Draw polygon by dragging mode (#362)

docs/api-reference/modes/overview.md

@@ -91,6 +91,17 @@ User can draw a new `Polygon` feature by clicking positions to add then closing
 
 User can draw a new `Polygon` feature with 90 degree corners (right angle) by clicking positions to add then closing the polygon (or double-clicking). After clicking the 2 points, the draw mode guides/allows to have right angle polygon.
 
+## [DrawPolygonByDraggingMode](https://github.com/uber/nebula.gl/blob/master/modules/edit-modes/src/lib/draw-polygon-by-dragging-mode.js)
+
+User can draw a new `Polygon` feature by dragging (similar to the lasso tool commonly found in photo editing software).
+
+### ModeConfig
+
+The following options can be provided in the `modeConfig` object:
+
+* `throttleMs` (optional):  `number`
+  * If provided, the dragging function will be throttled by the specified number of milliseconds.
+
 ## [DrawRectangleMode](https://github.com/uber/nebula.gl/blob/master/modules/edit-modes/src/lib/draw-rectangle-mode.js)
 
 User can draw a new rectangular `Polygon` feature by clicking two opposing corners of the rectangle.

examples/advanced/example.js

@@ -32,6 +32,7 @@ import {
   DrawEllipseUsingThreePointsMode,
   DrawRectangleUsingThreePointsMode,
   Draw90DegreePolygonMode,
+  DrawPolygonByDraggingMode,
   MeasureDistanceMode,
   MeasureAreaMode,
   MeasureAngleMode,
@@ -96,6 +97,7 @@ const ALL_MODES = [
       { label: 'Draw LineString', mode: DrawLineStringMode },
       { label: 'Draw Polygon', mode: DrawPolygonMode },
       { label: 'Draw 90° Polygon', mode: Draw90DegreePolygonMode },
+      { label: 'Draw Polygon By Dragging', mode: DrawPolygonByDraggingMode },
       { label: 'Draw Rectangle', mode: DrawRectangleMode },
       { label: 'Draw Rectangle Using 3 Points', mode: DrawRectangleUsingThreePointsMode },
       { label: 'Draw Circle From Center', mode: DrawCircleFromCenterMode },
@@ -127,6 +129,7 @@ const ALL_MODES = [
 const POLYGON_DRAWING_MODES = [
   DrawPolygonMode,
   Draw90DegreePolygonMode,
+  DrawPolygonByDraggingMode,
   DrawRectangleMode,
   DrawRectangleUsingThreePointsMode,
   DrawCircleFromCenterMode,
@@ -878,6 +881,11 @@ export default class Example extends Component<
           }
         ]
       };
+    } else if (mode === DrawPolygonByDraggingMode) {
+      modeConfig = {
+        ...modeConfig,
+        throttleMs: 100
+      };
     }
 
     // Demonstrate how to override sub layer properties

modules/edit-modes/package.json

@@ -67,6 +67,7 @@
     "@turf/transform-scale": ">=4.0.0",
     "@turf/transform-translate": ">=4.0.0",
     "@turf/union": ">=4.0.0",
+    "lodash.throttle": "^4.1.1",
     "viewport-mercator-project": ">=6.0.0"
   }
 }

modules/edit-modes/src/index.js

@@ -24,6 +24,7 @@ export { DrawEllipseByBoundingBoxMode } from './lib/draw-ellipse-by-bounding-box
 export { DrawEllipseUsingThreePointsMode } from './lib/draw-ellipse-using-three-points-mode.js';
 export { DrawRectangleUsingThreePointsMode } from './lib/draw-rectangle-using-three-points-mode.js';
 export { Draw90DegreePolygonMode } from './lib/draw-90degree-polygon-mode.js';
+export { DrawPolygonByDraggingMode } from './lib/draw-polygon-by-dragging-mode.js';
 export { ImmutableFeatureCollection } from './lib/immutable-feature-collection.js';
 
 // Other modes

modules/edit-modes/src/lib/draw-polygon-by-dragging-mode.js

@@ -0,0 +1,72 @@
+// @flow
+
+import throttle from 'lodash.throttle';
+import type {
+  ClickEvent,
+  StartDraggingEvent,
+  StopDraggingEvent,
+  DraggingEvent,
+  ModeProps
+} from '../types.js';
+import type { Polygon, FeatureCollection } from '../geojson-types.js';
+import { getPickedEditHandle } from '../utils.js';
+import { DrawPolygonMode } from './draw-polygon-mode';
+
+type DraggingHandler = (event: DraggingEvent, props: ModeProps<FeatureCollection>) => void;
+
+export class DrawPolygonByDraggingMode extends DrawPolygonMode {
+  handleDraggingThrottled: ?DraggingHandler = null;
+
+  handleClick(event: ClickEvent, props: ModeProps<FeatureCollection>) {
+    // No-op
+  }
+
+  handleStartDragging(event: StartDraggingEvent, props: ModeProps<FeatureCollection>) {
+    event.cancelPan();
+    if (props.modeConfig && props.modeConfig.throttleMs) {
+      this.handleDraggingThrottled = throttle(this.handleDraggingAux, props.modeConfig.throttleMs);
+    } else {
+      this.handleDraggingThrottled = this.handleDraggingAux;
+    }
+  }
+
+  handleStopDragging(event: StopDraggingEvent, props: ModeProps<FeatureCollection>) {
+    this.addClickSequence(event);
+    const clickSequence = this.getClickSequence();
+
+    if (this.handleDraggingThrottled && this.handleDraggingThrottled.cancel) {
+      this.handleDraggingThrottled.cancel();
+    }
+
+    if (clickSequence.length > 2) {
+      // Complete the polygon.
+      const polygonToAdd: Polygon = {
+        type: 'Polygon',
+        coordinates: [[...clickSequence, clickSequence[0]]]
+      };
+
+      this.resetClickSequence();
+
+      const editAction = this.getAddFeatureOrBooleanPolygonAction(polygonToAdd, props);
+      if (editAction) {
+        props.onEdit(editAction);
+      }
+    }
+  }
+
+  handleDraggingAux(event: DraggingEvent, props: ModeProps<FeatureCollection>) {
+    const { picks } = event;
+    const clickedEditHandle = getPickedEditHandle(picks);
+
+    if (!clickedEditHandle) {
+      // Don't add another point right next to an existing one.
+      this.addClickSequence(event);
+    }
+  }
+
+  handleDragging(event: DraggingEvent, props: ModeProps<FeatureCollection>) {
+    if (this.handleDraggingThrottled) {
+      this.handleDraggingThrottled(event, props);
+    }
+  }
+}

modules/layers/src/layers/editable-geojson-layer.js

@@ -23,6 +23,7 @@ import {
   DrawRectangleUsingThreePointsMode,
   DrawEllipseUsingThreePointsMode,
   Draw90DegreePolygonMode,
+  DrawPolygonByDraggingMode,
   SnappableMode,
   TransformMode
 } from '@nebula.gl/edit-modes';
@@ -184,7 +185,8 @@ const modeNameMapping = {
   drawEllipseByBoundingBox: DrawEllipseByBoundingBoxMode,
   drawRectangleUsing3Points: DrawRectangleUsingThreePointsMode,
   drawEllipseUsing3Points: DrawEllipseUsingThreePointsMode,
-  draw90DegreePolygon: Draw90DegreePolygonMode
+  draw90DegreePolygon: Draw90DegreePolygonMode,
+  drawPolygonByDragging: DrawPolygonByDraggingMode
 };
 
 type Props = {

modules/main/src/index.js

@@ -50,6 +50,7 @@ export { DrawEllipseByBoundingBoxMode } from '@nebula.gl/edit-modes';
 export { DrawEllipseUsingThreePointsMode } from '@nebula.gl/edit-modes';
 export { DrawRectangleUsingThreePointsMode } from '@nebula.gl/edit-modes';
 export { Draw90DegreePolygonMode } from '@nebula.gl/edit-modes';
+export { DrawPolygonByDraggingMode } from '@nebula.gl/edit-modes';
 export { ImmutableFeatureCollection } from '@nebula.gl/edit-modes';
 
 // Other modes