3.3.0 Change Notes

Table of contents:

Display system

Dynamic schedule scripts

Timeline animation enables the visualization of change within an iModel over a period of time. This can be a valuable tool for, among other things, animating the contents of a viewport to show the progress of an asset through the phases of its construction. However, one constraint has always limited the utility of this feature: the instructions for animating the view were required to be stored on a persistent element - either a DisplayStyle or a RenderTimeline - in the IModel.

That constraint has now been lifted. This makes it possible to create and apply ad-hoc animations entirely on the frontend. For now, support for this capability must be enabled when calling IModelApp.startup by setting TileAdmin.Props.enableFrontendScheduleScripts to true, as in this example:

await IModelApp.startup({
  tileAdmin: {
    enableFrontendScheduleScripts: true,

Then, you can create a new schedule script using RenderSchedule.ScriptBuilder or RenderSchedule.Script.fromJSON and apply it by assigning to DisplayStyleState.scheduleScript. For example, given a JSON representation of the script:

function updateScheduleScript(
  viewport: Viewport,
  props: RenderSchedule.ScriptProps
): void {
  viewport.displayStyle.scheduleScript = RenderSchedule.Script.fromJSON(props);

Hiliting models and subcategories

Support for hiliting models and subcategories using HiliteSet has been promoted from @beta to @public. This allows applications to toggle hiliting of all elements belonging to a set of Models and/or SubCategory's. This feature can work in one of two modes, specified by HiliteSet.modelSubCategoryMode:

  • Union - an element will be hilited if either its model or its subcategory is hilited; or
  • Intersection - an element will be hilited if both its model and its subcategory are hilited.

Applications often work with Category's instead of subcategories. You can use the new Categories API to obtain the Ids of the subcategories belonging to one or more categories.

Improved appearance overrides for animated views

The appearances of elements within a view can be customized in a variety of ways. Two such sources of customization are a FeatureOverrideProvider like EmphasizeElements, which can change the color, transparency, and/or emphasis effect applied to any number of elements; and a RenderSchedule.Script, which can modify the color and transparency of groups of elements over time. Previously, when these two sources of appearance overrides came into conflict, the results were less than ideal:

  • If any aspect of the element's appearance was overridden by a FeatureOverrideProvider, then none of the schedule script's appearance overrides would be applied to that element.
  • If some elements were being emphasized in the view (e.g., via EmphasizeElements.emphasizeElements), any non-emphasized elements whose appearance was modified by the schedule script would not be drawn using the de-emphasized (typically, light transparent grey) appearance, making it difficult for the emphasized elements to stand out.

Both of these problems are addressed in iTwin.js 3.3.0.

  • The schedule script's overrides are now combined with the element's overrides, but at a lower priority such that if a FeatureOverrideProvider changes the color of the element to red, and the script wants to change its color to green and make it semi-transparent, the element will be drawn as semi-transparent red.
  • EmphasizeElements now ignores the schedule script's color and transparency overrides for non-emphasized elements when other elements are being emphasized. Other FeatureOverrideProviders can do the same - or otherwise customize to which elements the script's overrides are applied - by supplying a function to do so to FeatureOverrides.ignoreAnimationOverrides.


Auto-hiding floating widgets

When a widget is in floating state, it will not automatically hide when the rest of the UI auto-hides. To create a widget that will automatically hide with the in-viewport tool widgets, set the prop AbstractWidgetProps.hideWithUiWhenFloating to true in your UiProvider.

Auto-hide UI feature will ignore dragged floating widgets and keep them visible until drag interaction is complete. Floating widgets are also animated correctly when hiding.

Tool Settings title

By default, when the Tool Settings widget is floating, the title will read "Tool Settings". To use the name of the active tool as the title instead, you can now use UiFramework.setUseToolAsToolSettingsLabel when your app starts.


ElectronApp changes

Reduced API surface of an ElectronApp class to only allow white-listed APIs from electron modules to be called. ElectronApp is updated to reflect the change: callShell and callApp methods are removed, callDialog is updated to only show dialogs and a message box.

Frontend category APIs

A Category provides a way to organize groups of GeometricElements. Each category contains at least one SubCategory which defines the appearance of geometry belonging to that subcategory. This information is important for frontend code - for example, the display system needs access to subcategory appearances so that it can draw elements correctly, and applications may want to hilite subcategories in a Viewport.

IModelConnection.categories now provides access to APIs for querying this information. The information is cached upon retrieval so that repeated requests need not query the backend.


The argument for IModelHost.startup has been changed from IModelHostConfiguration to the IModelHostOptions interface. This matches the approach on the frontend for IModelApp.startup and makes it easier to supply startup options. IModelHostConfiguration implements IModelHostOptions, so existing code will continue to work without changes.

Progress API for downloading changesets

BackendHubAccess interface now supports progress reporting and cancellation of changeset(s) download. BackendHubAccess.downloadChangeset and BackendHubAccess.downloadChangesets take optional argument progressCallback of type ProgressFunction. If function is passed, it is regularly called to report download progress. Changeset(s) download can be cancelled by returning ProgressStatus.Abort from said function.

RPC over IPC

When a web application is using IPC communication between its frontend and backend, the RPC protocols now delegate request and response transportation to the IPC system. After the initial "handshake" request, there are now no further HTTP requests. All traffic (both IPC and RPC) is sent over the WebSocket. This change yields security benefits by reducing the surface area of our frontend/backend communication and provides performance consistency for the application.


Relationship properties

Properties that are defined on ECRelationshipClass can now be included in content using newly added RelatedPropertiesSpecification.relationshipProperties attribute.

When relationship properties are shown, or RelatedPropertiesSpecification.forceCreateRelationshipProperties attribute is set to true, all information coming from that relationship, including related instance properties, will be organized within a category named after the relationship class.

Webpack 5

The @itwin/core-webpack-tools and @itwin/backend-webpack-tools packages have been updated to support Webpack 5 and now require a peer dependency of webpack@^5. Please refer to their changelog and migration guide as you update.



The AuthStatus enum has been removed. This enum has fallen out of use since the authorization refactor in 3.0.0, and is no longer a member of BentleyError.

The beta functions Element.collectPredecessorIds and Element.getPredecessorIds have been deprecated and replaced with Element.collectReferenceIds and Element.getReferenceIds, since the term "predecessor" has been inaccurate since 3.2.0, when the transformer became capable of handling cyclic references and not just references to elements that were inserted before itself (predecessors).


Growable array constructors now take an optional growth factor to control additional capacity during memory reallocations (default 1.5). This can make repeated additions to these arrays more efficient. Affected classes are GrowableBlockedArray, GrowableFloat64Array, GrowableXYArray, and GrowableXYZArray. In addition, loops in ensureCapacity, pushBlockCopy, resize, clone, etc. have been replaced with more efficient calls to typed array set, copyWithin, fill.

The GrowableXYArray method setXYZAtCheckedPointIndex is deprecated in favor of the more appropriately named new method setXYAtCheckedPointIndex.


IOSApp, IOSAppOpts, and AndroidApp have been removed in favor of MobileApp and MobileAppOpts. Developers were previously discouraged from making direct use of MobileApp, which was a base class of the two platform specific mobile apps. This distinction has been removed, as the implementation of the two apps was the same. IOSAppOpts, now MobileAppOpts, is an extension of NativeAppOpts with the added condition that an AuthorizationClient is never provided.

IOSHost, IOSHostOpts, AndroidHost, and AndroidHostOpts have been removed in favor of MobileHost for the same reasons described above.

Last Updated: 18 August, 2023