Examples: add font-variations demo

examples/font_variations.py

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+#!/usr/bin/env python3
+
+# This demo allows testing multiple combination of specific font variations.
+# Two lines will be printed for every entry in "variations[]",
+# First line showing the entry index and parametes,
+# Second line being "Hello World".
+#
+# Example:
+# If a printed line shows:
+#   variations[2] =
+#   Hello World
+#   F=b B U AL=R
+# It is the 3rd entry (zero-based index 2),
+# with Font="B", Bold, Underline, Align=right.
+
+from pprint import pprint
+from escpos import printer
+
+p = printer.Usb(0x04B8, 0x0E20, profile="TM-P80")
+
+p.set_with_default()
+p.textln("Default Text")
+
+# Use any combination of parameters allowed in set_with_default()
+# See: https://python-escpos.readthedocs.io/en/latest/user/methods.html
+variations = [
+    {"font": "a", "custom_size": True, "width": 3, "height": 1},
+    {"font": "a", "custom_size": True, "width": 1, "height": 2},
+    {"font": "a", "bold": True},
+    {"font": "a", "custom_size": True, "width": 2, "height": 2},
+    {"font": "b", "underline": True},
+    {"font": "b", "align": "right", "double_width": True, "double_height": True},
+]
+
+for idx, v in enumerate(variations):
+    p.set_with_default(**v)
+
+    txt = "variations[%d] =" % idx
+    p.textln(txt)
+
+    p.textln("Hello World")
+
+    tags = []
+    if v.get("font"):
+        tags.append("F=" + v["font"])
+    if v.get("align"):
+        tags.append("AL=" + v.get("align")[:1])
+    if v.get("custom_size"):
+        tags.append("CS")
+    if "width" in v:
+        tags.append("W=" + str(v["width"]))
+    if "height" in v:
+        tags.append("H=" + str(v["height"]))
+    if v.get("bold"):
+        tags.append("B")
+    if v.get("underline"):
+        tags.append("U")
+    if v.get("smooth"):
+        tags.append("S")
+    if v.get("flip"):
+        tags.append("F")
+
+    txt = " ".join(tags)
+    p.textln(txt)
+
+    p.ln(1)
+
+p.cut(mode="PART", feed=True)