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View Class

For detailed explanations and code examples about deck.gl's views system, visit the Views and Projections article.

The View class and its subclasses are used to specify where and how your deck.gl layers should be rendered. Applications typically instantiate at least one View subclass.

Views allow you to specify:

  • A unique id.
  • The position and extent of the view on the canvas: x, y, width, and height.
  • Certain camera parameters specifying how your data should be projected into this view, e.g. field of view, near/far planes, perspective vs. orthographic, etc.
  • The controller to be used for this view. A controller listens to pointer events and touch gestures, and translates user input into changes in the view state. If enabled, the camera becomes interactive.

deck.gl offers a set of View classes that package the camera and controller logic that you need to visualize and interact with your data. You may choose one or multiple View classes based on the type of data (e.g. geospatial, 2D chart) and the desired perspective (top down, first-person, etc).

Constructor​

const view = new View({id, x, y, width, height, ...});

Parameters:

id (string, optional)​

A unique id of the view. In a multi-view use case, this is important for matching view states and place contents into this view.

x (string | number, optional)​

A relative (e.g. '50%') or absolute position. Default 0.

y (string | number, optional)​

A relative (e.g. '50%') or absolute position. Default 0.

width (string | number, optional)​

A relative (e.g. '50%') or absolute extent. Default '100%'.

height (string | number, optional)​

A relative (e.g. '50%') or absolute extent. Default '100%'.

padding (object, optional)​

Padding around the viewport, in the shape of {left, right, top, bottom} where each value is either a relative (e.g. '50%') or absolute pixels. This can be used to move the "look at"/target/vanishing point away from the center of the viewport rectangle.

controller (Function | boolean | object, optional)​

Options for viewport interactivity.

  • null or false: this view is not interactive.
  • true: initiates the default controller with default options.
  • Controller class (not instance): initiates the provided controller with default options.
  • Object: controller options. This will be merged with the default controller options.
    • controller.type: the controller class
    • For other options, consult the documentation of Controller.

Default null.

viewState (string | object, optional)​

The optional viewState property enables a View to specify, select or select-and-modify its view state.

viewState is an overloaded property that can take either just a view state id string, or an object specifying view state parameters and optionally a view state id string:

  • null (default): Will select a view state based on view.id, falling back to using the first view state.
  • String: Will attempt to match the indicated view state.
  • Object (with id field): if the object contains an id field which matches a dynamic view state, the remaining fields in View.viewState will extend (be merged into a copy of) the selected dynamic view state.
  • Object (with no id field): If no id is provided, the View.viewState object will be used directly as the view state, essentially representing a fixed or constant view state.

Note that specifying viewState as an object with an id field effectively allows the View to modify a dynamic view state by overriding some of its fields. This is useful in multiview situations where it enables having one view that fixes some parameters (eg. zoom, pitch and bearing to show an overview map).

The viewState property is intended to support a number of use cases:

  • Sharing view states between multiple views - If a View id is different from the designed view state's id.
  • specify a complete, constant (fixed) view state directly in the view
  • Overriding a partial set of view state properties from a selected view state.

clear (boolean | object, optional)​

Clears the contents (pixels) of the viewport. The value of the clear prop is passed as an argument to luma.gl's clear function. If true clears color and depth buffers. If an object, behaviour is controlled by the following fields:

  • color (boolean or Array) - if not false, clears all active color buffers with either the provided color or the currently set clear color.
  • depth (boolean) - if true, clears the depth buffer.
  • stencil (boolean) - if true clears the stencil buffer.

Note that deck.gl always clears the screen before each render, and clearing, while cheap, is not totally free. This means that viewports should only specify the clear property if they need additional clearing, e.g. because they are rendering on top of another viewport, or want to have a different background color etc.

Default false.

Methods​

Note: most applications just create Views with the appropriate props and do not need to call the following View methods directly.

equals​

Returns true if deck.gl can determine that the supplied View instance is identical (equivalent) with this view.

view.equals(otherView)

  • otherView (View) - Another view instance to compare with.

Returns:

  • true - the given view is identical to the current one.

Note: For speed, deck.gl uses shallow equality. This means that a value of false does not guarantee that the views are not equivalent.

makeViewport​

view.makeViewport({width, height, viewState})

Parameters:

  • width (Number) - Dimension in pixels of the target viewport.
  • height (Number) - Dimension in pixels of the target viewport.
  • viewState (Object) - view state compatible with the current View subclass in use. Note that any prop provided to the View constructor will override that inside the viewState.

Returns a Viewport using the viewport type, props in the View and provided dimensions and view state.

getDimensions​

Returns the actual pixel position and size that this View will occupy in a given "canvas" size.

const {x, y, width, height} = view.getDimensions({width, height});

Parameters:

  • width (Number) - Dimension in CSS pixels of the deck.gl "canvas".
  • height (Number) - Dimension in CSS pixels of the deck.gl "canvas".

Returns an object containing the following fields:

  • x (Number) - x position in CSS pixels
  • y (Number) - y position in CSS pixels
  • width (Number) - width in CSS pixels
  • height (Number) - height in CSS pixels

Remarks​

  • The View class and its subclasses are perhaps best thought of as geospatially enabled counterparts of the typical Camera classes found in most 3D libraries.

Source​

modules/core/src/views/view.ts