Introduce `Program` and `State`

1 files changed, 39 insertions, 0 deletions

diff --git a/native/src/program.rs b/native/src/program.rs
new file mode 100644
index 00000000..2652dee9
--- /dev/null
+++ b/native/src/program.rs
@@ -0,0 +1,39 @@
+//! Build interactive programs using The Elm Architecture.
+use crate::{Command, Element, Renderer};
+
+mod state;
+
+pub use state::State;
+
+/// An interactive, native cross-platform program.
+pub trait Program: Sized {
+    /// The graphics backend to use to draw the [`Program`].
+    ///
+    /// [`Program`]: trait.Program.html
+    type Renderer: Renderer;
+
+    /// The type of __messages__ your [`Program`] will produce.
+    ///
+    /// [`Application`]: trait.Program.html
+    type Message: std::fmt::Debug + Send;
+
+    /// Handles a __message__ and updates the state of the [`Program`].
+    ///
+    /// This is where you define your __update logic__. All the __messages__,
+    /// produced by either user interactions or commands, will be handled by
+    /// this method.
+    ///
+    /// Any [`Command`] returned will be executed immediately in the
+    /// background by shells.
+    ///
+    /// [`Program`]: trait.Application.html
+    /// [`Command`]: struct.Command.html
+    fn update(&mut self, message: Self::Message) -> Command<Self::Message>;
+
+    /// Returns the widgets to display in the [`Program`].
+    ///
+    /// These widgets can produce __messages__ based on user interaction.
+    ///
+    /// [`Program`]: trait.Application.html
+    fn view(&mut self) -> Element<'_, Self::Message, Self::Renderer>;
+}