fixed two issues. First is that an exception occurred when sometimes moving cursor forwards. Cause of this issue was that callee functions depended on LineGap being moved to start of line, but this did not always happen (and now it does always happen). Second issue was that moving cursor down did not scroll as expected when line wrapped. The reason for this second issue was that the 'getStartLineAfter' function did not increment 'startLine' value in loop when line wrap occurred. Both issues are now fixed.

fcore/app-update.sml

@@ -24,13 +24,16 @@ struct
       let
         val {windowWidth, windowHeight, startLine, ...} = app
 
-        (* move LineGap to first line displayed on screen, and build new text *)
-        val buffer = 
-          LineGap.goToLine (startLine, buffer)
+        (* move LineGap to first line displayed on screen *)
+        val buffer = LineGap.goToLine (startLine, buffer)
 
+        (* get new startLine which may move screen depending on cursor movements *)
         val startLine = TextWindow.getStartLine
           (buffer, startLine, cursorIdx, windowWidth, windowHeight)
 
+        (* move buffer to new startLine as required by TextBuilder.build *)
+        val buffer = LineGap.goToLine (startLine, buffer)
+
         val drawMsg = 
           TextBuilder.build
             (startLine, cursorIdx, buffer, windowWidth, windowHeight)
@@ -59,14 +62,17 @@ struct
     if count = 0 then
       let
         val {windowWidth, windowHeight, startLine, ...} = app
-        (* todo: get new startLine if cursor has moved out of screen *)
 
-        (* move LineGap to first line displayed on screen, and build new text *)
+        (* move LineGap to first line displayed on screen *)
         val buffer = LineGap.goToLine (startLine, buffer)
 
+        (* get new startLine which may move screen depending on cursor movements *)
         val startLine = TextWindow.getStartLine
           (buffer, startLine, cursorIdx, windowWidth, windowHeight)
 
+        (* move buffer to new startLine as required by TextBuilder.build *)
+        val buffer = LineGap.goToLine (startLine, buffer)
+
         val drawMsg = TextBuilder.build
           (startLine, cursorIdx, buffer, windowWidth, windowHeight)
 

fcore/text-window.sml

@@ -65,7 +65,7 @@ struct
               if curHeight + (ySpace * 3) >= maxHeight then
                 getStartLineAfter 
                   ( sIdx + 1, shd, lineNum + 1, absIdx + 1, cursorIdx, stl
-                  , maxWidth, maxHeight, 0, 0
+                  , maxWidth, maxHeight, 0, curHeight + ySpace
                   , origLine + 1
                   )
               else
@@ -90,13 +90,13 @@ struct
                 if curHeight + (ySpace * 3) >= maxHeight then
                   getStartLineAfter
                     ( sIdx + 1, shd, lineNum + 1, absIdx + 1, cursorIdx, stl
-                    , maxWidth, maxHeight, 0, 0
+                    , maxWidth, maxHeight, 0, curHeight + ySpace
                     , origLine + 1
                     )
                 else
                   getStartLineAfter
                     ( sIdx + 1, shd, lineNum + 1, absIdx + 1, cursorIdx, stl
-                    , maxWidth, maxHeight, 0, 0
+                    , maxWidth, maxHeight, 0, curHeight + ySpace
                     , origLine
                     )
           end
@@ -132,12 +132,11 @@ struct
                 (startIdx + 1, rStrHd, oldLine, absIdx + 1, cursorIdx, leftStrings)
             else if cursorIdx > absIdx then
               (* possibly move downwards *)
-              let val _ = print "start 133\n" in
               getStartLineAfter 
                  ( startIdx, rStrHd, oldLine, absIdx, cursorIdx, rStrTl
                  , maxWidth, maxHeight, 0, 0
                  , oldLine
-                 ) end
+                 )
             else
               (* keep current line *)
               Int.max (oldLine - 1, 0)