var CustomLayerView2D = BaseLayerViewGL2D.createSubclass({
   render(renderParameters) {
     const gl = this.context;

     ...
   }

   attach() {
     const gl = this.context;

     ...
   }

   detach() {
     const gl = this.context;

     ...
   }
 });

 var CustomTileLayer = Layer.createSubclass({
   tileInfo: TileInfo.create({ spatialReference: { wkid: 3857 }}),

   createLayerView(view) {
     if (view.type === "2d") {
       return new CustomLayerView2D({
         view: view,
         layer: this
       });
     }
   }
 });

Property Overview

Property Details

context WebGLRenderingContext|WebGL2RenderingContext

The WebGL rendering context associated to this layer view.

declaredClass Stringreadonly inherited

The name of the class. The declared class name is formatted as esri.folder.className.

layer Layer

References the layer this LayerView represents.

suspended Booleanreadonly inherited

Value is true if the layer is suspended (i.e., layer will not redraw or update itself when the extent changes).

tiles Tile[]

The array of BaseLayerViewGL2D objects computed to cover the MapView's visible area. This array is updated when the view is animating or the user is interacting with it. Then if tiles have been added or removed, tilesChanged() is called.

See also:

• tilesChanged()

updating Booleanreadonly inherited

Value is true when the layer is updating; for example, if it is in the process of fetching data.

Default Value:false

view MapView

References the MapView this LayerView belongs to.

visible Boolean inherited

When true, the layer is visible in the view. Set this property to false to hide the layer from the view.

Default Value:true

Method Overview

Method Details

attach()

Method called after the LayerView is created and right before it starts drawing the layer's content. Typically this method is implemented to start watching property changes on the layer and to initialize WebGL objects such as shaders.

See also:

• detach()

Example:

// Create a shader program and a property watcher
attach() {
  var gl = this.context;

  this._shaderProgram = gl.createProgram();
  ...

  this._propertyHandle = this.layer.watch("opacity", function() {
    this.requestRender();
  });
}

detach()

Method called after the layer is removed and the LayerView is about to be removed. Typically, this method is implemented to free resources like watchers and destroy WebGL objects such as shader programs.

See also:

• attach()

Example:

// Remove the watchers and destroy the shader program created in attach()
detach() {
  this._propertyHandle.remove();
  this._propertyHandle = null;

  const gl = this.context;

  gl.deleteProgram(this._shaderProgram);
  this._shaderProgram = null;
}

hitTest(x, y){Promise<Graphic>}

Method to implement that is responsible for providing objects hit at the specified screen coordinates. This method is called internally by the MapView each time its hitTest() method is called.

Parameters:

x Number The x-coordinate in screen space of the desired hit.

y Number The y-coordinate in screen space of the desired hit.

Returns:

Type	Description
Promise<Graphic>	A Promise that can resolve with a hit graphic instance.

isFulfilled(){Boolean}inherited

isFulfilled() may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected). If it is fulfilled, true will be returned.

Returns:

Type	Description
Boolean	Indicates whether creating an instance of the class has been fulfilled (either resolved or rejected).

isRejected(){Boolean}inherited

isRejected() may be used to verify if creating an instance of the class is rejected. If it is rejected, true will be returned.

Returns:

Type	Description
Boolean	Indicates whether creating an instance of the class has been rejected.

isResolved(){Boolean}inherited

isResolved() may be used to verify if creating an instance of the class is resolved. If it is resolved, true will be returned.

Returns:

Type	Description
Boolean	Indicates whether creating an instance of the class has been resolved.

render(renderParameters)

The method to implement that is responsible of drawing the content of the layer. This method is called every time the MapView's state changes, or if requestRender() has been called.

Parameters:

Specification:

renderParameters Object Specification: context WebGLRenderingContext|WebGL2RenderingContext The WebGL or WebGL 2 context. Its concrete type depends on system configuration. Every time that render() is called, the API automatically resets WebGL to a conventional state which is almost the default one; the only two things that may be non-default are the bound framebuffer and the viewport, which is set to match the entire framebuffer. The body of render() must not change these settings. stationary Boolean The stationary state of the MapView. state ViewState The object that describes view state.

Example:

// Example of a render implementation that draws using a custom shader program
render(renderParameters) {
  const gl = this.context;
  gl.bindBuffer(gl.ARRAY_BUFFER, this._vertexBuffer);
  gl.vertexAttribPointer(0, 2, gl.SHORT, false, 10, 0);
  gl.vertexAttribPointer(1, 3, gl.SHORT, true, 10, 4);
  gl.bindBuffer(gl.ARRAY_BUFFER, null);
  gl.enableVertexAttribArray(0);
  gl.enableVertexAttribArray(1);
  ...
  // Update uniforms as needed by calling gl.uniform...
  ...
  gl.useProgram(this._shaderProgram);
  gl.drawArrays(gl.TRIANGLES, 0, this._vertexCount);
  gl.disableVertexAttribArray(0);
  gl.disableVertexAttribArray(1);
  gl.useProgram(null);
}

requestRender()

The LayerView can call this method to ask the MapView to schedule a new rendering frame.

Example:

// Call requestRender whenever the layer opacity has changed
attach() {
  this._propertyHandle = this.layer.watch("opacity", function() {
    this.requestRender();
  });
}

tessellateExtent(extent){Promise<TessellatedMesh>}

Since: ArcGIS API for JavaScript 4.14

Tessellate an Extent into a rectangle.

Parameter:

extent Extent The input geometry.

Returns:

Type	Description
Promise<TessellatedMesh>	A promise to a BaseLayerViewGL2D. The output mesh is composed of two triangles.

Example:

this.tessellateExtent(g.geometry).then(function (mesh) {
   // do something with mesh
 });

tessellateMultipoint(multipoint, footprint){Promise<TessellatedMesh>}

Since: ArcGIS API for JavaScript 4.14

Tessellate a Multipoint into quads (markers).

Parameters:

multipoint Multipoint The input geometry. These are the geographic points where each marker will me anchored.

footprint Rect The rectangle that describes the geometry of each marker. Coordinates x and y can be thought as being in screen-space, relative to the screen-space projection of the geographic point.

Returns:

Type	Description
Promise<TessellatedMesh>	A promise to a BaseLayerViewGL2D. Each marker is represented by two triangles.

Example:

this.tessellateMultipoint(g.geometry, {x: 0, : -12, width: 34, height: 10}).then(function (mesh) {
   // do something with mesh
 });

tessellatePoint(point, footprint){Promise<TessellatedMesh>}

Since: ArcGIS API for JavaScript 4.14

Tessellate a Point into a quad (marker).

Parameters:

point Point The input geometry. This is the geographic point where the marker will me anchored.

footprint Rect The rectangle that describes the geometry of the marker. Coordinates x and y are the position of the upper-left corner of the marker, and can be thought as being in screen-space, relative to the screen-space projection of the geographic point; width and height are in pixels. See Rect for a visual explanation of marker geometry.

Returns:

Type	Description
Promise<TessellatedMesh>	A promise to a TessellatedMesh. The output mesh is composed of two triangles.

Example:

this.tessellatePoint(g.geometry, {x: 0, : -12, width: 34, height: 10}).then(function (mesh) {
   // do something with mesh
 });

tessellatePolygon(polygon){Promise<TessellatedMesh>}

Since: ArcGIS API for JavaScript 4.14

Tessellate a Polygon into triangles.

Parameter:

polygon Polygon The input geometry. The geometry must be simple; if the input geometry is not simple, you must first create a simplified version of it using geometryEngine, and pass the simplified geometry to tessellatePolygon.

Returns:

Type	Description
Promise<TessellatedMesh>	A promise to a TessellatedMesh.

Example:

this.tessellatePolygon(g.geometry).then(function (mesh) {
   // do something with mesh
 });

tessellatePolyline(polyline, width){Promise<TessellatedMesh>}

Since: ArcGIS API for JavaScript 4.14

Tessellate a Polyline into triangles.

Parameters:

polyline Polyline The input geometry. The geometry must be simple; if the input geometry is not simple, you must first create a simplified version of it using geometryEngine, and pass the simplified geometry to tessellatePolyline.

width Number The width of the line; this will be used to scale xOffset and yOffset.

Returns:

Type	Description
Promise<TessellatedMesh>	A promise to a TessellatedMesh.

Example:

this.tessellatePolyline(g.geometry, 10).then(function (mesh) {
   // do something with mesh
 });

tilesChanged(added, removed)

Method to implement, which notifies of tiles being added or removed for the current view state. This function can be implemented to start and stop fetching new data, or allocate and dispose resources.

Parameters:

added Tile[] The tile objects added for the current view viewport.

removed Tile[] The tile objects removed from the view viewport.

when(callback, errback){Promise}inherited

when() may be leveraged once an instance of the class is created. This method takes two input parameters: a callback function and an errback function. The callback executes when the instance of the class loads. The errback executes if the instance of the class fails to load.

Parameters:

callback Function optional The function to call when the promise resolves.

errback Function optional The function to execute when the promise fails.

Returns:

Type	Description
Promise	Returns a new promise for the result of callback that may be used to chain additional functions.

Example:

// Although this example uses MapView, any class instance that is a promise may use then() in the same way
var view = new MapView();
view.when(function(){
  // This function will execute once the promise is resolved
}, function(error){
  // This function will execute if the promise is rejected due to an error
});

Type Definitions

MeshVertex Object

A vertex of a tessellated mesh.

There are five different tessellation algorithms, one for each supported geometry type. The attributes in a vertex can be used to populate vertex and index buffers that can be rendered using appropriate shaders. See the SDK sample for a possible way of doing this using a single universal shader program that can render any of the supported geometry types.

There are four attributes; the first three are 2D points, and the last one is a scalar value. In total a mesh vertex contains 7 numeric values.

Geographic position (x, y) The geographic point associated to that vertex. For Extent and Polygon is equivalent to the position of the vertex itself; for Point and Multipoint is the geographic position of the point, and the anchor that will be associated to the corresponding marker symbol; for Polyline it lies on the centerline. The geographic position is usually expressed in map units and a custom vertex shader will generally need to transform it to normalized device coordinates.

Offset vector (xOffset, yOffset) This is an offset that is generally expressed in units other than the view's ones, and drives the extrusion of the geographic position into lines and quads. For Extent and Polygon is zero; for Point and Multipoint it goes from the anchor to the four vertices of the quad on screen; for Polyline it goes from the centerline to a vertex on the polyline's edge. The offset vector is usually expressed in some other units than map and will not need to be transformed by the same transform used for the geographic position. A common convention is to express the offset in points or pixels and code the vertex shader accordingly.

Texture coordinates (uTexcoord, vTexcoord) The texture coordinates associated to this vertex. For Extent the lower left vertex has coordinates (0, 0) and the upper right (1, 1); for Polygon the coordinates at each vertex match the interpolated coordinates that the smallest enclosing extent for that polygon would have at the same fragment; for Point and Multipoint each quad has (0, 0) as the lower left texture coordinate and (1, 1) as the upper right one; for Polyline the start cap is made of two vertices with texture coordinates (0, 0) and (0, 1) while the end cap is associated to (1, 0) and (1, 1).

Distance Valid only for Polyline; it is the distance, in map units, from the beginning of the polyline to this vertex.

Properties:

x Number The x-coordinate, expressed in the same units as the MapView.

y Number The y-coordinate, expressed in the same units as the MapView.

xOffset Number The x-offset in screen space; this is used to extrude points (into quads) and polylines, and is 0 for polygons.

yOffset Number The y-offset in screen space; this is used to extrude points (into quads) and polylines, and is 0 for polygons.

uTexcoord Number The u-coordinate for texture mapping. It varies between 0 and 1 horizontally for quads and polygons, and along the entire length of a polyline.

vTexcoord Number The v-coordinate for texture mapping. It varies between 0 and 1 vertically for quads and polygons, and across the width of a polyline.

distance Number The distance parameter for this vertex; this only applies when tessellating polylines. It starts from 0 and runs up to the total length of the polyline. It is expressed in map units.

Rect Object

A rectangle in screen-space.

An instance of Rect is used to specify the screen-space geometry of the resulting marker when calling BaseLayerViewGL2D or BaseLayerViewGL2D. The exact interpretation of "screen-space" is ultimately implemented through a custom vertex shader; a common convention is to interpret the values in the rect as being expressed in pixels or points. See BaseLayerViewGL2D for more details.

Properties:

x Number The x-coordinate of the upper-left corner of the rectangle, relative to the anchor of the marker.

y Number The y-coordinate of the upper-left corner of the rectangle, relative to the anchor of the marker.

width Number Width of the rectangle.

height Number Height of the rectangle.

TessellatedMesh Object

The triangle mesh resulting from a tessellation operation.

An instance of Mesh can be obtained by calling one of the BaseLayerViewGL2D tessellate* methods and passing an instance of Geometry.

Properties:

vertices MeshVertex[] The vertices that make up the mesh. Each element is a BaseLayerViewGL2D.

indices Number[] The indices of the triangles that connect vertices together; each consecutive triplet of indices denotes a triangle.

Tile Object

Represents a tile reference.

Properties:

id String The tile string identifier in the format level/row/col/world

level Number The level identifier of the LOD to which the tile belongs

row Number The row identifier.

col Number The column identifier.

world Number When the projection allows world wrapping (e.g. Web Mercator), identifies the instance of the world this tile's level/row/col.

resolution Number The number of map units per pixel in the tile.

scale Number The map scale at the tile's level.

coords Number[] The coordinates of the top-left corner of the tile as an array of two numbers. The coordinates are in un-normalized map units.

bounds Number[] The bounds of the tile as an array of four numbers that be readily converted to an Extent object.