{"id":2502,"date":"2020-01-12T11:47:43","date_gmt":"2020-01-12T08:47:43","guid":{"rendered":"http:\/\/demensdeum.com\/blog\/?p=2502"},"modified":"2024-12-16T22:32:30","modified_gmt":"2024-12-16T19:32:30","slug":"porting-cpp-sdl-app-on-android","status":"publish","type":"post","link":"https:\/\/demensdeum.com\/blog\/hi\/2020\/01\/12\/porting-cpp-sdl-app-on-android\/","title":{"rendered":"Porting a C++ SDL application to Android"},"content":{"rendered":"

In this note I will describe my experience of porting the prototype of the 3D editor Cube Art Project<\/a> to Android.
First, let’s look at the result, the emulator runs an editor with a red 3D cube cursor:<\/p>\n

\"\"<\/p>\n

For a successful build, you had to do the following:<\/p>\n

    \n
  1. Install the latest Android SDK and NDK (the newer the NDK version, the better).<\/li>\n
  2. Download the SDL2 source code, take from there a template for building an android application.<\/li>\n
  3. Add SDL Image, SDL Mixer to the build.<\/li>\n
  4. Add my game engine and toolkit libraries, their dependencies (GLM, JSON for Modern C++)<\/li>\n
  5. Adapt build files for Gradle.<\/li>\n
  6. Adapt C++ code for compatibility with Android, changes affected platform-dependent components (OpenGL ES, initialization of the graphics context)<\/li>\n
  7. Build and test the project on the emulator.<\/li>\n<\/ol>\n

    Project template<\/h3>\n

    Download SDL, SDL Image, SDL Mixer sources:
    https:\/\/www.libsdl.org\/download-2.0.php<\/a>
    \nThe docs folder contains detailed instructions on working with the android project template; copy the android-project directory to a separate folder, make a symlink or copy the SDL folder to android-project\/app\/jni.
    We substitute the correct identifier for the avd flag, launch the android emulator from the Sdk directory:<\/p>\n

    \n
    cd ~\/Android\/Sdk\/emulator\n.\/emulator -avd Pixel_2_API_24\n\n<\/code><\/pre>\n<\/div>\n
    We specify the paths in the script, build the project:<\/p>\n
    \n
    rm -rf app\/build || true\nexport ANDROID_HOME=\/home\/demensdeum\/Android\/Sdk\/\nexport ANDROID_NDK_HOME=\/home\/demensdeum\/Android\/android-ndk-r21-beta2\/\n.\/gradlew clean build\n.\/gradlew installDebug\n\n<\/code><\/pre>\n<\/div>\n
    The SDL project template should build with the C code from the file<\/p>\n
    \n
    android-sdl-test-app\/cube-art-project-android\/app\/jni\/src\/YourSourceHere.c\n\n<\/code><\/pre>\n<\/div>\n
    Dependencies<\/h3>\n
    Download the source code in the archives for SDL_image, SDL_mixer:
    https:\/\/www.libsdl.org\/projects\/SDL_image\/<\/a>
    \n    https:\/\/www.libsdl.org\/projects\/SDL_mixer\/<\/a><\/p>\n
    Load your project’s dependencies, for example my shared libraries:
    https:\/\/gitlab.com\/demensdeum\/FlameSteelCore\/<\/a>
    \n    https:\/\/gitlab.com\/demensdeum\/FlameSteelCommonTraits<\/a>
    \n    https:\/\/gitlab.com\/demensdeum\/FlameSteelBattleHorn<\/a>
    \n    https:\/\/gitlab.com\/demensdeum\/FlameSteelEngineGameToolkit\/<\/a>
    \n    https:\/\/gitlab.com\/demensdeum\/FlameSteelEngineGameToolkitFSGL<\/a>
    \n    https:\/\/gitlab.com\/demensdeum\/FSGL<\/a>
    \n    https:\/\/gitlab.com\/demensdeum\/cube-art-project<\/a><\/p>\n
    We unload all this into app\/jni, each \u201cmodule\u201d into a separate folder, for example app\/jni\/FSGL. Next, you have the option of finding working generators for the Application.mk and Android.mk files, I did not find any, but perhaps there is a simple solution based on CMake. Follow the links and begin to get acquainted with the build file format for Android NDK:
    https:\/\/developer.android.com\/ndk\/guides\/application_mk<\/a>
    \n    https:\/\/developer.android.com\/ndk\/guides\/android_mk<\/a><\/p>\n
    You should also read about the different APP_STL implementations in the NDK:
    https:\/\/developer.android.com\/ndk\/guides\/cpp-support.html<\/a><\/p>\n
    After reviewing, we create an Android.mk file for each \u201cmodule\u201d, then an example of a shared library assembly file Cube-Art-Project:<\/p>\n
    \n
    LOCAL_PATH := $(call my-dir)\ninclude $(CLEAR_VARS)\n\nAPP_STL := c++_static\nAPP_CPPFLAGS := -fexceptions\nLOCAL_MODULE := CubeArtProject\nLOCAL_C_INCLUDES := $(LOCAL_PATH)\/src $(LOCAL_PATH)\/..\/include $(LOCAL_PATH)\/..\/include\/FlameSteelCommonTraits\/src\/FlameSteelCommonTraits\nLOCAL_EXPORT_C_INCLUDES = $(LOCAL_PATH)\/src\/\n\ndefine walk\n$(wildcard $(1)) $(foreach e, $(wildcard $(1)\/*), $(call walk, $(e)))\nendef\n\nALLFILES = $(call walk, $(LOCAL_PATH)\/src)\nFILE_LIST := $(filter %.cpp, $(ALLFILES))\n$(info CubeArtProject source code files list)\n$(info $(FILE_LIST))\nLOCAL_SRC_FILES := $(FILE_LIST:$(LOCAL_PATH)\/%=%)\n\nLOCAL_SHARED_LIBRARIES += FlameSteelCore\nLOCAL_SHARED_LIBRARIES += FlameSteelBattleHorn\nLOCAL_SHARED_LIBRARIES += FlameSteelCommonTraits\nLOCAL_SHARED_LIBRARIES += FlameSteelEngineGameToolkit\nLOCAL_SHARED_LIBRARIES += FlameSteelEngineGameToolkitFSGL\nLOCAL_SHARED_LIBRARIES += FSGL\nLOCAL_SHARED_LIBRARIES += SDL2\nLOCAL_SHARED_LIBRARIES += SDL2_image\n\nLOCAL_LDFLAGS := -static-libstdc++\ninclude $(BUILD_SHARED_LIBRARY)\n\n<\/code><\/pre>\n<\/div>\n
    Any experienced CMake user will understand this config from the first lines, the formats are very similar, Android.mk lacks GLOB_RECURSIVE, so you have to recursively search for source files using the walk function.<\/p>\n
    Change Application.mk, Android.mk so-but for building C++ and not C code:<\/p>\n
    \n
    APP_ABI := armeabi-v7a arm64-v8a x86 x86_64\nAPP_PLATFORM=android-16\nAPP_STL := c++_static\nAPP_CPPFLAGS := -fexceptions\n\n<\/code><\/pre>\n<\/div>\n
    Rename YourSourceHere.c -> YourSourceHere.cpp, grep for occurrences, change the path in the assembly, for example:<\/p>\n
    \n
    app\/jni\/src\/Android.mk:LOCAL_SRC_FILES := YourSourceHere.cpp\n\n<\/code><\/pre>\n<\/div>\n
    Then try to build the project, if you see errors from the compiler about the absence of headers, then check the correctness of the paths in Android.mk; if there are errors from the linker of the type \u201cundefined reference\u201d, then check the correctness of the source code files in the assemblies, you can trace the lists by specifying $(info $(FILE_LIST)) in the Android.mk file. Do not forget about the dual linking mechanism, using modules in the LOCAL_SHARED_LIBRARIES key and correct linking via LD, for example for FSGL:<\/p>\n
    \n
    LOCAL_LDLIBS := -lEGL -lGLESv2\n\n<\/code><\/pre>\n<\/div>\n
    Adaptation and launch<\/h3>\n
    I had to change some things, for example remove GLEW from the iOS and Android builds, rename some OpenGL calls, adding the EOS postfix (glGenVertexArrays -> glGenVertexArraysOES), include a macro for missing modern debug functions, the cherry on the cake is the implicit inclusion of GLES2 headers with the GL_GLEXT_PROTOTYPES 1: macro.<\/p>\n
    \n
    #define GL_GLEXT_PROTOTYPES 1\n#include \"SDL_opengles2.h\"\n\n<\/code><\/pre>\n<\/div>\n
    I also observed a black screen on the first launches with an error like \u201cE\/libEGL: validate_display:255 error 3008 (EGL_BAD_DISPLAY)\u201d, I changed the initialization of the SDL window, the OpenGL profile and everything worked:<\/p>\n
    \n
    SDL_DisplayMode mode;\nSDL_GetDisplayMode(0,0,&mode);\nint width = mode.w;\nint height = mode.h;\n\nwindow = SDL_CreateWindow(\n            title,\n            0,\n            0,\n            width,\n            height,\n            SDL_WINDOW_OPENGL | SDL_WINDOW_FULLSCREEN | SDL_WINDOW_RESIZABLE\n        );\n\nSDL_GL_SetAttribute( SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES );\n<\/code><\/pre>\n<\/div>\n
    On the emulator, the application is installed by default with the SDL icon and the name “Game”.<\/p>\n
    I’m left to explore the possibility of automatically generating build files based on CMake, or migrating builds for all platforms to Gradle; however, CMake remains the de facto choice for current C++ development.<\/p>\n
    Source code<\/h3>\n
    https:\/\/gitlab.com\/demensdeum\/android- sdl-test-app<\/a>
    https:\/\/gitlab.com\/demensdeum\/android-sdl-test-app\/tree\/master\/cube-art-project-android<\/a><\/p>\n
    Sources<\/h3>\n
    https:\/\/developer.android.com\/ ndk\/guides\/cpp-support.html<\/a>
    https:\/\/developer.android.com\/ndk\/guides\/application_mk<\/a>
    \n    https:\/\/developer.android.com\/ndk\/guides\/android_mk<\/a>
    \n    https:\/\/lazyfoo.net\/tutorials\/SDL\/52_hello_mobile\/android_windows\/index.php<\/a>
    \n    https:\/\/medium.com\/androiddevelopers\/getting-started-with-c-and-android-native-activities-2213b402ffff<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
    In this note I will describe my experience of porting the prototype of the 3D editor Cube Art Project to Android.First, let’s look at the result, the emulator runs an editor with a red 3D cube cursor: For a successful build, you had to do the following: Install the latest Android SDK and NDK (theContinue reading “Porting a C++ SDL application to Android”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[61,52],"tags":[37,124,145,146,77,147,148],"class_list":["post-2502","post","type-post","status-publish","format-standard","hentry","category-techie","category-tutorials","tag-android","tag-c","tag-cpp","tag-opengl-es","tag-sdl","tag-sdl-image","tag-sdl-mixer","entry"],"translation":{"provider":"WPGlobus","version":"3.0.2","language":"hi","enabled_languages":["en","ru","zh","de","fr","ja","pt","hi"],"languages":{"en":{"title":true,"content":true,"excerpt":false},"ru":{"title":true,"content":true,"excerpt":false},"zh":{"title":true,"content":true,"excerpt":false},"de":{"title":true,"content":true,"excerpt":false},"fr":{"title":true,"content":true,"excerpt":false},"ja":{"title":true,"content":true,"excerpt":false},"pt":{"title":true,"content":true,"excerpt":false},"hi":{"title":false,"content":false,"excerpt":false}}},"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/demensdeum.com\/blog\/hi\/wp-json\/wp\/v2\/posts\/2502","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/demensdeum.com\/blog\/hi\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/demensdeum.com\/blog\/hi\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/demensdeum.com\/blog\/hi\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/demensdeum.com\/blog\/hi\/wp-json\/wp\/v2\/comments?post=2502"}],"version-history":[{"count":31,"href":"https:\/\/demensdeum.com\/blog\/hi\/wp-json\/wp\/v2\/posts\/2502\/revisions"}],"predecessor-version":[{"id":3923,"href":"https:\/\/demensdeum.com\/blog\/hi\/wp-json\/wp\/v2\/posts\/2502\/revisions\/3923"}],"wp:attachment":[{"href":"https:\/\/demensdeum.com\/blog\/hi\/wp-json\/wp\/v2\/media?parent=2502"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/demensdeum.com\/blog\/hi\/wp-json\/wp\/v2\/categories?post=2502"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/demensdeum.com\/blog\/hi\/wp-json\/wp\/v2\/tags?post=2502"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}