Ely Office: six offline-first desktop apps in Rust and GPUI

ElyDoc, ElyTable, ElyShow (LibreOfficeKit), ElyPDF (MuPDF), ElyTree (Git),
ElyMark (Milkdown and CodeMirror in CEF). ElyMail and ElyAgent follow.

crates/ely-platform/src/graphics.rs

@@ -0,0 +1,25 @@
+use anyhow::Result;
+
+/// Fails when no graphics device exists; probed on macOS only.
+pub fn check() -> Result<()> {
+    #[cfg(target_os = "macos")]
+    {
+        let devices = metal::Device::all();
+        anyhow::ensure!(
+            !devices.is_empty() || metal::Device::system_default().is_some(),
+            "no Metal graphics device was found"
+        );
+        log::info!("graphics: {} Metal device(s)", devices.len());
+    }
+    #[cfg(not(target_os = "macos"))]
+    log::info!("graphics: the backend is not probed on this OS");
+    Ok(())
+}
+
+#[cfg(all(test, target_os = "macos"))]
+mod tests {
+    #[test]
+    fn this_mac_has_a_metal_device() {
+        super::check().unwrap();
+    }
+}