From 6aeb8b5045176cb1b2eacaee3801413c002ac82c Mon Sep 17 00:00:00 2001
From: Nick Krecklow <hello@github.nklow.com>
Date: Wed, 10 Jun 2020 18:42:51 -0500
Subject: [PATCH] prevent historical graph zoom state from resetting during
 data updates

---
 assets/js/graph.js   | 34 ++++++++++++++++++++++++++++++----
 assets/js/plugins.js | 24 ++++++++++++++++++++++++
 assets/js/servers.js |  2 +-
 3 files changed, 55 insertions(+), 5 deletions(-)

diff --git a/assets/js/graph.js b/assets/js/graph.js
index 123952a..cb59959 100644
--- a/assets/js/graph.js
+++ b/assets/js/graph.js
@@ -3,7 +3,7 @@ import uPlot from 'uplot'
 import { RelativeScale } from './scale'
 
 import { formatNumber, formatTimestampSeconds } from './util'
-import { uPlotTooltipPlugin } from './tooltip'
+import { uPlotTooltipPlugin, uPlotIsZoomedPlugin } from './plugins'
 
 import { FAVORITE_SERVERS_STORAGE_KEY } from './favorites'
 
@@ -18,6 +18,7 @@ export class GraphDisplayManager {
     this._hasLoadedSettings = false
     this._initEventListenersOnce = false
     this._showOnlyFavorites = false
+    this._isPlotZoomed = false
   }
 
   addGraphPoint (timestamp, playerCounts) {
@@ -49,8 +50,14 @@ export class GraphDisplayManager {
       }
     }
 
-    // Paint updated data structure
-    this._plotInstance.setData(this.getGraphData())
+    // If not zoomed, paint updated data structure
+    // Otherwise flag the plot data as dirty with repainting to be handled by #handlePlotZoomOut
+    // This prevents #addGraphPoint calls from resetting the graph's zoom state
+    if (!this._isPlotZoomed) {
+      this._plotInstance.setData(this.getGraphData())
+    } else {
+      this._isPlotZoomedDataDirty = true
+    }
   }
 
   loadLocalStorage () {
@@ -244,7 +251,8 @@ export class GraphDisplayManager {
           } else {
             this._app.tooltip.hide()
           }
-        })
+        }),
+        uPlotIsZoomedPlugin(this.handlePlotZoomIn, this.handlePlotZoomOut)
       ],
       ...this.getPlotSize(),
       cursor: {
@@ -339,6 +347,21 @@ export class GraphDisplayManager {
     this._resizeRequestTimeout = undefined
   }
 
+  handlePlotZoomIn = () => {
+    this._isPlotZoomed = true
+  }
+
+  handlePlotZoomOut = () => {
+    this._isPlotZoomed = false
+
+    // Test if the data has changed while the plot was zoomed in
+    if (this._isPlotZoomedDataDirty) {
+      this._isPlotZoomedDataDirty = false
+
+      this._plotInstance.setData(this.getGraphData())
+    }
+  }
+
   initEventListeners () {
     if (!this._initEventListenersOnce) {
       this._initEventListenersOnce = true
@@ -446,6 +469,9 @@ export class GraphDisplayManager {
     this._graphData = []
     this._hasLoadedSettings = false
 
+    this._isPlotZoomed = false
+    this._isPlotZoomedDataDirty = false
+
     // Fire #clearTimeout if the timeout is currently defined
     if (this._resizeRequestTimeout) {
       clearTimeout(this._resizeRequestTimeout)
diff --git a/assets/js/plugins.js b/assets/js/plugins.js
index 0595d7d..1027d61 100644
--- a/assets/js/plugins.js
+++ b/assets/js/plugins.js
@@ -26,3 +26,27 @@ export function uPlotTooltipPlugin (onHover) {
     }
   }
 }
+
+export function uPlotIsZoomedPlugin (onZoomIn, onZoomOut) {
+  return {
+    hooks: {
+      setSelect: u => {
+        u._zoomPluginIgnoreNextSetScale = true
+
+        if (onZoomIn) {
+          onZoomIn(u)
+        }
+      },
+      setScale: u => {
+        if (typeof u._zoomPluginIgnoreNextSetScale !== 'boolean') {
+          return
+        }
+        if (u._zoomPluginIgnoreNextSetScale) {
+          u._zoomPluginIgnoreNextSetScale = false
+        } else if (onZoomOut) {
+          onZoomOut(u)
+        }
+      }
+    }
+  }
+}
diff --git a/assets/js/servers.js b/assets/js/servers.js
index f103f67..717e0ac 100644
--- a/assets/js/servers.js
+++ b/assets/js/servers.js
@@ -3,7 +3,7 @@ import uPlot from 'uplot'
 import { RelativeScale } from './scale'
 
 import { formatNumber, formatTimestampSeconds, formatDate, formatMinecraftServerAddress, formatMinecraftVersions } from './util'
-import { uPlotTooltipPlugin } from './tooltip'
+import { uPlotTooltipPlugin } from './plugins'
 
 import MISSING_FAVICON from '../images/missing_favicon.svg'