OpenGL GLFW GLUT SDL FLTK Allegro OpenML OpenAL SFML

 OpenGL GLFW GLUT SDL FLTK Allegro OpenML OpenAL SFML

    EGL glTF NNEF OpenCL OpenVG OpenVX OpenXR SPIR SYCL Vulkan


https://www.khronos.org/
https://en.wikipedia.org/wiki/OpenGL
https://en.wikipedia.org/wiki/List_of_game_engines
https://en.wikipedia.org/wiki/Category:3D_scenegraph_APIs
https://en.wikipedia.org/wiki/Category:Graphics_libraries
https://en.wikipedia.org/wiki/Category:3D_graphics_APIs
https://en.wikipedia.org/wiki/List_of_WebGL_frameworks

OpenGL glad   glfw   glm  SDL freeglut
Computer Graphics with OpenGL
https://caiorss.github.io/C-Cpp-Notes/computer-graphics.html

https://www.khronos.org/opengl/wiki/Related_toolkits_and_APIs

https://stackoverflow.com/questions/tagged/opengl?tab=newest&page=21

https://github.com/mroam/learnOpenGL

Unity & Unreal & Godot & GameMaker V.S. Allegro & SDL & SFML & GLFW V.S. OpenGL & DirectX & Vulkan VS writing hardware-specific machine code on stone with a chisel

Unity UE probably GameMaker 
Framework SFML SDL libGDX Filament SceneKit
Low-Level GPU Specification OpenGL DX VULKAN METAL
Window context manager GLFW 

https://learnopengl.com/
https://learnopengl.com/Getting-started/Creating-a-window
https://learnopengl.com/In-Practice/2D-Game/Breakout
https://wiki.libsdl.org/SDL2/SDL_RenderCopyEx
https://wiki.libsdl.org/SDL2/FrontPage


https://www.fiverr.com/categories/graphics-design?source=gig_category_link
Graphic Design Services - Hire a Graphic Designer Today | Fiverr


Porting my engine from SFML to SDL
https://edw.is/porting-to-sdl/

SFML Alternatives: Top 10 Game Development Tools & Similar Apps | AlternativeTo
https://alternativeto.net/software/sfml/