public boolean isLoginFormUsernameInputDisabled(final WebEngineContext vars) {
        val requestContext = RequestContextHolder.getRequestContext();
        return requestContext == null || !WebUtils.isCasLoginFormViewable(requestContext)
               || WebUtils.isGraphicalUserAuthenticationEnabled(requestContext)
               || webflowExecutionPlan.getWebflowLoginContextProviders()
                   .stream()
                   .anyMatch(provider -> provider.isLoginFormUsernameInputDisabled(requestContext));
    }
Is login form username input disabled.

@param vars the vars
@return true/false
support/cas-server-support-thymeleaf-core/src/main/java/org/apereo/cas/services/web/CasThymeleafTemplatesDirector.java