in TextBuilder, forgot to build cursor when cursorIdx is over space, so now we build cursor when cursorIdx is over space

fcore/app-update.sml

@@ -19,14 +19,38 @@ struct
       (newApp, drawMsg)
     end
 
-  fun handleChr (app, chr) =
+  fun moveRight (app: app_type) =
     let
-      val chr = Char.toString chr ^ "\n"
-      val () = print chr
+      (* todo: proper implementation of moveRight
+       * currently, we also retrieve the newCursorIdx improperly.
+       * To do it properly, we have to look inside LineGap
+       * instead of just incrementing cursorIdx by 1.
+       * So:
+       * - Find newCursorIdx from LineGap
+       * *)
+
+      val {buffer, windowWidth, windowHeight, startLine, cursorIdx} = app
+
+      (* move LineGap to cursorIdx, which is necessary for finding newCursorIdx *)
+      val newBuffer = LineGap.goToIdx (cursorIdx, buffer)
+      (* todo: call to retrieve newCursorIdx should be below *)
+      val newCursorIdx = cursorIdx + 1
+
+      (* move LineGap to first line displayed on screen, and build new text *)
+      val newBuffer = LineGap.goToLine (startLine, newBuffer)
+      val drawMsg = TextBuilder.build
+        (startLine, cursorIdx, newBuffer, windowWidth, windowHeight)
+
+      val newApp = AppWith.bufferAndCursorIdx (app, newBuffer, newCursorIdx)
     in
-      (app, [])
+      (newApp, drawMsg)
     end
 
+  fun handleChr (app: app_type, chr) =
+    case chr of
+      #"l" => moveRight app
+    | _ => (app, [])
+
   fun update (app, msg) =
     case msg of
       RESIZE_EVENT (width, height) => resizeText (app, width, height)

fcore/app-with.sml

@@ -14,4 +14,17 @@ struct
       , cursorIdx = cursorIdx
       }
     end
+
+  fun bufferAndCursorIdx (app: app_type, newBuffer, newCursorIdx) =
+    let
+      val {buffer = _, cursorIdx = _, windowWidth, windowHeight, startLine} =
+        app
+    in
+      { buffer = newBuffer
+      , cursorIdx = newCursorIdx
+      , windowWidth = windowWidth
+      , windowHeight = windowHeight
+      , startLine = startLine
+      }
+    end
 end

fcore/text-builder.sml

@@ -286,17 +286,34 @@ struct
     if pos < String.size str then
       case String.sub (str, pos) of
         #" " =>
-          buildTextStringWithinCursor
-           ( pos + 1, str, acc, posX + xSpace, posY, startX
-           , windowWidth, windowHeight, fWindowWidth, fWindowHeight
-           , r, g, b, tl, absIdx + 1, cursorPos, cursorAcc, hr, hg, hb
-           )
+          (* if inside cursor, then create cursorAcc;
+           * else, just skip as usual *)
+          if absIdx <> cursorPos then
+            (* not in cursur *)
+            buildTextStringWithinCursor
+             ( pos + 1, str, acc, posX + xSpace, posY, startX
+             , windowWidth, windowHeight, fWindowWidth, fWindowHeight
+             , r, g, b, tl, absIdx + 1, cursorPos, cursorAcc, hr, hg, hb
+             )
+          else
+            (* in cursor *)
+            let
+              val cursorAcc = buildCursor (posX, posY, fWindowWidth, fWindowHeight, r, g ,b)
+            in
+              buildTextStringAfterCursor
+                ( pos + 1, str, acc, posX + xSpace, posY, startX
+                , windowWidth, windowHeight, fWindowWidth, fWindowHeight
+                , r, g, b, tl, cursorAcc
+                )
+            end
       | #"\t" =>
+          (* todo: draw cursor if cursor is on tab
+           * but this is not a priority right now *)
           buildTextStringWithinCursor
-           ( pos + 1, str, acc, posX + xSpace3, posY, startX
-           , windowWidth, windowHeight, fWindowWidth, fWindowHeight
-           , r, g, b, tl, absIdx + 1, cursorPos, cursorAcc, hr, hg, hb
-           )
+            ( pos + 1, str, acc, posX + xSpace3, posY, startX
+            , windowWidth, windowHeight, fWindowWidth, fWindowHeight
+            , r, g, b, tl, absIdx + 1, cursorPos, cursorAcc, hr, hg, hb
+            )
       | #"\n" =>
           if posY + ySpace < windowHeight then
             buildTextStringWithinCursor