Improve ticket legibility: larger fonts, spacing, indentation and thermal emphasized mode

pos/services/thermal_printer.py

@@ -16,9 +16,13 @@ ALIGN_CENTER = ESC + b'a' + b'\x01'
 ALIGN_RIGHT = ESC + b'a' + b'\x02'
 BOLD_ON = ESC + b'E' + b'\x01'
 BOLD_OFF = ESC + b'E' + b'\x00'
+EMPH_ON = ESC + b'G' + b'\x01'    # Double-strike / emphasized
+EMPH_OFF = ESC + b'G' + b'\x00'
 DOUBLE_HEIGHT = ESC + b'!' + b'\x10'
 NORMAL_SIZE = ESC + b'!' + b'\x00'
 LARGE_SIZE = ESC + b'!' + b'\x30'  # Double width + double height
+LINE_SPACING_140 = ESC + b'3' + b'\x28'  # ~1.4x line spacing
+LINE_SPACING_DEFAULT = ESC + b'2'
 
 
 def generate_ticket(sale_data, business_info, width=80):
@@ -34,6 +38,8 @@ def generate_ticket(sale_data, business_info, width=80):
     chars = 32 if width == 58 else 48  # characters per line
     buf = bytearray()
     buf += INIT
+    buf += EMPH_ON
+    buf += LINE_SPACING_140
 
     # Header: business name (centered, bold, large)
     buf += ALIGN_CENTER
@@ -100,6 +106,8 @@ def generate_ticket(sale_data, business_info, width=80):
     buf += 'Gracias por su compra!\n'.encode('cp437', errors='replace')
     buf += 'Nexus Autoparts POS\n'.encode('cp437', errors='replace')
     buf += b'\n\n\n'
+    buf += LINE_SPACING_DEFAULT
+    buf += EMPH_OFF
     buf += FEED + b'\x05'      # Feed 5 lines before cutting
     buf += CUT                  # Full cut
 
@@ -120,6 +128,8 @@ def generate_quotation_ticket(quote_data, business_info, width=80):
     chars = 32 if width == 58 else 48
     buf = bytearray()
     buf += INIT
+    buf += EMPH_ON
+    buf += LINE_SPACING_140
 
     # Header
     buf += ALIGN_CENTER
@@ -188,6 +198,8 @@ def generate_quotation_ticket(quote_data, business_info, width=80):
     buf += 'Precios sujetos a disponibilidad\n'.encode('cp437', errors='replace')
     buf += 'Nexus Autoparts POS\n'.encode('cp437', errors='replace')
     buf += b'\n\n\n'
+    buf += LINE_SPACING_DEFAULT
+    buf += EMPH_OFF
     buf += FEED + b'\x05'
     buf += CUT
 
@@ -226,6 +238,8 @@ def generate_service_order_ticket(so_data, business_info, width=80):
     chars = 32 if width == 58 else 48
     buf = bytearray()
     buf += INIT
+    buf += EMPH_ON
+    buf += LINE_SPACING_140
 
     # Header
     buf += ALIGN_CENTER
@@ -340,6 +354,8 @@ def generate_service_order_ticket(so_data, business_info, width=80):
     buf += "No es comprobante fiscal\n".encode("cp437", errors="replace")
     buf += "Nexus Autoparts POS\n".encode("cp437", errors="replace")
     buf += b"\n\n\n"
+    buf += LINE_SPACING_DEFAULT
+    buf += EMPH_OFF
     buf += FEED + b'\x05'
     buf += CUT