From ee29d42a5ccfe9b2fd01208ed1eedc5ee8f2eba9 Mon Sep 17 00:00:00 2001
From: csoft2k <csoft2k@hotmail.com>
Date: Mon, 24 Jul 2017 23:29:16 +0200
Subject: [PATCH] Fix tabs behaviour.

The changes done in this commit should help with the open issues:
#5, #27 and #161.
The old implementation lacked the NUL char at the end of the command, as
defined on the Epson ESC/POS Reference Guide (see
https://reference.epson-biz.com/modules/ref_escpos/index.php?content_id=53
). Also, the horizontal tab control character (CTL_HT) shouldn't be
there.

This implementation allows setting up to 32 tabs with a given tab width.
Both values are checked to be in the valid ranges defined on the guide.
Also, the TabPosError exception text has been rewritten to define the
stated above.
---
 src/escpos/escpos.py     | 14 ++++++++------
 src/escpos/exceptions.py |  3 ++-
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/src/escpos/escpos.py b/src/escpos/escpos.py
index ec4df3b..0047fec 100644
--- a/src/escpos/escpos.py
+++ b/src/escpos/escpos.py
@@ -689,7 +689,7 @@ class Escpos(object):
         else:
             raise ValueError("n must be betwen 0 and 255")
 
-    def control(self, ctl, pos=4):
+    def control(self, ctl, count=5, tab_size=8):
         """ Feed control sequences
 
         :param ctl: string for the following control sequences:
@@ -700,7 +700,8 @@ class Escpos(object):
             * HT *for Horizontal Tab*
             * VT *for Vertical Tab*
 
-        :param pos: integer between 1 and 16, controls the horizontal tab position
+        :param count: integer between 1 and 32, controls the horizontal tab count. Defaults to 5.
+        :param tab_size: integer between 1 and 255, controls the horizontal tab size in characters. Defaults to 8
         :raises: :py:exc:`~escpos.exceptions.TabPosError`
         """
         # Set position
@@ -711,13 +712,14 @@ class Escpos(object):
         elif ctl.upper() == "CR":
             self._raw(CTL_CR)
         elif ctl.upper() == "HT":
-            if not (1 <= pos <= 16):
+            if not (0 <= count <= 32 and 1 <= tab_size <= 255 and count * tab_size < 256):
                 raise TabPosError()
             else:
                 # Set tab positions
-                self._raw(CTL_SET_HT + six.int2byte(pos))
-
-            self._raw(CTL_HT)
+                self._raw(CTL_SET_HT)
+                for iterator in range(1, count):
+                    self._raw(six.int2byte(iterator * tab_size))
+                self._raw(NUL)
         elif ctl.upper() == "VT":
             self._raw(CTL_VT)
 
diff --git a/src/escpos/exceptions.py b/src/escpos/exceptions.py
index 0662792..781e3e9 100644
--- a/src/escpos/exceptions.py
+++ b/src/escpos/exceptions.py
@@ -150,7 +150,8 @@ class CashDrawerError(Error):
 
 
 class TabPosError(Error):
-    """ Valid tab positions must be in the range 0 to 16.
+    """ Valid tab positions must be set by using from 1 to 32 tabs, and between 1 and 255 tab size values.
+    Both values multiplied must not exceed 255, since it is the maximum tab value.
 
     This exception is raised by :py:meth:`escpos.escpos.Escpos.control`.
     The returncode for this exception is `70`.