in TextBuilder.build functions, when we encounter a space, check if we are before the scroll column's start, and set the x position to startX if so. This is done in preparation for the character which is actually at the scroll column's start, which will be added at the wrong offset unless we do this.

fcore/text-builder/text-builder-with-highlight.sml

@@ -208,6 +208,9 @@ struct
                     Utils.makeHighlight (posX, posY, env) :: acc
                   else
                     acc
+                val posX =
+                  if column < #scrollColumnStart env then #startX env
+                  else posX + TC.xSpace
               in
                 build
                   ( pos + 1
@@ -215,7 +218,7 @@ struct
                   , stl
                   , line
                   , ltl
-                  , posX + TC.xSpace
+                  , posX
                   , posY
                   , column + 1
                   , lineNumber