Downloads chart: Add display modes stacked/unstacked

app/lib/frontend/templates/views/pkg/score_tab.dart

@@ -195,6 +195,29 @@ d.Node _downloadsChart(WeeklyVersionDownloadCounts weeklyVersionDownloads) {
           initialValue: 'major')
     ],
   );
+
+  final displayModes = d.div(
+    classes: ['downloads-chart-display-modes'],
+    children: [
+      radioButtons(
+          leadingText: 'Display as: ',
+          name: 'display-modes',
+          radios: [
+            (
+              id: 'display-modes-unstacked',
+              value: 'unstacked',
+              label: 'Unstacked'
+            ),
+            (
+              id: 'version-modes-stacked',
+              value: 'stacked',
+              label: 'Stacked',
+            ),
+          ],
+          classes: ['downloads-chart-radio-button'],
+          initialValue: 'unstacked')
+    ],
+  );
   final container = d.div(
     classes: ['downloads-chart'],
     id: '-downloads-chart',
@@ -203,11 +226,13 @@ d.Node _downloadsChart(WeeklyVersionDownloadCounts weeklyVersionDownloads) {
       'data-downloads-chart-points':
           base64Encode(jsonUtf8Encoder.convert(weeklyVersionDownloads)),
       'data-downloads-chart-versions-radio': 'version-modes',
+      'data-downloads-chart-display-radio': 'display-modes',
     },
   );
 
   return d.fragment([
     d.h1(text: 'Weekly downloads'),
+    displayModes,
     versionModes,
     container,
   ]);

pkg/web_app/lib/src/widget/downloads_chart/widget.dart

@@ -26,6 +26,11 @@ String strokeColorClass(int i) => 'downloads-chart-stroke-${colors[i]}';
 String fillColorClass(int i) => 'downloads-chart-fill-${colors[i]}';
 String squareColorClass(int i) => 'downloads-chart-square-${colors[i]}';
 
+enum DisplayMode {
+  stacked,
+  unstacked,
+}
+
 void create(HTMLElement element, Map<String, String> options) {
   final dataPoints = options['points'];
   if (dataPoints == null) {
@@ -36,6 +41,12 @@ void create(HTMLElement element, Map<String, String> options) {
   if (versionsRadio == null) {
     throw UnsupportedError('data-downloads-chart-versions-radio required');
   }
+
+  final displayRadio = options['display-radio'];
+  if (displayRadio == null) {
+    throw UnsupportedError('data-downloads-chart-display-radio required');
+  }
+
   Element createNewSvg() {
     return document.createElementNS('http://www.w3.org/2000/svg', 'svg')
       ..setAttribute('height', '100%')
@@ -72,6 +83,9 @@ void create(HTMLElement element, Map<String, String> options) {
     weeksToDisplay,
   );
 
+  var currentDisplayList = majorDisplayLists;
+  var currentDisplayMode = DisplayMode.unstacked;
+
   final versionModesLists = {
     'major': majorDisplayLists,
     'minor': minorDisplayLists,
@@ -91,7 +105,34 @@ void create(HTMLElement element, Map<String, String> options) {
       element.removeChild(svg);
       svg = createNewSvg();
       element.append(svg);
-      drawChart(svg, toolTip, displayList, data.newestDate);
+      currentDisplayList = displayList;
+      drawChart(svg, toolTip, displayList, data.newestDate,
+          displayMode: currentDisplayMode);
+    });
+  });
+
+  final displayModesMap = <String, DisplayMode>{
+    'stacked': DisplayMode.stacked,
+    'unstacked': DisplayMode.unstacked
+  };
+
+  final displayModes = document.getElementsByName(displayRadio).toList();
+  displayModes.forEach((i) {
+    final radioButton = i as HTMLInputElement;
+    final value = radioButton.value;
+    final displayMode = displayModesMap[value];
+
+    if (displayMode == null) {
+      throw UnsupportedError('Unsupported display-radio value: "$value"');
+    }
+
+    radioButton.onClick.listen((e) {
+      element.removeChild(svg);
+      svg = createNewSvg();
+      element.append(svg);
+      currentDisplayMode = displayMode;
+      drawChart(svg, toolTip, currentDisplayList, data.newestDate,
+          displayMode: displayMode);
     });
   });
 
@@ -103,7 +144,7 @@ void drawChart(
     HTMLDivElement toolTip,
     ({List<String> ranges, List<List<int>> weekLists}) displayLists,
     DateTime newestDate,
-    {bool stacked = false}) {
+    {DisplayMode displayMode = DisplayMode.unstacked}) {
   final ranges = displayLists.ranges;
   final values = displayLists.weekLists;
 
@@ -128,8 +169,11 @@ void drawChart(
   /// Computes max value on y-axis such that we get a nice division for the
   /// interval length between the numbers shown by the ticks on the y axis.
   (int maxY, int interval) computeMaxYAndInterval(List<List<int>> values) {
-    final maxDownloads =
-        values.fold<int>(1, (a, b) => math.max<int>(a, b.reduce(math.max)));
+    final maxDownloads = displayMode == DisplayMode.unstacked
+        ? values.fold<int>(1, (a, b) => math.max<int>(a, b.reduce(math.max)))
+        : values.fold<int>(
+            1, (a, b) => math.max<int>(a, b.reduce((x, y) => x + y)));
+
     final digits = maxDownloads.toString().length;
     final buffer = StringBuffer()..write('1');
     if (digits > 2) {
@@ -244,14 +288,20 @@ void drawChart(
 
   // Chart lines and legends
 
+  final lastestDownloads = List.filled(values.length, 0);
   final lines = <StringBuffer>[];
   for (int versionRange = 0; versionRange < values[0].length; versionRange++) {
     final line = StringBuffer();
     var c = 'M';
     for (int week = 0; week < values.length; week++) {
+      if (displayMode == DisplayMode.stacked) {
+        lastestDownloads[week] += values[week][versionRange];
+      } else {
+        lastestDownloads[week] = values[week][versionRange];
+      }
       final (x, y) = computeCoordinates(
           computeDateForWeekNumber(newestDate, values.length, week),
-          values[week][versionRange]);
+          lastestDownloads[week]);
       line.write(' $c$x $y');
       c = 'L';
     }
@@ -265,14 +315,32 @@ void drawChart(
   final legendHeight = 8;
 
   for (int i = 0; i < lines.length; i++) {
-    final path = SVGPathElement();
-    path.setAttribute('class', '${strokeColorClass(i)} downloads-chart-line ');
     // We assign colors in reverse order so that main colors are chosen first for
     // the newest versions.
-    path.setAttribute('d', '${lines[lines.length - 1 - i]}');
+    final line = lines[lines.length - 1 - i];
+
+    final path = SVGPathElement();
+    path.setAttribute('class', '${strokeColorClass(i)} downloads-chart-line ');
+    path.setAttribute('d', '$line');
     path.setAttribute('clip-path', 'url(#clipRect)');
     chart.append(path);
 
+    if (displayMode == DisplayMode.stacked) {
+      final area = SVGPathElement();
+      area.setAttribute('class', '${fillColorClass(i)} downloads-chart-area ');
+      final prevLine = i == lines.length - 1
+          ? ' M $xZero $yZero L$xMax $yZero'
+          : lines[lines.length - 1 - i - 1];
+      final reversed = prevLine
+          .toString()
+          .replaceAll(' M', '')
+          .split('L')
+          .reversed
+          .join('L');
+      area.setAttribute('d', '$line  L$reversed Z');
+      chart.append(area);
+    }
+
     final legend = SVGRectElement();
     chart.append(legend);
     legend.setAttribute('class',

pkg/web_css/lib/src/_pkg.scss

@@ -289,6 +289,10 @@
     float: right;
   }
 
+  .downloads-chart-display-modes {
+    float: left;
+  }
+
   .downloads-chart-radio-button {
     margin-left: 10px;
   }
@@ -426,6 +430,10 @@
     stroke-linejoin: round;
   }
 
+  .downloads-chart-area {
+    opacity: 0.3;
+  }
+
   .downloads-chart-stroke-blue {
     stroke: var(--pub-downloads-chart-color-0);
   }