:
+    if _DEP_USB:
         usable = True
     return usable
 
@@ -38,7 +38,7 @@ def dependency_usb(func):
     @functools.wraps(func)
     def wrapper(*args, **kwargs):
         """Throw a RuntimeError if usb not installed."""
-        if is_usable():
+        if not is_usable():
             raise RuntimeError(
                 "Printing with USB connection requires a usb library to"
                 "be installed. Please refer to the documentation on"
@@ -61,6 +61,15 @@ class Usb(Escpos):
 
     """
 
+    @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()
+
     def __init__(
         self,
         idVendor,

src/escpos/printer/win32raw.py

@@ -23,10 +23,10 @@ except ImportError:
     pass
 
 
-def is_usable():
+def is_usable() -> bool:
     """Indicate whether this component can be used due to dependencies."""
     usable = False
-    if not _DEP_WIN32PRINT:
+    if _DEP_WIN32PRINT:
         usable = True
     return usable
 
@@ -37,7 +37,7 @@ def dependency_win32print(func):
     @functools.wraps(func)
     def wrapper(*args, **kwargs):
         """Throw a RuntimeError if win32print not installed."""
-        if is_usable():
+        if not is_usable():
             raise RuntimeError(
                 "Printing with Win32Raw requires a win32print library to"
                 "be installed. Please refer to the documentation on"
@@ -60,6 +60,15 @@ class Win32Raw(Escpos):
 
     """
 
+    @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."""