From 38c969db1b39badf9d58c72dc954bb25c954d30e Mon Sep 17 00:00:00 2001
From: mtkennerly <mtkennerly@gmail.com>
Date: Tue, 19 Mar 2024 17:40:59 -0400
Subject: [PATCH] test

---
 src/main.rs | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)

diff --git a/src/main.rs b/src/main.rs
index 0361d25..be978fb 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -47,6 +47,72 @@ fn prepare_logging() -> Result<flexi_logger::LoggerHandle, flexi_logger::FlexiLo
         .start()
 }
 
+/// Detach the current process from its console on Windows.
+///
+/// ## Testing
+/// This has several edge cases and has been the source of multiple bugs.
+/// If you change this, be careful and make sure to test this matrix:
+///
+/// * Arguments:
+///   * None (double click in Windows Explorer)
+///   * None (from console)
+///   * `--help` (has output, but before this function is called)
+///   * `backup --preview` (has output, after this function is called)
+/// * Consoles:
+///   * Command Prompt
+///   * PowerShell
+///   * Git Bash
+/// * Console host for double clicking in Windows Explorer:
+///   * Windows Console Host
+///   * Windows Terminal
+///
+/// ## Alternatives
+/// We have tried `#![windows_subsystem = "windows"]` plus `AttachConsole`/`AllocConsole`,
+/// but that messes up the console output in Command Prompt and PowerShell
+/// (a new prompt line is shown, and then the output bleeds into that line).
+///
+/// We have tried relaunching the program with a special environment variable,
+/// but that eventually raised a false positive from Windows Defender (`Win32/Wacapew.C!ml`).
+///
+/// We may eventually want to try using a manifest to set `<consoleAllocationPolicy>`,
+/// but that is not yet widely available:
+/// https://github.com/microsoft/terminal/blob/5383cb3a1bb8095e214f7d4da085ea4646db8868/doc/specs/%237335%20-%20Console%20Allocation%20Policy.md
+///
+/// ## Considerations
+/// The current approach is to let the console appear and then immediately `FreeConsole`.
+/// Previously, Windows Terminal wouldn't remove the console in that case,
+/// but that has been fixed: https://github.com/microsoft/terminal/issues/16174
+///
+/// There was also an issue where asynchronous Rclone commands would fail to spawn
+/// ("The request is not supported (os error 50)"),
+/// but that has been solved by resetting the standard device handles:
+/// https://github.com/rust-lang/rust/issues/113277
+#[cfg(target_os = "windows")]
+unsafe fn detach_console() {
+    use winapi::um::{
+        processenv::SetStdHandle,
+        winbase::{STD_ERROR_HANDLE, STD_INPUT_HANDLE, STD_OUTPUT_HANDLE},
+        wincon::FreeConsole,
+    };
+
+    if FreeConsole() == 0 {
+        eprintln!("Unable to detach the console");
+        std::process::exit(1);
+    }
+    if SetStdHandle(STD_INPUT_HANDLE, std::ptr::null_mut()) == 0 {
+        eprintln!("Unable to reset stdin handle");
+        std::process::exit(1);
+    }
+    if SetStdHandle(STD_OUTPUT_HANDLE, std::ptr::null_mut()) == 0 {
+        eprintln!("Unable to reset stdout handle");
+        std::process::exit(1);
+    }
+    if SetStdHandle(STD_ERROR_HANDLE, std::ptr::null_mut()) == 0 {
+        eprintln!("Unable to reset stderr handle");
+        std::process::exit(1);
+    }
+}
+
 fn main() {
     let args = cli::parse();
     if let Some(config_dir) = args.config.as_deref() {
@@ -54,6 +120,14 @@ fn main() {
     }
     match args.sub {
         None => {
+            #[cfg(target_os = "windows")]
+            if std::env::var(crate::prelude::ENV_DEBUG).is_err() {
+                unsafe {
+                    detach_console();
+                }
+            }
+
+            // We must do this after detaching the console, or else it will still be present, somehow.
             #[allow(unused)]
             let logger = prepare_logging();