Refactor histogram-set-view to an MVC pattern.

tracing/tracing/value/ui/histogram-set-view.md

Index: tracing/tracing/value/ui/histogram-set-view.md
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+<!-- Copyright 2017 The Chromium Authors. All rights reserved.
+     Use of this source code is governed by a BSD-style license that can be
+     found in the LICENSE file.
+-->
+
+# HistogramSet UI Architecture
+
+Documentation for users of this UI is in [metrics-results-ui](/docs/metrics-results-ui.md).
+
+This document outlines the MVC architecture of the implementation of the UI.
+ * Model: [HistogramSetViewState](/tracing/tracing/value/ui/histogram_set_view_state.html)
+    * searchQuery: regex filters Histogram names
+    * referenceDisplayLabel selects the reference column in the table
+    * showAll: when false, only sourceHistograms are shown in the table
+    * groupings: array of HistogramGroupings configures how the hierarchy is constructed
+    * sortColumnIndex
+    * sortDescending
+    * constrainNameColumn: whether the Name column in the table is constrained to 300px
+    * tableRowStates: Map from row name to HistogramSetTableRowState
+       * subRows: Map from row name to HistogramSetTableRowState
+       * isExpanded: whether the row is expanded to show its subRows
+       * isOverviewed: whether the overview charts are displayed
+       * cells: map from column names to HistogramSetTableCellState:
+          * isOpen: whether the cell's histogram-span is open and displaying the BarChart and Diagnostics
+          * brushedBinRange: which bins are brushed in the BarChart
+          * mergeSampleDiagnostics: whether sample diagnostics are merged
+    * Setters delegate to the main entry point, update(delta), which dispatches an update event to listeners
+ * View-Controllers:
+    * [histogram-set-view](/tracing/tracing/value/ui/histogram_set_view.html):
+       * Main entry point: build(HistogramSet, progressIndicator):Promise
+       * Displays "zero Histograms"
+       * Listens for download-csv event from [histogram-set-controls](/tracing/tracing/value/ui/histogram_set_controls.html)
+          * gets leafHistograms from the [histogram-set-table](/tracing/tracing/value/ui/histogram_set_table.html)
+          * builds a CSV using [CSVBuilder](/tracing/tracing/value/csv_builder.html)
+       * Collects possible configurations of the HistogramSet and passes them to the child elements directly (not through the HistogramSetViewState!):
+          * Possible groupings
+          * displayLabels
+          * baseStatisticNames
+       * Contains child elements:
+          * [histogram-set-controls](/tracing/tracing/value/ui/histogram_set_controls.html)
+             * visualizes and controls the top half of HistogramSetViewState:
+                * searchQuery
+                * toggle display of all isOvervieweds
+                * referenceDisplayLabel
+                * showAll
+                * groupings
+             * Displays a button to download a CSV of the leafHistograms
+             * Displays a "Help" link to [metrics-results-ui](/docs/metrics-results-ui.md)
+          * [histogram-set-table](/tracing/tracing/value/ui/histogram_set_table.html)
+             * Visualizes and controls the bottom half of HistogramSetViewState:
+                * sortColumnIndex
+                * sortDescending
+                * constrainNameColumn
+                * HistogramSetTableRowStates
+             * Builds [HistogramSetTableRow](/tracing/tracing/value/ui/histogram_set_table_row.html)s containing
+                * [histogram-set-table-name-cell](/tracing/tracing/value/ui/histogram_set_table_name_cell.html)
+                   * Toggles HistogramSetTableRowState.isOverviewed
+                   * Overview [NameLineChart](/tracing/tracing/ui/base/name_line_chart.html)
+                * [histogram-set-table-cell](/tracing/tracing/value/ui/histogram_set_table_cell.html)
+                   * (missing) / (empty) / (unmergeable)
+                   * when closed, [scalar-span](/tracing/tracing/value/ui/scalar_span.html) displays a single summary statistic
+                   * when open, [histogram-span](/tracing/tracing/value/ui/histogram_span.html) contains:
+                      * [NameBarChart](/tracing/tracing/ui/base/name_bar_chart.html) visualizes and controls HistogramSetTableCellState.brushedBinRange
+                      * [scalar-map-table](/tracing/tracing/value/ui/scalar_map_table.html) of statistics
+                      * Two [diagnostic-map-tables](/tracing/tracing/value/ui/diagnostic_map_table.html): one for Histogram.diagnostics and another for the sample diagnostics
+                      * A checkbox to visualize and control HistogramSetTableCellState.mergeSampleDiagnostics
+                   * Overview [NameLineChart](/tracing/tracing/ui/base/name_line_chart.html)
+             * Main entry points:
+                * build(allHistograms, sourceHistograms, displayLabels, progressIndicator):Promise
+                * onViewStateUpdate_(delta)
+    * Soon, another module will propagate settings back and forth between the HistogramSetViewState and the URL search params.