add expr functions for extensional selection predicates

packages/vega-functions/src/codegen.js

@@ -9,8 +9,10 @@ import {
 } from 'vega-dataflow';
 
 import {
+  selectionIdTest,
   selectionResolve,
   selectionTest,
+  selectionTuples,
   selectionVisitor
 } from 'vega-selections';
 
@@ -351,4 +353,6 @@ expressionFunction('treeAncestors', treeAncestors, dataVisitor);
 
 // register Vega-Lite selection functions
 expressionFunction('vlSelectionTest', selectionTest, selectionVisitor);
+expressionFunction('vlSelectionIdTest', selectionIdTest, selectionVisitor);
 expressionFunction('vlSelectionResolve', selectionResolve, selectionVisitor);
+expressionFunction('vlSelectionTuples', selectionTuples);

packages/vega-selections/index.js

@@ -1,3 +1,4 @@
-export {selectionTest} from './src/selectionTest';
+export {selectionTest, selectionIdTest} from './src/selectionTest';
+export {selectionTuples} from './src/selectionTuples';
 export {selectionResolve} from './src/selectionResolve';
 export {selectionVisitor} from './src/selectionVisitor';

packages/vega-selections/src/selectionTest.js

@@ -1,7 +1,9 @@
+import {bisector} from 'd3-array';
 import {Intersect} from './constants';
 import {field, inrange, isArray, isDate, toNumber} from 'vega-util';
 
-var TYPE_ENUM = 'E',
+const SELECTION_ID = '_vgsid_',
+    TYPE_ENUM = 'E',
     TYPE_RANGE_INC = 'R',
     TYPE_RANGE_EXC = 'R-E',
     TYPE_RANGE_LE = 'R-LE',
@@ -101,4 +103,28 @@ export function selectionTest(name, datum, op) {
   // if not intersecting, then we saw no matches
   // if no active selections, return false
   return n && intersect;
-}
+}
+
+const selectionId = field(SELECTION_ID),
+  bisect = bisector(selectionId),
+  bisectLeft = bisect.left,
+  bisectRight = bisect.right;
+
+export function selectionIdTest(name, datum, op) {
+  const data = this.context.data[name],
+      entries = data ? data.values.value : [],
+      unitIdx = data ? data[UNIT_INDEX] && data[UNIT_INDEX].value : undefined,
+      intersect = op === Intersect,
+      value = selectionId(datum),
+      index = bisectLeft(entries, value);
+
+  if (index === entries.length) return false;
+  if (selectionId(entries[index]) !== value) return false;
+
+  if (unitIdx && intersect) {
+    if (unitIdx.size === 1) return true;
+    if (bisectRight(entries, value) - index < unitIdx.size) return false;
+  }
+
+  return true;
+}

packages/vega-selections/src/selectionTuples.js

@@ -0,0 +1,14 @@
+import {extend, field} from 'vega-util';
+
+/**
+ * Maps an array of scene graph items to an array of selection tuples.
+ * @param {string} name  - The name of the dataset representing the selection.
+ * @param {string} unit  - The name of the unit view.
+ *
+ * @returns {array} An array of selection entries for the given unit.
+ */
+export function selectionTuples(array, base) {
+  return array.map(x => extend({
+    values: base.fields.map(f => (f.getter || (f.getter = field(f.field)))(x.datum))
+  }, base));
+}