From 020cddc76efdc489144eefe9ef7114350c419e05 Mon Sep 17 00:00:00 2001
From: Andrew Kingston <andrew@kingston.dev>
Date: Thu, 12 Jan 2023 14:42:05 +0000
Subject: [PATCH] Improve dropdown logic

---
 .../bbui/src/Actions/position_dropdown.js     | 96 ++++++++-----------
 1 file changed, 39 insertions(+), 57 deletions(-)

diff --git a/packages/bbui/src/Actions/position_dropdown.js b/packages/bbui/src/Actions/position_dropdown.js
index 88f8783633..e89f28a69e 100644
--- a/packages/bbui/src/Actions/position_dropdown.js
+++ b/packages/bbui/src/Actions/position_dropdown.js
@@ -2,86 +2,68 @@ export default function positionDropdown(
   element,
   { anchor, align, maxWidth, useAnchorWidth }
 ) {
-  let positionSide = "top"
-  let maxHeight = 0
-  let minWidth = 0
-  let dimensions = getDimensions(anchor)
-
-  function getDimensions() {
-    const {
-      bottom,
-      top: spaceAbove,
-      left,
-      width,
-    } = anchor.getBoundingClientRect()
-    const spaceBelow = window.innerHeight - bottom
-    const containerRect = element.getBoundingClientRect()
-
-    let y
-    if (window.innerHeight - bottom < 100) {
-      positionSide = "bottom"
-      maxHeight = spaceAbove - 20
-      y = window.innerHeight - spaceAbove + 5
-    } else {
-      positionSide = "top"
-      y = bottom + 5
-      maxHeight = spaceBelow - 20
+  const update = () => {
+    console.log("update")
+    const anchorBounds = anchor.getBoundingClientRect()
+    const elementBounds = element.getBoundingClientRect()
+    let styles = {
+      maxHeight: null,
+      minWidth: null,
+      maxWidth,
+      left: null,
+      top: null,
     }
 
+    // Determine vertical styles
+    if (window.innerHeight - anchorBounds.bottom < 100) {
+      styles.top = anchorBounds.top - elementBounds.height - 5
+    } else {
+      styles.top = anchorBounds.bottom + 5
+      styles.maxHeight = window.innerHeight - anchorBounds.bottom - 20
+    }
+
+    // Determine horizontal styles
     if (!maxWidth && useAnchorWidth) {
-      maxWidth = width
+      styles.maxWidth = anchorBounds.width
     }
     if (useAnchorWidth) {
-      minWidth = width
+      styles.minWidth = anchorBounds.width
     }
-
-    return {
-      [positionSide]: y,
-      left,
-      width,
-      containerWidth: containerRect.width,
-    }
-  }
-
-  function calcLeftPosition() {
-    let left
-
     if (align === "right") {
-      left = dimensions.left + dimensions.width - dimensions.containerWidth
+      styles.left = anchorBounds.left + anchorBounds.width - elementBounds.width
     } else if (align === "right-side") {
-      left = dimensions.left + dimensions.width
+      styles.left = anchorBounds.left + anchorBounds.width
     } else {
-      left = dimensions.left
+      styles.left = anchorBounds.left
     }
 
-    return left
+    // Apply styles
+    Object.entries(styles).forEach(([style, value]) => {
+      if (value) {
+        element.style[style] = `${value.toFixed(0)}px`
+      } else {
+        element.style[style] = null
+      }
+    })
   }
 
+  // Apply initial styles which don't need to change
   element.style.position = "absolute"
   element.style.zIndex = "9999"
-  if (maxWidth) {
-    element.style.maxWidth = `${maxWidth}px`
-  }
-  if (minWidth) {
-    element.style.minWidth = `${minWidth}px`
-  }
-  element.style.maxHeight = `${maxHeight.toFixed(0)}px`
-  element.style.transformOrigin = `center ${positionSide}`
-  element.style[positionSide] = `${dimensions[positionSide]}px`
-  element.style.left = `${calcLeftPosition(dimensions).toFixed(0)}px`
 
+  // Observe both anchor and element and resize the popover as appropriate
   const resizeObserver = new ResizeObserver(entries => {
-    entries.forEach(() => {
-      dimensions = getDimensions()
-      element.style[positionSide] = `${dimensions[positionSide]}px`
-      element.style.left = `${calcLeftPosition(dimensions).toFixed(0)}px`
-    })
+    entries.forEach(update)
   })
   resizeObserver.observe(anchor)
   resizeObserver.observe(element)
+
+  document.addEventListener("scroll", update, true)
+
   return {
     destroy() {
       resizeObserver.disconnect()
+      document.removeEventListener("scroll", update, true)
     },
   }
 }