From b735b587cda777ac481bb580c883d9734145f31e Mon Sep 17 00:00:00 2001
From: Liam DeBeasi <liamdebeasi@users.noreply.github.com>
Date: Thu, 1 Jul 2021 09:22:59 -0400
Subject: [PATCH] fix(datetime): scroll position no longer gets reset when
 using datetime in overlay (#23543)

---
 core/src/components/datetime/datetime.tsx     | 90 ++++++++++++++++---
 .../components/datetime/test/cover/index.html | 69 ++++++++++++++
 2 files changed, 149 insertions(+), 10 deletions(-)
 create mode 100644 core/src/components/datetime/test/cover/index.html

diff --git a/core/src/components/datetime/datetime.tsx b/core/src/components/datetime/datetime.tsx
index 727eead221..2e28491f3a 100644
--- a/core/src/components/datetime/datetime.tsx
+++ b/core/src/components/datetime/datetime.tsx
@@ -87,6 +87,11 @@ export class Datetime implements ComponentInterface {
   private parsedYearValues?: number[];
   private parsedDayValues?: number[];
 
+  private destroyCalendarIO?: () => void;
+  private destroyKeyboardMO?: () => void;
+  private destroyTimeScroll?: () => void;
+  private destroyMonthAndYearScroll?: () => void;
+
   private minParts?: any;
   private maxParts?: any;
 
@@ -441,6 +446,10 @@ export class Datetime implements ComponentInterface {
     const mo = new MutationObserver(checkCalendarBodyFocus);
     mo.observe(calendarBodyRef, { attributeFilter: ['class'], attributeOldValue: true });
 
+    this.destroyKeyboardMO = () => {
+      mo?.disconnect();
+    }
+
     /**
      * We must use keydown not keyup as we want
      * to prevent scrolling when using the arrow keys.
@@ -729,6 +738,11 @@ export class Datetime implements ComponentInterface {
         root: calendarBodyRef
        });
       startIO.observe(startMonth);
+
+      this.destroyCalendarIO = () => {
+        endIO?.disconnect();
+        startIO?.disconnect();
+      }
    });
   }
 
@@ -743,6 +757,31 @@ export class Datetime implements ComponentInterface {
     }
   }
 
+  /**
+   * Clean up all listeners except for the overlay
+   * listener. This is so that we can re-create the listeners
+   * if the datetime has been hidden/presented by a modal or popover.
+   */
+  private destroyListeners = () => {
+    const { destroyCalendarIO, destroyKeyboardMO, destroyTimeScroll, destroyMonthAndYearScroll } = this;
+
+    if (destroyCalendarIO !== undefined) {
+      destroyCalendarIO();
+    }
+
+    if (destroyKeyboardMO !== undefined) {
+      destroyKeyboardMO();
+    }
+
+    if (destroyTimeScroll !== undefined) {
+      destroyTimeScroll();
+    }
+
+    if (destroyMonthAndYearScroll !== undefined) {
+      destroyMonthAndYearScroll();
+    }
+  }
+
   componentDidLoad() {
     const mode = getIonMode(this);
 
@@ -758,11 +797,6 @@ export class Datetime implements ComponentInterface {
       const ev = entries[0];
       if (!ev.isIntersecting) { return; }
 
-      /**
-       * This needs to run at most once for initial setup.
-       */
-      visibleIO!.disconnect()
-
       this.initializeCalendarIOListeners();
       this.initializeKeyboardListeners();
       this.initializeTimeScrollListener();
@@ -786,6 +820,27 @@ export class Datetime implements ComponentInterface {
     }
     visibleIO = new IntersectionObserver(visibleCallback, { threshold: 0.01 });
     visibleIO.observe(this.el);
+
+    /**
+     * We need to clean up listeners when the datetime is hidden
+     * in a popover/modal so that we can properly scroll containers
+     * back into view if they are re-presented. When the datetime is hidden
+     * the scroll areas have scroll widths/heights of 0px, so any snapping
+     * we did originally has been lost.
+     */
+    let hiddenIO: IntersectionObserver | undefined;
+    const hiddenCallback = (entries: IntersectionObserverEntry[]) => {
+      const ev = entries[0];
+      if (ev.isIntersecting) { return; }
+
+      this.destroyListeners();
+
+      writeTask(() => {
+        this.el.classList.remove('datetime-ready');
+      });
+    }
+    hiddenIO = new IntersectionObserver(hiddenCallback, { threshold: 0 });
+    hiddenIO.observe(this.el);
   }
 
   /**
@@ -897,8 +952,15 @@ export class Datetime implements ComponentInterface {
      * does not fire when we do our initial scrollIntoView above.
      */
     raf(() => {
-      monthRef.addEventListener('scroll', () => scrollCallback('month'));
-      yearRef.addEventListener('scroll', () => scrollCallback('year'));
+      const monthScroll = () => scrollCallback('month');
+      const yearScroll = () => scrollCallback('year');
+      monthRef.addEventListener('scroll', monthScroll);
+      yearRef.addEventListener('scroll', yearScroll);
+
+      this.destroyMonthAndYearScroll = () => {
+        monthRef.removeEventListener('scroll', monthScroll);
+        yearRef.removeEventListener('scroll', yearScroll);
+      }
     });
   }
 
@@ -979,8 +1041,16 @@ export class Datetime implements ComponentInterface {
        * does not fire when we do our initial scrollIntoView above.
        */
       raf(() => {
-        timeHourRef.addEventListener('scroll', () => scrollCallback('hour'));
-        timeMinuteRef.addEventListener('scroll', () => scrollCallback('minute'));
+        const hourScroll = () => scrollCallback('hour');
+        const minuteScroll = () => scrollCallback('minute');
+
+        timeHourRef.addEventListener('scroll', hourScroll);
+        timeMinuteRef.addEventListener('scroll', minuteScroll);
+
+        this.destroyTimeScroll = () => {
+          timeHourRef.removeEventListener('scroll', hourScroll);
+          timeMinuteRef.removeEventListener('scroll', minuteScroll);
+        }
       });
     });
   }
@@ -1076,7 +1146,7 @@ export class Datetime implements ComponentInterface {
             <slot name="buttons">
               <ion-buttons>
                 <ion-button color={this.color} onClick={() => this.cancel(true)}>{this.cancelText}</ion-button>
-                <ion-button color={this.color} onClick={() => this.confirm()}>{this.doneText}</ion-button>
+                <ion-button color={this.color} onClick={() => this.confirm(true)}>{this.doneText}</ion-button>
               </ion-buttons>
             </slot>
           </div>
diff --git a/core/src/components/datetime/test/cover/index.html b/core/src/components/datetime/test/cover/index.html
new file mode 100644
index 0000000000..f0a00dbbc4
--- /dev/null
+++ b/core/src/components/datetime/test/cover/index.html
@@ -0,0 +1,69 @@
+<!DOCTYPE html>
+<html lang="en" dir="ltr">
+  <head>
+    <meta charset="UTF-8">
+    <title>Datetime - Cover</title>
+    <meta name="viewport"
+      content="width=device-width, initial-scale=1.0, minimum-scale=1.0">
+    <link href="../../../../../css/ionic.bundle.css" rel="stylesheet">
+    <link href="../../../../../scripts/testing/styles.css" rel="stylesheet">
+    <script src="../../../../../scripts/testing/scripts.js"></script>
+    <script type="module" src="../../../../../dist/ionic/ionic.esm.js"></script>
+    <style>
+      .grid {
+        display: grid;
+        grid-template-columns: repeat(2, minmax(250px, 1fr));
+        grid-gap: 20px;
+      }
+      h2 {
+        font-size: 12px;
+        font-weight: normal;
+
+        color: #6f7378;
+
+        margin-top: 10px;
+        margin-left: 5px;
+      }
+
+      ion-modal {
+        --width: 350px;
+      }
+
+      .placeholder {
+        color: #777;
+      }
+    </style>
+  </head>
+  <body>
+    <ion-app>
+      <ion-header translucent="true">
+        <ion-toolbar>
+          <ion-title>Datetime - Cover</ion-title>
+        </ion-toolbar>
+      </ion-header>
+      <ion-content class="ion-padding">
+        <ion-item button="true" id="datetime-trigger">
+          <ion-label>Birthday</ion-label>
+          <ion-text class="placeholder">Select a date</ion-text>
+        </ion-item>
+
+        <ion-modal trigger="datetime-trigger">
+          <ion-datetime
+            show-default-title="true"
+            show-default-buttons="true"
+          ></ion-datetime>
+        </ion-modal>
+      </ion-content>
+
+      <script>
+        const datetime = document.querySelector('ion-datetime');
+        const text = document.querySelector('ion-text');
+        datetime.addEventListener('ionChange', (ev) => {
+          const date = new Date(ev.detail.value);
+          text.innerText = new Intl.DateTimeFormat('en-US', { year: 'numeric', month: 'long', day: 'numeric' }).format(date);
+          text.classList.remove('placeholder');
+        });
+      </script>
+    </ion-app>
+  </body>
+</html>