Fix cursor position overrun (#515)

* Fix cursor position overrun

* Remove unnecessary local variable

Co-authored-by: Stan Lo <[email protected]>

---------

Co-authored-by: Stan Lo <[email protected]>

Author: tompng

lib/reline/line_editor.rb

@@ -995,22 +995,18 @@ def just_move_cursor
         calculate_height_by_lines(@buffer_of_lines[0..(@line_index - 1)], prompt_list || prompt)
       end
     first_line_diff = new_first_line_started_from - @first_line_started_from
-    new_cursor, new_cursor_max, new_started_from, new_byte_pointer = calculate_nearest_cursor(@buffer_of_lines[@line_index], @cursor, @started_from, @byte_pointer, false)
-    new_started_from = calculate_height_by_width(prompt_width + new_cursor) - 1
+    @cursor, @cursor_max, _, @byte_pointer = calculate_nearest_cursor(@buffer_of_lines[@line_index], @cursor, @started_from, @byte_pointer, false)
+    new_started_from = calculate_height_by_width(prompt_width + @cursor) - 1
     calculate_scroll_partial_screen(@highest_in_all, new_first_line_started_from + new_started_from)
     @previous_line_index = nil
+    @line = @buffer_of_lines[@line_index]
     if @rerender_all
-      @line = @buffer_of_lines[@line_index]
       rerender_all_lines
       @rerender_all = false
       true
     else
-      @line = @buffer_of_lines[@line_index]
       @first_line_started_from = new_first_line_started_from
       @started_from = new_started_from
-      @cursor = new_cursor
-      @cursor_max = new_cursor_max
-      @byte_pointer = new_byte_pointer
       move_cursor_down(first_line_diff + @started_from)
       Reline::IOGate.move_cursor_column((prompt_width + @cursor) % @screen_size.last)
       false

test/reline/yamatanooroti/test_rendering.rb

@@ -661,6 +661,30 @@ def each_top_level_statement
       EOC
     end
 
+    def test_longer_than_screen_height_nearest_cursor_with_scroll_back
+      start_terminal(5, 30, %W{ruby -I#{@pwd}/lib #{@pwd}/test/reline/yamatanooroti/multiline_repl}, startup_message: 'Multiline REPL.')
+      write(<<~EOC.chomp)
+        if 1
+          if 2
+            if 3
+              if 4
+                puts
+              end
+            end
+          end
+        end
+      EOC
+      write("\C-p" * 4 + "\C-e" + "\C-p" * 4)
+      write("2")
+      assert_screen(<<~EOC)
+        prompt> if 12
+        prompt>   if 2
+        prompt>     if 3
+        prompt>       if 4
+        prompt>         puts
+      EOC
+    end
+
     def test_update_cursor_correctly_when_just_cursor_moving
       start_terminal(5, 30, %W{ruby -I#{@pwd}/lib #{@pwd}/test/reline/yamatanooroti/multiline_repl}, startup_message: 'Multiline REPL.')
       write("def hoge\n  01234678")