From 43d3d9756285caec2621707471f7e08a86f6771e Mon Sep 17 00:00:00 2001
From: Leon Sorokin <leeoniya@gmail.com>
Date: Thu, 3 Jun 2021 20:05:47 -0500
Subject: [PATCH] Histogram: enable client-side zoom (with bucket snapping)
 (#35220)

---
 .../uPlot/config/UPlotConfigBuilder.ts        | 46 +++++++++----------
 .../app/plugins/panel/histogram/Histogram.tsx | 35 +++++++++++++-
 2 files changed, 55 insertions(+), 26 deletions(-)

diff --git a/packages/grafana-ui/src/components/uPlot/config/UPlotConfigBuilder.ts b/packages/grafana-ui/src/components/uPlot/config/UPlotConfigBuilder.ts
index 0c9f705c301..6672233641e 100644
--- a/packages/grafana-ui/src/components/uPlot/config/UPlotConfigBuilder.ts
+++ b/packages/grafana-ui/src/components/uPlot/config/UPlotConfigBuilder.ts
@@ -1,5 +1,5 @@
 import uPlot, { Cursor, Band, Hooks, Select } from 'uplot';
-import { defaultsDeep } from 'lodash';
+import { merge } from 'lodash';
 import {
   DataFrame,
   DefaultTimeZone,
@@ -17,6 +17,24 @@ import { AxisPlacement } from '../config';
 import { pluginLog } from '../utils';
 import { getThresholdsDrawHook, UPlotThresholdOptions } from './UPlotThresholds';
 
+const cursorDefaults: Cursor = {
+  // prevent client-side zoom from triggering at the end of a selection
+  drag: { setScale: false },
+  points: {
+    /*@ts-ignore*/
+    size: (u, seriesIdx) => u.series[seriesIdx].points.size * 2,
+    /*@ts-ignore*/
+    width: (u, seriesIdx, size) => size / 4,
+    /*@ts-ignore*/
+    stroke: (u, seriesIdx) => u.series[seriesIdx].points.stroke(u, seriesIdx) + '80',
+    /*@ts-ignore*/
+    fill: (u, seriesIdx) => u.series[seriesIdx].points.stroke(u, seriesIdx),
+  },
+  focus: {
+    prox: 30,
+  },
+};
+
 export class UPlotConfigBuilder {
   private series: UPlotSeriesBuilder[] = [];
   private axes: Record<string, UPlotAxisBuilder> = {};
@@ -98,7 +116,7 @@ export class UPlotConfigBuilder {
   }
 
   setCursor(cursor?: Cursor) {
-    this.cursor = { ...this.cursor, ...cursor };
+    this.cursor = merge({}, this.cursor, cursor);
   }
 
   setSelect(select: Select) {
@@ -153,11 +171,9 @@ export class UPlotConfigBuilder {
 
     config.hooks = this.hooks;
 
-    /* @ts-ignore */
-    // uPlot types don't export the Select interface prior to 1.6.4
     config.select = this.select;
 
-    config.cursor = this.cursor || {};
+    config.cursor = merge({}, cursorDefaults, this.cursor);
 
     config.tzDate = this.tzDate;
 
@@ -181,26 +197,6 @@ export class UPlotConfigBuilder {
       }
     }
 
-    const cursorDefaults: Cursor = {
-      // prevent client-side zoom from triggering at the end of a selection
-      drag: { setScale: false },
-      points: {
-        /*@ts-ignore*/
-        size: (u, seriesIdx) => u.series[seriesIdx].points.size * 2,
-        /*@ts-ignore*/
-        width: (u, seriesIdx, size) => size / 4,
-        /*@ts-ignore*/
-        stroke: (u, seriesIdx) => u.series[seriesIdx].points.stroke(u, seriesIdx) + '80',
-        /*@ts-ignore*/
-        fill: (u, seriesIdx) => u.series[seriesIdx].points.stroke(u, seriesIdx),
-      },
-      focus: {
-        prox: 30,
-      },
-    };
-
-    defaultsDeep(config.cursor, cursorDefaults);
-
     return config;
   }
 
diff --git a/public/app/plugins/panel/histogram/Histogram.tsx b/public/app/plugins/panel/histogram/Histogram.tsx
index d3bfffb1a67..2895301c217 100644
--- a/public/app/plugins/panel/histogram/Histogram.tsx
+++ b/public/app/plugins/panel/histogram/Histogram.tsx
@@ -27,6 +27,14 @@ import {
 import { PanelOptions } from './models.gen';
 import { ScaleDistribution } from '@grafana/ui/src/components/uPlot/models.gen';
 
+function incrRoundDn(num: number, incr: number) {
+  return Math.floor(num / incr) * incr;
+}
+
+function incrRoundUp(num: number, incr: number) {
+  return Math.ceil(num / incr) * incr;
+}
+
 export interface HistogramProps extends Themeable2 {
   options: PanelOptions; // used for diff
   alignedFrame: DataFrame; // This could take HistogramFields
@@ -70,7 +78,24 @@ const prepConfig = (frame: DataFrame, theme: GrafanaTheme2) => {
     distribution: ScaleDistribution.Linear,
     orientation: ScaleOrientation.Horizontal,
     direction: ScaleDirection.Right,
-    range: (u) => [u.data[0][0], u.data[0][u.data[0].length - 1] + bucketSize],
+    range: (u, wantedMin, wantedMax) => {
+      let fullRangeMin = u.data[0][0];
+      let fullRangeMax = u.data[0][u.data[0].length - 1];
+
+      // snap to bucket divisors...
+
+      if (wantedMax === fullRangeMax) {
+        wantedMax += bucketSize;
+      } else {
+        wantedMax = incrRoundUp(wantedMax, bucketSize);
+      }
+
+      if (wantedMin > fullRangeMin) {
+        wantedMin = incrRoundDn(wantedMin, bucketSize);
+      }
+
+      return [wantedMin, wantedMax];
+    },
   });
 
   builder.addScale({
@@ -114,6 +139,14 @@ const prepConfig = (frame: DataFrame, theme: GrafanaTheme2) => {
     theme,
   });
 
+  builder.setCursor({
+    drag: {
+      x: true,
+      y: false,
+      setScale: true,
+    },
+  });
+
   let pathBuilder = uPlot.paths.bars!({ align: 1, size: [1, Infinity] });
 
   let seriesIndex = 0;