win: Add WinConsoleInfo struct

 Parallel API to terminfo terminals is also added:
  * WinConsoleInfo::from_env()
  * WinConsole::new_with_consoleinfo()

 Just like terminfo, this allows to check if we are going to get
 errors before moving `out`.

 Related: Stebalien#57

Signed-off-by: Mohammad AlSaleh <CE.Mohammad.AlSaleh@gmail.com>

src/win.rs

@@ -32,6 +32,16 @@ use win::winapi::um::handleapi::{CloseHandle, INVALID_HANDLE_VALUE};
 use win::winapi::um::fileapi::{CreateFileA, OPEN_EXISTING};
 use win::winapi::um::winnt::{FILE_SHARE_WRITE, GENERIC_READ, GENERIC_WRITE, HANDLE};
 
+
+/// Console info which can be used by a Terminal implementation
+/// which uses the Win32 Console API.
+pub struct WinConsoleInfo {
+    def_foreground: color::Color,
+    def_background: color::Color,
+    foreground: color::Color,
+    background: color::Color,
+}
+
 /// A Terminal implementation which uses the Win32 Console API.
 pub struct WinConsole<T> {
     buf: T,
@@ -133,22 +143,10 @@ fn test_conout() {
     assert!(conout().is_ok())
 }
 
-impl<T: Write + Send> WinConsole<T> {
-    fn apply(&mut self) -> io::Result<()> {
-        let out = conout()?;
-        let _unused = self.buf.flush();
-        let mut accum: WORD = 0;
-        accum |= color_to_bits(self.foreground);
-        accum |= color_to_bits(self.background) << 4;
-        unsafe {
-            SetConsoleTextAttribute(*out, accum);
-        }
-        Ok(())
-    }
-
-    /// Returns `Err` whenever the terminal cannot be created for some
+impl WinConsoleInfo {
+    /// Returns `Err` whenever console info cannot be retrieved for some
     /// reason.
-    pub fn new(out: T) -> io::Result<WinConsole<T>> {
+    pub fn from_env() -> io::Result<()> {
         let fg;
         let bg;
         let handle = conout()?;
@@ -161,8 +159,7 @@ impl<T: Write + Send> WinConsole<T> {
                 return Err(io::Error::last_os_error());
             }
         }
-        Ok(WinConsole {
-            buf: out,
+        Ok(WinConsoleInfo {
             def_foreground: fg,
             def_background: bg,
             foreground: fg,
@@ -171,6 +168,38 @@ impl<T: Write + Send> WinConsole<T> {
     }
 }
 
+impl<T: Write + Send> WinConsole<T> {
+    fn apply(&mut self) -> io::Result<()> {
+        let out = conout()?;
+        let _unused = self.buf.flush();
+        let mut accum: WORD = 0;
+        accum |= color_to_bits(self.foreground);
+        accum |= color_to_bits(self.background) << 4;
+        unsafe {
+            SetConsoleTextAttribute(*out, accum);
+        }
+        Ok(())
+    }
+
+    /// Create a new WinConsole with the given WinConsoleInfo and out
+    pub fn new_with_consoleinfo(out: T, consoleinfo: WinConsoleInfo) -> WinConsole<T> {
+        Ok(WinConsole {
+            buf: out,
+            def_foreground: consoleinfo.def_foreground,
+            def_background: consoleinfo.def_background,
+            foreground: consoleinfo.foreground,
+            background: consoleinfo.background,
+        })
+    }
+
+    /// Returns `Err` whenever the terminal cannot be created for some
+    /// reason.
+    pub fn new(out: T) -> io::Result<WinConsole<T>> {
+        let consoleinfo = WinConsoleInfo::from_env()?;
+        Self::new_with_consoleinfo(out, consoleinfo)
+    }
+}
+
 impl<T: Write> Write for WinConsole<T> {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
         self.buf.write(buf)