GL version defines for main templates / PG

[danoli3]

OpenGL / WebGL version selection

Projects can now choose which graphics version they want without editing openFrameworks core files or main.mm.

The Project Generator provides dropdowns and automatically adds the required define to the generated project.

• Emscripten / Web: OF_WEBGL_VERSION=1 or 2
  Default: WebGL 2
  • WebGL 1 automatically uses the ES2 Emscripten flags.
  • WebGL 2 uses the existing ES3 flags.
  • Shader setup remains compatible with both.
• iOS / tvOS: OF_GLES_VERSION=1, 2, or 3
  Default: OpenGL ES 2
  • New projects use the define to select the GLES version.
  • Existing projects that explicitly select ES2 in main.mm keep working unchanged.
• Desktop: OF_GL_VERSION_MAJOR + OF_GL_VERSION_MINOR
  Default: OpenGL 2.1, unchanged.
  • Example: OF_GL_VERSION_MAJOR=4 and OF_GL_VERSION_MINOR=6 selects OpenGL 4.6.
  • This removes the need for separate GL 3.1–4.5 templates.
  • Both defines must be provided; otherwise the project keeps its existing/default behaviour.

[danoli3]

Everything will still continue as normal, this just adds more depth to the projectGenerators ability to define OpenGL versions