Add a pointer hover marker line to the rulers (#4088)

* Add a pointer hover marker line to the rulers

* Fix rulers and pointer marker when document is flipped

* Reduce duplicate code

* Fix ruler label placement

* Performance

editor/src/messages/frontend/frontend_message.rs

@@ -245,6 +245,7 @@ pub enum FrontendMessage {
 		interval: f64,
 		visible: bool,
 		tilt: f64,
+		flip: bool,
 	},
 	UpdateDocumentScrollbars {
 		position: (f64, f64),

editor/src/messages/portfolio/document/document_message_handler.rs

@@ -844,6 +844,7 @@ impl MessageHandler<DocumentMessage, DocumentMessageContext<'_>> for DocumentMes
 					interval: ruler_interval,
 					visible: self.rulers_visible,
 					tilt: if self.graph_view_overlay_open { 0. } else { current_ptz.tilt() },
+					flip: !self.graph_view_overlay_open && current_ptz.flip,
 				});
 			}
 			DocumentMessage::RenderScrollbars => {