add function to go to first non-space character in line

fcore/app-update.sml

@@ -59,6 +59,30 @@ struct
       (newApp, drawMsg)
     end
 
+  fun firstNonSpaceChr (app: app_type) =
+    let
+      val {buffer, windowWidth, windowHeight, startLine, cursorIdx, ...} = app
+
+      (* move LineGap and buffer to start of line *)
+      val buffer = LineGap.goToIdx (cursorIdx, buffer)
+      val cursorIdx = Cursor.vi0 (buffer, cursorIdx)
+
+      (* move cursorIdx to first character on line *)
+      val buffer = LineGap.goToIdx (cursorIdx, buffer)
+      val cursorIdx = Cursor.firstNonSpaceChr (buffer, cursorIdx)
+
+      (* todo: get new startLine if cursor has moved out of screen *)
+
+      (* move LineGap to first line displayed on screen, and build new text *)
+      val buffer = LineGap.goToLine (startLine, buffer)
+      val drawMsg = TextBuilder.build
+        (startLine, cursorIdx, buffer, windowWidth, windowHeight)
+
+      val newApp = AppWith.bufferAndCursorIdx (app, buffer, cursorIdx)
+    in
+      (newApp, drawMsg)
+    end
+
   fun handleChr (app: app_type, chr) =
     case chr of
       #"h" => moveBackward (app, Cursor.viH) 
@@ -73,6 +97,7 @@ struct
     | #"B" => moveBackward (app, Cursor.prevWORD)
     | #"e" => moveFowrards (app, Cursor.endOfWord)
     | #"E" => moveFowrards (app, Cursor.endOfWORD)
+    | #"^" => firstNonSpaceChr app
     | _ => (app, [])
 
   fun update (app, msg) =