Misc · Codes and checks: a QR code scanner and a captcha

misc::QrCodeScanner reads QR codes with rqrr 0.11 from the frames the
host hands in, one at a time off the main thread, and hands each code
to the owner once. misc::Captcha shows the owner's picture over an
answer field that empties and keeps focus with each answer; the owner
says how it stood. BarcodeDisplay, Signature and Rating Widget point
to their homes.

Cargo.lock

@@ -1601,6 +1601,7 @@ dependencies = [
  "qrcode",
  "raw-window-handle",
  "regex",
+ "rqrr",
  "rust-embed",
  "rustix 1.1.5",
  "serde",
@@ -1916,6 +1917,12 @@ version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d9c4f5dac5e15c24eb999c26181a6ca40b39fe946cbe4c263c7209467bc83af2"
 
+[[package]]
+name = "foldhash"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "77ce24cb58228fbb8aa041425bb1050850ac19177686ea6e0f41a70416f56fdb"
+
 [[package]]
 name = "font-types"
 version = "0.12.5"
@@ -2135,6 +2142,34 @@ dependencies = [
  "slab",
 ]
 
+[[package]]
+name = "g2gen"
+version = "1.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c5a7e0eb46f83a20260b850117d204366674e85d3a908d90865c78df9a6b1dfc"
+dependencies = [
+ "g2poly",
+ "proc-macro2",
+ "quote",
+ "syn 2.0.119",
+]
+
+[[package]]
+name = "g2p"
+version = "1.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "539e2644c030d3bf4cd208cb842d2ce2f80e82e6e8472390bcef83ceba0d80ad"
+dependencies = [
+ "g2gen",
+ "g2poly",
+]
+
+[[package]]
+name = "g2poly"
+version = "1.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "312d2295c7302019c395cfb90dacd00a82a2eabd700429bba9c7a3f38dbbe11b"
+
 [[package]]
 name = "generic-array"
 version = "0.14.7"
@@ -2608,7 +2643,7 @@ version = "0.15.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9229cfe53dfd69f0609a49f65461bd93001ea1ef889cd5529dd176593f5338a1"
 dependencies = [
- "foldhash",
+ "foldhash 0.1.5",
 ]
 
 [[package]]
@@ -2616,6 +2651,9 @@ name = "hashbrown"
 version = "0.17.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ed5909b6e89a2db4456e54cd5f673791d7eca6732202bbf2a9cc504fe2f9b84a"
+dependencies = [
+ "foldhash 0.2.0",
+]
 
 [[package]]
 name = "heck"
@@ -3345,6 +3383,15 @@ dependencies = [
  "imgref",
 ]
 
+[[package]]
+name = "lru"
+version = "0.18.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ef9ac18847474e638e3702b76c65d4eb93428471a74778ef0f1be711717f89b5"
+dependencies = [
+ "hashbrown 0.17.1",
+]
+
 [[package]]
 name = "lru-slab"
 version = "0.1.3"
@@ -4819,6 +4866,16 @@ version = "0.20.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6c20b6793b5c2fa6553b250154b78d6d0db37e72700ae35fad9387a46f487c97"
 
+[[package]]
+name = "rqrr"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8d084c50c5cfa397a081850da329566c8667b0b6c4e81da16abff1fef27de93b"
+dependencies = [
+ "g2p",
+ "lru",
+]
+
 [[package]]
 name = "rust-embed"
 version = "8.12.0"