From dfb7ecb8679fd429ce12a33a4aaf0db22f20d198 Mon Sep 17 00:00:00 2001
From: Humza Shahid <humzasaur@gmail.com>
Date: Thu, 11 Sep 2025 17:30:49 +0100
Subject: [PATCH] add new function to calculate the startLine

---
 fcore/normal-mode/normal-finish.sml |  1 -
 fcore/text-scroll.sml               | 21 +++++++++++++++++++--
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/fcore/normal-mode/normal-finish.sml b/fcore/normal-mode/normal-finish.sml
index 1dabf31..95dd165 100644
--- a/fcore/normal-mode/normal-finish.sml
+++ b/fcore/normal-mode/normal-finish.sml
@@ -17,7 +17,6 @@ struct
       (* calculate scroll column *)
       val buffer = LineGap.goToIdx (cursorIdx, buffer)
       val visualScrollColumn = TextScroll.getScrollColumn (buffer, cursorIdx, windowWidth)
-      val () = print (Int.toString visualScrollColumn ^ "\n")
 
       (* move LineGap to first line displayed on screen *)
       val buffer = LineGap.goToLine (startLine, buffer)
diff --git a/fcore/text-scroll.sml b/fcore/text-scroll.sml
index 0fea775..fb8dfef 100644
--- a/fcore/text-scroll.sml
+++ b/fcore/text-scroll.sml
@@ -17,8 +17,25 @@ struct
             else windowWidth div TC.xSpace
         in
           if columnDifference < howManyColumnsCanWeFit then 0
-          else
-            columnDifference - howManyColumnsCanWeFit
+          else columnDifference - howManyColumnsCanWeFit
         end
     end
+
+  fun getStartLine (prevLineNumber, cursorLine, windowHeight) =
+    if cursorLine <= prevLineNumber then
+      (* if cursorLine is prior or same as prevLineNumber, 
+       * then use cursorLine as scroll-line-start *)
+      cursorLine
+    else
+      (* cursorLine > prevLineNumber *)
+      let
+        val howManyLinesWeCanFit = windowHeight div TC.ySpace
+      in
+        if prevLineNumber + howManyLinesWeCanFit >= cursorLine then
+          prevLineNumber
+        else
+          let val lineDifference = cursorLine - prevLineNumber
+          in prevLineNumber + lineDifference
+          end
+      end
 end