# hooks.ludic - the scene a frame draws, as callbacks the program registers. They used to be
# functions every program had to define by name (scene_draw, scene_draw_casters, stream_fill),
# a contract only the linker enforced and that allowed one scene per program.

# what a frame draws, for every pass that draws the scene (the view, the reflection)
function r3d_on_draw(render3d_st: mut Render3dState, f: fn()) -> void { render3d_st.r3d_draw_cb = f }
# what casts a shadow, drawn into the light's view `light_vp`
function r3d_on_casters(render3d_st: mut Render3dState, f: fn(floats)) -> void { render3d_st.r3d_casters_cb = f }
# a streamed layer's chunk (cx, cz) at detail `band`, filled with its instances
function r3d_on_stream_fill(render3d_st: mut Render3dState, f: fn(Stream, int, int, int)) -> void { render3d_st.r3d_fill_cb = f }

function r3d_scene_draw(render3d_st: Render3dState) -> void { if render3d_st.r3d_draw_cb != null { render3d_st.r3d_draw_cb() } }
function r3d_scene_casters(render3d_st: Render3dState, light_vp: floats) -> void { if render3d_st.r3d_casters_cb != null { render3d_st.r3d_casters_cb(light_vp) } }
function r3d_stream_fill(render3d_st: Render3dState, s: Stream, cx: int, cz: int, band: int) -> void { if render3d_st.r3d_fill_cb != null { render3d_st.r3d_fill_cb(s, cx, cz, band) } }