back

Back, and the claims a world holds on it. Backs Zin.back.

Back is the platform's own Back: Android's Back button and back gesture, and a keyboard's Back key (BrowserBack, which a browser names the same). A world binds any control of its own to it with Zin.back.press, which is how Escape or a pad's button becomes Back too.

The engine routes every Back press to the first of these that stands:

1. the topmost overlay on screen that states how it is dismissed: an open popup carrying onDismiss, or an open, dismissible modal carrying onClose. Its dismissal runs, the way Escape runs it.
2. the claim held that takes it (Zin.back.claim: the highest priority, and the most recent among equals): its handler runs.
3. nothing: the platform's own default answers. On Android the app moves to the background; a desktop window and a browser page stay where they are.

A claim says ahead of the press that the world takes Back, which is what Android's predictive back asks for: the system decides before a back gesture begins whether it previews going home. Hold a claim while Back means something to the world and release it when Back should leave.

Every press is a back event in input.events(): { kind = "back", taker = "overlay" | "claim" | "none" }.

Exports

• M.claim(handler, { priority? }) -> Claim: take Back. Of the claims held, the highest priority (0 when omitted) takes a press no overlay takes, and the most recent among equals. The editor's claim that leaves play is held at -1, under every claim a played world makes. claim:release() gives it up, claim:held() says whether it is held. A claim a component makes is released when its entity is destroyed.
• M.press(): press Back, routed as above.
• M.claims() -> number: how many claims are held.

Usage

local Zin = require("@builtin::modules.zinput")

local claim
local function closeMenu()
    menu.close()
    if claim then claim:release() claim = nil end
end
local function openMenu()
    menu.open()
    claim = Zin.back.claim(closeMenu)
end

-- Escape as Back too, through the world's own control.
controls.pause:onPressed(Zin.back.press)