Class: View

ol/View~View


import View from 'ol/View';

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)

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:

Extends

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)

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)

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)

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)

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)

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()

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}

Calculate the extent for the current view state and the passed size. The size is the pixel dimensions of the box into which the calculated extent should fit. In most cases you want to get the extent of the entire map, that is map.getSize().

Name Type Description
size Size | undefined

Box pixel size. If not provided, the size of the map that uses this view will be used.

Returns:
Extent.

cancelAnimations()

Cancel any ongoing animations.

centerOn(coordinate, size, position)

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.

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

dispatchEvent(event){boolean | undefined} inherited

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)

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)

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. Default is the current size of the first map in the DOM that uses this view, or [100, 100] if no such map is found.

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.

Gets a value.

Name Type Description
key string

Key name.

Returns:
Value.

getAnimating(){boolean}

Determine if the view is being animated.

Returns:
The view is being animated.

getCenter(){Coordinate | undefined}

Get the view center.

Returns:
The center of the view.

getInteracting(){boolean}

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

Get a list of object property names.

Returns:
List of property names.

getMaxResolution(){number}

Get the maximum resolution of the view.

Returns:
The maximum resolution of the view.

getMaxZoom(){number}

Get the maximum zoom level for the view.

Returns:
The maximum zoom level.

getMinResolution(){number}

Get the minimum resolution of the view.

Returns:
The minimum resolution of the view.

getMinZoom(){number}

Get the minimum zoom level for the view.

Returns:
The minimum zoom level.

getProjection(){Projection}

Get the view projection.

Returns:
The projection of the view.

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

Get an object of all property names and values.

Returns:
Object.

getResolution(){number | undefined}

Get the view resolution.

Returns:
The resolution of the view.

getResolutionForExtent(extent, size){number}

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}

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}

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

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

Returns:
Revision.

getRotation(){number}

Get the view rotation.

Returns:
The rotation of the view in radians.

getZoom(){number | undefined}

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}

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

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

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

Sets a value.

Name Type Description
key string

Key name.

value *

Value.

silent boolean | undefined

Update without triggering an event.

setCenter(center)

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)

Set whether the view should allow intermediary zoom levels.

Name Type Description
enabled boolean

Whether the resolution is constrained.

setMaxZoom(zoom)

Set a new maximum zoom level for the view.

Name Type Description
zoom number

The maximum zoom level.

setMinZoom(zoom)

Set a new minimum zoom level for the view.

Name Type Description
zoom number

The minimum zoom level.

setProperties(values, silent) inherited

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)

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

Name Type Description
resolution number | undefined

The resolution of the view.

setRotation(rotation)

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)

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

Name Type Description
zoom number

Zoom level.

un(type, listener) inherited

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

Unsets a property.

Name Type Description
key string

Key name.

silent boolean | undefined

Unset without triggering an event.