Android: Build rules

This sets up Gradle / CMake rules for Android build.

.gitignore

@@ -0,0 +1,4 @@
+out
+android/.gradle
+android/app/.externalNativeBuild
+android/app/build

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 {
+                // system3 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 +6,31 @@ 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
+)
 
-# 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()
 
+# The main CMakeLists.txt of system3
+add_subdirectory(../../../src src)

src/CMakeLists.txt

@@ -59,12 +59,21 @@ target_compile_definitions(common INTERFACE
 target_include_directories(common INTERFACE . sys)
 target_sources(common INTERFACE ${SRC_COMMON} ${SRC_PLATFORM} ${SRC_MAKO})
 
-add_executable(system3)
+if (ANDROID)
+  add_library(system3 SHARED)
+else()
+  add_executable(system3)
+endif()
+
 target_sources(system3 PRIVATE sys/nact_sys3.cpp ${RES3} sys/ags_bmp.cpp sys/ags_pms.cpp)
 target_compile_definitions(system3 PRIVATE _SYSTEM3)
 target_link_libraries(system3 PRIVATE common)
 
-if (NOT EMSCRIPTEN)
+if (ANDROID)
+
+  target_link_libraries(system3 PRIVATE SDL2 SDL2_ttf)
+
+elseif (NOT EMSCRIPTEN)
 
   add_executable(system1)
   target_sources(system1 PRIVATE sys/nact_sys1.cpp ${RES1} sys/ags_gl3.cpp sys/ags_gm3.cpp sys/ags_vsp2l.cpp)