feat: use ShellExecuteW for detached spawning on Windows

src/lib.rs

@@ -237,16 +237,24 @@ pub fn with_in_background<T: AsRef<OsStr>>(
 ///
 /// See documentation of [`that()`] for more details.
 pub fn that_detached(path: impl AsRef<OsStr>) -> io::Result<()> {
-    let mut last_err = None;
-    for mut cmd in commands(path) {
-        match cmd.spawn_detached() {
-            Ok(_) => {
-                return Ok(());
+    #[cfg(not(windows))]
+    {
+        let mut last_err = None;
+        for mut cmd in commands(path) {
+            match cmd.spawn_detached() {
+                Ok(_) => {
+                    return Ok(());
+                }
+                Err(err) => last_err = Some(err),
             }
-            Err(err) => last_err = Some(err),
         }
+        Err(last_err.expect("no launcher worked, at least one error"))
+    }
+
+    #[cfg(windows)]
+    {
+        windows::that_detached(path)
     }
-    Err(last_err.expect("no launcher worked, at least one error"))
 }
 
 /// Open path with the given application using a detached process, which is useful if
@@ -255,8 +263,16 @@ pub fn that_detached(path: impl AsRef<OsStr>) -> io::Result<()> {
 ///
 /// See documentation of [`with()`] for more details.
 pub fn with_detached<T: AsRef<OsStr>>(path: T, app: impl Into<String>) -> io::Result<()> {
-    let mut cmd = with_command(path, app);
-    cmd.spawn_detached()
+    #[cfg(not(windows))]
+    {
+        let mut cmd = with_command(path, app);
+        cmd.spawn_detached()
+    }
+
+    #[cfg(windows)]
+    {
+        windows::with_detached(path, app)
+    }
 }
 
 trait IntoResult<T> {

src/windows.rs

@@ -1,6 +1,9 @@
 use std::{
     ffi::{OsStr, OsString},
+    io, iter,
+    os::windows::ffi::OsStrExt,
     process::Command,
+    ptr,
 };
 
 use std::os::windows::process::CommandExt;
@@ -35,3 +38,91 @@ fn wrap_in_quotes<T: AsRef<OsStr>>(path: T) -> OsString {
 
     result
 }
+
+pub fn that_detached<T: AsRef<OsStr>>(path: T) -> std::io::Result<()> {
+    let path = wide(path);
+
+    unsafe {
+        ShellExecuteW(
+            0,
+            ffi::OPEN,
+            path.as_ptr(),
+            ptr::null(),
+            ptr::null(),
+            ffi::SW_SHOW,
+        )
+    }
+}
+
+pub fn with_detached<T: AsRef<OsStr>>(path: T, app: impl Into<String>) -> std::io::Result<()> {
+    let app = wide(app.into());
+    let path = wide(path);
+
+    unsafe {
+        ShellExecuteW(
+            0,
+            ffi::OPEN,
+            app.as_ptr(),
+            path.as_ptr(),
+            ptr::null(),
+            ffi::SW_SHOW,
+        )
+    }
+}
+
+/// Encodes as wide and adds a null character.
+fn wide<T: AsRef<OsStr>>(input: T) -> Vec<u16> {
+    input.as_ref().encode_wide().chain(iter::once(0)).collect()
+}
+
+/// Performs an operation on a specified file.
+///
+/// <https://learn.microsoft.com/en-us/windows/win32/api/shellapi/nf-shellapi-shellexecutew>
+#[allow(non_snake_case)]
+pub unsafe fn ShellExecuteW(
+    hwnd: isize,
+    lpoperation: *const u16,
+    lpfile: *const u16,
+    lpparameters: *const u16,
+    lpdirectory: *const u16,
+    nshowcmd: i32,
+) -> std::io::Result<()> {
+    let hr = ffi::ShellExecuteW(
+        hwnd,
+        lpoperation,
+        lpfile,
+        lpparameters,
+        lpdirectory,
+        nshowcmd,
+    );
+
+    // ShellExecuteW returns > 32 on success
+    // https://learn.microsoft.com/en-us/windows/win32/api/shellapi/nf-shellapi-shellexecutew#return-value
+    if hr > 32 {
+        Ok(())
+    } else {
+        Err(io::Error::last_os_error())
+    }
+}
+
+mod ffi {
+    /// Activates the window and displays it in its current size and position.
+    ///
+    /// <https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-showwindow>
+    pub const SW_SHOW: i32 = 5;
+
+    /// Null-terminated UTF-16 encoding of `open`.  
+    pub const OPEN: *const u16 = [111, 112, 101, 110, 0].as_ptr();
+
+    #[link(name = "Shell32")]
+    extern "C" {
+        pub fn ShellExecuteW(
+            hwnd: isize,
+            lpoperation: *const u16,
+            lpfile: *const u16,
+            lpparameters: *const u16,
+            lpdirectory: *const u16,
+            nshowcmd: i32,
+        ) -> i32;
+    }
+}