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grabowski cb1b1b04c8 Desktop GUI, cross-platform reader detection

- nfc-writer is now a native egui window (Windows, macOS, Linux); the web
  version moves to the nfc-writer-web binary. Both share src/reader.rs and
  src/ndef.rs through the library crate.
- Reader choice no longer depends on the ACR1252U's Windows naming: skip SAM
  slots, prefer contactless names (PICC/Contactless/NFC/CL), then a reader
  with a card present; NFC_READER forces one by name substring.
- ATR via SCardStatus instead of SCardGetAttrib, which macOS lacks.
- Platform-specific "no reader" hints (pcscd/libccid on Linux, ACS driver on
  macOS); Thai fallback font for the GUI from the system fonts.
- Clippy clean for x86_64-pc-windows-msvc, x86_64-unknown-linux-gnu and
  aarch64-apple-darwin; README with per-OS setup and a test matrix.

2026-10-29 09:30:31 +07:00

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NFC tag writer

Programs NFC tags through a USB PC/SC reader such as the ACS ACR1252U-M1. Type a URL or some text, put a tag on the reader, press Program.

There are two ways to run it, with the same reader logic behind both:

Program	What it is
`nfc-writer`	Desktop window. No browser or network needed.
`nfc-writer-web`	Local web page at http://127.0.0.1:7252 (port: `NFC_PORT`), reachable from this machine only.

What it writes

Input that starts with http://, https://, www., tel:, mailto:, sms: or geo:, or any scheme://, becomes an NDEF link record. www. gets https:// in front.
Anything else becomes an NDEF text record (language en).
Supported tags: NTAG213, NTAG215, NTAG216 and MIFARE Ultralight / EV1 / C (NFC Forum Type 2). MIFARE Classic, DESFire and bank cards are recognised and refused with a message.
A write first empties the tag's NDEF message and writes its header last. If the tag is pulled away halfway, it ends up empty rather than holding broken data. After writing, the tag is read back and compared.

Which reader it uses

The program asks the operating system's smart-card service (PC/SC) for readers. Any PC/SC contactless reader should work, not only the ACR1252U.

It skips SAM slots (the ACR1252U shows up as two readers, … PICC and … SAM).
It prefers a reader whose name says contactless (PICC, Contactless, NFC, CL), then a reader that has a card on it.
To force a reader, set NFC_READER to part of its name, e.g. NFC_READER="ACR1252".
Plugging the reader in or out while the program runs is fine; it is picked up within a second.

Build and run

You need Rust (https://rustup.rs). Then, in this folder:

cargo run --release                      # desktop window
cargo run --release --bin nfc-writer-web # web page

The binaries end up in target/release/. Build on the operating system you want to run it on.

Windows

Nothing else to install: the smart-card service and a driver for the ACR1252U come with Windows.

macOS

Install the Xcode command line tools (xcode-select --install). macOS has the smart-card service built in. If the reader is not listed, install the ACR1252U driver from the ACS website.

Linux (Debian, Ubuntu)

sudo apt install pkg-config libpcsclite-dev pcscd libccid
sudo systemctl enable --now pcscd.socket

Fedora: sudo dnf install pkgconf pcsc-lite-devel pcsc-lite pcsc-lite-ccid. Arch: sudo pacman -S pkgconf pcsclite ccid.

Tested

	Windows 11	macOS	Linux
Builds, unit tests, clippy	yes	type-checked only	type-checked only
Finds the ACR1252U	yes	not yet	not yet
Reads and writes a tag	not yet	not yet	not yet

Code

src/ndef.rs: NDEF records and Type 2 TLVs (unit-tested).
src/reader.rs: reader choice, card type from the ATR, reading and writing tag memory.
src/main.rs: desktop window (egui).
src/bin/nfc-writer-web.rs and static/index.html: web version (axum).

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