Flamegraph widget

Reusable icicle-flamegraph widget over Z.canvas. Engine-agnostic — consumes anything shaped like { stacks = { { stack, self_us }, ... } }, which is exactly what luau_profile.snapshot() returns. Drop into any tab that has folded-stack data; the Rust side never sees this module, the engine just paints whatever rect / text canvas commands come out.

API

local Flame = require("@builtin::modules.ui.flamegraph")

local view = Flame.build({
    snapshot = luau_profile.snapshot(),
    width    = 720,
    height   = 280,
    search   = "physics",            -- optional: dim non-matching frames
    onClick  = "my-tab/flame-click", -- optional: forwarded to canvas event
})

Returns a single Z.canvas node ready to mount under any parent.

Frame format

The stack string per StackEntry is ;-separated frames; each frame is short_src,name,linedefined,currentline (the wire format emitted by the engine's sampler), innermost frame first. currentline is the line executing when the sampler caught the stack, which splits long functions into per-line hot spots. Native work a Luau call reached appears as a [C],<binding>,, frame under the Luau that called it, and time with no Luau running as the single frame [engine],native,,.

Layout

Top-down icicle. Row 0 = whole sampled time. Each row below = its callees, widths proportional to their share of the parent's total. Matches Brendan Gregg's flamegraph convention and tools/perfgraph.py.

Colour

Stable hash of the source-file basename, mapped into a warm palette. Two frames from the same file always get the same colour, so visual scanning across rows lines up.

Other consumers

Anywhere folded-stack data shows up. Network timings, GPU passes, arbitrary nested timing trees — they all benefit from the same visualisation. The widget knows nothing about the Luau profiler specifically.