ffmpeg.rb

require 'formula'

class Ffmpeg <Formula
  head 'svn://svn.ffmpeg.org/ffmpeg/trunk',
    :revisions => { :trunk => 22916, 'libswscale' => 31045 }
  homepage 'http://ffmpeg.org/'

  feature :x264_support, :depends_on => 'x264', :default => true
  feature :faac_support, :depends_on => 'faac', :default => true
  feature :faad2_support, :depends_on => 'faad2', :default => true
  feature :lame_support, :depends_on => 'lame', :default => true
  
  # :default => true could also be implied if the opposite is not specified 
  # That might be a bit more concise.
  
  # The current depends_on method would describe a common dependency needed for all features.
  depends_on :xlib
  
  # Further examples:
  #
  
  # EX1: Some features could require specific features enabled on their dependencies:
  #
  feature :feature_a, :depends_on => ['libx(y_support,z_support)']
  
  # Homebrew would in such a situation select the installed 'libx' with y_support and z_support
  # features installed.
  
  
  # EX2: Some features might require other features or prohibit them:
  #
  feature :feature_a, ...
  feature :feature_b, ..., :requires => [:feature_a], :prohibits => [:feature_c]
  #
  # CONFLICT:
  
  feature :feature_c, ..., :requires => [:feature_b], :prohibits => [:feature_a]
  
  # This sort of conflict would have to be handled when validating a formula.
  
  
  # EX3: For a variant of 'libx' having eg. feature_a and feature_b enabled and version at 2.3
  # its keg path could look like this:
  #
  # Cellar/xlib/2.3(a,b)/
  #
  # Others could be:
  #
  # Cellar/xlib/2.3(b)/
  # Cellar/xlib/2.3(a,b,c)/
  #
  # Listing features alphabetically would enable homebrew to quickly figure out if a feature is enabled
  # without the need for meta files. The current path structure could be used in the way it is now.
  #
  # If eg. a feature depends on a library 'xlib' with features 'a' and 'b' enabled, that is xlib(a,b),
  # and several versions are already installed. Homebrew should (I think) select the the version with the
  # least features satisfying the requirement. In the 3 versions listed above that would be 
  # Cellar/xlib/2.3(a,b)/ even though Cellar/xlib/2.3(a,b,c)/ also has all the features.
  # This could potentially lower build size.
  
  # These ideas are of course just off the top of my head and there are alot of details I  

  def install
    configure_flags = [
      "--prefix=#{prefix}",
      "--disable-debug",
      "--enable-shared",
      "--enable-pthreads",
      "--enable-nonfree",
      "--enable-gpl"
    ]

    # You can then query for enabled features.
    configure_flags << "--enable-libx264" if features.include?('x264')
    configure_flags << "--enable-libfaac" if features.include?('faac')
    configure_flags << "--enable-libfaad" if features.include?('faad2')
    configure_flags << "--enable-libmp3lame" if features.include?('lame')

    # For 32-bit compilation under gcc 4.2, see:
    # http://trac.macports.org/ticket/20938#comment:22
    if MACOS_VERSION >= 10.6 and not Hardware.is_64_bit?
      ENV.append_to_cflags "-mdynamic-no-pic"
    end

    system "./configure", *configure_flags

    inreplace 'config.mak' do |s|
      if MACOS_VERSION >= 10.6 and Hardware.is_64_bit?
        shflags = s.get_make_var 'SHFLAGS'
        s.change_make_var! 'SHFLAGS', shflags.gsub!(' -Wl,-read_only_relocs,suppress', '')
      end
    end

    system "make install"
  end
end