1. Toolbar Button Events: Request EventCallback properties for the toolbar buttons, much like OnRenderingBegin and OnRenderingEnd. The event(s) should be fired when the respective toolbar button is clicked. At a bare minimum, request that the 'Stop Rendering' (Cancel) button fire its own event (OnRenderingCancel) or at least fire the existing OnRenderingEnd.

2. Toolbar Button Properties: Along with this, since IReportViewerTool exposes the Icon and CommandName, request it also expose an Enabled property. At a bare minimum, it would be helpful if, while rendering, all but the 'Stop Rendering' (Cancel) and Pager buttons are disabled by default or by setting a new viewer property.

Currently we must use JSInterop to accomplish these things.

The reason we are managing these things in the first place is because we are using Custom Parameter Editors (CPEs). When a long-running report is in the process of rendering, and a user changes a parameter and re-requests the report (either via our 'Retrieve' button or a viewer toolbar button), an unhandled exception occurs in _content/Telerik.ReportViewer.BlazorNative/js/reporting-blazor-viewer.js. So we make use of the OnRenderingBegin and OnRenderingEnd events to disable/enable the CPEs. The problem arises when the 'Stop Rendering' (Cancel) button is clicked. Since we cannot detect the button click, our CPEs remain disabled.