Note: The guide and screenshots are talking about Xcode 3. I am not sure if anyone has tried this with Xcode 4.

In Xcode, create a new 'Application/Cocoa Application' project.

Remove & trash the following files:

• Resources/MainMenu.nib (or .xib, depending on the version of Xcode)
• Other Sources/main.m
• Classes/...AppDelegate.h and Classes/...AppDelegate.m

Note: You can remove & trash the precompiled prefix header too. You will need to remove it from the target settings as well then; just right-click your application target and look for 'prefix' in the search field.

Then right-click "Other Frameworks" and add a reference to an existing framework, namely Gosu.framework. Make sure you did not put Gosu.framework into a system directory like /System/Library/Frameworks because Xcode treats these directories differently.

Your application bundle also needs to contain the Gosu.framework bundle. To instruct Xcode to automatically copy it into your application, choose Project/New Build Phase and select "Frameworks" as the Copy Files' target directory. Then locate this new build phase in the targets list and add Gosu.framework to it as well. (Note: You may have to drag & drop the framework into the build phase from the finder, instead of adding it via a right-click.)

Note: If you want to be backwards compatible with 10.4, you will have to fiddle with the settings. Gosu supports 10.4, 32-bit and PowerPC just fine. For starters, you may have to set your project's GCC version to 4.0 to get 10.4 support to work; you can set a more recent GCC and OS X SDK by adding user-defined GCC_VERSION_x86_64=4.2 and SDKROOT_x86_64=/Developer/SDKs/MacOSX10.6.sdk)

You can then add new code files, for example the ones from the tutorial or this minimal application code:

#include <Gosu/Gosu.hpp>

class MyWindow : public Gosu::Window
{
public:
    MyWindow()
    :   Gosu::Window(640, 480, false)
    {
        setCaption(L"Hello World!");
    }
};

int main()
{
    MyWindow window;
    window.show();
}

Note: Usually, you want to right-click your target, Get Info, select Build/All Configurations/Build Locations and change the Per-configuration Build Products Path to '.' or something similar, so the application will have the correct position relative to your game's resources.

Gosu supports 64-bit builds, but there is a catch. Custom TTF file font loading for 64-bit uses an API not yet available on 10.5. This means you should include a flag to keep 10.5 from starting your 64-bit build: To do this, edit the .plist file of your project to add this key:

<key>LSMinimumSystemVersionByArchitecture</key>
<dict>
	<key>x86_64</key>
	<string>10.6.0</string>
	<key>i386</key>
	<string>10.4.0</string>
	<key>ppc</key>
	<string>10.4.0</string>
</dict>

If you edit the file through Xcode, the editing will be a bit more intuitive.

Getting started with Ruby is a lot easier (surprise). Just install the gem via sudo gem install gosu. If you are using Ruby 1.8 or Ruby 1.9, this will installed the precompiled gem for your and you do not even need Xcode. If you are using MacRuby or Rubinius, you will need to explicitly sudo gem install ruby --platform=ruby, which requires Xcode to be installed on your system.

To test whether everything works as expected, you can use this Hello World script:

require 'rubygems' # only necessary in Ruby 1.8
require 'gosu'

class MyWindow < Gosu::Window
  def initialize
   super(640, 480, false)
   self.caption = 'Hello World!'
  end
end

window = MyWindow.new
window.show

That's it -- have fun!