Detect X11 when ENV.x11 is requested; dump in --config.

2 files changed, 6 insertions, 0 deletions

diff --git a/Library/Homebrew/brew.h.rb b/Library/Homebrew/brew.h.rb
index 2ae9ed669..cad038360 100644
--- a/Library/Homebrew/brew.h.rb
+++ b/Library/Homebrew/brew.h.rb
@@ -504,3 +504,7 @@ def llvm_build
     $1.to_i
   end
 end
+
+def x11_installed?
+  Pathname.new('/usr/X11/lib/libpng.dylib').exist?
+end
diff --git a/Library/Homebrew/extend/ENV.rb b/Library/Homebrew/extend/ENV.rb
index 9fbd04749..09d8a7beb 100644
--- a/Library/Homebrew/extend/ENV.rb
+++ b/Library/Homebrew/extend/ENV.rb
@@ -164,6 +164,8 @@ module HomebrewEnvExtension
     append_to_cflags ' -I/usr/include/libxml2'
   end
   def x11
+    opoo "You do not have X11 installed, this formula may not build." if not x11_installed?
+    
     # CPPFLAGS are the C-PreProcessor flags, *not* C++!
     append 'CPPFLAGS', '-I/usr/X11R6/include'
     append 'LDFLAGS', '-L/usr/X11R6/lib'