[ruby/reline] Support custom bg color

https://github.com/ruby/reline/commit/cd0cbf53d5

lib/reline.rb

@@ -211,7 +211,7 @@ module Reline
       cursor_pos_to_render = Reline::CursorPos.new(x, y)
       context.clear
       context.push(cursor_pos_to_render, result, pointer)
-      [cursor_pos_to_render, result, pointer]
+      [cursor_pos_to_render, result, pointer, nil]
     }
 
     require 'rdoc'
@@ -247,7 +247,7 @@ module Reline
       formatter.width = 40
       str = doc.accept(formatter)
 
-      [Reline::CursorPos.new(cursor_pos_to_render.x + 40, cursor_pos_to_render.y + pointer), str.split("\n"), nil]
+      [Reline::CursorPos.new(cursor_pos_to_render.x + 40, cursor_pos_to_render.y + pointer), str.split("\n"), nil, '40']
     }
 
     def readmultiline(prompt = '', add_hist = false, &confirm_multiline_termination)

lib/reline/line_editor.rb

@@ -560,7 +560,7 @@ class Reline::LineEditor
       return
     end
     dialog.set_cursor_pos(cursor_column, @first_line_started_from + @started_from)
-    pos, result, pointer = dialog.call
+    pos, result, pointer, bg = dialog.call
     old_dialog_contents = dialog.contents
     old_dialog_column = dialog.column
     old_dialog_vertical_offset = dialog.vertical_offset
@@ -605,7 +605,11 @@ class Reline::LineEditor
       if i == pointer
         bg_color = '45'
       else
-        bg_color = '46'
+        if bg
+          bg_color = bg
+        else
+          bg_color = '46'
+        end
       end
       @output.write "\e[#{bg_color}m%-#{DIALOG_WIDTH}s\e[49m" % item.slice(0, DIALOG_WIDTH)
       Reline::IOGate.move_cursor_column(dialog.column)