fix(master): keep the scroll position when toggling auto mode on the overview (#34)

internal/master/web/server.go

@@ -628,6 +628,10 @@ func (s *Server) setMode(w http.ResponseWriter, r *http.Request) {
 		}
 		var nu *model.NotUpdatableError
 		if err := s.jobs.AutoAllowed(svc); errors.As(err, &nu) {
+			if isHTMX(r) {
+				// htmx does not swap a 409; the service page shows the reason.
+				w.Header().Set("HX-Redirect", "/services/"+strconv.FormatInt(id, 10))
+			}
 			s.renderServiceError(w, r, id, http.StatusConflict, "Cannot enable auto: "+nu.Reason+".")
 			return
 		} else if err != nil {
@@ -641,6 +645,11 @@ func (s *Server) setMode(w http.ResponseWriter, r *http.Request) {
 	}
 	s.broker.Publish(events.Services)
 	if r.PostFormValue("return") == "overview" {
+		if isHTMX(r) {
+			// Swap the list in place instead of redirecting, so the page keeps its scroll position.
+			s.servicesFragment(w, r)
+			return
+		}
 		http.Redirect(w, r, "/", http.StatusSeeOther)
 		return
 	}
@@ -881,6 +890,11 @@ func (s *Server) fail(w http.ResponseWriter, err error) {
 	http.Error(w, "internal error", http.StatusInternalServerError)
 }
 
+// isHTMX reports whether r was sent by htmx rather than by a plain form submit.
+func isHTMX(r *http.Request) bool {
+	return r.Header.Get("HX-Request") == "true"
+}
+
 // agentSnippet is the compose file shown once when an agent is added.
 func agentSnippet(cfg Config, token string) string {
 	return fmt.Sprintf(`services: