Switch backend with cargo features

Use `termion` feature and disable default features to use the termion
backend.

Cargo.toml

@@ -16,7 +16,7 @@ skeptic = "0.6"
 
 [dependencies]
 odds = "0.2"
-termion = "1.1.1"
+termion = {version="1.1.1", optional=true}
 toml = "0.2"
 unicode-segmentation = "0.1"
 unicode-width = "0.1"
@@ -24,6 +24,7 @@ unicode-width = "0.1"
 [dependencies.ncurses]
 features = ["wide"]
 version = "5.82.0"
+optional=true
 
 [dev-dependencies]
 rand = "0.3"
@@ -31,3 +32,6 @@ skeptic = "0.6"
 
 [lib]
 name = "cursive"
+
+[features]
+default = ["ncurses"]

src/backend/mod.rs

@@ -2,11 +2,10 @@ use event;
 use theme;
 
 // Module is not named `ncurses` to avoir naming conflict
-mod curses;
-mod termion;
-
-pub use self::curses::NcursesBackend;
-pub use self::termion::TermionBackend;
+#[cfg(feature = "ncurses")]
+pub mod curses;
+#[cfg(feature = "termion")]
+pub mod termion;
 
 pub trait Backend {
     fn init() -> Self;

src/lib.rs

@@ -56,12 +56,15 @@
 //! and log to it instead of stdout.
 #![deny(missing_docs)]
 
+#[cfg(feature = "ncurses")]
 extern crate ncurses;
+#[cfg(feature = "termion")]
+extern crate termion;
+
 extern crate toml;
 extern crate unicode_segmentation;
 extern crate unicode_width;
 extern crate odds;
-extern crate termion;
 
 macro_rules! println_stderr(
     ($($arg:tt)*) => { {
@@ -155,8 +158,13 @@ new_default!(Cursive);
 
 // Use the Ncurses backend.
 // TODO: make this feature-driven
+#[cfg(feature = "termion")]
 #[doc(hidden)]
-pub type B = backend::TermionBackend;
+pub type B = backend::termion::TermionBackend;
+
+#[doc(hidden)]
+#[cfg(feature = "ncurses")]
+pub type B = backend::curses::NcursesBackend;
 
 impl Cursive {
     /// Creates a new Cursive root, and initialize ncurses.