Roll Observatory packages and add a roll script

charted/lib/layout/src/pie_layout.dart

-/*
- * Copyright 2014 Google Inc. All rights reserved.
- *
- * Use of this source code is governed by a BSD-style
- * license that can be found in the LICENSE file or at
- * https://developers.google.com/open-source/licenses/bsd
- */
-part of charted.layout;
-
-/**
- * Utility class to create arc definitions that can be used by the SvgArc
- * to generate arcs for pie and donut charts
- */
-class PieLayout {
-  /**
-   * Callback to convert datum to values used for layout
-   * Defaults to [defaultValueAccessor]
-   */
-  SelectionValueAccessor<num> accessor = defaultValueAccessor;
-
-  /**
-   * Callback to get the start angle for the pie. This callback is
-   * called once per list of value (i.e once per call to [layout])
-   * Defaults to [defaultStartAngleCallback]
-   */
-  SelectionCallback<num> startAngleCallback = defaultStartAngleCallback;
-
-  /**
-   * Callback to get the start angle for the pie. This callback is
-   * called once per list of value (i.e once per call to [layout])
-   * Defaults to [defaultEndAngleCallback]
-   */
-  SelectionCallback<num> endAngleCallback = defaultEndAngleCallback;
-
-  /**
-   * Comparator that is used to set the sort order of values. If not
-   * specified, the input order is used.
-   */
-  Comparator<num> compare = null;
-
-  /**
-   * Return a list of SvgArcData objects that could be used to create
-   * arcs in a pie-chart or donut-chart.
-   */
-  List layout(List data, [int ei, Element e]) {
-    var values = new List.generate(data.length,
-            (int i) => accessor(data[i], i)),
-        startAngle = startAngleCallback(data, ei, e),
-        endAngle = endAngleCallback(data, ei, e),
-        total = sum(values),
-        scaleFactor = (endAngle - startAngle) / (total > 0 ? total : 1),
-        index = new Range.integers(values.length).toList(),
-        arcs = new List(data.length);
-
-    if (compare != null) {
-      index.sort((left, right) => compare(data[left], data[right]));
-    }
-
-    int count = 0;
-    index.forEach((i) {
-      endAngle = startAngle + values[i] * scaleFactor;
-      arcs[count++] = new SvgArcData(data[i], values[i], startAngle, endAngle);
-      startAngle = endAngle;
-    });
-
-    return arcs;
-  }
-
-  /** Sets a constant value to start angle of the layout */
-  set startAngle(num value) =>
-      startAngleCallback = toCallback(value);
-
-  /** Sets a constant value to end angle of the layout */
-  set endAngle(num value) =>
-      endAngleCallback = toCallback(value);
-
-  /** Default value accessor */
-  static num defaultValueAccessor(num d, i) => d;
-
-  /** Default start angle callback - returns 0 */
-  static num defaultStartAngleCallback(d, i, _) => 0;
-
-  /** Default end angle callback - returns 2 * PI */
-  static num defaultEndAngleCallback(d, i, _) => 2 * PI;
-}