Correct padding space calculation

fix ruby/irb#308

This bug occurred when `dialog.width - calculate_width(s, true)` was negative.

When `dialog.width` is shorter than `old_dialog.width`, it calculates how much padding it has to do. However, there are cases where `s` is longer than `dialog.width`, as in the issue. In that case, `padding_space_with_escape_sequences` will crash.

Here, `old_dialog.width` is longer than `dialog.width`, so I changed the padding width to `old_dialog.width - dialog.width`.

lib/reline/line_editor.rb

@@ -858,7 +858,8 @@ def add_dialog_proc(name, p, context = nil)
           s = ' ' * width
         else
           s = Reline::Unicode.take_range(visual_lines[start + i], old_dialog.column + dialog.width, width)
-          s = padding_space_with_escape_sequences(s, dialog.width)
+          rerender_width = old_dialog.width - dialog.width
+          s = padding_space_with_escape_sequences(s, rerender_width)
         end
         Reline::IOGate.move_cursor_column(dialog.column + dialog.width)
         @output.write "\e[0m#{s}\e[0m"

test/reline/yamatanooroti/multiline_repl

@@ -137,6 +137,28 @@ opt.on('--autocomplete-super-long') {
     2000.times.map{ s = "Str_#{c}"; c.succ!; s }.select{ |c| c.start_with?(target) }
   }
 }
+
+opt.on('--autocomplete-width-long') {
+  Reline.autocompletion = true
+  Reline.completion_proc = lambda { |target, preposing = nil, postposing = nil|
+    %w{
+        remove_instance_variable
+        respond_to?
+        ruby2_keywords
+        rand
+        readline
+        readlines
+        require
+        require_relative
+        raise
+        respond_to_missing?
+        redo
+        rescue
+        retry
+        return
+    }.select{ |c| c.start_with?(target) }
+  }
+}
 opt.parse!(ARGV)
 
 begin

test/reline/yamatanooroti/test_rendering.rb

@@ -1172,6 +1172,21 @@ def test_rerender_argument_prompt_after_pasting
       EOC
     end
 
+    def test_autocomplete_old_dialog_width_greater_than_dialog_width
+      start_terminal(40, 40, %W{ruby -I#{@pwd}/lib #{@pwd}/test/reline/yamatanooroti/multiline_repl --autocomplete-width-long}, startup_message: 'Multiline REPL.')
+      write("0+ \n12345678901234")
+      write("\C-p")
+      write("r")
+      write("a")
+      close
+      assert_screen(<<~'EOC')
+        Multiline REPL.
+        prompt> 0+ ra
+        prompt> 123rand 901234
+                   raise
+      EOC
+    end
+
     def write_inputrc(content)
       File.open(@inputrc_file, 'w') do |f|
         f.write content