add pickObject API in layer

docs/api-reference/layer.md

@@ -577,6 +577,18 @@ Returns:
 
 * a "null" picking color which is equal the the color of pixels not covered by the layer. This color is guaranteed not to match any index value greater than or equal to zero.
 
+##### `pickObject`
+
+Get the closest pickable and visible object at the given screen coordinate.
+
+* `x` (Number) - x position in pixels
+* `y` (Number) - y position in pixels
+* `radius` (Number, optional) - radius of tolerance in pixels. Default `0`.
+
+Returns:
+
+* a single [`info`](/docs/get-started/interactivity.md#the-picking-info-object) object, or `null` if nothing is found.
+
 ## Source
 
 [modules/core/src/core/lib/layer.js](https://github.com/uber/deck.gl/blob/master/modules/core/src/lib/layer.js)

modules/core/src/lib/deck.js

@@ -528,6 +528,7 @@ export default class Deck {
     const viewport = this.viewManager.getViewports()[0];
     // Note: avoid React setState due GL animation loop / setState timing issue
     this.layerManager = new LayerManager(gl, {
+      deck: this,
       stats: this.stats,
       viewport
     });

modules/core/src/lib/layer-manager.js

@@ -43,6 +43,7 @@ const LOG_PRIORITY_LIFECYCLE_MINOR = 4;
 // CONTEXT IS EXPOSED TO LAYERS
 const INITIAL_CONTEXT = Object.seal({
   layerManager: null,
+  deck: null,
   gl: null,
 
   // Settings
@@ -64,7 +65,7 @@ const layerName = layer => (layer instanceof Layer ? `${layer}` : !layer ? 'null
 
 export default class LayerManager {
   // eslint-disable-next-line
-  constructor(gl, {stats, viewport = null} = {}) {
+  constructor(gl, {deck, stats, viewport = null} = {}) {
     // Currently deck.gl expects the DeckGL.layers array to be different
     // whenever React rerenders. If the same layers array is used, the
     // LayerManager's diffing algorithm will generate a fatal error and
@@ -79,7 +80,7 @@ export default class LayerManager {
 
     this.context = Object.assign({}, INITIAL_CONTEXT, {
       layerManager: this,
-
+      deck,
       gl,
       // Enabling luma.gl Program caching using private API (_cachePrograms)
       shaderCache: gl && new ShaderCache({gl, _cachePrograms: true}),

modules/core/src/lib/layer.js

@@ -288,6 +288,14 @@ export default class Layer extends Component {
     return index;
   }
 
+  // Return the closest pickable and visible object at the given screen coordinate.
+  pickObject({x, y, radius = 0}) {
+    if (this.context.deck) {
+      return this.context.deck.pickObject({x, y, radius, layerIds: [this.props.id]});
+    }
+    return null;
+  }
+
   // //////////////////////////////////////////////////
   // LIFECYCLE METHODS, overridden by the layer subclasses