app: reverse-DNS app id and the Windows executable icon

The window's Wayland app_id / X11 class is io.github.jyviko.fieldcraft, the id the release
packages use for the .desktop entry and the macOS bundle (#72). Windows builds embed
assets/app-icon/icon.ico in fieldcraft.exe through embed-resource (MIT, a build dependency only).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

Cargo.lock

@@ -1035,6 +1035,20 @@ dependencies = [
  "bytemuck",
 ]
 
+[[package]]
+name = "embed-resource"
+version = "3.0.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6168487b5e7eb2673e6efe1200b1848016e436a6ca0b8031bf04bd9d493a249f"
+dependencies = [
+ "cc",
+ "memchr",
+ "rustc_version",
+ "toml",
+ "vswhom",
+ "winreg",
+]
+
 [[package]]
 name = "endi"
 version = "1.1.1"
@@ -1177,6 +1191,7 @@ version = "0.1.0"
 dependencies = [
  "eframe",
  "egui",
+ "embed-resource",
  "fieldcraft-engine",
  "fieldcraft-io",
  "fieldcraft-ui-egui",
@@ -3206,6 +3221,15 @@ dependencies = [
  "syn 3.0.9",
 ]
 
+[[package]]
+name = "serde_spanned"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4e7523beb55eece201a2356bee0bbca0d1ab466c14c07703b2e0ee6d42cb0c2c"
+dependencies = [
+ "serde_core",
+]
+
 [[package]]
 name = "sha2"
 version = "0.10.9"
@@ -3658,6 +3682,21 @@ dependencies = [
  "pin-project-lite",
 ]
 
+[[package]]
+name = "toml"
+version = "1.1.8+spec-1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "20489e00e4d8741d6be680764cc12e270655e375a20d1011e844a9c3379e678d"
+dependencies = [
+ "indexmap",
+ "serde_core",
+ "serde_spanned",
+ "toml_datetime",
+ "toml_parser",
+ "toml_writer",
+ "winnow",
+]
+
 [[package]]
 name = "toml_datetime"
 version = "1.1.2+spec-1.1.0"
@@ -3688,6 +3727,12 @@ dependencies = [
  "winnow",
 ]
 
+[[package]]
+name = "toml_writer"
+version = "1.1.3+spec-1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "06bdbd8cfc056b8d2e2e85f29b56a3bdbecb527cef81eb39e3e7b98af4652770"
+
 [[package]]
 name = "tracing"
 version = "0.1.44"
@@ -3981,6 +4026,26 @@ version = "0.9.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"
 
+[[package]]
+name = "vswhom"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "be979b7f07507105799e854203b470ff7c78a1639e330a58f183b5fea574608b"
+dependencies = [
+ "libc",
+ "vswhom-sys",
+]
+
+[[package]]
+name = "vswhom-sys"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fb067e4cbd1ff067d1df46c9194b5de0e98efd2810bbc95c5d5e5f25a3231150"
+dependencies = [
+ "cc",
+ "libc",
+]
+
 [[package]]
 name = "walkdir"
 version = "2.5.0"
@@ -4750,6 +4815,16 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "winreg"
+version = "0.56.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7d6f32a0ff4a9f6f01231eb2059cc85479330739333e0e58cadf03b6af2cca10"
+dependencies = [
+ "cfg-if",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "wit-bindgen"
 version = "0.57.1"

apps/fieldcraft/Cargo.toml

@@ -18,3 +18,7 @@ eframe = { workspace = true, features = ["default_fonts", "wgpu", "accesskit", "
 egui = { workspace = true }
 serde_json = { workspace = true }
 log = { workspace = true }
+
+[build-dependencies]
+# The Windows executable's icon resource (build.rs).
+embed-resource = "3.0.12"

apps/fieldcraft/build.rs

@@ -0,0 +1,20 @@
+//! Windows builds embed the application icon (assets/app-icon/icon.ico) in `fieldcraft.exe`, so
+//! Explorer, the taskbar and shortcuts show it. Other targets need nothing here.
+#![forbid(unsafe_code)]
+
+use std::path::PathBuf;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let icon = PathBuf::from(std::env::var("CARGO_MANIFEST_DIR")?).join("../../assets/app-icon/icon.ico");
+    println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-changed={}", icon.display());
+    if std::env::var("CARGO_CFG_TARGET_OS")? != "windows" {
+        return Ok(());
+    }
+    let out = PathBuf::from(std::env::var("OUT_DIR")?);
+    let rc = out.join("fieldcraft.rc");
+    std::fs::write(&rc, format!("1 ICON \"{}\"\n", icon.display().to_string().replace('\\', "/")))?;
+    // Missing resource tools are a build error, rather than silently shipping a generic icon.
+    embed_resource::compile_for(&rc, ["fieldcraft"], embed_resource::NONE).manifest_required()?;
+    Ok(())
+}

apps/fieldcraft/src/main.rs

@@ -22,6 +22,9 @@ const DEPTH_BITS: u8 = 24;
 /// The window draws its own caption buttons where the OS ones would sit apart from the app bar.
 const CUSTOM_TITLEBAR: bool = !cfg!(target_os = "macos");
 const MSAA: u16 = 4;
+/// The reverse-DNS application id: the Wayland app_id / X11 class, matched to the packaged
+/// `.desktop` entry (packaging/linux), and the macOS bundle id (packaging/macos/Info.plist.in).
+const APP_ID: &str = "io.github.jyviko.fieldcraft";
 
 /// The window and Dock icon: the 256 px export of the application icon (assets/app-icon).
 const ICON_PNG: &[u8] = include_bytes!("../../../assets/app-icon/icon.iconset/icon_128x128@2x.png");
@@ -148,6 +151,7 @@ fn main() -> eframe::Result {
     let options = eframe::NativeOptions {
         viewport: egui::ViewportBuilder::default()
             .with_title("FieldCraft")
+            .with_app_id(APP_ID)
             .with_icon(app_icon())
             .with_inner_size([1400.0, 900.0])
             .with_min_inner_size([960.0, 600.0])