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/internal/render_process_app.rs

@@ -0,0 +1,59 @@
+use cef::rc::{Rc, RcImpl};
+use cef::sys::{_cef_app_t, cef_base_ref_counted_t};
+use cef::{App, ImplApp, RenderProcessHandler, SchemeRegistrar, WrapApp};
+
+use super::render_process_handler::RenderProcessHandlerImpl;
+use super::scheme_handler_factory::register_schemes;
+
+pub(crate) struct RenderProcessAppImpl {
+	object: *mut RcImpl<_cef_app_t, Self>,
+	render_process_handler: RenderProcessHandler,
+}
+impl RenderProcessAppImpl {
+	pub(crate) fn app() -> App {
+		App::new(Self {
+			object: std::ptr::null_mut(),
+			render_process_handler: RenderProcessHandler::new(RenderProcessHandlerImpl::new()),
+		})
+	}
+}
+
+impl ImplApp for RenderProcessAppImpl {
+	fn on_register_custom_schemes(&self, registrar: Option<&mut SchemeRegistrar>) {
+		register_schemes(registrar);
+	}
+
+	fn render_process_handler(&self) -> Option<RenderProcessHandler> {
+		Some(self.render_process_handler.clone())
+	}
+
+	fn get_raw(&self) -> *mut _cef_app_t {
+		self.object.cast()
+	}
+}
+
+impl Clone for RenderProcessAppImpl {
+	fn clone(&self) -> Self {
+		unsafe {
+			let rc_impl = &mut *self.object;
+			rc_impl.interface.add_ref();
+		}
+		Self {
+			object: self.object,
+			render_process_handler: self.render_process_handler.clone(),
+		}
+	}
+}
+impl Rc for RenderProcessAppImpl {
+	fn as_base(&self) -> &cef_base_ref_counted_t {
+		unsafe {
+			let base = &*self.object;
+			std::mem::transmute(&base.cef_object)
+		}
+	}
+}
+impl WrapApp for RenderProcessAppImpl {
+	fn wrap_rc(&mut self, object: *mut RcImpl<_cef_app_t, Self>) {
+		self.object = object;
+	}
+}