1 files changed, 99 insertions, 0 deletions
diff --git a/crates/platform/src/lib.rs b/crates/platform/src/lib.rs
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+++ b/crates/platform/src/lib.rs
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+//! Platform abstraction: the trait every backend (X11, Wayland, Windows,
+//! macOS) implements, plus auto-detection of which backend to use.
+//!
+//! This mirrors the intent of the legacy C++ `Platform` interface
+//! (see docs/PRIOR_ART.md) with one deliberate change: `poll_events` is the
+//! only place backends need to bridge their native event model (X11's
+//! blocking `XNextEvent`, Wayland's callback-driven dispatch, Win32's message
+//! pump, macOS's event taps) into the common [`srdwm_core::Event`] queue -
+//! everything downstream of that is platform-independent.
+
+use srdwm_core::{Monitor, Rect, Window, WindowId};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum PlatformKind {
+    X11,
+    Wayland,
+    Windows,
+    MacOS,
+}
+
+impl PlatformKind {
+    pub fn name(self) -> &'static str {
+        match self {
+            PlatformKind::X11 => "x11",
+            PlatformKind::Wayland => "wayland",
+            PlatformKind::Windows => "windows",
+            PlatformKind::MacOS => "macos",
+        }
+    }
+}
+
+/// Chooses a backend the way the legacy `PlatformFactory` did: prefer
+/// Wayland when a compositor is reachable, fall back to X11, otherwise use
+/// the compile-time native backend on Windows/macOS.
+pub fn detect() -> PlatformKind {
+    #[cfg(target_os = "windows")]
+    {
+        return PlatformKind::Windows;
+    }
+    #[cfg(target_os = "macos")]
+    {
+        return PlatformKind::MacOS;
+    }
+    #[cfg(all(unix, not(target_os = "macos")))]
+    {
+        let wayland = std::env::var_os("WAYLAND_DISPLAY").is_some()
+            || std::env::var("XDG_SESSION_TYPE").map(|v| v == "wayland").unwrap_or(false);
+        if wayland {
+            PlatformKind::Wayland
+        } else {
+            PlatformKind::X11
+        }
+    }
+}
+
+#[derive(thiserror::Error, Debug)]
+pub enum PlatformError {
+    #[error("failed to connect to display server: {0}")]
+    ConnectionFailed(String),
+    #[error("another window manager is already running")]
+    AnotherWmRunning,
+    #[error("unsupported operation on this platform: {0}")]
+    Unsupported(&'static str),
+    #[error("{0}")]
+    Other(String),
+}
+
+pub type Result<T> = std::result::Result<T, PlatformError>;
+
+/// A platform backend: owns the connection to the display server and
+/// translates between real surfaces/windows and srdwm-core's `Window` state.
+pub trait Platform {
+    fn kind(&self) -> PlatformKind;
+
+    /// Blocks until at least one event is available (or a short timeout
+    /// elapses), then drains everything currently pending.
+    fn poll_events(&mut self) -> Result<Vec<srdwm_core::Event>>;
+
+    fn monitors(&mut self) -> Result<Vec<Monitor>>;
+
+    fn apply_geometry(&mut self, window: WindowId, geometry: Rect) -> Result<()>;
+    fn set_title(&mut self, window: WindowId, title: &str) -> Result<()>;
+    fn focus(&mut self, window: WindowId) -> Result<()>;
+    fn minimize(&mut self, window: WindowId) -> Result<()>;
+    fn restore(&mut self, window: WindowId) -> Result<()>;
+    fn close(&mut self, window: WindowId) -> Result<()>;
+
+    fn set_decorated(&mut self, window: WindowId, decorated: bool) -> Result<()>;
+    fn set_border_color(&mut self, window: WindowId, rgb: (u8, u8, u8)) -> Result<()>;
+    fn set_border_width(&mut self, window: WindowId, width: u32) -> Result<()>;
+
+    /// Redraws the decoration (titlebar + buttons) for `window`, e.g. after
+    /// a focus change or resize. No-op on platforms with native
+    /// decorations (Windows/macOS).
+    fn redraw_decoration(&mut self, window: WindowId, win: &Window, focused: bool) -> Result<()>;
+
+    fn grab_keyboard(&mut self) -> Result<()>;
+    fn ungrab_keyboard(&mut self) -> Result<()>;
+}