Make wrapping respect non-breaking spaces (#1780)

Non-breaking space and Narrow non-breaking space will
not permit line breaks during text rewrapping.

GG1 respects NBS, but not NNBS. GG2 now respects both.

Also respect Figure Space

Since Figure Space is used, e.g. for space in phone numbers,
it too is normally thought of as non-breaking.

Author: windymilla

src/guiguts/maintext.py

@@ -45,6 +45,9 @@
 INDEX_NEXT_LINE_MARK = "IndexLineStart"
 WRAP_END_MARK = "WrapSectionEnd"
 PAGEMARK_PIN = "\x7f"  # Temp char to pin page mark locations
+# Temp chars to replace non-breaking space are from Unicode Private Use Area,
+# so we know they won't appear in any of our books
+NBS_DICT = {"\xa0": "\ue123", "\u2007": "\ue124", "\u202f": "\ue125"}
 PAGEMARK_PREFIX = "Pg"
 REPLACE_END_MARK = "ReplaceEnd"
 SELECTION_MARK_START = "SelectionMarkStart"
@@ -3570,25 +3573,35 @@ def wrap_paragraph(
             wrap_params: Wrapping parameters.
             wrapper: TextWrapper object to perform the wrapping - re-used for efficiency.
         """
+
         if paragraph.startswith("       *" * 5):
             return
         # Remove leading/trailing space
         paragraph = paragraph.strip()
-        # Replace all multiple whitespace with single space
-        paragraph = re.sub(r"\s+", " ", paragraph)
+        # Replace all multiple space/newline with single space
+        paragraph = re.sub(r"[\n ]+", " ", paragraph)
         # Don't want pagemark pins to trap spaces around them, so...
         # Remove space between pagemark pins
         paragraph = re.sub(rf"(?<={PAGEMARK_PIN}) (?={PAGEMARK_PIN})", "", paragraph)
         # Remove space after pagemark pins if space (or linestart) before
         paragraph = re.sub(rf"(( |^){PAGEMARK_PIN}+) ", r"\1", paragraph)
         # Remove space before pagemark pins if space (or lineend) after
         paragraph = re.sub(rf" ({PAGEMARK_PIN}+( |$)) ", r"\1", paragraph)
+        # Convert non-breaking spaces to temporary non-space characters
+        # to stop the wrapper from putting a break there
+        for nbs, temp in NBS_DICT.items():
+            paragraph = paragraph.replace(nbs, temp)
 
         wrapper.width = wrap_params.right
         wrapper.initial_indent = wrap_params.first * " "
         wrapper.subsequent_indent = wrap_params.left * " "
 
         wrapped = wrapper.fill(paragraph)
+
+        # Restore non-breaking spaces
+        for nbs, temp in NBS_DICT.items():
+            wrapped = wrapped.replace(temp, nbs)
+
         self.delete(paragraph_start, paragraph_end)
         self.insert(paragraph_start, wrapped + "\n")