Allow linespacing reset. Make this the default.

src/escpos/constants.py

@@ -102,6 +102,7 @@ TXT_INVERT_ON  = GS  + b'\x42\x01'  # Inverse Printing ON
 TXT_INVERT_OFF = GS  + b'\x42\x00'  # Inverse Printing OFF
 
 # Spacing
+LINESPACING_RESET = ESC + b'2'
 LINESPACING_FUNCS = {
   60: ESC + b'A',  # line_spacing/60 of an inch, 0 <= line_spacing <= 85
   360: ESC + b'+', # line_spacing/360 of an inch, 0 <= line_spacing <= 255

src/escpos/escpos.py

@@ -565,9 +565,11 @@ class Escpos(object):
         else:
             self._raw(TXT_INVERT_OFF)
 
-    def line_spacing(self, spacing=30, divisor=180):
+    def line_spacing(self, spacing=None, divisor=180):
         """ Set line character spacing.
 
+        If no spacing is given, we reset it to the default.
+
         There are different commands for setting the line spacing, using
         a different denominator:
 
@@ -578,6 +580,10 @@ class Escpos(object):
         Some printers may not support all of them. The most commonly
         available command (using a divisor of 180) is chosen.
         """
+        if spacing is None:
+            self._raw(LINESPACING_RESET)
+            return
+
         if divisor not in LINESPACING_FUNCS:
             raise ValueError("divisor must be either 360, 180 or 60")
         if (divisor in [360, 180] \