improve scrolling to in-page location

Author: RobinMalfait

packages/@headlessui-react/src/components/dialog/dialog.tsx

@@ -101,6 +101,7 @@ function useScrollLock(
     if (!ownerDocument) return
 
     let d = disposables()
+    let scrollPosition = window.pageYOffset
 
     function style(node: HTMLElement, property: string, value: string) {
       let previous = node.style.getPropertyValue(property)
@@ -123,10 +124,36 @@ function useScrollLock(
     }
 
     if (isIOS()) {
-      let scrollPosition = window.pageYOffset
-      style(document.body, 'marginTop', `-${scrollPosition}px`)
+      style(ownerDocument.body, 'marginTop', `-${scrollPosition}px`)
       window.scrollTo(0, 0)
 
+      // Relatively hacky, but if you click a link like `<a href="#foo">` in the Dialog, and there
+      // exists an element on the page (outside of the Dialog) with that id, then the browser will
+      // scroll to that position. However, this is not the case if the element we want to scroll to
+      // is higher and the browser needs to scroll up, but it doesn't do that.
+      //
+      // Let's try and capture that element and store it, so that we can later scroll to it once the
+      // Dialog closes.
+      let scrollToElement: HTMLElement | null = null
+      d.addEventListener(
+        ownerDocument,
+        'click',
+        (e) => {
+          if (e.target instanceof HTMLElement) {
+            try {
+              let anchor = e.target.closest('a')
+              if (!anchor) return
+              let { hash } = new URL(anchor.href)
+              let el = ownerDocument.querySelector(hash)
+              if (el && !resolveAllowedContainers().some((container) => container.contains(el))) {
+                scrollToElement = el as HTMLElement
+              }
+            } catch (err) {}
+          }
+        },
+        true
+      )
+
       d.addEventListener(
         ownerDocument,
         'touchmove',
@@ -161,6 +188,13 @@ function useScrollLock(
         // (Since the value of window.pageYOffset is 0 in the first case, we should be able to
         // always sum these values)
         window.scrollTo(0, window.pageYOffset + scrollPosition)
+
+        // If we captured an element that should be scrolled to, then we can try to do that if the
+        // element is still connected (aka, still in the DOM).
+        if (scrollToElement && scrollToElement.isConnected) {
+          scrollToElement.scrollIntoView({ block: 'nearest' })
+          scrollToElement = null
+        }
       })
     }
 

packages/@headlessui-vue/src/components/dialog/dialog.ts

@@ -227,6 +227,7 @@ export let Dialog = defineComponent({
       if (!owner) return
 
       let d = disposables()
+      let scrollPosition = window.pageYOffset
 
       function style(node: HTMLElement, property: string, value: string) {
         let previous = node.style.getPropertyValue(property)
@@ -249,10 +250,36 @@ export let Dialog = defineComponent({
       }
 
       if (isIOS()) {
-        let scrollPosition = window.pageYOffset
-        style(document.body, 'marginTop', `-${scrollPosition}px`)
+        style(owner.body, 'marginTop', `-${scrollPosition}px`)
         window.scrollTo(0, 0)
 
+        // Relatively hacky, but if you click a link like `<a href="#foo">` in the Dialog, and there
+        // exists an element on the page (outside of the Dialog) with that id, then the browser will
+        // scroll to that position. However, this is not the case if the element we want to scroll to
+        // is higher and the browser needs to scroll up, but it doesn't do that.
+        //
+        // Let's try and capture that element and store it, so that we can later scroll to it once the
+        // Dialog closes.
+        let scrollToElement: HTMLElement | null = null
+        d.addEventListener(
+          owner,
+          'click',
+          (e) => {
+            if (e.target instanceof HTMLElement) {
+              try {
+                let anchor = e.target.closest('a')
+                if (!anchor) return
+                let { hash } = new URL(anchor.href)
+                let el = owner!.querySelector(hash)
+                if (el && !resolveAllowedContainers().some((container) => container.contains(el))) {
+                  scrollToElement = el as HTMLElement
+                }
+              } catch (err) {}
+            }
+          },
+          true
+        )
+
         d.addEventListener(
           owner,
           'touchmove',
@@ -288,6 +315,13 @@ export let Dialog = defineComponent({
           // (Since the value of window.pageYOffset is 0 in the first case, we should be able to
           // always sum these values)
           window.scrollTo(0, window.pageYOffset + scrollPosition)
+
+          // If we captured an element that should be scrolled to, then we can try to do that if the
+          // element is still connected (aka, still in the DOM).
+          if (scrollToElement && scrollToElement.isConnected) {
+            scrollToElement.scrollIntoView({ block: 'nearest' })
+            scrollToElement = null
+          }
         })
       }