Class: View

ol/View~View

import View from 'ol/View.js';

A View object represents a simple 2D view of the map.

This is the object to act upon to change the center, resolution, and rotation of the map.

A View has a projection. The projection determines the coordinate system of the center, and its units determine the units of the resolution (projection units per pixel). The default projection is Web Mercator (EPSG:3857).

The view states

A View is determined by three states: center, resolution, and rotation. Each state has a corresponding getter and setter, e.g. getCenter and setCenter for the center state.

The zoom state is actually not saved on the view: all computations internally use the resolution state. Still, the setZoom and getZoom methods are available, as well as getResolutionForZoom and getZoomForResolution to switch from one system to the other.

The constraints

setCenter, setResolution and setRotation can be used to change the states of the view, but any constraint defined in the constructor will be applied along the way.

A View object can have a resolution constraint, a rotation constraint and a center constraint.

The resolution constraint typically restricts min/max values and snaps to specific resolutions. It is determined by the following options: resolutions, maxResolution, maxZoom and zoomFactor. If resolutions is set, the other three options are ignored. See documentation for each option for more information. By default, the view only has a min/max restriction and allow intermediary zoom levels when pinch-zooming for example.

The rotation constraint snaps to specific angles. It is determined by the following options: enableRotation and constrainRotation. By default rotation is allowed and its value is snapped to zero when approaching the horizontal.

The center constraint is determined by the extent option. By default the view center is not constrained at all.

Changing the view state

It is important to note that setZoom, setResolution, setCenter and setRotation are subject to the above mentioned constraints. As such, it may sometimes not be possible to know in advance the resulting state of the View. For example, calling setResolution(10) does not guarantee that getResolution() will return 10.

A consequence of this is that, when applying a delta on the view state, one should use adjustCenter, adjustRotation, adjustZoom and adjustResolution rather than the corresponding setters. This will let view do its internal computations. Besides, the adjust* methods also take an anchor argument which allows specifying an origin for the transformation.

Interacting with the view

View constraints are usually only applied when the view is at rest, meaning that no interaction or animation is ongoing. As such, if the user puts the view in a state that is not equivalent to a constrained one (e.g. rotating the view when the snap angle is 0), an animation will be triggered at the interaction end to put back the view to a stable state;

new View(options) View.js, line 313

Name	Type	Description
`center`	Coordinate \| undefined	The initial center for the view. If a user projection is not set, the coordinate system for the center is specified with the `projection` option. Layer sources will not be fetched if this is not set, but the center can be set later with `#setCenter`.
`constrainRotation`	boolean \| number (defaults to true)	Rotation constraint. `false` means no constraint. `true` means no constraint, but snap to zero near zero. A number constrains the rotation to that number of values. For example, `4` will constrain the rotation to 0, 90, 180, and 270 degrees.
`enableRotation`	boolean (defaults to true)	Enable rotation. If `false`, a rotation constraint that always sets the rotation to zero is used. The `constrainRotation` option has no effect if `enableRotation` is `false`.
`extent`	Extent \| undefined	The extent that constrains the view, in other words, nothing outside of this extent can be visible on the map.
`constrainOnlyCenter`	boolean (defaults to false)	If true, the extent constraint will only apply to the view center and not the whole extent.
`smoothExtentConstraint`	boolean (defaults to true)	If true, the extent constraint will be applied smoothly, i.e. allow the view to go slightly outside of the given `extent`.
`maxResolution`	number \| undefined	The maximum resolution used to determine the resolution constraint. It is used together with `minResolution` (or `maxZoom`) and `zoomFactor`. If unspecified it is calculated in such a way that the projection's validity extent fits in a 256x256 px tile. If the projection is Spherical Mercator (the default) then `maxResolution` defaults to `40075016.68557849 / 256 = 156543.03392804097`.
`minResolution`	number \| undefined	The minimum resolution used to determine the resolution constraint. It is used together with `maxResolution` (or `minZoom`) and `zoomFactor`. If unspecified it is calculated assuming 29 zoom levels (with a factor of 2). If the projection is Spherical Mercator (the default) then `minResolution` defaults to `40075016.68557849 / 256 / Math.pow(2, 28) = 0.0005831682455839253`.
`maxZoom`	number (defaults to 28)	The maximum zoom level used to determine the resolution constraint. It is used together with `minZoom` (or `maxResolution`) and `zoomFactor`. Note that if `minResolution` is also provided, it is given precedence over `maxZoom`.
`minZoom`	number (defaults to 0)	The minimum zoom level used to determine the resolution constraint. It is used together with `maxZoom` (or `minResolution`) and `zoomFactor`. Note that if `maxResolution` is also provided, it is given precedence over `minZoom`.
`multiWorld`	boolean (defaults to false)	If `false` the view is constrained so only one world is visible, and you cannot pan off the edge. If `true` the map may show multiple worlds at low zoom levels. Only used if the `projection` is global. Note that if `extent` is also provided it is given precedence.
`constrainResolution`	boolean (defaults to false)	If true, the view will always animate to the closest zoom level after an interaction; false means intermediary zoom levels are allowed.
`smoothResolutionConstraint`	boolean (defaults to true)	If true, the resolution min/max values will be applied smoothly, i. e. allow the view to exceed slightly the given resolution or zoom bounds.
`showFullExtent`	boolean (defaults to false)	Allow the view to be zoomed out to show the full configured extent. By default, when a view is configured with an extent, users will not be able to zoom out so the viewport exceeds the extent in either dimension. This means the full extent may not be visible if the viewport is taller or wider than the aspect ratio of the configured extent. If showFullExtent is true, the user will be able to zoom out so that the viewport exceeds the height or width of the configured extent, but not both, allowing the full extent to be shown.
`projection`	ProjectionLike (defaults to 'EPSG:3857')	The projection. The default is Spherical Mercator.
`resolution`	number \| undefined	The initial resolution for the view. The units are `projection` units per pixel (e.g. meters per pixel). An alternative to setting this is to set `zoom`. Layer sources will not be fetched if neither this nor `zoom` are defined, but they can be set later with `#setZoom` or `#setResolution`.
`resolutions`	Array.<number> \| undefined	Resolutions that determine the zoom levels if specified. The index in the array corresponds to the zoom level, therefore the resolution values have to be in descending order. It also constrains the resolution by the minimum and maximum value. If set the `maxResolution`, `minResolution`, `minZoom`, `maxZoom`, and `zoomFactor` options are ignored.
`rotation`	number (defaults to 0)	The initial rotation for the view in radians (positive rotation clockwise, 0 means North).
`zoom`	number \| undefined	Only used if `resolution` is not defined. Zoom level used to calculate the initial resolution for the view.
`zoomFactor`	number (defaults to 2)	The zoom factor used to compute the corresponding resolution.
`padding`	Array.<number> (defaults to [0, 0, 0, 0])	Padding (in css pixels). If the map viewport is partially covered with other content (overlays) along its edges, this setting allows to shift the center of the viewport away from that content. The order of the values is top, right, bottom, left.

Fires:

change (BaseEvent) - Generic change event. Triggered when the revision counter is increased.
change:center (ObjectEvent)
change:resolution (ObjectEvent)
change:rotation (ObjectEvent)
error (BaseEvent) - Generic error event. Triggered when an error occurs.
propertychange (ObjectEvent) - Triggered when a property is changed.

Extends

BaseObject

Observable Properties

Name	Type	Settable	ObjectEvent type	Description
`center`	Coordinate \| undefined	yes	`change:center`	The center of the view.
`resolution`	number \| undefined	yes	`change:resolution`	The resolution of the view.
`rotation`	number	yes	`change:rotation`	The rotation of the view in radians.

Members

padding{Array.<number>} {undefined}

Padding (in css pixels). If the map viewport is partially covered with other content (overlays) along its edges, this setting allows to shift the center of the viewport away from that content. The order of the values in the array is top, right, bottom, left. The default is no padding, which is equivalent to [0, 0, 0, 0].

Methods

adjustCenter(deltaCoordinates) View.js, line 1545

Adds relative coordinates to the center of the view. Any extent constraint will apply.

Name	Type	Description
`deltaCoordinates`	Coordinate	Relative value to add.

adjustResolution(ratio, anchor) View.js, line 1572

Multiply the view resolution by a ratio, optionally using an anchor. Any resolution constraint will apply.

Name	Type	Description
`ratio`	number	The ratio to apply on the view resolution.
`anchor`	Coordinate \| undefined	The origin of the transformation.

adjustRotation(delta, anchor) View.js, line 1619

Adds a value to the view rotation, optionally using an anchor. Any rotation constraint will apply.

Name	Type	Description
`delta`	number	Relative value to add to the zoom rotation, in radians.
`anchor`	Coordinate \| undefined	The rotation center.

adjustZoom(delta, anchor) View.js, line 1608

Adds a value to the view zoom level, optionally using an anchor. Any resolution constraint will apply.

Name	Type	Description
`delta`	number	Relative value to add to the zoom level.
`anchor`	Coordinate \| undefined	The origin of the transformation.

animate(var_args) View.js, line 587

Animate the view. The view's center, zoom (or resolution), and rotation can be animated for smooth transitions between view states. For example, to animate the view to a new zoom level:

view.animate({zoom: view.getZoom() + 1});

By default, the animation lasts one second and uses in-and-out easing. You can customize this behavior by including duration (in milliseconds) and easing options (see ol/easing).

To chain together multiple animations, call the method with multiple animation objects. For example, to first zoom and then pan:

view.animate({zoom: 10}, {center: [0, 0]});

If you provide a function as the last argument to the animate method, it will get called at the end of an animation series. The callback will be called with true if the animation series completed on its own or false if it was cancelled.

Animations are cancelled by user interactions (e.g. dragging the map) or by calling view.setCenter(), view.setResolution(), or view.setRotation() (or another method that calls one of these).

Name Type Description

var_args

Animation options. Multiple animations can be run in series by passing multiple options objects. To run multiple animations in parallel, call the method multiple times. An optional callback can be provided as a final argument. The callback will be called with a boolean indicating whether the animation completed without being cancelled.

Name	Type	Description
`center`	Coordinate \| undefined	The center of the view at the end of the animation.
`zoom`	number \| undefined	The zoom level of the view at the end of the animation. This takes precedence over `resolution`.
`resolution`	number \| undefined	The resolution of the view at the end of the animation. If `zoom` is also provided, this option will be ignored.
`rotation`	number \| undefined	The rotation of the view at the end of the animation.
`anchor`	Coordinate \| undefined	Optional anchor to remain fixed during a rotation or resolution animation.
`duration`	number (defaults to 1000)	The duration of the animation in milliseconds.
`easing`	function \| undefined	The easing function used during the animation (defaults to `inAndOut`). The function will be called for each frame with a number representing a fraction of the animation's duration. The function should return a number between 0 and 1 representing the progress toward the destination state.

beginInteraction() View.js, line 1835

Notify the View that an interaction has started. The view state will be resolved to a stable one if needed (depending on its constraints).

calculateExtent(size){Extent} View.js, line 999

Calculate the extent for the current view state and the passed box size.

Name	Type	Description
`size`	Size \| undefined	The pixel dimensions of the box into which the calculated extent should fit. Defaults to the size of the map the view is associated with. If no map or multiple maps are connected to the view, provide the desired box size (e.g. `map.getSize()`).

Returns:

Extent.

cancelAnimations() View.js, line 727

Cancel any ongoing animations.

centerOn(coordinate, size, position) View.js, line 1480

Center on coordinate and view position.

Name	Type	Description
`coordinate`	Coordinate	Coordinate.
`size`	Size	Box pixel size.
`position`	Pixel	Position on the view to center on.

changed() inherited Observable.js, line 68

Increases the revision counter and dispatches a 'change' event.

dispatchEvent(event){boolean | undefined} inherited events/Target.js, line 85

Dispatches an event and calls all listeners listening for events of this type. The event parameter can either be a string or an Object with a type property.

Name	Type	Description
`event`	BaseEvent \| string	Event object.

Returns:

false if anyone called preventDefault on the event object or if any of the listeners returned false.

endInteraction(duration, resolutionDirection, anchor) View.js, line 1849

Notify the View that an interaction has ended. The view state will be resolved to a stable one if needed (depending on its constraints).

Name	Type	Description
`duration`	number \| undefined	Animation duration in ms.
`resolutionDirection`	number \| undefined	Which direction to zoom.
`anchor`	Coordinate \| undefined	The origin of the transformation.

fit(geometryOrExtent, options) View.js, line 1344

Fit the given geometry or extent based on the given map size and border. The size is pixel dimensions of the box to fit the extent into. In most cases you will want to use the map size, that is map.getSize(). Takes care of the map angle.

Name Type Description

geometryOrExtent

SimpleGeometry | Extent

The geometry or extent to fit the view to.

options

Options.

Name	Type	Description
`size`	Size \| undefined	The size in pixels of the box to fit the extent into. Defaults to the size of the map the view is associated with. If no map or multiple maps are connected to the view, provide the desired box size (e.g. `map.getSize()`).
`padding`	Array.<number> (defaults to [0, 0, 0, 0])	Padding (in pixels) to be cleared inside the view. Values in the array are top, right, bottom and left padding.
`nearest`	boolean (defaults to false)	If the view `constrainResolution` option is `true`, get the nearest extent instead of the closest that actually fits the view.
`minResolution`	number (defaults to 0)	Minimum resolution that we zoom to.
`maxZoom`	number \| undefined	Maximum zoom level that we zoom to. If `minResolution` is given, this property is ignored.
`duration`	number \| undefined	The duration of the animation in milliseconds. By default, there is no animation to the target extent.
`easing`	function \| undefined	The easing function used during the animation (defaults to `inAndOut`). The function will be called for each frame with a number representing a fraction of the animation's duration. The function should return a number between 0 and 1 representing the progress toward the destination state.
`callback`	function \| undefined	Function called when the view is in its final position. The callback will be called with `true` if the animation series completed on its own or `false` if it was cancelled.

get(key){*} inherited Object.js, line 135

Gets a value.

Name	Type	Description
`key`	string	Key name.

Returns:

Value.

getAnimating(){boolean} View.js, line 710

Determine if the view is being animated.

Returns:

The view is being animated.

getCenter(){Coordinate | undefined} View.js, line 944

Get the view center.

Returns:

The center of the view.

getInteracting(){boolean} View.js, line 719

Determine if the user is interacting with the view, such as panning or zooming.

Returns:

The view is being interacted with.

getKeys(){Array.<string>} inherited Object.js, line 148

Get a list of object property names.

Returns:

List of property names.

getMaxResolution(){number} View.js, line 1028

Get the maximum resolution of the view.

Returns:

The maximum resolution of the view.

getMaxZoom(){number} View.js, line 1046

Get the maximum zoom level for the view.

Returns:

The maximum zoom level.

getMinResolution(){number} View.js, line 1037

Get the minimum resolution of the view.

Returns:

The minimum resolution of the view.

getMinZoom(){number} View.js, line 1066

Get the minimum zoom level for the view.

Returns:

The minimum zoom level.

getProjection(){Projection} View.js, line 1095

Get the view projection.

Returns:

The projection of the view.

getProperties(){Object.<string, *>} inherited Object.js, line 157

Get an object of all property names and values.

Returns:

Object.

getResolution(){number | undefined} View.js, line 1105

Get the view resolution.

Returns:

The resolution of the view.

getResolutionForExtent(extent, size){number} View.js, line 1127

Get the resolution for a provided extent (in map units) and size (in pixels).

Name	Type	Description
`extent`	Extent	Extent.
`size`	Size \| undefined	Box pixel size.

Returns:

The resolution at which the provided extent will render at the given size.

getResolutionForZoom(zoom){number} View.js, line 1312

Get the resolution for a zoom level.

Name	Type	Description
`zoom`	number	Zoom level.

Returns:

The view resolution for the provided zoom level.

getResolutions(){Array.<number> | undefined} View.js, line 1115

Get the resolutions for the view. This returns the array of resolutions passed to the constructor of the View, or undefined if none were given.

Returns:

The resolutions of the view.

getRevision(){number} inherited Observable.js, line 79

Get the version number for this object. Each time the object is modified, its version number will be incremented.

Returns:

Revision.

getRotation(){number} View.js, line 1177

Get the view rotation.

Returns:

The rotation of the view in radians.

getZoom(){number | undefined} View.js, line 1272

Get the current zoom level. This method may return non-integer zoom levels if the view does not constrain the resolution, or if an interaction or animation is underway.

Returns:

Zoom.

getZoomForResolution(resolution){number | undefined} View.js, line 1287

Get the zoom level for a resolution.

Name	Type	Description
`resolution`	number	The resolution.

Returns:

The zoom level for the provided resolution.

on(type, listener){EventsKey | Array<EventsKey>} inherited Observable.js, line 152

Listen for a certain type of event.

Name	Type	Description
`type`	string \| Array.<string>	The event type or array of event types.
`listener`	function	The listener function.

Returns:

Unique key for the listener. If called with an array of event types as the first argument, the return will be an array of keys.

once(type, listener){EventsKey | Array<EventsKey>} inherited Observable.js, line 164

Listen once for a certain type of event.

Name	Type	Description
`type`	string \| Array.<string>	The event type or array of event types.
`listener`	function	The listener function.

Returns:

Unique key for the listener. If called with an array of event types as the first argument, the return will be an array of keys.

set(key, value, silent) inherited Object.js, line 215

Sets a value.

Name	Type	Description
`key`	string	Key name.
`value`	*	Value.
`silent`	boolean \| undefined	Update without triggering an event.

setCenter(center) View.js, line 1649

Set the center of the current view. Any extent constraint will apply.

Name	Type	Description
`center`	Coordinate \| undefined	The center of the view.

setConstrainResolution(enabled) View.js, line 1086

Set whether the view should allow intermediary zoom levels.

Name	Type	Description
`enabled`	boolean	Whether the resolution is constrained.

setMaxZoom(zoom) View.js, line 1057

Set a new maximum zoom level for the view.

Name	Type	Description
`zoom`	number	The maximum zoom level.

setMinZoom(zoom) View.js, line 1077

Set a new minimum zoom level for the view.

Name	Type	Description
`zoom`	number	The minimum zoom level.

setProperties(values, silent) inherited Object.js, line 235

Sets a collection of key-value pairs. Note that this changes any existing properties and adds new ones (it does not remove any existing properties).

Name	Type	Description
`values`	Object.<string, *>	Values.
`silent`	boolean \| undefined	Update without triggering an event.

setResolution(resolution) View.js, line 1681

Set the resolution for this view. Any resolution constraint will apply.

Name	Type	Description
`resolution`	number \| undefined	The resolution of the view.

setRotation(rotation) View.js, line 1692

Set the rotation for this view. Any rotation constraint will apply.

Name	Type	Description
`rotation`	number	The rotation of the view in radians.

setZoom(zoom) View.js, line 1702

Zoom to a specific zoom level. Any resolution constrain will apply.

Name	Type	Description
`zoom`	number	Zoom level.

un(type, listener) inherited Observable.js, line 173

Unlisten for a certain type of event.

Name	Type	Description
`type`	string \| Array.<string>	The event type or array of event types.
`listener`	function	The listener function.

unset(key, silent) inherited Object.js, line 259

Unsets a property.

Name	Type	Description
`key`	string	Key name.
`silent`	boolean \| undefined	Unset without triggering an event.