UXGL

UXGL.xc declares the GL 3.2-core calls a renderer makes: buffers, vertex arrays, shaders, textures, framebuffers, uniforms and their deletes, with glViewport and glGetError. A renderer imports it instead of declaring its own gl* externs, and the same source builds on every backend with GL.

#import "UXGL.xc"

A client of the installed library imports it after #use <UXKit> — the #use puts the library’s xc/ contract directory on the quote path, where the file ships as 3p/uxkit/xc/UXGL.xc — and links GL itself:

#use <UXKit>
#import "UXGL.xc"

Overview

On macOS, Linux, iOS, Android and the web the calls are the platform’s own. The build’s link line names the GL library, and only that differs between platforms:

Backend	Link
macOS (AppKit or GTK)	`-framework OpenGL`
Linux (GTK)	`-lGL`
iOS	`-framework OpenGLES`
Android	`libGLESv3.so` as a dependency of the app library
Web	nothing: the calls are host imports, backed by WebGL2
Windows	nothing: see below

opengl32.dll exports only GL 1.1, and the win64 toolchain links none of it. On win64 each call in UXGL.xc is a small function instead. The first time it is called, with a context current, it finds the real entry point through the driver’s glProc (wglGetProcAddress, else opengl32’s own export), then calls it. A call the context does not have does nothing and answers 0.

The shading language follows UXGLView.glKind: UX_GL_GL33 takes #version 150 or later, and UX_GL_GLES3 and UX_GL_WEBGL2 take #version 300 es.

To read back what was drawn, use UXGLView.snapshot after presentGL. glReadPixels cannot read a multisampled framebuffer, and on AppKit the renderer draws into one.

UXGL

Overview

See also