scons: Put the tool logic in a frontend tool.

More logic can be shared between public and private branches this way.
diff --git a/SConstruct b/SConstruct
index 8c8a82b..4fddcc5 100644
--- a/SConstruct
+++ b/SConstruct
@@ -53,8 +53,12 @@
 
 env = Environment(
 	MSVS_VERSION = '7.1',
-	options = opts, 
-	ENV = os.environ)
+	options = opts,
+	tools = ['gallium'],
+	toolpath = ['scons'],	
+	ENV = os.environ,
+)
+
 Help(opts.GenerateHelpText(env))
 
 # replicate options values in local variables
@@ -82,25 +86,6 @@
 
 #######################################################################
 # Environment setup
-#
-# TODO: put the compiler specific settings in separate files
-# TODO: auto-detect as much as possible
-
-if platform == 'winddk':
-	env.Tool('winddk', ['scons'])
-	
-	env.Append(CPPPATH = [
-		env['SDK_INC_PATH'],
-		env['DDK_INC_PATH'],
-		env['WDM_INC_PATH'],
-		env['CRT_INC_PATH'],
-	])
-
-if platform == 'wince':
-	env.Tool('evc', ['scons'])
-
-common.generate(env)
-
 
 # Includes
 env.Append(CPPPATH = [
@@ -111,13 +96,6 @@
 ])
 
 
-# x86 assembly
-if x86:
-	if gcc:	
-		env.Append(CFLAGS = '-m32')
-		env.Append(CXXFLAGS = '-m32')
-
-
 # Posix
 if platform in ('posix', 'linux', 'freebsd', 'darwin'):
 	env.Append(CPPDEFINES = [
@@ -182,6 +160,6 @@
 
 SConscript(
 	'src/SConscript',
-	build_dir = common.make_build_dir(env),
+	build_dir = env['build'],
 	duplicate = 0 # http://www.scons.org/doc/0.97/HTML/scons-user/x2261.html
 )
diff --git a/common.py b/common.py
index c82f302..dd64e0f 100644
--- a/common.py
+++ b/common.py
@@ -62,283 +62,3 @@
 	opts.Add(BoolOption('llvm', 'use LLVM', 'no'))
 	opts.Add(BoolOption('dri', 'build DRI drivers', default_dri))
 
-
-#######################################################################
-# Quiet command lines
-#
-# See also http://www.scons.org/wiki/HidingCommandLinesInOutput
-
-def quietCommandLines(env):
-	env['CCCOMSTR'] = "Compiling $SOURCE ..."
-	env['CXXCOMSTR'] = "Compiling $SOURCE ..."
-	env['ARCOMSTR'] = "Archiving $TARGET ..."
-	env['RANLIBCOMSTR'] = ""
-	env['LINKCOMSTR'] = "Linking $TARGET ..."
-
-
-#######################################################################
-# Convenience Library Builder
-# based on the stock StaticLibrary and SharedLibrary builders
-
-import SCons.Action
-import SCons.Builder
-
-def createConvenienceLibBuilder(env):
-    """This is a utility function that creates the ConvenienceLibrary
-    Builder in an Environment if it is not there already.
-
-    If it is already there, we return the existing one.
-    """
-
-    try:
-        convenience_lib = env['BUILDERS']['ConvenienceLibrary']
-    except KeyError:
-        action_list = [ SCons.Action.Action("$ARCOM", "$ARCOMSTR") ]
-        if env.Detect('ranlib'):
-            ranlib_action = SCons.Action.Action("$RANLIBCOM", "$RANLIBCOMSTR")
-            action_list.append(ranlib_action)
-
-        convenience_lib = SCons.Builder.Builder(action = action_list,
-                                  emitter = '$LIBEMITTER',
-                                  prefix = '$LIBPREFIX',
-                                  suffix = '$LIBSUFFIX',
-                                  src_suffix = '$SHOBJSUFFIX',
-                                  src_builder = 'SharedObject')
-        env['BUILDERS']['ConvenienceLibrary'] = convenience_lib
-        env['BUILDERS']['Library'] = convenience_lib
-
-    return convenience_lib
-
-
-#######################################################################
-# Build
-
-def make_build_dir(env):
-	# Put build output in a separate dir, which depends on the current configuration
-	# See also http://www.scons.org/wiki/AdvancedBuildExample
-	build_topdir = 'build'
-	build_subdir = env['platform']
-	if env['dri']:
-		build_subdir += "-dri"
-	if env['llvm']:
-		build_subdir += "-llvm"
-	if env['machine'] != 'generic':
-		build_subdir += '-' + env['machine']
-	if env['debug']:
-		build_subdir += "-debug"
-	if env['profile']:
-		build_subdir += "-profile"
-	build_dir = os.path.join(build_topdir, build_subdir)
-	# Place the .sconsign file on the builddir too, to avoid issues with different scons
-	# versions building the same source file
-	env.SConsignFile(os.path.join(build_dir, '.sconsign'))
-	return build_dir
-
-
-#######################################################################
-# Common environment generation code
-
-def generate(env):
-	# FIXME: this is already too late
-	#if env.get('quiet', False):
-	#	quietCommandLines(env)
-	
-	# shortcuts
-	debug = env['debug']
-	machine = env['machine']
-	platform = env['platform']
-	x86 = env['machine'] == 'x86'
-	gcc = env['platform'] in ('linux', 'freebsd', 'darwin')
-	msvc = env['platform'] in ('windows', 'winddk', 'wince')
-
-	# C preprocessor options
-	cppdefines = []
-	if debug:
-		cppdefines += ['DEBUG']
-	else:
-		cppdefines += ['NDEBUG']
-	if env['profile']:
-		cppdefines += ['PROFILE']
-	if platform == 'windows':
-		cppdefines += [
-			'WIN32', 
-			'_WINDOWS', 
-			'_UNICODE',
-			'UNICODE',
-			# http://msdn2.microsoft.com/en-us/library/6dwk3a1z.aspx,
-			'WIN32_LEAN_AND_MEAN',
-			'VC_EXTRALEAN', 
-			'_CRT_SECURE_NO_DEPRECATE',
-		]
-		if debug:
-			cppdefines += ['_DEBUG']
-	if platform == 'winddk':
-		# Mimic WINDDK's builtin flags. See also:
-		# - WINDDK's bin/makefile.new i386mk.inc for more info.
-		# - buildchk_wxp_x86.log files, generated by the WINDDK's build
-		# - http://alter.org.ua/docs/nt_kernel/vc8_proj/
-		cppdefines += [
-			('_X86_', '1'), 
-			('i386', '1'), 
-			'STD_CALL', 
-			('CONDITION_HANDLING', '1'),
-			('NT_INST', '0'), 
-			('WIN32', '100'),
-			('_NT1X_', '100'),
-			('WINNT', '1'),
-			('_WIN32_WINNT', '0x0501'), # minimum required OS version
-			('WINVER', '0x0501'),
-			('_WIN32_IE', '0x0603'),
-			('WIN32_LEAN_AND_MEAN', '1'),
-			('DEVL', '1'),
-			('__BUILDMACHINE__', 'WinDDK'),
-			('FPO', '0'),
-		]
-		if debug:
-			cppdefines += [('DBG', 1)]
-	if platform == 'wince':
-		cppdefines += [
-			('_WIN32_WCE', '500'), 
-			'WCE_PLATFORM_STANDARDSDK_500',
-			'_i386_',
-			('UNDER_CE', '500'),
-			'UNICODE',
-			'_UNICODE',
-			'_X86_',
-			'x86',
-			'_USRDLL',
-			'TEST_EXPORTS' ,
-		]
-	if platform == 'windows':
-		cppdefines += ['PIPE_SUBSYSTEM_WINDOWS_USER']
-	if platform == 'winddk':
-		cppdefines += ['PIPE_SUBSYSTEM_WINDOWS_DISPLAY']
-	if platform == 'wince':
-		cppdefines += ['PIPE_SUBSYSTEM_WINDOWS_CE']
-	env.Append(CPPDEFINES = cppdefines)
-
-	# C compiler options
-	cflags = []
-	if gcc:
-		if debug:
-			cflags += ['-O0', '-g3']
-		else:
-			cflags += ['-O3', '-g3']
-		if env['profile']:
-			cflags += ['-pg']
-		if env['machine'] == 'x86' and default_machine == 'x86_64':
-			cflags += ['-m32']
-		if env['machine'] == 'x86_64' and default_machine == 'x86':
-			cflags += ['-m64']
-		cflags += [
-			'-Wall', 
-			'-Wmissing-prototypes',
-			'-Wno-long-long',
-			'-ffast-math',
-			'-pedantic',
-			'-fmessage-length=0', # be nice to Eclipse 
-		]
-	if msvc:
-		# See also:
-		# - http://msdn2.microsoft.com/en-us/library/y0zzbyt4.aspx
-		# - cl /?
-		if debug:
-			cflags += [
-			  '/Od', # disable optimizations
-			  '/Oi', # enable intrinsic functions
-			  '/Oy-', # disable frame pointer omission
-			]
-		else:
-			cflags += [
-			  '/Ox', # maximum optimizations
-			  '/Oi', # enable intrinsic functions
-			  '/Os', # favor code space
-			]
-		if env['profile']:
-			cflags += [
-				'/Gh', # enable _penter hook function
-				'/GH', # enable _pexit hook function
-			]
-		cflags += [
-			'/W3', # warning level
-			#'/Wp64', # enable 64 bit porting warnings
-		]
-		if platform == 'windows':
-			cflags += [
-				# TODO
-			]
-		if platform == 'winddk':
-			cflags += [
-				'/Zl', # omit default library name in .OBJ
-				'/Zp8', # 8bytes struct member alignment
-				'/Gy', # separate functions for linker
-				'/Gm-', # disable minimal rebuild
-				'/WX', # treat warnings as errors
-				'/Gz', # __stdcall Calling convention
-				'/GX-', # disable C++ EH
-				'/GR-', # disable C++ RTTI
-				'/GF', # enable read-only string pooling
-				'/G6', # optimize for PPro, P-II, P-III
-				'/Ze', # enable extensions
-				'/Gi-', # disable incremental compilation
-				'/QIfdiv-', # disable Pentium FDIV fix
-				'/hotpatch', # prepares an image for hotpatching.
-				#'/Z7', #enable old-style debug info
-			]
-		if platform == 'wince':
-			cflags += [
-				'/Gs8192',
-				'/GF', # enable read-only string pooling
-			]
-		# Put debugging information in a separate .pdb file for each object file as
-		# described in the scons manpage
-		env['CCPDBFLAGS'] = '/Zi /Fd${TARGET}.pdb'
-	env.Append(CFLAGS = cflags)
-	env.Append(CXXFLAGS = cflags)
-
-	# Linker options
-	linkflags = []
-	if gcc:
-		if env['machine'] == 'x86' and default_machine == 'x86_64':
-			linkflags += ['-m32']
-		if env['machine'] == 'x86_64' and default_machine == 'x86':
-			linkflags += ['-m64']
-	if platform == 'winddk':
-		# See also:
-		# - http://msdn2.microsoft.com/en-us/library/y0zzbyt4.aspx
-		linkflags += [
-			'/merge:_PAGE=PAGE',
-			'/merge:_TEXT=.text',
-			'/section:INIT,d',
-			'/opt:ref',
-			'/opt:icf',
-			'/ignore:4198,4010,4037,4039,4065,4070,4078,4087,4089,4221',
-			'/incremental:no',
-			'/fullbuild',
-			'/release',
-			'/nodefaultlib',
-			'/wx',
-			'/debug',
-			'/debugtype:cv',
-			'/version:5.1',
-			'/osversion:5.1',
-			'/functionpadmin:5',
-			'/safeseh',
-			'/pdbcompress',
-			'/stack:0x40000,0x1000',
-			'/driver', 
-			'/align:0x80',
-			'/subsystem:native,5.01',
-			'/base:0x10000',
-			
-			'/entry:DrvEnableDriver',
-		]
-	env.Append(LINKFLAGS = linkflags)
-
-
-	createConvenienceLibBuilder(env)
-	
-	
-	# for debugging
-	#print env.Dump()
-
diff --git a/scons/gallium.py b/scons/gallium.py
new file mode 100644
index 0000000..1787adb
--- /dev/null
+++ b/scons/gallium.py
@@ -0,0 +1,323 @@
+"""gallium
+
+Frontend-tool for Gallium3D architecture.
+
+"""
+
+# 
+# Copyright 2008 Tungsten Graphics, Inc., Cedar Park, Texas.
+# All Rights Reserved.
+# 
+# Permission is hereby granted, free of charge, to any person obtaining a
+# copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sub license, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+# 
+# The above copyright notice and this permission notice (including the
+# next paragraph) shall be included in all copies or substantial portions
+# of the Software.
+# 
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
+# IN NO EVENT SHALL TUNGSTEN GRAPHICS AND/OR ITS SUPPLIERS BE LIABLE FOR
+# ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+# 
+
+
+import os.path
+
+import SCons.Action
+import SCons.Builder
+
+
+def quietCommandLines(env):
+	# Quiet command lines
+	# See also http://www.scons.org/wiki/HidingCommandLinesInOutput
+	env['CCCOMSTR'] = "Compiling $SOURCE ..."
+	env['CXXCOMSTR'] = "Compiling $SOURCE ..."
+	env['ARCOMSTR'] = "Archiving $TARGET ..."
+	env['RANLIBCOMSTR'] = ""
+	env['LINKCOMSTR'] = "Linking $TARGET ..."
+
+
+def createConvenienceLibBuilder(env):
+    """This is a utility function that creates the ConvenienceLibrary
+    Builder in an Environment if it is not there already.
+
+    If it is already there, we return the existing one.
+    
+    Based on the stock StaticLibrary and SharedLibrary builders.
+    """
+
+    try:
+        convenience_lib = env['BUILDERS']['ConvenienceLibrary']
+    except KeyError:
+        action_list = [ SCons.Action.Action("$ARCOM", "$ARCOMSTR") ]
+        if env.Detect('ranlib'):
+            ranlib_action = SCons.Action.Action("$RANLIBCOM", "$RANLIBCOMSTR")
+            action_list.append(ranlib_action)
+
+        convenience_lib = SCons.Builder.Builder(action = action_list,
+                                  emitter = '$LIBEMITTER',
+                                  prefix = '$LIBPREFIX',
+                                  suffix = '$LIBSUFFIX',
+                                  src_suffix = '$SHOBJSUFFIX',
+                                  src_builder = 'SharedObject')
+        env['BUILDERS']['ConvenienceLibrary'] = convenience_lib
+        env['BUILDERS']['Library'] = convenience_lib
+
+    return convenience_lib
+
+
+def generate(env):
+	"""Common environment generation code"""
+	
+	# FIXME: this is already too late
+	#if env.get('quiet', False):
+	#	quietCommandLines(env)
+	
+	# shortcuts
+	debug = env['debug']
+	machine = env['machine']
+	platform = env['platform']
+	x86 = env['machine'] == 'x86'
+	gcc = env['platform'] in ('linux', 'freebsd', 'darwin')
+	msvc = env['platform'] in ('windows', 'winddk', 'wince')
+
+	# Tool
+	if platform == 'winddk':
+		env.Tool('winddk')
+	elif platform == 'wince':
+		env.Tool('evc')
+	else:
+		env.Tool('default')
+
+	# Put build output in a separate dir, which depends on the current 
+	# configuration. See also http://www.scons.org/wiki/AdvancedBuildExample
+	build_topdir = 'build'
+	build_subdir = env['platform']
+	if env['dri']:
+		build_subdir += "-dri"
+	if env['llvm']:
+		build_subdir += "-llvm"
+	if env['machine'] != 'generic':
+		build_subdir += '-' + env['machine']
+	if env['debug']:
+		build_subdir += "-debug"
+	if env['profile']:
+		build_subdir += "-profile"
+	build_dir = os.path.join(build_topdir, build_subdir)
+	# Place the .sconsign file in the build dir too, to avoid issues with 
+	# different scons versions building the same source file
+	env['build'] = build_dir
+	env.SConsignFile(os.path.join(build_dir, '.sconsign'))
+
+	# C preprocessor options
+	cppdefines = []
+	if debug:
+		cppdefines += ['DEBUG']
+	else:
+		cppdefines += ['NDEBUG']
+	if env['profile']:
+		cppdefines += ['PROFILE']
+	if platform == 'windows':
+		cppdefines += [
+			'WIN32', 
+			'_WINDOWS', 
+			'_UNICODE',
+			'UNICODE',
+			# http://msdn2.microsoft.com/en-us/library/6dwk3a1z.aspx,
+			'WIN32_LEAN_AND_MEAN',
+			'VC_EXTRALEAN', 
+			'_CRT_SECURE_NO_DEPRECATE',
+		]
+		if debug:
+			cppdefines += ['_DEBUG']
+	if platform == 'winddk':
+		# Mimic WINDDK's builtin flags. See also:
+		# - WINDDK's bin/makefile.new i386mk.inc for more info.
+		# - buildchk_wxp_x86.log files, generated by the WINDDK's build
+		# - http://alter.org.ua/docs/nt_kernel/vc8_proj/
+		cppdefines += [
+			('_X86_', '1'), 
+			('i386', '1'), 
+			'STD_CALL', 
+			('CONDITION_HANDLING', '1'),
+			('NT_INST', '0'), 
+			('WIN32', '100'),
+			('_NT1X_', '100'),
+			('WINNT', '1'),
+			('_WIN32_WINNT', '0x0501'), # minimum required OS version
+			('WINVER', '0x0501'),
+			('_WIN32_IE', '0x0603'),
+			('WIN32_LEAN_AND_MEAN', '1'),
+			('DEVL', '1'),
+			('__BUILDMACHINE__', 'WinDDK'),
+			('FPO', '0'),
+		]
+		if debug:
+			cppdefines += [('DBG', 1)]
+	if platform == 'wince':
+		cppdefines += [
+			('_WIN32_WCE', '500'), 
+			'WCE_PLATFORM_STANDARDSDK_500',
+			'_i386_',
+			('UNDER_CE', '500'),
+			'UNICODE',
+			'_UNICODE',
+			'_X86_',
+			'x86',
+			'_USRDLL',
+			'TEST_EXPORTS' ,
+		]
+	if platform == 'windows':
+		cppdefines += ['PIPE_SUBSYSTEM_WINDOWS_USER']
+	if platform == 'winddk':
+		cppdefines += ['PIPE_SUBSYSTEM_WINDOWS_DISPLAY']
+	if platform == 'wince':
+		cppdefines += ['PIPE_SUBSYSTEM_WINDOWS_CE']
+	env.Append(CPPDEFINES = cppdefines)
+
+	# C preprocessor includes
+	if platform == 'winddk':
+		env.Append(CPPPATH = [
+			env['SDK_INC_PATH'],
+			env['DDK_INC_PATH'],
+			env['WDM_INC_PATH'],
+			env['CRT_INC_PATH'],
+		])
+
+	# C compiler options
+	cflags = []
+	if gcc:
+		if debug:
+			cflags += ['-O0', '-g3']
+		else:
+			cflags += ['-O3', '-g3']
+		if env['profile']:
+			cflags += ['-pg']
+		if env['machine'] == 'x86':
+			cflags += ['-m32']
+		if env['machine'] == 'x86_64':
+			cflags += ['-m64']
+		cflags += [
+			'-Wall', 
+			'-Wmissing-prototypes',
+			'-Wno-long-long',
+			'-ffast-math',
+			'-pedantic',
+			'-fmessage-length=0', # be nice to Eclipse 
+		]
+	if msvc:
+		# See also:
+		# - http://msdn2.microsoft.com/en-us/library/y0zzbyt4.aspx
+		# - cl /?
+		if debug:
+			cflags += [
+			  '/Od', # disable optimizations
+			  '/Oi', # enable intrinsic functions
+			  '/Oy-', # disable frame pointer omission
+			]
+		else:
+			cflags += [
+			  '/Ox', # maximum optimizations
+			  '/Oi', # enable intrinsic functions
+			  '/Os', # favor code space
+			]
+		if env['profile']:
+			cflags += [
+				'/Gh', # enable _penter hook function
+				'/GH', # enable _pexit hook function
+			]
+		cflags += [
+			'/W3', # warning level
+			#'/Wp64', # enable 64 bit porting warnings
+		]
+		if platform == 'windows':
+			cflags += [
+				# TODO
+			]
+		if platform == 'winddk':
+			cflags += [
+				'/Zl', # omit default library name in .OBJ
+				'/Zp8', # 8bytes struct member alignment
+				'/Gy', # separate functions for linker
+				'/Gm-', # disable minimal rebuild
+				'/WX', # treat warnings as errors
+				'/Gz', # __stdcall Calling convention
+				'/GX-', # disable C++ EH
+				'/GR-', # disable C++ RTTI
+				'/GF', # enable read-only string pooling
+				'/G6', # optimize for PPro, P-II, P-III
+				'/Ze', # enable extensions
+				'/Gi-', # disable incremental compilation
+				'/QIfdiv-', # disable Pentium FDIV fix
+				'/hotpatch', # prepares an image for hotpatching.
+				#'/Z7', #enable old-style debug info
+			]
+		if platform == 'wince':
+			cflags += [
+				'/Gs8192',
+				'/GF', # enable read-only string pooling
+			]
+		# Automatic pdb generation
+		# See http://scons.tigris.org/issues/show_bug.cgi?id=1656
+		env.EnsureSConsVersion(0, 98, 0)
+		env['PDB'] = '${TARGET.base}.pdb'
+	env.Append(CFLAGS = cflags)
+	env.Append(CXXFLAGS = cflags)
+
+	# Linker options
+	linkflags = []
+	if gcc:
+		if env['machine'] == 'x86':
+			linkflags += ['-m32']
+		if env['machine'] == 'x86_64':
+			linkflags += ['-m64']
+	if platform == 'winddk':
+		# See also:
+		# - http://msdn2.microsoft.com/en-us/library/y0zzbyt4.aspx
+		linkflags += [
+			'/merge:_PAGE=PAGE',
+			'/merge:_TEXT=.text',
+			'/section:INIT,d',
+			'/opt:ref',
+			'/opt:icf',
+			'/ignore:4198,4010,4037,4039,4065,4070,4078,4087,4089,4221',
+			'/incremental:no',
+			'/fullbuild',
+			'/release',
+			'/nodefaultlib',
+			'/wx',
+			'/debug',
+			'/debugtype:cv',
+			'/version:5.1',
+			'/osversion:5.1',
+			'/functionpadmin:5',
+			'/safeseh',
+			'/pdbcompress',
+			'/stack:0x40000,0x1000',
+			'/driver', 
+			'/align:0x80',
+			'/subsystem:native,5.01',
+			'/base:0x10000',
+			
+			'/entry:DrvEnableDriver',
+		]
+	env.Append(LINKFLAGS = linkflags)
+
+	# Convenience Library Builder
+	createConvenienceLibBuilder(env)
+	
+	# for debugging
+	#print env.Dump()
+
+
+def exists(env):
+	return 1