Android: Build rules

This sets up Gradle / CMake rules for Android build.

.gitignore

@@ -1,2 +1,5 @@
-*~
-/out
+out
+android/.gradle
+android/app/.externalNativeBuild
+android/app/build
+android/build

CMakeLists.txt

@@ -39,6 +39,12 @@ if (EMSCRIPTEN)
   set(SDL2_FOUND 1)
   set(FREETYPE_FOUND 1)
   set(DEFAULT_FONT_PATH .)
+elseif (ANDROID)
+  set(SDL2_FOUND 1)
+  set(SDL2MIXER_FOUND 1)
+  set(SDL2TTF_FOUND 1)
+  set(DEFAULT_FONT_PATH .)
+  find_library(ndk_zlib z)
 else()
   include(TestBigEndian)
   TEST_BIG_ENDIAN(WORDS_BIGENDIAN)
@@ -153,7 +159,7 @@ if (EMSCRIPTEN)
   list(APPEND SRC_MIDI midi.emscripten.c)
   list(APPEND SUMMARY_MIDI "Emscripten")
 else()
-  if (HAVE_SIGACTION)
+  if (HAVE_SIGACTION AND NOT ANDROID)
     list(APPEND SRC_MIDI midi.rawmidi.c midifile.c)
     list(APPEND SUMMARY_MIDI "raw")
     set(MIDI_DEVICE "/dev/midi" CACHE STRING "midi device")
@@ -182,7 +188,7 @@ endif()
 
 # Joystick
 
-if (EMSCRIPTEN)
+if (EMSCRIPTEN OR ANDROID)
   set(SRC_JOYSTICK joystick_dmy.c)
 elseif (SDL2_FOUND)
   set(SRC_JOYSTICK joystick_sdl.c)

android/app/build.gradle

@@ -18,15 +18,11 @@ android {
         versionCode 1
         versionName "1.0"
         externalNativeBuild {
-            ndkBuild {
-                arguments "APP_PLATFORM=android-16"
-                abiFilters 'armeabi-v7a', 'arm64-v8a', 'x86', 'x86_64'
+            cmake {
+                arguments "-DANDROID_APP_PLATFORM=android-16", "-DANDROID_STL=c++_static"
+                // abiFilters 'armeabi-v7a', 'arm64-v8a', 'x86', 'x86_64'
+                abiFilters 'arm64-v8a'
             }
-            // cmake {
-            //     arguments "-DANDROID_APP_PLATFORM=android-16", "-DANDROID_STL=c++_static"
-            //     // abiFilters 'armeabi-v7a', 'arm64-v8a', 'x86', 'x86_64'
-            //     abiFilters 'arm64-v8a'
-            // }
         }
     }
     buildTypes {
@@ -40,12 +36,12 @@ android {
             jniLibs.srcDir 'libs'
         }
         externalNativeBuild {
-            ndkBuild {
-                path 'jni/Android.mk'
+            cmake {
+                // xsystem35 requires CMake >=3.13, so SDK-bundled CMake
+                // (3.6 or 3.10.2) cannot be used.
+                version getInstalledCmakeVersion()
+                path 'jni/CMakeLists.txt'
             }
-            // cmake {
-            //     path 'jni/CMakeLists.txt'
-            // }
         }
        
     }
@@ -69,3 +65,7 @@ android {
 dependencies {
     implementation fileTree(include: ['*.jar'], dir: 'libs')
 }
+
+String getInstalledCmakeVersion() {
+    ('cmake --version'.execute().text =~ /cmake version ([0-9.]+)/)[0][1]
+}

android/app/jni/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.6)
+cmake_minimum_required(VERSION 3.13)
 
 project(GAME)
 
@@ -6,15 +6,44 @@ project(GAME)
 # include(AndroidNdkModules)
 # android_ndk_import_module_cpufeatures()
 
+include(FetchContent)
+# TODO: Use SDL2 2.0.11 once released
+FetchContent_Declare(
+  SDL
+  URL https://hg.libsdl.org/SDL/archive/a5f93b21dfe0.tar.gz # rev 13383
+  URL_HASH SHA1=a7e9696f7ef8af7c4b89671b096c38d1a4cbf90c
+)
+# TODO: Use SDL2_ttf 2.0.16 once released
+FetchContent_Declare(
+  SDL_ttf
+  URL https://hg.libsdl.org/SDL_ttf/archive/d56d67db41d8.tar.gz # rev 420
+  URL_HASH SHA1=143089a2b2973a5baeee0914af43608cfe8e1d87
+)
+# TODO: Use SDL2_mixer 2.0.5 once released
+FetchContent_Declare(
+  SDL_mixer
+  URL https://hg.libsdl.org/SDL_mixer/archive/d2686bcfcba2.tar.gz # rev 1127
+  URL_HASH SHA1=4e62e29bd5628b262b3ffb6d5d29861c76a1500e
+)
 
-# SDL sources are in a subfolder named "SDL"
-add_subdirectory(SDL)
-
-# Compilation of companion libraries
-#add_subdirectory(SDL_image)
-#add_subdirectory(SDL_mixer)
-#add_subdirectory(SDL_ttf)
-
-# Your game and its CMakeLists.txt are in a subfolder named "src"
-add_subdirectory(src)
+# Compilation of SDL and companion libraries
+FetchContent_GetProperties(SDL)
+if(NOT sdl_POPULATED)
+  FetchContent_Populate(SDL)
+  add_subdirectory(${sdl_SOURCE_DIR} ${sdl_BINARY_DIR})
+endif()
+FetchContent_GetProperties(SDL_ttf)
+if(NOT sdl_ttf_POPULATED)
+  FetchContent_Populate(SDL_ttf)
+  add_subdirectory(${sdl_ttf_SOURCE_DIR} ${sdl_ttf_BINARY_DIR})
+endif()
+FetchContent_GetProperties(SDL_mixer)
+if(NOT sdl_mixer_POPULATED)
+  FetchContent_Populate(SDL_mixer)
+  add_subdirectory(${sdl_mixer_SOURCE_DIR} ${sdl_mixer_BINARY_DIR})
+  # TODO: Fix this in upstream
+  target_include_directories(SDL2_mixer PUBLIC ${sdl_mixer_SOURCE_DIR}/include)
+endif()
 
+# The main CMakeLists.txt of xsystem35
+add_subdirectory(../../.. xsystem35)

src/CMakeLists.txt

@@ -7,7 +7,11 @@ if (ENABLE_MODULES)
   endif()
 endif()
 
-add_executable(xsystem35)
+if (ANDROID)
+  add_library(xsystem35 SHARED)
+else()
+  add_executable(xsystem35)
+endif()
 
 target_compile_options(xsystem35 PRIVATE -Wno-pointer-sign -Wno-invalid-source-encoding)
 
@@ -79,7 +83,11 @@ if (EMSCRIPTEN)
 	"SHELL:-s EXPORTED_FUNCTIONS=\"['_main','_ags_setAntialiasedStringMode', '_ald_getdata', '_ald_freedata']\""
 	"SHELL:-s EXTRA_EXPORTED_RUNTIME_METHODS=\"['getValue','getMemory','addRunDependency','removeRunDependency']\"")
 
-else()  # non-emscripten
+elseif (ANDROID)
+
+  target_link_libraries(xsystem35 PRIVATE SDL2 SDL2_ttf SDL2_mixer ${ndk_zlib})
+
+else()  # non-emscripten, non-android
   target_link_libraries(xsystem35 PRIVATE m ZLIB::ZLIB)
   if (X11_FOUND)
 	target_include_directories(xsystem35 PRIVATE ${X11_INCLUDE_DIR})
@@ -108,7 +116,7 @@ else()  # non-emscripten
 endif()
 
 # FIXME: set up dependency for xsystem35 on this
-if (ENABLE_SDL AND NOT EMSCRIPTEN)
+if (ENABLE_SDL AND NOT EMSCRIPTEN AND NOT ANDROID)
   add_custom_target(sdl_input.c
 	COMMAND perl xsyskey.pl ${SDL2_INCLUDE_DIRS} > sdl_input.c
 	WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})

src/xsystem35.c

@@ -41,6 +41,10 @@
 #  include <gtk/gtk.h>
 #endif
 
+#ifdef ENABLE_SDL
+#  include <SDL.h>
+#endif
+
 #ifdef __EMSCRIPTEN__
 #include <emscripten.h>
 #endif