Desktop: Isolate CEF-rendered UI into separate crate and process (#4321)

* Extract CEF rendered UI into a separate process and crate

* Review

* Review

* Review

* Review

* Remove necessary workarounds

* Block on frame copy ack

* Crop and resample frames correctly

* Skip blank frames

* Fix deps

* Fix fmt

* Fix clippy warning

* Review

* Fix todo

desktop/ui/src/dirs.rs

@@ -0,0 +1,50 @@
+use std::fs;
+use std::io;
+use std::path::{Path, PathBuf};
+
+#[cfg(target_os = "linux")]
+const APP_DIRECTORY_NAME: &str = "graphite";
+#[cfg(not(target_os = "linux"))]
+const APP_DIRECTORY_NAME: &str = "Graphite";
+
+pub(crate) fn app_tmp_dir() -> PathBuf {
+	let path = std::env::temp_dir().join(APP_DIRECTORY_NAME);
+	if let Err(e) = fs::create_dir_all(&path) {
+		tracing::error!("Failed to create temp directory at {path:?}: {e}");
+	}
+	path
+}
+
+/// Temporary directory that is automatically deleted when dropped.
+pub struct TempDir {
+	path: PathBuf,
+}
+
+impl TempDir {
+	pub fn new() -> io::Result<Self> {
+		Self::new_with_parent(app_tmp_dir())
+	}
+
+	pub fn new_with_parent(parent: impl AsRef<Path>) -> io::Result<Self> {
+		let random_suffix = format!("{:032x}", rand::random::<u128>());
+		let name = format!("{}_{}", std::process::id(), random_suffix);
+		let path = parent.as_ref().join(name);
+		fs::create_dir_all(&path)?;
+		Ok(Self { path })
+	}
+}
+
+impl Drop for TempDir {
+	fn drop(&mut self) {
+		let result = fs::remove_dir_all(&self.path);
+		if let Err(e) = result {
+			tracing::error!("Failed to remove temporary directory at {:?}: {}", self.path, e);
+		}
+	}
+}
+
+impl AsRef<Path> for TempDir {
+	fn as_ref(&self) -> &Path {
+		&self.path
+	}
+}