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🌊 S P A C E 🪐 🅱 O X 💫

       /\         +-------------------------------------------------------+
  ____/  \____   /| Open source game framework licensed to freely use,    |
  \          /  / | copy, and modify. Created for [dank.game]             |
+--\ ^__^   /--+  |                                                       |
| ~/        \~ |  | Download at https://open.shampoo.ooo/shampoo/spacebox |
| ~~~~~~~~~~~~ |  +-------------------------------------------------------+
| SPACE ~~~~~  | /
|  ~~~~~~~ BOX |/
+--------------+

SPACE🪐BOX is a C++ framework that makes creating cross-platform games and other interactive applications easier and faster by providing an added layer of abstraction between SDL + OpenGL and the project.

Users can start a project by extending only a single function, the Game class's update function. Using a standard Makefile that can be taken from the examples, the framework can export the same code to multiple platforms such as, in order of current stability, Linux, Web, Android, macOS, Windows, and Raspberry Pi.

It is in an early, untested state. It comes with a few simple examples that demonstrate how to use it.

Requirements

The repository includes some external libraries in lib/ that the default Makefile included with the demo shows how to compile, but there are other requirements, including external libraries that must be linked to a project in order to compile it.

libSDL2 (currently tested against 2.26.3)
libSDL2-image
libSDL2-ttf
libSDL2-mixer
OpenGL/GLES/GLES2
compiler that supports C++17

Installing Requirements

libSDL2, libSDL2-image, libSDL2-ttf, and libSDL2-mixer must be available to link with your project, so you can try your package manager's libSDL2 dev packages or build from source. The included sdl2-config utility program can be used to generate flags for linking to SDL2 when it is installed outside of your platform's usual library location.

libSDL2

Download the SDL source package
Run ./configure --prefix=[YOUR LIBRARIES PATH] (for example, $HOME/local/sdl)
Run make && make install

libSDL2-image, libSDL2-ttf, libSDL2-mixer

Download from:
Run ./configure --prefix=[YOUR LIB PATH] --with-sdl-prefix=[YOUR SDL PATH]
For example, prefix and SDL prefix might be $HOME/local/sdl

OpenGL/GLES/GLES2

Install GL/GLES according to your platform and link to it during compilation. GLEW is included in the lib/ folder of this framework and should find GL on your platform (excluding Raspberry Pi and Android) if it is installed.

Builds

Building a SPACEBOX project is currently best accomplished by duplicating and adapting the fill_screen demo included in this repository or an in-progress game like Gunkiss or Pepy. The library requirements described above (SDL and OpenGL), a copy of this repository, and a Makefile based on the one in the project being duplicated are necessary for compilation.

SPACEBOX itself currently needs to be compiled along with the project's source, since there aren't any library builds of it.

Linux

This is the platform SPACEBOX is built on, so it has the most straightforward build process. Copy the Makefile from the fill_screen demo, which demonstrates how to compile SPACEBOX and link to required libraries, adapt it to fit a new project, and build a Linux executable with GNU make.

Linux Distributable

Stack Overflow thread

There are few techniques that can be used to increase compatibility among Linux versions for the resulting binary.

Checking dependencies

Use readelf to see which libraries a binary uses and what the extra search path is

$ readelf -d build/x86_64/Cakefoot-linux.x86_64
Dynamic section at offset 0x1a2c10 contains 36 entries:
Tag        Type                         Name/Value
0x0000000000000001 (NEEDED)             Shared library: [libSDL2-2.0.so.0]
0x0000000000000001 (NEEDED)             Shared library: [libGL.so.1]
0x0000000000000001 (NEEDED)             Shared library: [libGLESv2.so.2]
0x0000000000000001 (NEEDED)             Shared library: [libSDL2_image-2.0.so.0]
0x0000000000000001 (NEEDED)             Shared library: [libSDL2_ttf-2.0.so.0]
0x0000000000000001 (NEEDED)             Shared library: [libSDL2_mixer-2.0.so.0]
0x0000000000000001 (NEEDED)             Shared library: [libstdc++.so.6]
0x0000000000000001 (NEEDED)             Shared library: [libm.so.6]
0x0000000000000001 (NEEDED)             Shared library: [libgcc_s.so.1]
0x0000000000000001 (NEEDED)             Shared library: [libc.so.6]
...

Use objdump to see which symbols a binary uses. In this case ios_base is needed from GLIBCXX_3.4.32 (an older version of GLIBCXX couldn't be used for the ios_base_library_init symbol during compilation).

$ objdump -x build/x64/Cakefoot-linux.x64 | grep GLIBCXX_3.4.32 | c++filt
0x0297f842 0x00 23 GLIBCXX_3.4.32
0000000000000000       F *UND*  0000000000000000              std::ios_base_library_init()@GLIBCXX_3.4.32

Static flags

Adding -static-libgcc and -static-libstdc++ to the linker flags will remove the dependencies on libstdc++ and libgcc_s.

Older compiler

Using an older version of GCC to compile can lower the version of some symbols.

Packaging shared libraries

The rpath property can be used to add a local library search path to the linker, and any libraries to package with the distributable can be added to the local path. For example, this is how SDL is packaged with Cakefoot.

This flag is used to add a relative library lookup path

-Wl,-rpath $(X64_BUILD_LIB_DIR)

This block is used to copy the SDL libraries into the local library folder

cp $$(ldd $(X64_BUILD_DIR)/$@ | grep libSDL2-2.0 | cut -d" " -f3) \
    $$(ldd $(X64_BUILD_DIR)/$@ | grep libSDL2_image | cut -d" " -f3) \
    $$(ldd $(X64_BUILD_DIR)/$@ | grep libSDL2_ttf | cut -d" " -f3) \
    $$(ldd $(X64_BUILD_DIR)/$@ | grep libSDL2_mixer | cut -d" " -f3) ${basename $@}/$(X64_BUILD_LIB_DIR)

Virtualization using Docker

Docker can be used to compile for a target platform with a desired baseline compatibility profile, for example, Ubuntu 16.04.

apt install docker.io

Make sure your user has sudo permissions to use /usr/bin/docker by editing either /etc/sudoers/ or a file in /etc/sudoers.d/. Then pull the Ubuntu 16.04 image.

sudo docker pull ubuntu:16.04

Emscripten

Exporting a browser build with Emscripten and its built-in version of SDL has worked well on a few projects. The general process is to create a separate make target that uses Emscripten's C++ to WebAssembly compiler. See the browser webcam demo below for an example.

Raspberry Pi

Raspberry Pi builds, like Android and Emscripten, require using OpenGL ES. The build process is similar to standard desktop Linux.

GLEW is not available for OpenGL ES, so GLES headers are included directly from the expected system directories.

The flag -DGLEW_NO_GLU may also be necessary since there may not be a glu.h file on Raspberry Pi installations. This flag can also just be used by default because GLU is deprecated.

SDL

SDL should be built with --enable-video-kmsdrm. This will require the installation of external packages. OpenGL ES will also need to be installed.

sudo apt install libgbm-dev libdrm-dev libegl-dev libgles2-mesa-dev

Otherwise, SDL can be installed in the same way described above.

KMS

If using the Raspberry Pi without X-windows, SDL will run in KMS mode. The config for the latest versions of the Raspberry Pi OS Lite should be setup correctly by default, and the installation of SDL from source should enable KMS by default if the necessary packages above have been installed. However, it is good to verify that /boot/firmware/config.txt is setup correctly and that SDL is built with KMS video output enabled.

To verify /boot/firmware/config.txt, make sure the line dtoverlay=vc4-kms-v3d is included in the file. This activates KMS mode for the console instead of either Fake KMS or the older framebuffer modes.

Build the `testgles2.c` SDL test

In the SDL source downloaded in the previous step, there is a test/testgles2.c program that draws a rotating cube using GLES. This can be used to verify that the SDL installation is working on the Pi.

cd [SDL_source]/test/
gcc $(sdl-config --cflags --libs) -LSDL_test -o testgles
./testgles

Raspberry Pi Model 3B+

This model only supports up to Open GL ES 2.0.

Raspberry Pi Model 4

This model supports up to Open GL ES 3.2.

External demos

Try these non-SPACEBOX demos for verifying the Raspberry Pi OpenGL ES setup with KMS.

Android

The fill_screen demo has a working example of how to build for Android. It may be worthwhile to read the SDL wiki Android page and SDL docs Android README and compile an SDL example for Linux before doing a SPACEBOX Android build. The source distributions for SDL, SDL image, SDL ttf, and SDL mixer, and the Android SDK are required.

After building the demo, see the following for further information on using SDL on Android.

SDL wiki
SDL Android README
In the SDL source package, SDL_android.h and the Android section of SDL_system.h

Building an SDL example for Linux

Install Java packages
```
  apt install openjdk-17-jdk ant
```
Make a folder for Android to store the SDK, NDK, emulator, tools, etc.
```
  mkdir -p ~/local/Android/
```
Download Android command line tools to that folder, extract them, and install an NDK (the gradle tool included with SDL defaults to NDK 21.4.7075529). Note that the gradle tool may download Android tools, but this step seems to be necessary for signing the license, which gets created in licenses
```
  $ cd ~/local/Android/
  $ unzip commandlinetools-linux-8512546_latest.zip
  $ cmdline-tools/bin/sdkmanager --sdk_root=$HOME/local/Android/ "ndk;21.4.7075529"
```

Download and extract SDL source

  $ wget "https://github.com/libsdl-org/SDL/releases/download/release-2.24.0/SDL2-2.24.0.tar.gz"
  $ tar -xf SDL2-2.24.0.tar.gz
  $ cd SDL2-2.24.0/

Copy android-project/ to another folder, symlink the SDL source,

  $ cp -r android-project org.my.testgles
  $ cd org.my.testgles/app/jni
  $ ln -s ../../.. SDL

Edit the line with YourSourcehere.c in org.my.testgles/app/jni/src/Android.mk to point to an SDL example
```
  $ cd src/ && sed -i s#YourSourceHere.c#../SDL/test/testgles.c# Android.mk
```
Build with gradlew in the root of the project, specifying where to find the Android folder
```
  $ ANDROID_SDK_ROOT=$HOME/local/Android ./gradlew build
```

The APK should be output to app/build/outputs/apk/debug/app-debug.apk. It can be uploaded to the phone for testing or run on an emulator. To create an emulator, use the Android SDK's tools. For example, to create an Android emulator for API level 31 (Android 12.0) with ABI x86_64.

  # Install a version of command line tools with support for later versions of Java
  $ cmdline-tools/bin/sdkmanager --sdk_root=$HOME/local/Android "cmdline-tools;latest"

  # Install a system image
  $ cmdline-tools/bin/sdkmanager --sdk_root=$HOME/local/Android "system-images;android-31;default;x86_64"

  # Create emulator
  $ cmdline-tools/latest/bin/avdmanager create avd -n android_31_x86_64 -k "system-images;android-31;default;x86_64"

  # Launch in the background
  $ ~/local/Android/tools/emulator -avd android_31_x86_64 &

  # Install the APK to the running emulator
  $ ~/local/Android/platform-tools/adb -e install -r app/build/outputs/apk/debug/app-debug.apk

  # Start the log viewer
  $ ~/local/Android/platform-tools/adb [-s device_name] logcat

fill_screen demo

The fill_screen demo has a Makefile that should work for building for Android if the paths in the file are adjusted to match the project. Edit the Makefile and run make build/android/[org.my.app]. If that isn't working, see below for notes on how the build was originally done manually.

Custom assets

Assets can be copied to app/src/main/assets. The box demo has an example of how to include custom assets like config JSON and shaders.

Creating the fill_screen Android build

These steps were taken to build the fill_screen demo for Android. The Android SDK is assumed to be installed as explained above in the SDL test example. The instructions are based on SDL 2.24.0. There is also a Makefile target that scripts this process in [demo/fill_screen/Makefile][].

Copy the included Android project in the SDL source into the root of the fill_screen project folder.

  $ cp -r path/to/SDL2-2.24.0/android-project [fill_screen root]/ooo.shampoo.fill_screen
  $ cd [fill_screen root]/ooo.shampoo.fill_screen

Edit the application ID

  $ sed -i s/org.libsdl.app/ooo.shampoo.fill_screen/ app/build.gradle app/src/main/AndroidManifest.xml

Enable C++ STL

  $ sed -i "s/^#.*\(APP_STL\)/\1/" app/jni/Application.mk

Enable C++ 17 features and exceptions

  $ echo "APP_CPPFLAGS := -std=c++17 -fexceptions -frtti" >> app/jni/Application.mk

Modify rules to allow OpenGL ES 3.0 (necessary for example for using GL_RGBA8)

  $ sed -i -e 's/^LOCAL_LDLIBS.*/& -lGLESv3/' app/jni/src/Android.mk
  $ sed -i 's/0x0002/0x0003/' app/src/main/AndroidManifest.xml
  $ sed -i 's/\(minSdkVersion\).*16/\1 18/' app/build.gradle
  $ sed -i 's/\(android\)-16/\1-18/' app/build.gradle app/jni/Application.mk

std::filesystem is only available in NDK 22+, so install NDK version 22 and set the project to use it

  $ ~/local/Android/cmdline-tools/bin/sdkmanager --sdk_root=$HOME/local/Android --install "ndk;22.1.7171670"
  $ sed -i '11i\    ndkVersion "22.1.7171670"' app/build.gradle

Link to SDL source packages (versions other than the listed ones may work)

  $ ln -s path/to/SDL2-2.24.0 app/jni/SDL
  $ ln -s path/to/SDL2_image-2.6.2 app/jni/SDL2_image
  $ ln -s path/to/SDL2_mixer-2.6.2 app/jni/SDL2_mixer
  $ ln -s path/to/SDL2_ttf-2.20.1 app/jni/SDL2_ttf

Add SDL packages as libraries in the Makefile

  $ sed -i 's/^LOCAL_SHARED_LIBRARIES.*/& SDL2_image SDL2_mixer SDL2_ttf/' app/jni/src/Android.mk

Add SPACEBOX lib/ and src/ to include search path. In this command, the paths are relative to the path of Android.mk and based on the location of fill_screen as included in the SPACEBOX repository, but they can be edited to other paths if necessary.
```
  $ sed -i 's#^LOCAL_C_INCLUDES.*#& $(LOCAL_PATH)/../../../../../../lib $(LOCAL_PATH)/../../../../../../src#' \
      app/jni/src/Android.mk
```

Add SPACEBOX source files from lib/ src/ and source files for fill_screen

  $ sed -i 's#YourSourceHere.c#$(LOCAL_PATH)/../../../../fill_screen.cpp#' app/jni/src/Android.mk
  $ sed -i 's#^LOCAL_SRC_FILES.*#& $(wildcard $(LOCAL_PATH)/../../../../../../src/*.cpp)#' app/jni/src/Android.mk
  $ sed -i 's#^LOCAL_SRC_FILES.*#& $(wildcard $(LOCAL_PATH)/../../../../../../lib/sdl2-gfx/*.c)#' app/jni/src/Android.mk

Create a file at app/src/main/java/ooo/shampoo/fill_screen/FillScreen.java with the following contents

  package ooo.shampoo.fill_screen;

  import org.libsdl.app.SDLActivity;

  public class FillScreen extends SDLActivity {
      protected String getMainFunction() {
          return "main";
      }
  }

Edit the manifest to point to that class

  $ sed -i 's/\(name=\)"SDLActivity"/\1"FillScreen"/' app/src/main/AndroidManifest.xml

Run gradle

  $ ANDROID_SDK_ROOT=$HOME/local/Android ./gradlew build

Screen rotation

Note that SDL_WINDOW_RESIZABLE is required for screen rotation to work

Cross compilation considerations

std::filesystem::exists will not work with files stored in the Android APK

Windows

Windows builds are made with MinGW. The box demo contains a make target for building a Windows 32-bit executable from a Linux system. To build from Windows itself, the make target will have to be modified. The SDL MinGW releases and MinGW itself must be downloaded separately.

Download SDL's MinGW libraries from the SDL releases page. Download the libraries for SDL image, SDL mixer, and SDL ttf as well.

mkdir SDL2-mingw
cd SDL2-mingw
wget "https://github.com/libsdl-org/SDL/releases/download/release-2.24.2/SDL2-devel-2.24.2-mingw.zip"
unzip SDL2-devel-2.24.2-mingw.zip
wget "https://github.com/libsdl-org/SDL_image/releases/download/prerelease-2.5.2/SDL2_image-devel-2.5.2-mingw.tar.gz"
tar -xf SDL2_image-devel-2.5.2-mingw.tar.gz
wget "https://github.com/libsdl-org/SDL_ttf/releases/download/release-2.0.15/SDL2_ttf-devel-2.0.15-mingw.tar.gz"
tar -xf SDL2_ttf-devel-2.0.15-mingw.tar.gz
wget "https://github.com/libsdl-org/SDL_mixer/releases/download/prerelease-2.5.2/SDL2_mixer-devel-2.5.2-mingw.tar.gz"
tar -xf SDL2_mixer-devel-2.5.2-mingw.tar.gz

Install MinGW. The simplest way to install is through the package manager. On Debian the command is

apt install mingw-w64

Add -DGLEW_STATIC to compile the GLEW library into a [SPACE BOX] project using MinGW.

Add -static-libgcc and -static-libstdc++ to the linker flags to compile GCC and C++ STD runtime DLLs into the executable instead of distributing the DLL file with the executable.

Add -mwindows to the linker flags to prevent Windows from opening a console window in the background when launching the game.

See the Windows section of demo/box/Makefile for a complete list of necessary flags and build process.

Cross compilation considerations

std::filesystem::path::c_str returns a const wchar_t* instead of const char*. To make a platform generic call, convert the path to a string, then use std::filesystem::path::string::c_str instead.
In order to use std::thread with MinGW, you must use the POSIX version of the compiler, for example x86_64-w64-mingw32-g++-posix and add -lpthread to the linker flags.

macOS

SDL Wiki - macOS

To fully support macOS, both Intel x86_64-macos and ARM aarch64-macos architecture versions must be compiled.

Make sure the version of macOS on the build host system is supported by the version of SDL being used. There is information in the documentation in the SDL source at SDL2-2.X.X/docs/README-macos.md. If possible, upgrade the macOS operating system, one version at a time, until the version installed is supported by SDL, using the official Apple support links, or downgrade SDL by downloading a lower version.

Demos

The demo/ folder contains programs that demonstrate and test the capabilities of the framework. In order to compile each, you should edit the definitions in the Makefile.

Fill screen

This is intended to be a bare minimum test of the framework which loads the framework and fills the screen with a new color each frame. It currently builds to Linux and Android.

Box

Test OpenGL context by drawing a textured, rotating cube. It currently builds to Linux, Android, and web browsers.

Browser webcam

An example for using a C++ program to display a webcam stream in the browser using Emscripten to translate the code from C++ to WebAssembly. Get the frame pixel data from a canvas element, read it into a SPACEBOX object, write the pixel data to an OpenGL texture, and use Emscripten to display the video.

Squircle

Map an image from a rectangle to a circle or from a circle to a rectangle using a shader program. Based on a blog post about elliptical grid mapping equations.

OpenCV camera

Get camera input using the OpenCV library on Linux or Android.

Other libraries

These are other libraries that have been used in projects that use this framework but aren't required by the framework

OpenCV

Download a source package and follow the specific instructions for each platform.

Linux

Create a build directory, then configure and make. This example uses a custom installation path ~/local/opencv:

$ mkdir build_linux/ && cd build_linux/
$ cmake -DCMAKE_INSTALL_PREFIX=$HOME/local/opencv ..
$ make && make install

The core, imgproc, videoio, and highgui modules can then be linked to by adding the following to the linker flags:

-L$(HOME)/local/opencv/lib -Wl,-rpath,$(HOME)/local/opencv/lib -lopencv_videoio -lopencv_core -lopencv_highgui \ 
    -lopencv_imgproc

The specific modules needed may vary depending on the project. See detailed instructions for building OpenCV on Linux for more advanced installation. There are also contributed modules available, which can be downloaded separately and compiled with the core modules. For example, this command builds all the modules in ../../opencv_contrib-4.x/modules, except python3, along with the core modules.

$ cmake -D CMAKE_INSTALL_PREFIX=$HOME/local/opencv -D OPENCV_EXTRA_MODULES_PATH="../../opencv_contrib-4.x/modules" -D \ 
    BUILD_opencv_python3=OFF ..

Emscripten

To build the WASM libraries necessary to include OpenCV in an Emscripten build of a SPACEBOX project, set up the Emscripten environment and run OpenCV's build_js.py script with the WASM output option. Note that OpenCV's cv::VideoCapture object will not be available in the libraries built this way because OpenCV emulates that object in its JS implementation.

$ source [EMSDK_PATH]/emsdk_env.sh
$ python3 [OPENCV_PATH]/platforms/js/build_js.py --emscripten_dir [EMSCRIPTEN_PATH] build_wasm --build_wasm

There is a detailed explanation of this process at [https://docs.opencv.org/4.6.0/d4/da1/tutorial_js_setup.html]. And useful information for getting around the absence of cv::VideoCapture at [https://docs.opencv.org/4.6.0/dd/d00/tutorial_js_video_display.html]. Check out a minimal example of using OpenCV with C++ and Emscripten at [https://github.com/mpizenberg/emscripten-opencv]. There is also information on how to build the contributed modules as WASM libraries in the first link.

At the time of writing this, the contributed module for barcode scanning needs -DBUILD_PROTOBUF=ON added to the build_js.py script and needs js added to its list of wrapper languages in its CMakeLists.txt file to compile successfully.

To link to the WASM libraries, add the *.a files from the build directory to Emscripten's linker flags. Add both lib/*.a and 3rdparty/lib/*.a. For GNU Make, this might look like the following.

$(wildcard $(addprefix $(WASM_BUILD_DIR)/lib/,*.a)) $(wildcard $(addprefix $(WASM_BUILD_DIR)/3rdparty/lib/,*.a))

Android

Follow the steps at Building an SDL example for Linux up to the NDK installation steps, using 24.0.8215888 as the NDK version. This version or higher is necessary for using cv::VideoCapture.

$ ~/local/Android/cmdline-tools/bin/sdkmanager --sdk_root=$HOME/local/Android --install "ndk;24.0.8215888"

To build the OpenCV Android SDK, including shared object files, one for each Android ABI, run the build_sdk.py script packaged with the OpenCV source.

$ cd [opencv_source]
$ python3 platforms/android/build_sdk.py --sdk_path ~/local/Android/ --ndk_path ~/local/Android/ndk/24.0.8215888/ \ 
    --extra_modules_path ../opencv_contrib-4.7.0-subset/ --shared --no_samples_build \
    --config ndk-18-api-level-24.config.py build_android/
$ ls -R build_android/OpenCV-android-sdk/sdk/native/libs/
build_android/OpenCV-android-sdk/sdk/native/libs/:
arm64-v8a  armeabi-v7a  x86  x86_64

build_android/OpenCV-android-sdk/sdk/native/libs/arm64-v8a:
libopencv_world.so  libtbb.so

build_android/OpenCV-android-sdk/sdk/native/libs/armeabi-v7a:
libopencv_world.so  libtbb.so

build_android/OpenCV-android-sdk/sdk/native/libs/x86:
libopencv_world.so  libtbb.so

build_android/OpenCV-android-sdk/sdk/native/libs/x86_64:
libopencv_world.so  libtbb.so

This SDK can be included in an Android NDK project. See the camera demo for an example of how to add it to a SPACEBOX project build.

Full example

This builds the local, WASM, and Android libraries by downloading OpenCV 4.7.0 and the contributed modules source packages. See Gunkiss for an example of using these libraries in a project with multiple target platforms.

$ wget https://github.com/opencv/opencv/archive/4.7.0.zip
$ unzip 4.7.0.zip
$ tar -xf opencv_contrib-4.7.0.tar.gz
$ mkdir opencv_contrib-4.7.0-subset
$ cp -r opencv_contrib-4.7.0/modules/barcode/ opencv_contrib-4.7.0-subset/
$ rm -rf ~/local/opencv/
$ cd opencv-4.7.0/
$ mkdir build_linux
$ cd build_linux/
$ cmake -D CMAKE_INSTALL_PREFIX=$HOME/local/opencv -D OPENCV_EXTRA_MODULES_PATH="../../opencv_contrib-4.7.0-subset/" ..
...
--   OpenCV modules:
--     To be built: barcode calib3d core dnn features2d flann gapi highgui imgcodecs imgproc java ml objdetect
                    photo python3 stitching ts video videoio
...
$ make -j3 && make install
$ cd ..
$ source ~/ext/software/emsdk/emsdk_env.sh
$ python3 platforms/js/build_js.py --cmake_option="-DOPENCV_EXTRA_MODULES_PATH=../../opencv_contrib-4.7.0-subset/" \
    --emscripten_dir ~/ext/software/emsdk/upstream/emscripten build_wasm_contrib --build_wasm
$ python3 platforms/android/build_sdk.py --sdk_path ~/local/Android/ --ndk_path ~/local/Android/ndk/22.1.7171670/ \ 
    --extra_modules_path ../opencv_contrib-4.7.0-subset/ --shared --no_samples_build build_android/

curl

Linux

Install from the package manager

sudo apt install libcurl4-openssl-dev

Emscripten

Use Emscripten's Fetch API instead of curl

Android

There are instructions on how to build for Android in the curl documentation. There is also a project libcurl-android that facilitates the build process.

$ git clone --recursive https://github.com/ibaoger/libcurl-android

Add x86 to the APP_ABI parameter in build_for_android.sh. Then run the build script.

$ NDK_ROOT=/path/to/NDK ./build_for_android.sh

The libraries should be written the jni/build folder. The folder libs/x86-64 should actually be named libs/x86_64, so rename it.

$ mv jni/build/zlib/x86-64 jni/build/zlib/x86_64
$ mv jni/build/curl/x86-64 jni/build/curl/x86_64
$ mv jni/build/openssl/x86-64/ jni/build/openssl/x86_64

See how the OpenCV libraries are included in an Android NDK project in the camera demo for an example of how to use pre-built shared libraries.

ZBar

Linux

Download from http://zbar.sourceforge.net/download.html and configure to only use image processing features (requires the imagemagickwand library, available from, for example apt get libmagickwand-dev) and choose your installation directory:

./configure --without-gtk --without-python --without-qt --without-xshm --without-xv --without-jpeg \
    --disable-video --prefix=$HOME/local/zbar

make

make && make install

Emscripten

To build a WASM library that can be used to build an Emscripten version of a SPACEBOX project, set up the Emscripten environment and configure using emconfigure with the same disable flags as above.

$ source emsdk_env.sh
$ emconfigure ./configure --without-gtk --without-python --without-qt --without-xshm --without-xv --without-jpeg \
    --disable-video
$ emmake make
$ find . -iname *.a
./zbar/.libs/libzbar.a

There is a detailed tutorial on using Zbar with WebAssembly at https://barkeywolf.consulting/posts/barcode-scanner-webassembly/

External Resources

Font

When initializing a Game object, the framework will attempt to load the font file BPmono.ttf from the project root (where the compiled executable is located). If this file isn't found, the program can still run successfully, but the repository contains BPmono.ttf if you want to create a symlink to the file in the project root.

License

[SPACEBOX] is released under the zlib license. It is free to use, copy, modify and sell. See LICENSE.txt for details.

Included libraries are included under various permissive licenses compatible with the zlib license:

BPmono.ttf is licensed under the Creative Commons Attribution * No Derivative Works 3.0 license. See LICENSE_BPmono.txt
gif-h is unlicensed, public domain code released under the The Unlicense. See lib/gif-h/LICENSE
GLEW is included under the license in lib/glew/LICENSE.txt
GLM is included under the MIT license in lib/glm/LICENSE
nlohmann's json library is included under the MIT license in lib/json/LICENSE.MIT
SDL2 GFX is included under the license in lib/sdl2-gfx/LICENSE
superxbr.cpp is included under the license at the top of lib/superxbr.cpp

Contact

mailbox at shampoo.ooo https://twitter.com/diskmem

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Requirements

Installing Requirements

libSDL2

libSDL2-image, libSDL2-ttf, libSDL2-mixer

OpenGL/GLES/GLES2

Builds

Linux

Linux Distributable

Checking dependencies

Static flags

Older compiler

Packaging shared libraries

Virtualization using Docker

Emscripten

Raspberry Pi

SDL

KMS

Build the testgles2.c SDL test

Raspberry Pi Model 3B+

Raspberry Pi Model 4

External demos

Android

Building an SDL example for Linux

fill_screen demo

Custom assets

Creating the fill_screen Android build

Screen rotation

Cross compilation considerations

Windows

Cross compilation considerations

macOS

Demos

Fill screen

Box

Browser webcam

Squircle

OpenCV camera

Other libraries

OpenCV

Linux

Emscripten

Android

Full example

curl

Linux

Emscripten

Android

ZBar

Linux

Emscripten

External Resources

Font

License

Contact

31 KiB

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Build the `testgles2.c` SDL test