Fast preview before pager

lib/irb.rb

@@ -1369,40 +1369,63 @@ def signal_status(status)
     end
 
     def output_value(omit = false) # :nodoc:
-      str = @context.inspect_last_value
-      multiline_p = str.include?("\n")
+      return_format = @context.return_format
+      unless return_format.include?('%')
+        puts return_format
+        return
+      end
+      unless return_format.include?('%s')
+        puts return_format % @context.inspect_last_value.chomp
+        return
+      end
+
+      return_format_pre, return_format_post = return_format.split('%s', 2)
+
+      winheight, winwidth = @context.io.winsize
       if omit
-        winwidth = @context.io.winsize.last
-        if multiline_p
-          first_line = str.split("\n").first
-          result = @context.newline_before_multiline_output? ? (@context.return_format % first_line) : first_line
-          output_width = Reline::Unicode.calculate_width(result, true)
-          diff_size = output_width - Reline::Unicode.calculate_width(first_line, true)
-          if diff_size.positive? and output_width > winwidth
-            lines, _ = Reline::Unicode.split_by_width(first_line, winwidth - diff_size - 3)
-            str = "%s..." % lines.first
-            str += "\e[0m" if Color.colorable?
-            multiline_p = false
-          else
-            str = str.gsub(/(\A.*?\n).*/m, "\\1...")
-            str += "\e[0m" if Color.colorable?
+        out = IRB::Pager::PagingIO.new(winwidth, 2) do |lines|
+          puts return_format_pre if @context.newline_before_multiline_output?
+          omission = "\e[0m" if Color.colorable?
+          puts "#{lines.first}...#{omission}#{return_format_post}"
+          return
+        end
+        out << return_format_pre unless @context.newline_before_multiline_output?
+        @context.inspect_last_value(out)
+        unless out.multipage?
+          print return_format_pre if @context.newline_before_multiline_output?
+          puts out.string.chomp + return_format_post
+        end
+      elsif !IRB::Pager.should_page?
+        puts return_format % @context.inspect_last_value.chomp
+      else
+        out = IRB::Pager::PagingIO.new(winwidth, winheight - (@context.newline_before_multiline_output? ? 1 : 0)) do |lines|
+          if @context.newline_before_multiline_output?
+            lines = [return_format_pre + "\n", *lines]
           end
-        else
-          output_width = Reline::Unicode.calculate_width(@context.return_format % str, true)
-          diff_size = output_width - Reline::Unicode.calculate_width(str, true)
-          if diff_size.positive? and output_width > winwidth
-            lines, _ = Reline::Unicode.split_by_width(str, winwidth - diff_size - 3)
-            str = "%s..." % lines.first
-            str += "\e[0m" if Color.colorable?
+          puts lines.take(winheight - 1).join
+          print "\e[0mPress SPACE key to show full content:"
+          unless STDIN.raw { |io| io.readpartial(1024) }&.start_with?(' ')
+            print "\r\e[K"
+            return
           end
+          print "\r\e[KPreparing content..."
+        end
+        out << return_format_pre unless @context.newline_before_multiline_output?
+        @context.inspect_last_value(out)
+        content = out.string
+        if @context.newline_before_multiline_output?
+          content = return_format_pre + (out.multiline? ? "\n" : '') + content
+        end
+        content = content.chomp + return_format_post
+        if out.multipage?
+          print "\r\e[K"
+          Pager.page(retain_content: true) do |io|
+            io.puts content
+          end
+        else
+          puts content
         end
       end
-
-      if multiline_p && @context.newline_before_multiline_output?
-        str = "\n" + str
-      end
-
-      Pager.page_content(format(@context.return_format, str), retain_content: true)
     end
 
     # Outputs the local variables to this current session, including #signal_status

lib/irb/context.rb

@@ -673,8 +673,8 @@ def colorize_input(input, complete:)
       end
     end
 
-    def inspect_last_value # :nodoc:
-      @inspect_method.inspect_value(@last_value)
+    def inspect_last_value(output = nil) # :nodoc:
+      @inspect_method.inspect_value(@last_value, output)
     end
 
     NOPRINTING_IVARS = ["@last_value"] # :nodoc:

lib/irb/inspector.rb

@@ -93,8 +93,9 @@ def init
     end
 
     # Proc to call when the input is evaluated and output in irb.
-    def inspect_value(v)
-      @inspect.call(v)
+    def inspect_value(v, output)
+      @inspect.arity == 2 ? @inspect.call(v, output) : output.write(@inspect.call(v))
+    rescue IRB::Pager::Abort
     rescue => e
       puts "An error occurred when inspecting the object: #{e.inspect}"
 
@@ -113,8 +114,8 @@ def inspect_value(v)
   Inspector.def_inspector([:p, :inspect]){|v|
     Color.colorize_code(v.inspect, colorable: Color.colorable? && Color.inspect_colorable?(v))
   }
-  Inspector.def_inspector([true, :pp, :pretty_inspect], proc{require_relative "color_printer"}){|v|
-    IRB::ColorPrinter.pp(v, +'').chomp
+  Inspector.def_inspector([true, :pp, :pretty_inspect], proc{require_relative "color_printer"}){|v, output|
+    IRB::ColorPrinter.pp(v, output)
   }
   Inspector.def_inspector([:yaml, :YAML], proc{require "yaml"}){|v|
     begin

lib/irb/pager.rb

@@ -6,6 +6,11 @@ module IRB
   class Pager
     PAGE_COMMANDS = [ENV['RI_PAGER'], ENV['PAGER'], 'less', 'more'].compact.uniq
 
+    # Maximum size of a single cell in terminal
+    # assuming the worst case: bold, italic, underline, reverse, RGB forgound and background color
+    # "\e[1;3;4;7;38;2;255;128;128;48;2;128;128;255mA\e[0m"
+    MAX_CHAR_PER_CELL = 50
+
     class << self
       def page_content(content, **options)
         if content_exceeds_screen_height?(content)
@@ -47,12 +52,12 @@ def page(retain_content: false)
       rescue Errno::EPIPE
       end
 
-      private
-
       def should_page?
         IRB.conf[:USE_PAGER] && STDIN.tty? && (ENV.key?("TERM") && ENV["TERM"] != "dumb")
       end
 
+      private
+
       def content_exceeds_screen_height?(content)
         screen_height, screen_width = begin
           Reline.get_screen_size
@@ -63,9 +68,9 @@ def content_exceeds_screen_height?(content)
         pageable_height = screen_height - 3 # leave some space for previous and the current prompt
 
         # If the content has more lines than the pageable height
-        content.lines.count > pageable_height ||
-          # Or if the content is a few long lines
-          pageable_height * screen_width < Reline::Unicode.calculate_width(content, true)
+        content.lines.count > pageable_height || content.size >= pageable_height * screen_width * MAX_CHAR_PER_CELL
+        # Or if the content is a few long lines
+        pageable_height * screen_width < Reline::Unicode.calculate_width(content, true)
       end
 
       def setup_pager(retain_content:)
@@ -96,5 +101,72 @@ def setup_pager(retain_content:)
         nil
       end
     end
+
+    class PagingIO
+      attr_reader :string
+      def initialize(width, height, &block)
+        @lines = []
+        @width = width
+        @height = height
+        @buffer = +''
+        @block = block
+        @col = 0
+        @string = +''
+        @multipage = false
+      end
+
+      def puts(text = '')
+        write(text)
+        write("\n") unless text.end_with?("\n")
+      end
+
+      def write(text)
+        @string << text
+        return if @multipage
+
+        overflow_size = @width * @height * MAX_CHAR_PER_CELL
+        if text.size >= overflow_size
+          text = text[0, overflow_size]
+          overflow = true
+        end
+
+        @buffer << text
+        @col += Reline::Unicode.calculate_width(text)
+        if text.include?("\n") || @col >= @width
+          @buffer.lines.each do |line|
+            wrapped_lines = Reline::Unicode.split_by_width(line.chomp, @width).first.compact
+            wrapped_lines.pop if wrapped_lines.last == ''
+            @lines.concat(wrapped_lines)
+            if @lines.empty?
+              @lines << "\n"
+            elsif line.end_with?("\n")
+              @lines[-1] += "\n"
+            end
+          end
+          @buffer.clear
+          @buffer << @lines.pop unless @lines.last.end_with?("\n")
+          @col = Reline::Unicode.calculate_width(@buffer)
+        end
+        if overflow || @lines.size >= @height
+          @block.call(@lines)
+          @multipage = true
+        end
+      end
+
+      def finish
+        @block.call(@lines) unless @multipage
+      end
+
+      def multipage?
+        @multipage
+      end
+
+      def multiline?
+        @lines.size >= 2
+      end
+
+      alias print write
+      alias << write
+    end
   end
 end