messagegui: tweak updateReadMessages, possibly fixing off by one

Author: thyttan

apps/messagegui/app.js

@@ -374,11 +374,19 @@ function showMessagesScroller(msg, persist) {
 
     for (let i=0; i<firstTitleLinePerMsg.length-1 ; i++) {
 
-      if (shownScrollIdxFirst<=firstTitleLinePerMsg[i] && shownScrollIdxFirst+LINES_PER_SCREEN>firstTitleLinePerMsg[i]) {
+      if (
+        shownScrollIdxFirst
+          <= firstTitleLinePerMsg[i] && firstTitleLinePerMsg[i]
+            < shownScrollIdxFirst+LINES_PER_SCREEN
+      ) {
         shownMsgIdxFirst = i;
       }
 
-      if (shownScrollIdxLast>=firstTitleLinePerMsg[i+1] && shownScrollIdxLast-LINES_PER_SCREEN<firstTitleLinePerMsg[i+1]) {
+      if (
+        shownScrollIdxLast-LINES_PER_SCREEN
+          < firstTitleLinePerMsg[i+1]-1 && firstTitleLinePerMsg[i+1]-1
+            <= shownScrollIdxLast
+      ) {
         shownMsgIdxLast = i;
         //print(i)
       }