[makspll]

Functions of the reactive ui can take dependencies: values handed back to them as their first arguments, instead of captured.

local double = ui.computed(function(n) return n:get() * 2 end, { n })     -- also effect, show, list
ui.node({ on_click = { function(selected, name) selected:set(name) end, selected, name } })
ui.element(Slot, slot, { name, entity, is_selected })                      -- slot(name, entity, is_selected)

• computed(f, deps), effect(f, deps), show(f, deps), list(items, f, deps)
• a handler or bound property is a list starting with the function: { f, a, b }
• element(Def, f, deps, key) renders a component with f(deps..) instead of a props table

Why: closures of Rune can only capture numbers and strings when handed to Rust (rune_function_to_script), not signals or entities, so without this a Rune component can only share state through the per-script state() store, one instance per component. In Lua it is optional, captures work as before.

This replaces the Lua only "function instead of props" of the first version of this PR (that form still works in Lua, it is element(Def, f) without dependencies).

Cost, same binary, 3 rounds, the Closures ui with every function taking dependencies instead of capturing:

bench	captures	dependencies
inventory mount or unmount 200	1.79 ms	2.44 ms (+37%)
inventory search	1.49 ms	1.99 ms (+33%)
inventory select	23.0 µs	24.1 µs (+5%)

The cost is the references (signals, entities) converted on every call, about ten per slot when mounting. A first version with a ui.callback(f, deps) function was +55%, each one being its own call into Rust, hence the list form. So: capture where the language can, and use row templates for large lists, which need neither.

[semanticdiff-com]

Review changes with  

Changed Files

File	Status
crates/bevy_mod_scripting_reactive_ui/src/runtime.rs	56% smaller
assets/tests/reactive_ui/inventory/inventory.lua	49% smaller
crates/bevy_mod_scripting_reactive_ui/src/lib.rs	46% smaller
assets/macro_benchmarks/reactive_ui/closures.lua	34% smaller
assets/macro_benchmarks/reactive_ui/paths.lua	34% smaller
crates/bevy_mod_scripting_reactive_ui/src/element.rs	0% smaller

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Bencher Report

Project	Bevy Scripting
Branch	agent/reactive-ui-script-props
Testbed	linux-gha

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