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# frozen_string_literal: true
module IRB
# The implementation of this class is borrowed from RDoc's lib/rdoc/ri/driver.rb.
# Please do NOT use this class directly outside of IRB.
class Pager
PAGE_COMMANDS = [ENV['RI_PAGER'], ENV['PAGER'], 'less', 'more'].compact.uniq
class << self
def page_content(content, **options)
if content_exceeds_screen_height?(content)
page(**options) do |io|
io.puts content
end
else
$stdout.puts content
end
end
def page(retain_content: false)
if should_page? && pager = setup_pager(retain_content: retain_content)
begin
pid = pager.pid
yield pager
ensure
pager.close
end
else
yield $stdout
end
# When user presses Ctrl-C, IRB would raise `IRB::Abort`
# But since Pager is implemented by running paging commands like `less` in another process with `IO.popen`,
# the `IRB::Abort` exception only interrupts IRB's execution but doesn't affect the pager
# So to properly terminate the pager with Ctrl-C, we need to catch `IRB::Abort` and kill the pager process
rescue IRB::Abort
Process.kill("TERM", pid) if pid
nil
rescue Errno::EPIPE
end
private
def should_page?
IRB.conf[:USE_PAGER] && STDIN.tty? && (ENV.key?("TERM") && ENV["TERM"] != "dumb")
end
def content_exceeds_screen_height?(content)
screen_height, screen_width = begin
Reline.get_screen_size
rescue Errno::EINVAL
[24, 80]
end
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)
end
def setup_pager(retain_content:)
require 'shellwords'
PAGE_COMMANDS.each do |pager_cmd|
cmd = Shellwords.split(pager_cmd)
next if cmd.empty?
if cmd.first == 'less'
cmd << '-R' unless cmd.include?('-R')
cmd << '-X' if retain_content && !cmd.include?('-X')
end
begin
io = IO.popen(cmd, 'w')
rescue
next
end
if $? && $?.pid == io.pid && $?.exited? # pager didn't work
next
end
return io
end
nil
end
end
end
end
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