metal:frame

(metal:frame ctx fn)

Draws one frame: takes the next drawable, clears it, calls fn with the render command encoder so the program can set its pipeline and draw, then presents and commits. fn runs on the main thread. When the layer has no drawable free the frame is skipped, which is what a dropped frame is. Part of the metal package, a Metal drawing surface written in rontolisp over objc and loaded on first use: macOS (java -jar, the rontolisp binary, or a compiled .class / .jar; never a .wasm), with a display. See the macOS GUI guide.

CL-USER> (metal:frame *ctx*
    (lambda (encoder)
      (objc:send encoder "setRenderPipelineState:" *solid*)
      (objc:send encoder "drawPrimitives:vertexStart:vertexCount:" metal:+triangle+ 0 3)))