Forward webkit_server's stdout to Ruby's stdout.

This allows console.log() messages to be visible, and prevents
large numbers of console.log() calls from filling up webkit_server's pipe
which would block the process.

lib/capybara/driver/webkit/browser.rb

@@ -1,4 +1,5 @@
 require 'socket'
+require 'thread'
 require 'capybara/util/timeout'
 require 'json'
 
@@ -8,6 +9,9 @@ class Browser
 
     def initialize(options = {})
       @socket_class = options[:socket_class] || TCPSocket
+      @stdout       = options.has_key?(:stdout) ?
+                        options[:stdout] :
+                        $stdout
       start_server
       connect
     end
@@ -79,6 +83,10 @@ def render(path, width, height)
     def start_server
       read_pipe, write_pipe = fork_server
       @server_port = discover_server_port(read_pipe)
+      @stdout_thread = Thread.new do
+        Thread.current.abort_on_exception = true
+        forward_stdout(read_pipe)
+      end
     end
 
     def fork_server
@@ -100,6 +108,17 @@ def discover_server_port(read_pipe)
       return unless IO.select([read_pipe], nil, nil, 10)
       ((read_pipe.first || '').match(/listening on port: (\d+)/) || [])[1].to_i
     end
+
+    def forward_stdout(pipe)
+      while !pipe.eof?
+        line = pipe.readline
+        if @stdout
+          @stdout.write(line)
+          @stdout.flush
+        end
+      end
+    rescue EOFError
+    end
 
     def connect
       Capybara.timeout(5) do

spec/browser_spec.rb

@@ -1,4 +1,5 @@
 require 'spec_helper'
+require 'stringio'
 require 'capybara/driver/webkit/browser'
 
 describe Capybara::Driver::Webkit::Browser do
@@ -22,5 +23,13 @@
       new_browser.server_port.should_not == browser.server_port
     end
   end
+
+  it 'forwards stdout to the given IO object' do
+    io = StringIO.new
+    new_browser = Capybara::Driver::Webkit::Browser.new(:stdout => io)
+    new_browser.execute_script('console.log("hello world")')
+    sleep(0.5)
+    io.string.should == "hello world\n"
+  end
 
 end

spec/spec_helper.rb

@@ -18,7 +18,7 @@
 require File.join(spec_dir,"spec_helper")
 
 require 'capybara/driver/webkit/browser'
-$webkit_browser = Capybara::Driver::Webkit::Browser.new(:socket_class => TCPSocket)
+$webkit_browser = Capybara::Driver::Webkit::Browser.new(:socket_class => TCPSocket, :stdout => nil)
 
 Capybara.register_driver :reusable_webkit do |app|
   Capybara::Driver::Webkit.new(app, :browser => $webkit_browser)