Support linking against an external tinyxml if EXTERNAL_TINYXML is set

As best as I can tell, the copy of tinyxml dfhack uses is unmodified
from whenever it was first bundled. This commit adds an option to CMake,
EXTERNAL_TINYXML, that if set to ON, will attempt to link against a system
tinyxml instead of using the dfhack-bundled one.  It defaults to OFF,
so there is no change in default behavior.

The DFHACK_TINYXML variable is then set to either "tinyxml" or "dfhack-tinyxml"
so the library (and any plugins that need updating) can link against one
or the other.

The FindTinyXML.cmake script was taken from https://github.com/ros/cmake_modules
(licensed under the 3-clause BSD license).

Add license text to new CMake file.

CMake/Modules/FindTinyXML.cmake

@@ -0,0 +1,107 @@
+# Sourced from:
+# https://raw.githubusercontent.com/ros/cmake_modules/0.4-devel/cmake/Modules/FindTinyXML.cmake
+# under the following license: https://github.com/ros/cmake_modules/blob/0.4-devel/LICENSE,
+# reproduced here:
+
+# Copyright (c) 2013, Open Source Robotics Foundation
+# All rights reserved.
+
+# Redistribution and use in source and binary forms, with or without modification,
+# are permitted provided that the following conditions are met:
+
+#  Redistributions of source code must retain the above copyright notice, this
+#   list of conditions and the following disclaimer.
+
+#   Redistributions in binary form must reproduce the above copyright notice, this
+#   list of conditions and the following disclaimer in the documentation and/or
+#   other materials provided with the distribution.
+
+#   Neither the name of the {organization} nor the names of its
+#   contributors may be used to endorse or promote products derived from
+#   this software without specific prior written permission.
+
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+# ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+# ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+##################################################################################################
+# 
+# CMake script for finding TinyXML.
+# 
+# Input variables:
+# 
+# - TinyXML_ROOT_DIR (optional): When specified, header files and libraries will be searched for in
+#     ${TinyXML_ROOT_DIR}/include
+#     ${TinyXML_ROOT_DIR}/libs
+#   respectively, and the default CMake search order will be ignored. When unspecified, the default
+#   CMake search order is used.
+#   This variable can be specified either as a CMake or environment variable. If both are set,
+#   preference is given to the CMake variable.
+#   Use this variable for finding packages installed in a nonstandard location, or for enforcing
+#   that one of multiple package installations is picked up.
+# 
+# 
+# Cache variables (not intended to be used in CMakeLists.txt files)
+# 
+# - TinyXML_INCLUDE_DIR: Absolute path to package headers.
+# - TinyXML_LIBRARY: Absolute path to library.
+# 
+# 
+# Output variables:
+# 
+# - TinyXML_FOUND: Boolean that indicates if the package was found
+# - TinyXML_INCLUDE_DIRS: Paths to the necessary header files
+# - TinyXML_LIBRARIES: Package libraries
+# 
+# 
+# Example usage:
+# 
+#  find_package(TinyXML)
+#  if(NOT TinyXML_FOUND)
+#    # Error handling
+#  endif()
+#  ...
+#  include_directories(${TinyXML_INCLUDE_DIRS} ...)
+#  ...
+#  target_link_libraries(my_target ${TinyXML_LIBRARIES})
+# 
+##################################################################################################
+
+# Get package location hint from environment variable (if any)
+if(NOT TinyXML_ROOT_DIR AND DEFINED ENV{TinyXML_ROOT_DIR})
+  set(TinyXML_ROOT_DIR "$ENV{TinyXML_ROOT_DIR}" CACHE PATH
+      "TinyXML base directory location (optional, used for nonstandard installation paths)")
+endif()
+
+# Search path for nonstandard package locations
+if(TinyXML_ROOT_DIR)
+  set(TinyXML_INCLUDE_PATH PATHS "${TinyXML_ROOT_DIR}/include" NO_DEFAULT_PATH)
+  set(TinyXML_LIBRARY_PATH PATHS "${TinyXML_ROOT_DIR}/lib"     NO_DEFAULT_PATH)
+endif()
+
+# Find headers and libraries
+find_path(TinyXML_INCLUDE_DIR NAMES tinyxml.h PATH_SUFFIXES "tinyxml" ${TinyXML_INCLUDE_PATH})
+find_library(TinyXML_LIBRARY  NAMES tinyxml   PATH_SUFFIXES "tinyxml" ${TinyXML_LIBRARY_PATH})
+
+mark_as_advanced(TinyXML_INCLUDE_DIR
+                 TinyXML_LIBRARY)
+
+# Output variables generation
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(TinyXML DEFAULT_MSG TinyXML_LIBRARY
+                                                      TinyXML_INCLUDE_DIR)
+
+set(TinyXML_FOUND ${TINYXML_FOUND}) # Enforce case-correctness: Set appropriately cased variable...
+unset(TINYXML_FOUND) # ...and unset uppercase variable generated by find_package_handle_standard_args
+
+if(TinyXML_FOUND)
+  set(TinyXML_INCLUDE_DIRS ${TinyXML_INCLUDE_DIR})
+  set(TinyXML_LIBRARIES ${TinyXML_LIBRARY})
+endif()

CMakeLists.txt

@@ -186,7 +186,22 @@ include_directories(depends/protobuf)
 include_directories(depends/lua/include)
 include_directories(depends/md5)
 include_directories(depends/jsoncpp)
+
+# Support linking against external tinyxml
+# If we find an external tinyxml, set the DFHACK_TINYXML variable to "tinyxml"
+# Otherwise, set it to "dfhack-tinyxml"
+option(EXTERNAL_TINYXML "Choose to link against external TinyXML" OFF)
+if(EXTERNAL_TINYXML)
+    find_package(TinyXML REQUIRED)
+    if(NOT TinyXML_FOUND)
+        message(SEND_ERROR "Could not find an external TinyXML, consider setting EXTERNAL_TINYXML to OFF.")
+    endif()
+    SET(DFHACK_TINYXML "tinyxml")
+else()
     include_directories(depends/tinyxml)
+    SET(DFHACK_TINYXML "dfhack-tinyxml")
+endif()
+
 include_directories(depends/tthread)
 include_directories(${ZLIB_INCLUDE_DIRS})
 include_directories(depends/clsocket/src)

depends/CMakeLists.txt

@@ -2,7 +2,12 @@
 add_subdirectory(lua)
 add_subdirectory(md5)
 add_subdirectory(protobuf)
+
+# Don't build tinyxml if it's being externally linked against.
+if(NOT TinyXML_FOUND)
     add_subdirectory(tinyxml)
+endif()
+
 add_subdirectory(tthread)
 add_subdirectory(jsoncpp)
 # build clsocket static and only as a dependency. Setting those options here overrides its own default settings.

depends/tinyxml/CMakeLists.txt

@@ -1,3 +1,5 @@
+if(NOT TinyXML_FOUND)
     project(dfhack-tinyxml)
     ADD_LIBRARY(dfhack-tinyxml STATIC EXCLUDE_FROM_ALL tinystr.cpp tinyxml.cpp tinyxmlerror.cpp tinyxmlparser.cpp)
     IDE_FOLDER(dfhack-tinyxml "Depends")
+endif()

library/CMakeLists.txt

@@ -269,12 +269,12 @@ IF(UNIX)
 ENDIF()
 
 IF(APPLE)
-  SET(PROJECT_LIBS dl dfhack-md5 dfhack-tinyxml dfhack-tinythread)
+  SET(PROJECT_LIBS dl dfhack-md5 ${DFHACK_TINYXML} dfhack-tinythread)
 ELSEIF(UNIX)
-  SET(PROJECT_LIBS rt dl dfhack-md5 dfhack-tinyxml dfhack-tinythread)
+  SET(PROJECT_LIBS rt dl dfhack-md5 ${DFHACK_TINYXML} dfhack-tinythread)
 ELSE(WIN32)
   #FIXME: do we really need psapi?
-  SET(PROJECT_LIBS psapi dfhack-md5 dfhack-tinyxml dfhack-tinythread)
+  SET(PROJECT_LIBS psapi dfhack-md5 ${DFHACK_TINYXML} dfhack-tinythread)
 ENDIF()
 
 ADD_LIBRARY(dfhack-version STATIC DFHackVersion.cpp)