CMake: Kill support for <2.8.12

The rationale for this is in a comment at the top of the main
CMakeLists.txt file. It was getting harder to maintain support for a
version this old, and pretty much no current system has CMake <3.

Good riddance.

CMakeLists.txt

@@ -1,6 +1,12 @@
-# We require 2.8.4 because earlier releases had a bug
-# with invalid HEADER_FILE_ONLY behavior in MSVC 2010.
-cmake_minimum_required(VERSION 2.8.4)
+# We require 2.8.12+ for three reasons:
+# 1) CMake 3 is so common these days that it's really not a burden on the user
+#    to expect them to have it.
+# 2) As of this writing, this is the oldest version included in a supported
+#    release of Ubuntu. Older versions are actually somewhat difficult to track
+#    down, so we don't test against them.
+# 3) CMake's INTERFACE_INCLUDE_DIRECTORIES feature, which we rely on
+#    extensively, finally became stable in this release.
+cmake_minimum_required(VERSION 2.8.12)
 set(CMAKE_DISABLE_SOURCE_CHANGES ON) # Must go before project() below
 set(CMAKE_DISABLE_IN_SOURCE_BUILD ON) # Must go before project() below
 project(Panda3D)
@@ -25,6 +31,10 @@ endif()
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/modules/")
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/macros/")
 
+# Set certain CMake flags we expect
+set(CMAKE_INCLUDE_CURRENT_DIR_IN_INTERFACE ON)
+set(CMAKE_INCLUDE_CURRENT_DIR ON)
+
 # Include global modules needed for configure scripts
 include(PackageConfig)      # Defines package_option AND target_use_packages
 
@@ -34,7 +44,6 @@ include(dtool/Package.cmake)
 include(dtool/Config.cmake)
 
 # Include global modules
-include(AutoInclude)        # Implements automatic include_directories finding
 include(AddBisonTarget)     # Defines add_bison_target function
 include(AddFlexTarget)      # Defines add_flex_target function
 include(CompositeSources)   # Defines composite_sources function

cmake/macros/Interrogate.cmake

@@ -167,28 +167,14 @@ function(interrogate_sources target output database module)
     endforeach(source)
 
     # Interrogate also needs the include paths, so we'll extract them from the
-    # target. Usually these are available via a generator expression, however
-    # versions of CMake before 2.8.10 don't support the TARGET_PROPERTY genex
-    # so we have to extract the property at configuration-time. Versions after
-    # 2.8.11 support CMAKE_INCLUDE_CURRENT_DIR_IN_INTERFACE which ONLY makes
-    # this information available at generator-time (i.e. after
-    # configuration-time) so the generator expression is necessary then.
-    if(CMAKE_VERSION VERSION_LESS 2.8.10)
-      set(include_flags)
-      get_target_property(include_dirs "${target}" INTERFACE_INCLUDE_DIRECTORIES)
-      foreach(include_dir ${include_dirs})
-        list(APPEND include_flags "-I${include_dir}")
-      endforeach(include_dir)
-      # The above must also be included when compiling the resulting _igate.cxx file:
-      include_directories(${include_dirs})
-    else()
-      # Note, the \t is a workaround for a CMake bug where using a plain space in
-      # a JOIN will cause it to be escaped. Tabs are not escaped and will
-      # separate correctly.
-      set(include_flags "-I$<JOIN:$<TARGET_PROPERTY:${target},INTERFACE_INCLUDE_DIRECTORIES>,\t-I>")
-      # The above must also be included when compiling the resulting _igate.cxx file:
-      include_directories("$<TARGET_PROPERTY:${target},INTERFACE_INCLUDE_DIRECTORIES>")
-    endif()
+    # target. These are available via a generator expression.
+
+    # Note, the \t is a workaround for a CMake bug where using a plain space in
+    # a JOIN will cause it to be escaped. Tabs are not escaped and will
+    # separate correctly.
+    set(include_flags "-I$<JOIN:$<TARGET_PROPERTY:${target},INTERFACE_INCLUDE_DIRECTORIES>,\t-I>")
+    # The above must also be included when compiling the resulting _igate.cxx file:
+    include_directories("$<TARGET_PROPERTY:${target},INTERFACE_INCLUDE_DIRECTORIES>")
 
     # Get the compiler definition flags. These must be passed to Interrogate
     # in the same way that they are passed to the compiler so that Interrogate

cmake/modules/AutoInclude.cmake

@@ -1,55 +0,0 @@
-# Filename: AutoInclude.cmake
-# Description: This file backports the CMAKE_INCLUDE_CURRENT_DIR_IN_INTERFACE
-#   introduced in CMake 2.8.11 to previous versions of cmake, and enables the
-#   behavior by default.
-#
-
-# Emulate CMake 2.8.11's CMAKE_INCLUDE_CURRENT_DIR_IN_INTERFACE behavior if
-# this version doesn't define CMAKE_INCLUDE_CURRENT_DIR_IN_INTERFACE.
-if(CMAKE_VERSION VERSION_LESS 2.8.11)
-  # Replace some built-in functions in order to extend their functionality.
-  function(add_library target)
-    _add_library(${target} ${ARGN})
-    set_target_properties("${target}" PROPERTIES INTERFACE_INCLUDE_DIRECTORIES "${CMAKE_CURRENT_SOURCE_DIR};${CMAKE_CURRENT_BINARY_DIR}")
-  endfunction()
-
-  function(add_executable target)
-    _add_executable(${target} ${ARGN})
-    set_target_properties("${target}" PROPERTIES INTERFACE_INCLUDE_DIRECTORIES "${CMAKE_CURRENT_SOURCE_DIR};${CMAKE_CURRENT_BINARY_DIR}")
-  endfunction()
-
-  function(target_link_libraries target)
-    set(interface_dirs)
-    get_target_property(target_interface_dirs "${target}" INTERFACE_INCLUDE_DIRECTORIES)
-
-    foreach(lib ${ARGN})
-      if(TARGET "${lib}")
-        get_target_property(lib_interface_dirs "${lib}" INTERFACE_INCLUDE_DIRECTORIES)
-
-        if(lib_interface_dirs)
-          list(APPEND interface_dirs ${lib_interface_dirs})
-        endif()
-      endif()
-    endforeach()
-
-    if(interface_dirs)
-      list(REMOVE_DUPLICATES interface_dirs)
-
-      #NB. target_include_directories is new in 2.8.8.
-      #target_include_directories("${target}" ${interface_dirs})
-      include_directories(${interface_dirs})
-
-      # Update this target's interface inc dirs.
-      set_target_properties("${target}" PROPERTIES INTERFACE_INCLUDE_DIRECTORIES "${target_interface_dirs};${interface_dirs}")
-    endif()
-
-    # Call to the built-in function we are overriding.
-    _target_link_libraries(${target} ${ARGN})
-  endfunction()
-
-else()
-  # 2.8.11 supports this natively.
-  set(CMAKE_INCLUDE_CURRENT_DIR_IN_INTERFACE ON)
-endif()
-
-set(CMAKE_INCLUDE_CURRENT_DIR ON)

cmake/scripts/MakeComposite.cmake

@@ -10,8 +10,6 @@
 #
 
 if(CMAKE_SCRIPT_MODE_FILE)
-  #cmake_minimum_required(VERSION 2.8.4)
-
   if(NOT DEFINED COMPOSITE_FILE)
     message(FATAL_ERROR "COMPOSITE_FILE should be defined when running MakeComposite.cmake!")
     return()

panda/src/express/CMakeLists.txt

@@ -144,18 +144,11 @@ set(P3EXPRESS_IGATEEXT
 
 composite_sources(p3express P3EXPRESS_SOURCES)
 
+add_library(p3express ${P3EXPRESS_SOURCES} ${P3EXPRESS_HEADERS})
+
 # p3express needs to include from p3interrogatedb for py_panda.h and extension.h
-if(CMAKE_VERSION VERSION_LESS 2.8.11)
-  get_target_property(interrogatedb_interface_dirs p3interrogatedb INTERFACE_INCLUDE_DIRECTORIES)
-  include_directories(${interrogatedb_interface_dirs})
-  add_library(p3express ${P3EXPRESS_SOURCES} ${P3EXPRESS_HEADERS})
-  set_target_properties(p3express PROPERTIES INTERFACE_INCLUDE_DIRECTORIES
-    "${interrogatedb_interface_dirs};${CMAKE_CURRENT_SOURCE_DIR}")
-else()
-  add_library(p3express ${P3EXPRESS_SOURCES} ${P3EXPRESS_HEADERS})
-  target_include_directories(p3express PUBLIC
-    $<TARGET_PROPERTY:p3interrogatedb,INTERFACE_INCLUDE_DIRECTORIES>)
-endif()
+target_include_directories(p3express PUBLIC
+  $<TARGET_PROPERTY:p3interrogatedb,INTERFACE_INCLUDE_DIRECTORIES>)
 target_link_libraries(p3express p3pandabase p3dtool p3prc p3dconfig)
 target_use_packages(p3express TAR ZLIB)
 target_interrogate(p3express ALL EXTENSIONS ${P3EXPRESS_IGATEEXT})