Viewport Class

A Viewport renders the contents of one or more Models onto an HTMLCanvasElement.

It holds a ViewState object that defines its viewing parameters. ViewTools may modify the ViewState object. Changes to the ViewState are only reflected in a Viewport after the Viewport.synchWithView method is called.

In general, because the Viewport essentially takes control of its attached ViewState, changes to the ViewState should be made indirectly through the Viewport's own API. Doing so ensures that synchronization between the Viewport and its ViewState is reliable and automatic. For example:

• To change the set of categories or models displayed in the Viewport, use Viewport.changeCategoryDisplay and Viewport.changeModelDisplay rather than modifying the ViewState's CategorySelectorState or ModelSelectorState directly.
• To change the ViewFlags, set Viewport.viewFlags rather than modifying the ViewState's DisplayStyleState directly.
• To modify the DisplayStyleState:

  const style = viewport.displayStyle.clone();
  style.backgroundColor = ColorDef.red.clone(); // or any other desired modifications
  viewport.displayStyle = style;

As changes to ViewState are made, Viewports also hold a stack of previous copies of it, to allow for undo/redo (i.e. View Previous and View Next) of viewing tools.

Changes to a Viewport's state can be monitored by attaching an event listener to a variety of specific events. Most such events are triggered only once per frame, just before the Viewport's contents are rendered. For example, if the following sequence of events occurs:

• First frame is rendered
• ViewFlags are modified
• ViewFlags are modified again
• Second frame is rendered

The Viewport.onDisplayStyleChanged event will be invoked exactly once, when the second frame is rendered.

see ViewManager

Extended by

• ScreenViewport

Implements

• IDisposable

Methods

Properties

Defined in

• core/frontend/src/Viewport.ts

Last Updated: 05 June, 2020