Fix text overlapping in offsets in register diagrams.

registers.py

@@ -213,19 +213,33 @@ def symbols( self ):
 
     def columnWidth( self ):
         """Return the width of the column in boxes."""
-        charWidth = .33
+        offsetCharWidth = .26
+        nameCharWidth = .33
         xlen_symbol = sympy.symbols('XLEN')
+        lengthCharWidth = .22
         try:
             # Pretend XLEN=32. This makes 32-bit registers with just a single
             # field be wide, while registers with XLEN-32 width be narrow.
             length = int(self.length().subs(xlen_symbol, 32))
         except TypeError:
             length = 20
+        if self.length() == 1:
+            bitText = f"{self.lowBit}"
+        else:
+            # There is no dash in what we're displaying, but we want some space
+            # for separation between the two values.
+            bitText = f"{self.highBit} - {self.lowBit}"
         width = math.ceil(max(
+            # Minimum length
             1,
+            # Make fields with more bits take up more space visually
             1 + math.log(max(length, 0.1), 1.7),
-            len( str( self.length() )) * charWidth,
-            len( self.name ) * charWidth))
+            # Wide enough to accommodate the string showing the field length
+            len( str( self.length() )) * lengthCharWidth,
+            # Wide enough to accommodate the high/low bit strings
+            len( bitText ) * offsetCharWidth,
+            # Wide enough to accommodate the name of the field
+            len( self.name ) * nameCharWidth))
         # Make longer widths odd, so we can center the bit.
         if width > 1 and width % 2 == 0:
             width += 1
@@ -879,14 +893,26 @@ def write_bytefield_row( fd, fields ):
             else:
                 headers.append(f.lowBit)
         else:
-            assert columnWidth >= 2
-            headers.append(f.lowBit)
-            headers += [""] * (columnWidth - 2)
-            headers.append(f.highBit)
+            # If low/high bit need more than 2 characters, place them one in
+            # from the end so they don't overflow into the neighboring field.
+            # Really this should be done with right/left alignment, but
+            # bytefield doesn't seem to support that.
+            if len(f.lowBit) > 2:
+                start = ["", f.lowBit]
+            else:
+                start = [f.lowBit]
+            if len(f.highBit) > 2:
+                end = [f.highBit, ""]
+            else:
+                end = [f.highBit]
+            assert columnWidth >= len(start) + len(end)
+            headers += start
+            headers += [""] * (columnWidth - len(start) - len(end))
+            headers += end
         columnOffset += columnWidth
     # remove whitespace to save space
     headers = [h.replace(" ", "") for h in headers]
-    fd.write('(draw-column-headers {:font-size 15 :height 16 :labels [%s]})\n' % " ".join(f'"{h}"' for h in reversed(headers)))
+    fd.write('(draw-column-headers {:font-size 15 :height 17 :labels [%s]})\n' % " ".join(f'"{h}"' for h in reversed(headers)))
 
     for f in fields:
         fd.write('(draw-box (text "%s" {:font-size 20}) {:span %s})\n' % ( f.name, f.columnWidth() ))