replace some control characters with their symbol counterparts

src/ui/bigtext/bigtext.py

@@ -421,15 +421,7 @@ class InnerBigText(QWidget):
         left_offset = int(-1 * self._left_offset * self.char_width)
         y_line_offset = self.char_height;
         for l in self.lines:
-            text = l.line_tabs_replaced()
+            text = l.line_prepared_for_display()
-            text = text.replace("\0", "␀") # qt throws error if we try to draw a null character
-            text = text.replace("\1", "␁")
-            text = text.replace("\2", "␂")
-            text = text.replace("\3", "␃")
-            text = text.replace("\4", "␄")
-            text = text.replace("\5", "␅")
-            text = text.replace("\6", "␆")
-            text = text.replace("\a", "␇")
             painter.drawText(left_offset, y_line_offset, text)
             y_line_offset = y_line_offset + self.char_height
 

src/ui/bigtext/line.py

@@ -36,12 +36,34 @@ class Line:
         prefix_chars = prefix_bytes.decode("utf8", errors="ignore")
         return len(prefix_chars)
 
-    def line_tabs_replaced(self):
+    def line_prepared_for_display(self):
+        line = self._line_tabs_replaced()
+        line = self._replace_control_chars_with_pictures(line)
+        return line
+
+    def _replace_control_chars_with_pictures(self, line: str):
+        length = len(line)
+        for i in range(length):
+            c = line[i]
+
+            if unicodedata.category(c) == "Cc" and c != "\r" and c != "\n" and c != "\t":
+                ordinal_value = ord(c)
+                if ordinal_value < 32 and not ordinal_value in [9, 10, 11]:
+                    # print(ord(c), " -> ", hex(ord(c)), " -> ", unicodedata.category(c), " -> ", chr(9216 + ord(c)))
+                    line = line.replace(c, chr(9216 + ord(c)))  # see Unicode Block “Control Pictures”
+                else:
+                    # print(ord(c), " -> ", hex(ord(c)), " -> ", unicodedata.category(c), " -> \u2421")
+                    line = line.replace(c, "\u2421")  # symbol for delete (␡)
+                # print(line)
+
+        return line;
+
+    def _line_tabs_replaced(self):
         line = self._line;
         i = 0
         offset = 0
         result = ""
-        length = len(line)
+        # length = len(line)
         while True:
             tab_index = line.find("\t", offset)
             if tab_index < 0:

src/ui/bigtext/testline.py

@@ -1,6 +1,9 @@
+import numbers
 import unittest
 
 import unicodedata
+import base64
+import urllib
 
 from line import Line
 
@@ -111,6 +114,20 @@ class MyTestCase(unittest.TestCase):
             print("%s %s cat: %s" % (c, unicodedata.name(c), unicodedata.category(c)))
             i = i + 1
 
+    def test_replace_control_characters(self):
+        byte_offset = 0
+        text = ""
+        for i in range(128):
+            if unicodedata.category(chr(i)) == "Cc":
+                # print(i, " -> ", ord(chr(i)), " --> ", chr(9216 + i))
+                if not i in [9, 10, 11, 13]:
+                    text = text + chr(i)
+
+        line = Line(byte_offset=byte_offset, byte_end=byte_offset + len(text.encode("utf8")), line=text)
+        actual = line.line_prepared_for_display()
+        self.assertEqual("␀␁␂␃␄␅␆␇␈␌␎␏␐␑␒␓␔␕␖␗␘␙␚␛␜␝␞␟␡", actual)
+        # self.assertEqual("␀␁␂␃␄␅␆␇␈\n␎␏␐␑␒␓␔␕␖␗␘␙␚␛␜␝␞␟␡", actual)
+
 
 if __name__ == '__main__':
     unittest.main()