Use modern CMake targets for SDL2 (#6132)

cmake/modules/FindSDL2.cmake

@@ -1,16 +1,17 @@
-
 # This module defines
+# SDL2::SDL2, a target providing SDL2 itself
+# SDL2::SDL2main, a target providing an entry point for applications
 # SDL2_LIBRARY, the name of the library to link against
 # SDL2_FOUND, if false, do not try to link to SDL2
 # SDL2_INCLUDE_DIR, where to find SDL.h
 #
 # This module responds to the the flag:
 # SDL2_BUILDING_LIBRARY
-# If this is defined, then no SDL2main will be linked in because
+# If this is defined, then no SDL2::SDL2main target will be created because
 # only applications need main().
 # Otherwise, it is assumed you are building an application and this
 # module will attempt to locate and set the the proper link flags
-# as part of the returned SDL2_LIBRARY variable.
+# as part of the SDL2::SDL2main target.
 #
 # Don't forget to include SDLmain.h and SDLmain.m your project for the
 # OS X framework based version. (Other versions link to -lSDL2main which
@@ -18,15 +19,17 @@
 # module will automatically add the -framework Cocoa on your behalf.
 #
 #
-# Additional Note: If you see an empty SDL2_LIBRARY_TEMP in your configuration
-# and no SDL2_LIBRARY, it means CMake did not find your SDL2 library
-# (SDL2.dll, libsdl2.so, SDL2.framework, etc).
-# Set SDL2_LIBRARY_TEMP to point to your SDL2 library, and configure again.
+# Additional Note: If you see an empty SDL2_LIBRARY in your configuration, it
+# means CMake did not find your SDL2 library (SDL2.dll, libsdl2.so,
+# SDL2.framework, etc).
+# Set SDL2_LIBRARY to point to your SDL2 library, and configure again.
 # Similarly, if you see an empty SDL2MAIN_LIBRARY, you should set this value
-# as appropriate. These values are used to generate the final SDL2_LIBRARY
-# variable, but when these values are unset, SDL2_LIBRARY does not get created.
+# as appropriate.
 #
 #
+# Modified by Dominic Clark.
+# Added modern CMake targets to match those SDL2 itself uses.
+#
 # $SDL2DIR is an environment variable that would
 # correspond to the ./configure --prefix=$SDL2DIR
 # used in building SDL2.
@@ -92,7 +95,7 @@ else()
 	set(PATH_SUFFIXES lib/x86 lib)
 endif() 
 
-FIND_LIBRARY(SDL2_LIBRARY_TEMP
+FIND_LIBRARY(SDL2_LIBRARY
 	NAMES SDL2
 	HINTS
 	$ENV{SDL2DIR}
@@ -130,41 +133,42 @@ IF(MINGW)
 	SET(MINGW32_LIBRARY mingw32 "-mwindows" CACHE STRING "mwindows for MinGW")
 ENDIF(MINGW)
 
-IF(SDL2_LIBRARY_TEMP)
-	# For SDL2main
-	IF(NOT SDL2_BUILDING_LIBRARY)
-		IF(SDL2MAIN_LIBRARY)
-			SET(SDL2_LIBRARY_TEMP ${SDL2MAIN_LIBRARY} ${SDL2_LIBRARY_TEMP})
-		ENDIF(SDL2MAIN_LIBRARY)
-	ENDIF(NOT SDL2_BUILDING_LIBRARY)
+IF(SDL2_LIBRARY)
+	ADD_LIBRARY(SDL2::SDL2 UNKNOWN IMPORTED)
+	SET_TARGET_PROPERTIES(SDL2::SDL2 PROPERTIES
+		IMPORTED_LOCATION "${SDL2_LIBRARY}"
+		INTERFACE_INCLUDE_DIRECTORIES "${SDL2_INCLUDE_DIR}"
+	)
 
 	# For OS X, SDL2 uses Cocoa as a backend so it must link to Cocoa.
-	# CMake doesn't display the -framework Cocoa string in the UI even
-	# though it actually is there if I modify a pre-used variable.
-	# I think it has something to do with the CACHE STRING.
-	# So I use a temporary variable until the end so I can set the
-	# "real" variable in one-shot.
 	IF(APPLE)
-		SET(SDL2_LIBRARY_TEMP ${SDL2_LIBRARY_TEMP} "-framework Cocoa")
+		SET_PROPERTY(TARGET SDL2::SDL2 APPEND PROPERTY
+			INTERFACE_LINK_OPTIONS "-framework Cocoa"
+		)
 	ENDIF(APPLE)
 
 	# For threads, as mentioned Apple doesn't need this.
 	# In fact, there seems to be a problem if I used the Threads package
 	# and try using this line, so I'm just skipping it entirely for OS X.
-	IF(NOT APPLE)
-		SET(SDL2_LIBRARY_TEMP ${SDL2_LIBRARY_TEMP} ${CMAKE_THREAD_LIBS_INIT})
-	ENDIF(NOT APPLE)
+	IF(NOT APPLE AND Threads_FOUND)
+		SET_PROPERTY(TARGET SDL2::SDL2 APPEND PROPERTY
+			INTERFACE_LINK_LIBRARIES "Threads::Threads"
+		)
+	ENDIF(NOT APPLE AND Threads_FOUND)
+ENDIF(SDL2_LIBRARY)
 
-	# For MinGW library
+IF(NOT SDL2_BUILDING_LIBRARY AND SDL2MAIN_LIBRARY)
+	ADD_LIBRARY(SDL2::SDL2main STATIC IMPORTED)
+	SET_TARGET_PROPERTIES(SDL2::SDL2main PROPERTIES
+		IMPORTED_LOCATION "${SDL2MAIN_LIBRARY}"
+		INTERFACE_INCLUDE_DIRECTORIES "${SDL2_INCLUDE_DIR}"
+	)
 	IF(MINGW)
-		SET(SDL2_LIBRARY_TEMP ${MINGW32_LIBRARY} ${SDL2_LIBRARY_TEMP})
+		SET_PROPERTY(TARGET SDL2::SDL2main APPEND PROPERTY
+			INTERFACE_LINK_OPTIONS "${MINGW32_LIBRARY}"
+		)
 	ENDIF(MINGW)
-
-	# Set the final string here so the GUI reflects the final state.
-	SET(SDL2_LIBRARY ${SDL2_LIBRARY_TEMP} CACHE STRING "Where the SDL2 Library can be found")
-	# Set the temp variable to INTERNAL so it is not seen in the CMake GUI
-	SET(SDL2_LIBRARY_TEMP "${SDL2_LIBRARY_TEMP}" CACHE INTERNAL "")
-ENDIF(SDL2_LIBRARY_TEMP)
+ENDIF(NOT SDL2_BUILDING_LIBRARY AND SDL2MAIN_LIBRARY)
 
 # message("</FindSDL2.cmake>")