Display headings with a line break on a single line

novelwriter/constants.py

@@ -586,21 +586,14 @@ class nwUnicode:
     U_TIMES  = "\u00d7"  # Multiplication sign
     U_DIVIDE = "\u00f7"  # Division sign
 
-    # Arrows
-    U_UTRI   = "\u25b2"  # Up-pointing triangle
-    U_UTRIS  = "\u25b4"  # Up-pointing triangle, small
-    U_RTRI   = "\u25b6"  # Right-pointing triangle
-    U_RTRIS  = "\u25b8"  # Right-pointing triangle, small
-    U_DTRI   = "\u25bc"  # Down-pointing triangle
-    U_DTRIS  = "\u25be"  # Down-pointing triangle, small
-    U_LTRI   = "\u25c0"  # Left-pointing triangle
-    U_LTRIS  = "\u25c2"  # Left-pointing triangle, small
-
     # Special
     U_UNKN   = "\ufffd"  # Unknown character
     U_NAC1   = "\ufffe"  # Not a character
     U_NAC2   = "\uffff"  # Not a character
 
+    # Placeholders
+    U_LBREAK = "\u21b2"  # Downwards Arrow With Tip Leftwards
+
     # HTML Equivalents
     # ================
 
@@ -655,15 +648,15 @@ class nwUnicode:
     H_TIMES  = "×"
     H_DIVIDE = "÷"
 
-    # Arrows
-    H_UTRI   = "▲"
-    H_UTRIS  = "▴"
-    H_RTRI   = "▶"
-    H_RTRIS  = "▸"
-    H_DTRI   = "▼"
-    H_DTRIS  = "▾"
-    H_LTRI   = "◀"
-    H_LTRIS  = "◂"
+    # Unicode symbols expected to be used on the UI
+    UI_SYMBOLS: Final[list[str]] = [
+        U_QUOT, U_APOS, U_LAQUO, U_RAQUO, U_LSQUO, U_RSQUO, U_SBQUO, U_SUQUO,
+        U_LDQUO, U_RDQUO, U_BDQUO, U_UDQUO, U_LSAQUO, U_RSAQUO, U_BDRQUO,
+        U_LCQUO, U_RCQUO, U_LWCQUO, U_RWCQUO, U_FGDASH, U_ENDASH, U_EMDASH,
+        U_HBAR, U_HELLIP, U_MAPOS, U_PRIME, U_DPRIME, U_NBSP, U_THSP, U_THNBSP,
+        U_ENSP, U_EMSP, U_MMSP, U_CHECK, U_CROSS, U_BULL, U_TRBULL, U_HYBULL,
+        U_FLOWER, U_PERMIL, U_DEGREE, U_MINUS, U_TIMES, U_DIVIDE, U_LBREAK,
+    ]
 
 
 class nwHtmlUnicode: