Add WITH_APPDIR_INSTALLATION configuration option

With this option enabled, `make install` will install the files in an
AppDir-compatible directory structure suitable for creating an AppImage.

CMakeLists.txt

@@ -48,6 +48,7 @@ CMAKE_DEPENDENT_OPTION(USE_COCOA         "Use Apple Cocoa widgets." ON "APPLE" O
 CMAKE_DEPENDENT_OPTION(USE_WIN32_WINDOWS "Use Microsoft Desktop App User Interface widgets." ON "WIN32" OFF)
 CMAKE_DEPENDENT_OPTION(USE_SDL_MAINLOOP  "Use SDL to create windows etc. Qt editor." ON "NOT USE_COCOA AND NOT USE_WIN32_WINDOWS AND NOT HEADLESS_ONLY" OFF)
 option(WITH_AUTOMATIC_UPDATE "Automatic updates are downloaded from the project website." OFF)
+CMAKE_DEPENDENT_OPTION(WITH_APPDIR_INSTALLATION "Install into an AppDir" OFF "UNIX AND NOT APPLE AND WITH_AUTOMATIC_UPDATE" ON)
 option(HEADLESS_ONLY "Only build headless parts. Somewhat reduces dependencies. (still needs libpng because that one's small and hard to remove.) Only tested with make/gcc/linux." OFF)
 option(C4GROUP_TOOL_ONLY "Only build c4group binary." OFF)
 
@@ -170,10 +171,6 @@ if(WIN32 AND MINGW)
 	set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,--nxcompat -Wl,--dynamicbase")
 endif()
 
-if(UNIX)
-	add_definitions("-DOC_SYSTEM_DATA_DIR=\"${CMAKE_INSTALL_PREFIX}/share/games/openclonk\"")
-endif()
-
 if(APPLE)
 	set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fobjc-arc -headerpad_max_install_names")
 endif()
@@ -1463,7 +1460,11 @@ endif()
 # Don't allow installation for WITH_AUTOMATIC_UPDATE because otherwise
 # the installed binary wouldn't find its game data in the system data path.
 IF(WITH_AUTOMATIC_UPDATE)
-	INSTALL(CODE "MESSAGE(SEND_ERROR \"Installation is only supported for WITH_AUTOMATIC_UPDATE disabled\")")
+	if(WITH_APPDIR_INSTALLATION)
+		INSTALL(CODE "MESSAGE(\"WITH_APPDIR_INSTALLATION is enabled, installation will create an AppDir\")")
+	else()
+		INSTALL(CODE "MESSAGE(SEND_ERROR \"Installation is only supported for WITH_AUTOMATIC_UPDATE disabled\")")
+	endif()
 ENDIF()
 
 if(NOT C4GROUP_TOOL_ONLY)
@@ -1606,7 +1607,12 @@ if(NOT HEADLESS_ONLY AND NOT C4GROUP_TOOL_ONLY)
 		install(FILES ${CMAKE_CURRENT_SOURCE_DIR}/openclonk.appdata.xml DESTINATION share/appdata)
 
 		# Install binaries
-		install(TARGETS openclonk DESTINATION games)
+		if(WITH_APPDIR_INSTALLATION)
+			# AppDir expects binaries in /usr/bin
+			install(TARGETS openclonk DESTINATION bin)
+		else()
+			install(TARGETS openclonk DESTINATION games)
+		endif()
 	else()
 		install(TARGETS openclonk
 			BUNDLE DESTINATION .

config.h.cmake

@@ -105,12 +105,13 @@
 
 /* Enable automatic update system */
 #cmakedefine WITH_AUTOMATIC_UPDATE 1
+#cmakedefine WITH_APPDIR_INSTALLATION 1
 
 /* Select an audio provider */
 #define AUDIO_TK AUDIO_TK_${Audio_TK_UPPER}
 #else
 #define AUDIO_TK AUDIO_TK_NONE
-#endif
+#endif // USE_CONSOLE
 
 #define AUDIO_TK_NONE 0
 #define AUDIO_TK_OPENAL 1
@@ -119,5 +120,12 @@
 /* Include OpenAL extensions (alext.h) for sound modifiers */
 #cmakedefine HAVE_ALEXT 1
 
+/* Path to data directory */
+#ifdef WITH_APPDIR_INSTALLATION
+#define OC_SYSTEM_DATA_DIR "../share/games/openclonk"
+#else
+#define OC_SYSTEM_DATA_DIR "${CMAKE_INSTALL_PREFIX}/share/games/openclonk"
+#endif
+
 /* Path to /proc/self/exe (Linux) or equivalent */
 #cmakedefine PROC_SELF_EXE "${PROC_SELF_EXE}"

src/config/C4Config.cpp

@@ -477,6 +477,10 @@ void C4ConfigGeneral::DeterminePaths()
 	SCopy(ExePath.getMData(),SystemDataPath);
 #elif defined(__APPLE__)
 	SCopy(::Application.GetGameDataPath().c_str(),SystemDataPath);
+#elif defined(WITH_APPDIR_INSTALLATION)
+	// AppDir: layout like normal unix installation, but relative to executable.
+	auto str = FormatString("%s%s", ExePath.getMData(), OC_SYSTEM_DATA_DIR);
+	SCopy(str.getMData(), SystemDataPath);
 #elif defined(WITH_AUTOMATIC_UPDATE)
 	// WITH_AUTOMATIC_UPDATE builds are our tarball releases and
 	// development snapshots, i.e. where the game data is at the