`nx_viz_zoom.nx` source

1// nx_viz_zoom.nx -- the ZOOM math core of the sovereign Nishi viz library's INTERACTION layer (the d3-zoom
2// transform, bits-up). Transform state st[0]=k (scale, permil 1000=1x), st[1]=tx, st[2]=ty. screen = data*k/1000+t.
3// Zooming by factor f around screen point (px,py) keeps the data point under the cursor FIXED (the d3-zoom
4// invariant). Pure integer -> emits cleanly to WASM (nx_wat_compiler) for in-browser pan/zoom. Closes interact-zoom
5// (math). license_tier: ORIGINAL
6import "nx_syscalls.nx"
7
8// zoom by factor f (permil) about screen point (px,py); mutates st in place. returns new k.
9func vz_zoom(st: *i64, px: i64, py: i64, f: i64) -> i64 {
10    let tx: i64 = st[1]; let ty: i64 = st[2]
11    st[0] = st[0] * f / 1000
12    st[1] = px - ((px - tx) * f) / 1000
13    st[2] = py - ((py - ty) * f) / 1000
14    return st[0]
15}
16// pan by (dx,dy) screen pixels.
17func vz_pan(st: *i64, dx: i64, dy: i64) -> i64 { st[1] = st[1] + dx; st[2] = st[2] + dy; return 0 }
18// apply the transform: data coord -> screen coord.
19func vz_apply_x(st: *i64, dx: i64) -> i64 { return dx * st[0] / 1000 + st[1] }
20func vz_apply_y(st: *i64, dy: i64) -> i64 { return dy * st[0] / 1000 + st[2] }
21func main() -> i64 { return 0 }

nx_viz_zoom.nx source

`nx_viz_zoom.nx` source