nushell/crates/nu-ansi-term/src/windows.rs

/// Enables ANSI code support on Windows 10.
///
/// This uses Windows API calls to alter the properties of the console that
/// the program is running in.
///
/// https://msdn.microsoft.com/en-us/library/windows/desktop/mt638032(v=vs.85).aspx
///
/// Returns a `Result` with the Windows error code if unsuccessful.
#[cfg(windows)]
pub fn enable_ansi_support() -> Result<(), u32> {
    // ref: https://docs.microsoft.com/en-us/windows/console/console-virtual-terminal-sequences#EXAMPLE_OF_ENABLING_VIRTUAL_TERMINAL_PROCESSING @@ https://archive.is/L7wRJ#76%

    use std::ffi::OsStr;
    use std::iter::once;
    use std::os::windows::ffi::OsStrExt;
    use std::ptr::null_mut;
    use winapi::um::consoleapi::{GetConsoleMode, SetConsoleMode};
    use winapi::um::errhandlingapi::GetLastError;
    use winapi::um::fileapi::{CreateFileW, OPEN_EXISTING};
    use winapi::um::handleapi::INVALID_HANDLE_VALUE;
    use winapi::um::winnt::{FILE_SHARE_WRITE, GENERIC_READ, GENERIC_WRITE};

    const ENABLE_VIRTUAL_TERMINAL_PROCESSING: u32 = 0x0004;

    unsafe {
        // ref: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilew
        // Using `CreateFileW("CONOUT$", ...)` to retrieve the console handle works correctly even if STDOUT and/or STDERR are redirected
        let console_out_name: Vec<u16> =
            OsStr::new("CONOUT$").encode_wide().chain(once(0)).collect();
        let console_handle = CreateFileW(
            console_out_name.as_ptr(),
            GENERIC_READ | GENERIC_WRITE,
            FILE_SHARE_WRITE,
            null_mut(),
            OPEN_EXISTING,
            0,
            null_mut(),
        );
        if console_handle == INVALID_HANDLE_VALUE {
            return Err(GetLastError());
        }

        // ref: https://docs.microsoft.com/en-us/windows/console/getconsolemode
        let mut console_mode: u32 = 0;
        if 0 == GetConsoleMode(console_handle, &mut console_mode) {
            return Err(GetLastError());
        }

        // VT processing not already enabled?
        if console_mode & ENABLE_VIRTUAL_TERMINAL_PROCESSING == 0 {
            // https://docs.microsoft.com/en-us/windows/console/setconsolemode
            if 0 == SetConsoleMode(
                console_handle,
                console_mode | ENABLE_VIRTUAL_TERMINAL_PROCESSING,
            ) {
                return Err(GetLastError());
            }
        }
    }

    Ok(())
}