C

Hello rectangle!

hello_rectangle.c

#define USING_NAMESPACE_P8G
#include "p8g.h"

void draw() {
    background(220);
    rect(50, 50, 100, 100);
}

void keyPressed() {}
void keyReleased() {}
void mouseMoved() {}
void mousePressed() {}
void mouseReleased() {}
void mouseWheel(float delta) {}

int main() {
    run(320, 320, "Hello rectangle!");
}

Build and run from the command line

Windows

.
├── glfw.dll
├── hello_rectangle.c
├── p8g.dll
└── p8g.h

gcc hello_rectangle.c -L. -lp8g
.\a.exe

Tested on Windows 10 with https://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win64/Personal%20Builds/mingw-builds/8.1.0/threads-posix/seh/x86_64-8.1.0-release-posix-seh-rt_v6-rev0.7z extracted to C:\Program Files and C:\Program Files\mingw64\bin added to PATH environment variable.

macOS

.
├── hello_rectangle.c
├── libglfw.3.dylib
├── libp8g.dylib
└── p8g.h

gcc hello_rectangle.c -L. -lp8g
install_name_tool -add_rpath @executable_path/. a.out
./a.out

Tested on macOS Mojave 10.14.6 with command line tools installed via xcode-select --install.

Linux

.
├── hello_rectangle.c
├── libglfw.so.3
├── libp8g.so
└── p8g.h

gcc hello_rectangle.c -L. -lp8g -Wl,-rpath=.
./a.out

Tested on Ubuntu 20.04.3 LTS with build essentials installed via sudo apt install build-essential.

Web

.
├── hello_rectangle.c
├── p8g.h
├── p8g.wasm
└── p8g.html

emcc -s MAIN_MODULE=2 -sEXPORTED_FUNCTIONS=_main -o hello_rectangle.html hello_rectangle.c p8g.wasm -s MIN_WEBGL_VERSION=2 -s MAX_WEBGL_VERSION=2 -s FULL_ES3=1 -s USE_GLFW=3 -s ALLOW_MEMORY_GROWTH=1 --shell-file p8g.html
emrun --no_browser hello_rectangle.html

Tested on macOS Mojave 10.14.6 with Emscripten SDK 3.1.17 downloaded and installed from https://emscripten.org/docs/getting_started/downloads.html.