begin moving text window when cursor goes off screen (currently, we only move the window when cursor goes backwards but this works fine and as expected)

fcore/app-update.sml

@@ -24,6 +24,8 @@ struct
       let
         val {windowWidth, windowHeight, startLine, ...} = app
         (* todo: get new startLine if cursor has moved out of screen *)
+        val startLine = TextWindow.getStartLine
+          (buffer, startLine, cursorIdx, windowWidth, windowHeight)
 
         (* move LineGap to first line displayed on screen, and build new text *)
         val buffer = LineGap.goToLine (startLine, buffer)
@@ -31,7 +33,8 @@ struct
           (startLine, cursorIdx, buffer, windowWidth, windowHeight)
 
         val mode = NORMAL_MODE ""
-        val newApp = AppWith.bufferAndCursorIdx (app, buffer, cursorIdx, mode)
+        val newApp = AppWith.bufferAndCursorIdx
+          (app, buffer, cursorIdx, mode, startLine)
       in
         (newApp, drawMsg)
       end
@@ -61,7 +64,8 @@ struct
           (startLine, cursorIdx, buffer, windowWidth, windowHeight)
 
         val mode = NORMAL_MODE ""
-        val newApp = AppWith.bufferAndCursorIdx (app, buffer, cursorIdx, mode)
+        val newApp = AppWith.bufferAndCursorIdx
+          (app, buffer, cursorIdx, mode, startLine)
       in
         (newApp, drawMsg)
       end
@@ -99,7 +103,8 @@ struct
         (startLine, cursorIdx, buffer, windowWidth, windowHeight)
 
       val mode = NORMAL_MODE ""
-      val newApp = AppWith.bufferAndCursorIdx (app, buffer, cursorIdx, mode)
+      val newApp = AppWith.bufferAndCursorIdx
+        (app, buffer, cursorIdx, mode, startLine)
     in
       (newApp, drawMsg)
     end
@@ -109,11 +114,8 @@ struct
     if pos = String.size str then
       pos
     else
-      let
+      let val chr = String.sub (str, pos)
-        val chr = String.sub (str, pos)
+      in if Char.isDigit chr then getNumLength (pos + 1, str) else pos
-      in
-        if Char.isDigit chr then getNumLength (pos + 1, str)
-        else pos
       end
 
   fun appendChr (app: app_type, chr, str) =
@@ -180,10 +182,7 @@ struct
          * such as "2dw" to delete two word
          * so add current chr to mode, and save it in the app state *)
         let
-          val str =
+          val str = if Char.isDigit chr then str ^ Char.toString chr else ""
-            if Char.isDigit chr 
-            then str ^ Char.toString chr
-            else ""
           val mode = NORMAL_MODE str
           val newApp = AppWith.mode (app, mode)
         in
@@ -202,7 +201,8 @@ struct
           (startLine, cursorIdx, buffer, windowWidth, windowHeight)
 
         val mode = NORMAL_MODE ""
-        val newApp = AppWith.bufferAndCursorIdx (app, buffer, cursorIdx, mode)
+        val newApp = AppWith.bufferAndCursorIdx
+          (app, buffer, cursorIdx, mode, startLine)
       in
         (newApp, drawMsg)
       end
@@ -262,24 +262,16 @@ struct
     | #"T" =>
         (* to just before chr, backward *)
         handleNextChr (1, app, Cursor.tillPrevChr, newCmd)
-    | #"y" => 
+    | #"y" => (* yank *) clearMode app
-        (* yank *) 
+    | #"d" => (* delete *) clearMode app
-        clearMode app
-    | #"d" => 
-        (* delete *) 
-        clearMode app
     | #"f" =>
         (* to chr, forward *)
         handleNextChr (count, app, Cursor.toNextChr, newCmd)
     | #"F" =>
         (* to chr, backward *)
         handleNextChr (count, app, Cursor.toPrevChr, newCmd)
-    | #"g" => 
+    | #"g" => (* go *) handleGo (count, app, newCmd)
-        (* go *) 
+    | #"c" => (* change *) clearMode app
-        handleGo (count, app, newCmd)
-    | #"c" => 
-        (* change *) 
-        clearMode app
     | _ =>
         (* isn't a non-terminal cmd
          * this case should never happen*)

fcore/app-with.sml

@@ -22,7 +22,8 @@ struct
       }
     end
 
-  fun bufferAndCursorIdx (app: app_type, newBuffer, newCursorIdx, newMode) =
+  fun bufferAndCursorIdx
+    (app: app_type, newBuffer, newCursorIdx, newMode, newStartLine) =
     let
       val
         { mode = _
@@ -30,15 +31,15 @@ struct
         , cursorIdx = _
         , windowWidth
         , windowHeight
-        , startLine
+        , startLine = _
         } = app
     in
       { mode = newMode
       , buffer = newBuffer
       , cursorIdx = newCursorIdx
+      , startLine = newStartLine
       , windowWidth = windowWidth
       , windowHeight = windowHeight
-      , startLine = startLine
       }
     end
 

fcore/text-builder.sml

@@ -7,10 +7,7 @@ end
 
 structure TextBuilder :> TEXT_BUILDER =
 struct
-  val xSpace = 13
+  open TextConstants
-  val xSpace3 = xSpace * 3
-  val ySpace = 25
-  val fontSize = 30.0
 
   fun accToDrawMsg (textAcc, cursorAcc) =
     let
@@ -480,7 +477,6 @@ struct
   fun build
     (startLine, cursorPos, lineGap: LineGap.t, windowWidth, windowHeight) =
     let
-      val lineGap = LineGap.goToLine (startLine, lineGap)
       val {rightStrings, rightLines, line = curLine, idx = curIdx, ...} = lineGap
     in
       case (rightStrings, rightLines) of
@@ -504,9 +500,7 @@ struct
                 end
               else
                 0
-
               val absIdx = curIdx + startIdx
-
           in
             if cursorPos < curIdx + String.size rStrHd then
               (* if cursor is within string *)

fcore/text-constants.sml

@@ -0,0 +1,7 @@
+structure TextConstants =
+struct
+  val xSpace = 13
+  val xSpace3 = xSpace * 3
+  val ySpace = 25
+  val fontSize : Real32.real = 30.0
+end

fcore/text-window.sml

@@ -0,0 +1,81 @@
+structure TextWindow =
+struct
+  open TextConstants
+
+  fun isPrevChrLn (str, strPos, strTl) =
+    if strPos > 0 then
+      String.sub (str, strPos - 1) = #"\n"
+    else
+      case strTl of
+        hd :: _ =>
+          String.sub (hd, String.size hd - 1) = #"\n"
+      | [] => false
+
+  fun getStartLineBefore (sIdx, shd, lineNum, absIdx, cursorIdx, stl) =
+    if sIdx < 0 then
+      case stl of
+        hd :: tl =>
+          getStartLineBefore 
+            (String.size hd - 1, hd, lineNum, absIdx, cursorIdx, tl)
+      | [] =>
+          0
+    else
+      let
+        val chr = String.sub (shd, sIdx)
+      in
+        if chr = #"\n" then
+          if absIdx <> cursorIdx then
+            getStartLineBefore
+              (sIdx - 1, shd, lineNum - 1, absIdx - 1, cursorIdx, stl)
+          else
+            (* we have found cursor, and it is at \n *)
+            lineNum - 1
+        else
+          if absIdx <> cursorIdx then
+            getStartLineBefore
+              (sIdx - 1, shd, lineNum, absIdx - 1, cursorIdx, stl)
+          else
+            (* we have found cursor; return line *)
+            lineNum - 1
+      end
+
+  (* Prerequisite: LineGap is moved to oldLine first. *)
+  fun getStartLine (lineGap: LineGap.t, oldLine, cursorIdx, maxWidth, maxHeight) =
+    let
+      val {rightStrings, rightLines, line = curLine, idx = curIdx, leftStrings, ...} = lineGap
+    in
+      case (rightStrings, rightLines) of
+        (rStrHd :: rStrTl, rLnHd :: _) =>
+          let
+            (* get index of line to start building from *)
+            val startIdx =
+              if oldLine > curLine then
+                let
+                  val lnPos = oldLine - curLine - 1
+                  val startIdx = Vector.sub (rLnHd, lnPos)
+                in
+                  startIdx - 1
+                end
+              else
+                0
+              val absIdx = curIdx + startIdx
+          in
+            if cursorIdx < absIdx then
+              (* move upwards *)
+              getStartLineBefore 
+                (startIdx, rStrHd, oldLine, absIdx, cursorIdx, leftStrings)
+            else if cursorIdx = absIdx + 1 then
+              (* double linebreak *)
+              getStartLineBefore 
+                (startIdx + 1, rStrHd, oldLine, absIdx + 1, cursorIdx, leftStrings)
+            else if cursorIdx > absIdx then
+              (* possibly move downwards *)
+              oldLine
+            else
+              (* keep current line *)
+              Int.max (oldLine - 1, 0)
+          end
+      | (_, _) => 
+          oldLine
+    end
+end

shf.mlb

@@ -11,11 +11,15 @@ message-types/mailbox-type.sml
 
 fcore/app-type.sml
 fcore/app-with.sml
+
+fcore/text-constants.sml
 ann
   "allowVectorExps true"
 in
   fcore/text-builder.sml
 end
+fcore/text-window.sml
+
 fcore/cursor.sml
 fcore/app-update.sml