From e986f40667cb3ab0a21df448cfa8ca11c79b6a12 Mon Sep 17 00:00:00 2001
From: Oskar Nyberg <oskar@mullvad.net>
Date: Tue, 5 May 2020 11:15:58 +0200
Subject: [PATCH] Scroll to expose expanded items in location list

---
 gui/src/renderer/components/Accordion.tsx     | 36 ++++++--
 .../renderer/components/BridgeLocations.tsx   |  8 +-
 gui/src/renderer/components/CityRow.tsx       | 24 +++++-
 gui/src/renderer/components/CountryRow.tsx    | 24 +++++-
 .../renderer/components/CustomScrollbars.tsx  | 48 ++++++-----
 gui/src/renderer/components/ExitLocations.tsx |  8 +-
 gui/src/renderer/components/LocationList.tsx  |  6 ++
 .../renderer/components/SelectLocation.tsx    | 84 ++++++++++++++-----
 8 files changed, 186 insertions(+), 52 deletions(-)

diff --git a/gui/src/renderer/components/Accordion.tsx b/gui/src/renderer/components/Accordion.tsx
index ca3723584583..1a26d765cd14 100644
--- a/gui/src/renderer/components/Accordion.tsx
+++ b/gui/src/renderer/components/Accordion.tsx
@@ -5,6 +5,8 @@ interface IProps {
   expanded: boolean;
   animationDuration: number;
   children?: React.ReactNode;
+  onWillExpand?: (contentHeight: number) => void;
+  onTransitionEnd?: () => void;
 }
 
 interface IState {
@@ -28,6 +30,7 @@ const Content = styled.div({
 
 export default class Accordion extends React.Component<IProps, IState> {
   private containerRef = React.createRef<HTMLDivElement>();
+  private contentRef = React.createRef<HTMLDivElement>();
 
   public static defaultProps = {
     expanded: true,
@@ -54,25 +57,30 @@ export default class Accordion extends React.Component<IProps, IState> {
         height={this.state.containerHeight}
         animationDuration={this.props.animationDuration}
         onTransitionEnd={this.onTransitionEnd}>
-        <Content>{this.state.mountChildren && this.props.children}</Content>
+        <Content ref={this.contentRef}>{this.state.mountChildren && this.props.children}</Content>
       </Container>
     );
   }
 
   private expand() {
     // Make sure the children are mounted first before expanding the accordion
+    this.mountChildren(() => {
+      this.onWillExpand();
+      this.setState({ containerHeight: this.getContentHeightWithUnit() });
+    });
+  }
+
+  private mountChildren(childrenDidMount: () => void) {
     if (!this.state.mountChildren) {
-      this.setState({ mountChildren: true }, () => {
-        this.setState({ containerHeight: this.getContentHeight() });
-      });
+      this.setState({ mountChildren: true }, childrenDidMount);
     } else {
-      this.setState({ containerHeight: this.getContentHeight() });
+      childrenDidMount();
     }
   }
 
   private collapse() {
     // First change height to height in px since it's not possible to transition to/from auto
-    this.setState({ containerHeight: this.getContentHeight() }, () => {
+    this.setState({ containerHeight: this.getContentHeightWithUnit() }, () => {
       // Make sure new height has been applied
       // eslint-disable-next-line @typescript-eslint/no-unused-expressions
       this.containerRef.current?.offsetHeight;
@@ -80,11 +88,23 @@ export default class Accordion extends React.Component<IProps, IState> {
     });
   }
 
-  private getContentHeight(): string {
-    return (this.containerRef.current?.scrollHeight ?? 0) + 'px';
+  private getContentHeightWithUnit(): string {
+    return (this.getContentHeight() ?? 0) + 'px';
+  }
+
+  private getContentHeight(): number | undefined {
+    return this.contentRef.current?.offsetHeight;
+  }
+
+  private onWillExpand() {
+    const contentHeight = this.getContentHeight();
+    if (contentHeight) {
+      this.props.onWillExpand?.(contentHeight);
+    }
   }
 
   private onTransitionEnd = () => {
+    this.props.onTransitionEnd?.();
     if (this.props.expanded) {
       // Height auto enables the container to grow if the content changes size
       this.setState({ containerHeight: 'auto' });
diff --git a/gui/src/renderer/components/BridgeLocations.tsx b/gui/src/renderer/components/BridgeLocations.tsx
index 7d464e092685..802797eb7769 100644
--- a/gui/src/renderer/components/BridgeLocations.tsx
+++ b/gui/src/renderer/components/BridgeLocations.tsx
@@ -21,6 +21,8 @@ interface IBridgeLocationsProps {
   selectedValue?: LiftedConstraint<RelayLocation>;
   selectedElementRef?: React.Ref<React.ReactInstance>;
   onSelect?: (value: LocationSelection<SpecialBridgeLocationType>) => void;
+  onWillExpand?: (locationRect: DOMRect, expandedContentHeight: number) => void;
+  onTransitionEnd?: () => void;
 }
 
 const BridgeLocations = React.forwardRef(function BridgeLocationsT(
@@ -49,7 +51,11 @@ const BridgeLocations = React.forwardRef(function BridgeLocationsT(
           {messages.pgettext('select-location-view', 'Closest to exit server')}
         </SpecialLocation>
       </SpecialLocations>
-      <RelayLocations source={props.source} />
+      <RelayLocations
+        source={props.source}
+        onWillExpand={props.onWillExpand}
+        onTransitionEnd={props.onTransitionEnd}
+      />
     </LocationList>
   );
 });
diff --git a/gui/src/renderer/components/CityRow.tsx b/gui/src/renderer/components/CityRow.tsx
index c8041abdbdf3..c015bd5f762c 100644
--- a/gui/src/renderer/components/CityRow.tsx
+++ b/gui/src/renderer/components/CityRow.tsx
@@ -1,4 +1,5 @@
 import * as React from 'react';
+import ReactDOM from 'react-dom';
 import { Component, Styles, Types, View } from 'reactxp';
 import { colors } from '../../config.json';
 import { compareRelayLocation, RelayLocation } from '../../shared/daemon-rpc-types';
@@ -18,6 +19,8 @@ interface IProps {
   expanded: boolean;
   onSelect?: (location: RelayLocation) => void;
   onExpand?: (location: RelayLocation, value: boolean) => void;
+  onWillExpand?: (locationRect: DOMRect, expandedContentHeight: number) => void;
+  onTransitionEnd?: () => void;
   children?: RelayRowElement | RelayRowElement[];
 }
 
@@ -30,6 +33,8 @@ const styles = {
 };
 
 export default class CityRow extends Component<IProps> {
+  private buttonRef = React.createRef<Cell.CellButton>();
+
   public static compareProps(oldProps: IProps, nextProps: IProps): boolean {
     if (React.Children.count(oldProps.children) !== React.Children.count(nextProps.children)) {
       return false;
@@ -70,6 +75,7 @@ export default class CityRow extends Component<IProps> {
     return (
       <View>
         <Cell.CellButton
+          ref={this.buttonRef}
           onPress={this.handlePress}
           disabled={!this.props.hasActiveRelays}
           selected={this.props.selected}
@@ -83,7 +89,15 @@ export default class CityRow extends Component<IProps> {
           {hasChildren && <ChevronButton onPress={this.toggleCollapse} up={this.props.expanded} />}
         </Cell.CellButton>
 
-        {hasChildren && <Accordion expanded={this.props.expanded}>{this.props.children}</Accordion>}
+        {hasChildren && (
+          <Accordion
+            expanded={this.props.expanded}
+            onWillExpand={this.onWillExpand}
+            onTransitionEnd={this.props.onTransitionEnd}
+            animationDuration={150}>
+            {this.props.children}
+          </Accordion>
+        )}
       </View>
     );
   }
@@ -100,4 +114,12 @@ export default class CityRow extends Component<IProps> {
       this.props.onSelect(this.props.location);
     }
   };
+
+  private onWillExpand = (nextHeight: number) => {
+    const buttonNode = ReactDOM.findDOMNode(this.buttonRef.current);
+    if (buttonNode instanceof HTMLElement) {
+      const buttonRect = buttonNode.getBoundingClientRect();
+      this.props.onWillExpand?.(buttonRect, nextHeight);
+    }
+  };
 }
diff --git a/gui/src/renderer/components/CountryRow.tsx b/gui/src/renderer/components/CountryRow.tsx
index 026a55343d41..5218afdf73d6 100644
--- a/gui/src/renderer/components/CountryRow.tsx
+++ b/gui/src/renderer/components/CountryRow.tsx
@@ -1,4 +1,5 @@
 import * as React from 'react';
+import ReactDOM from 'react-dom';
 import { Component, Styles, Types, View } from 'reactxp';
 import { compareRelayLocation, RelayLocation } from '../../shared/daemon-rpc-types';
 import Accordion from './Accordion';
@@ -17,6 +18,8 @@ interface IProps {
   expanded: boolean;
   onSelect?: (location: RelayLocation) => void;
   onExpand?: (location: RelayLocation, value: boolean) => void;
+  onWillExpand?: (locationRect: DOMRect, expandedContentHeight: number) => void;
+  onTransitionEnd?: () => void;
   children?: CityRowElement | CityRowElement[];
 }
 
@@ -32,6 +35,8 @@ const styles = {
 };
 
 export default class CountryRow extends Component<IProps> {
+  private buttonRef = React.createRef<Cell.CellButton>();
+
   public static compareProps(oldProps: IProps, nextProps: IProps) {
     if (React.Children.count(oldProps.children) !== React.Children.count(nextProps.children)) {
       return false;
@@ -78,6 +83,7 @@ export default class CountryRow extends Component<IProps> {
     return (
       <View style={styles.container}>
         <Cell.CellButton
+          ref={this.buttonRef}
           style={styles.base}
           onPress={this.handlePress}
           disabled={!this.props.hasActiveRelays}
@@ -92,7 +98,15 @@ export default class CountryRow extends Component<IProps> {
           ) : null}
         </Cell.CellButton>
 
-        {hasChildren && <Accordion expanded={this.props.expanded}>{this.props.children}</Accordion>}
+        {hasChildren && (
+          <Accordion
+            expanded={this.props.expanded}
+            onWillExpand={this.onWillExpand}
+            onTransitionEnd={this.props.onTransitionEnd}
+            animationDuration={150}>
+            {this.props.children}
+          </Accordion>
+        )}
       </View>
     );
   }
@@ -109,4 +123,12 @@ export default class CountryRow extends Component<IProps> {
       this.props.onSelect(this.props.location);
     }
   };
+
+  private onWillExpand = (nextHeight: number) => {
+    const buttonNode = ReactDOM.findDOMNode(this.buttonRef.current);
+    if (buttonNode instanceof HTMLElement) {
+      const buttonRect = buttonNode.getBoundingClientRect();
+      this.props.onWillExpand?.(buttonRect, nextHeight);
+    }
+  };
 }
diff --git a/gui/src/renderer/components/CustomScrollbars.tsx b/gui/src/renderer/components/CustomScrollbars.tsx
index fc91d7d23975..aca32e5f60dc 100644
--- a/gui/src/renderer/components/CustomScrollbars.tsx
+++ b/gui/src/renderer/components/CustomScrollbars.tsx
@@ -1,4 +1,5 @@
 import * as React from 'react';
+import { Scheduler } from '../../shared/scheduler';
 
 const AUTOHIDE_TIMEOUT = 1000;
 
@@ -54,7 +55,7 @@ export default class CustomScrollbars extends React.Component<IProps, IState> {
   private scrollableRef = React.createRef<HTMLDivElement>();
   private trackRef = React.createRef<HTMLDivElement>();
   private thumbRef = React.createRef<HTMLDivElement>();
-  private autoHideTimer?: NodeJS.Timeout;
+  private autoHideScheduler = new Scheduler();
 
   public scrollToTop() {
     const scrollable = this.scrollableRef.current;
@@ -86,6 +87,29 @@ export default class CustomScrollbars extends React.Component<IProps, IState> {
     }
   }
 
+  public scrollIntoView(elementRect: DOMRect) {
+    const scrollable = this.scrollableRef.current;
+    if (scrollable) {
+      const scrollableRect = scrollable.getBoundingClientRect();
+      // The element position needs to be relative to the parent, not the document
+      const elementTop = elementRect.top - scrollableRect.top;
+      const bottomOverflow = elementTop + elementRect.height - scrollableRect.height;
+
+      let scrollDistance = 0;
+      if (elementTop < 0) {
+        scrollDistance = elementTop;
+      } else if (bottomOverflow > 0) {
+        // Prevent the elements top from being scrolled out of the visible area
+        scrollDistance = Math.min(bottomOverflow, elementTop);
+      }
+
+      scrollable.scrollBy({
+        top: scrollDistance,
+        behavior: 'smooth',
+      });
+    }
+  }
+
   public getScrollPosition(): [number, number] {
     const scroll = this.scrollableRef.current;
     if (scroll) {
@@ -130,7 +154,7 @@ export default class CustomScrollbars extends React.Component<IProps, IState> {
   }
 
   public componentWillUnmount() {
-    this.stopAutoHide();
+    this.autoHideScheduler.cancel();
 
     document.removeEventListener('mousemove', this.handleMouseMove);
     document.removeEventListener('mouseup', this.handleMouseUp);
@@ -206,7 +230,7 @@ export default class CustomScrollbars extends React.Component<IProps, IState> {
   };
 
   private handleEnterTrack = () => {
-    this.stopAutoHide();
+    this.autoHideScheduler.cancel();
     this.setState({
       isTrackHovered: true,
       showScrollIndicators: true,
@@ -326,10 +350,7 @@ export default class CustomScrollbars extends React.Component<IProps, IState> {
   }
 
   private startAutoHide() {
-    if (this.autoHideTimer) {
-      clearTimeout(this.autoHideTimer);
-    }
-    this.autoHideTimer = global.setTimeout(() => {
+    this.autoHideScheduler.schedule(() => {
       this.setState({
         showScrollIndicators: false,
         showTrack: false,
@@ -339,11 +360,7 @@ export default class CustomScrollbars extends React.Component<IProps, IState> {
   }
 
   private startAutoShrink() {
-    if (this.autoHideTimer) {
-      clearTimeout(this.autoHideTimer);
-    }
-
-    this.autoHideTimer = global.setTimeout(() => {
+    this.autoHideScheduler.schedule(() => {
       this.setState({
         showTrack: false,
         isWide: false,
@@ -351,13 +368,6 @@ export default class CustomScrollbars extends React.Component<IProps, IState> {
     }, AUTOHIDE_TIMEOUT);
   }
 
-  private stopAutoHide() {
-    if (this.autoHideTimer) {
-      clearTimeout(this.autoHideTimer);
-      this.autoHideTimer = undefined;
-    }
-  }
-
   private isPointInsideOfElement(element: HTMLElement, point: { x: number; y: number }) {
     const rect = element.getBoundingClientRect();
     return (
diff --git a/gui/src/renderer/components/ExitLocations.tsx b/gui/src/renderer/components/ExitLocations.tsx
index 9fcc1e8ad418..e4174a0e7cb0 100644
--- a/gui/src/renderer/components/ExitLocations.tsx
+++ b/gui/src/renderer/components/ExitLocations.tsx
@@ -13,6 +13,8 @@ interface IExitLocationsProps {
   selectedValue?: RelayLocation;
   selectedElementRef?: React.Ref<React.ReactInstance>;
   onSelect?: (value: LocationSelection<never>) => void;
+  onWillExpand?: (locationRect: DOMRect, expandedContentHeight: number) => void;
+  onTransitionEnd?: () => void;
 }
 
 const ExitLocations = React.forwardRef(function ExitLocationsT(
@@ -30,7 +32,11 @@ const ExitLocations = React.forwardRef(function ExitLocationsT(
       selectedValue={selectedValue}
       selectedElementRef={props.selectedElementRef}
       onSelect={props.onSelect}>
-      <RelayLocations source={props.source} />
+      <RelayLocations
+        source={props.source}
+        onWillExpand={props.onWillExpand}
+        onTransitionEnd={props.onTransitionEnd}
+      />
     </LocationList>
   );
 });
diff --git a/gui/src/renderer/components/LocationList.tsx b/gui/src/renderer/components/LocationList.tsx
index 2acb1adf6684..efd8969e4faa 100644
--- a/gui/src/renderer/components/LocationList.tsx
+++ b/gui/src/renderer/components/LocationList.tsx
@@ -246,6 +246,8 @@ interface IRelayLocationsProps {
   expandedItems?: RelayLocation[];
   onSelect?: (location: RelayLocation) => void;
   onExpand?: (location: RelayLocation, expand: boolean) => void;
+  onWillExpand?: (locationRect: DOMRect, expandedContentHeight: number) => void;
+  onTransitionEnd?: () => void;
 }
 
 interface ICommonCellProps<T> {
@@ -269,6 +271,8 @@ export class RelayLocations extends Component<IRelayLocationsProps> {
               expanded={this.isExpanded(countryLocation)}
               onSelect={this.handleSelection}
               onExpand={this.handleExpand}
+              onWillExpand={this.props.onWillExpand}
+              onTransitionEnd={this.props.onTransitionEnd}
               {...this.getCommonCellProps<CountryRow>(countryLocation)}>
               {relayCountry.cities.map((relayCity) => {
                 const cityLocation: RelayLocation = {
@@ -283,6 +287,8 @@ export class RelayLocations extends Component<IRelayLocationsProps> {
                     expanded={this.isExpanded(cityLocation)}
                     onSelect={this.handleSelection}
                     onExpand={this.handleExpand}
+                    onWillExpand={this.props.onWillExpand}
+                    onTransitionEnd={this.props.onTransitionEnd}
                     {...this.getCommonCellProps<CityRow>(cityLocation)}>
                     {relayCity.relays.map((relay) => {
                       const relayLocation: RelayLocation = {
diff --git a/gui/src/renderer/components/SelectLocation.tsx b/gui/src/renderer/components/SelectLocation.tsx
index 8ea980a5ae7b..de2f98128abf 100644
--- a/gui/src/renderer/components/SelectLocation.tsx
+++ b/gui/src/renderer/components/SelectLocation.tsx
@@ -44,6 +44,7 @@ interface ISelectLocationSnapshot {
 
 export default class SelectLocation extends Component<IProps> {
   private scrollView = React.createRef<CustomScrollbars>();
+  private spacePreAllocationViewRef = React.createRef<SpacePreAllocationView>();
   private selectedExitLocationRef = React.createRef<React.ReactInstance>();
   private selectedBridgeLocationRef = React.createRef<React.ReactInstance>();
 
@@ -128,27 +129,33 @@ export default class SelectLocation extends Component<IProps> {
               </NavigationBar>
               <View style={styles.container}>
                 <NavigationScrollbars ref={this.scrollView}>
-                  <View style={styles.content}>
-                    {this.props.locationScope === LocationScope.relay ? (
-                      <ExitLocations
-                        ref={this.exitLocationList}
-                        source={this.props.relayLocations}
-                        defaultExpandedLocations={this.getExpandedLocationsFromSnapshot()}
-                        selectedValue={this.props.selectedExitLocation}
-                        selectedElementRef={this.selectedExitLocationRef}
-                        onSelect={this.onSelectExitLocation}
-                      />
-                    ) : (
-                      <BridgeLocations
-                        ref={this.bridgeLocationList}
-                        source={this.props.bridgeLocations}
-                        defaultExpandedLocations={this.getExpandedLocationsFromSnapshot()}
-                        selectedValue={this.props.selectedBridgeLocation}
-                        selectedElementRef={this.selectedBridgeLocationRef}
-                        onSelect={this.onSelectBridgeLocation}
-                      />
-                    )}
-                  </View>
+                  <SpacePreAllocationView ref={this.spacePreAllocationViewRef}>
+                    <View style={styles.content}>
+                      {this.props.locationScope === LocationScope.relay ? (
+                        <ExitLocations
+                          ref={this.exitLocationList}
+                          source={this.props.relayLocations}
+                          defaultExpandedLocations={this.getExpandedLocationsFromSnapshot()}
+                          selectedValue={this.props.selectedExitLocation}
+                          selectedElementRef={this.selectedExitLocationRef}
+                          onSelect={this.onSelectExitLocation}
+                          onWillExpand={this.onWillExpand}
+                          onTransitionEnd={this.spacePreAllocationViewRef.current?.reset}
+                        />
+                      ) : (
+                        <BridgeLocations
+                          ref={this.bridgeLocationList}
+                          source={this.props.bridgeLocations}
+                          defaultExpandedLocations={this.getExpandedLocationsFromSnapshot()}
+                          selectedValue={this.props.selectedBridgeLocation}
+                          selectedElementRef={this.selectedBridgeLocationRef}
+                          onSelect={this.onSelectBridgeLocation}
+                          onWillExpand={this.onWillExpand}
+                          onTransitionEnd={this.spacePreAllocationViewRef.current?.reset}
+                        />
+                      )}
+                    </View>
+                  </SpacePreAllocationView>
                 </NavigationScrollbars>
               </View>
             </NavigationContainer>
@@ -219,4 +226,39 @@ export default class SelectLocation extends Component<IProps> {
       this.props.onSelectClosestToExit();
     }
   };
+
+  private onWillExpand = (locationRect: DOMRect, expandedContentHeight: number) => {
+    locationRect.height += expandedContentHeight;
+    this.spacePreAllocationViewRef.current?.allocate(expandedContentHeight);
+    this.scrollView.current?.scrollIntoView(locationRect);
+  };
+}
+
+interface ISpacePreAllocationView {
+  children?: React.ReactNode;
+}
+
+class SpacePreAllocationView extends Component<ISpacePreAllocationView> {
+  private ref = React.createRef<HTMLDivElement>();
+
+  public allocate(height: number) {
+    if (this.ref.current) {
+      this.minHeight = this.ref.current.offsetHeight + height + 'px';
+    }
+  }
+
+  public reset = () => {
+    this.minHeight = 'auto';
+  };
+
+  public render() {
+    return <div ref={this.ref}>{this.props.children}</div>;
+  }
+
+  private set minHeight(value: string) {
+    const element = this.ref.current;
+    if (element) {
+      element.style.minHeight = value;
+    }
+  }
 }