Ignore non-rendered elements

dividat · Sep 17, 2024 · 75d8e41 · 75d8e41
1 parent 2956641
commit 75d8e41
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Showing 3 changed files with 97 additions and 2 deletions.
diff --git a/cypress/e2e/spec.cy.ts b/cypress/e2e/spec.cy.ts
@@ -280,4 +280,12 @@ describe("focus-shift spec", () => {
       expect(before).to.not.equal(after)
     })
   })
+
+  it(
+    "ignores non-rendered elements",
+    testFor("./cypress/fixtures/non-rendered-elements.html", { className: "columns" }, [
+      { eventType: "keydown", selector: "#first-button", options: keyevent({ key: "ArrowRight" }) },
+      { eventType: "keydown", selector: "#last-button", options: keyevent({ key: "ArrowRight" }) }
+    ])
+  )
 })
diff --git a/cypress/fixtures/non-rendered-elements.html b/cypress/fixtures/non-rendered-elements.html
@@ -0,0 +1,42 @@
+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <link rel="stylesheet" href="styles.css" />
+    <style>
+      .opacityZero {
+        opacity: 0;
+      }
+      .displayNone {
+        display: none;
+      }
+      .visibilityHidden {
+        visibility: hidden;
+      }
+      .visibilityCollapse {
+        visibility: collapse;
+      }
+      .zeroWidth {
+        display: inline-block;
+        width: 0;
+        overflow: hidden;
+      }
+      .zeroHeight {
+        display: inline-block;
+        height: 0;
+        overflow: hidden;
+      }
+    </style>
+  </head>
+  <body>
+    <button id="first-button">First Button</button>
+    <button class="opacityZero">Transparent Button</button>
+    <button class="displayNone">Hidden Button</button>
+    <button class="visibilityHidden">Hidden Button</button>
+    <button class="visibilityCollapse">Hidden Button</button>
+    <span tabindex="1" class="zeroWidth">Hidden Element</span>
+    <span tabindex="1" class="zeroHeight">Hidden Element</span>
+    <button id="last-button">Last Button</button>
+    <script src="../../index.js"></script>
+  </body>
+</html>
diff --git a/index.js b/index.js
@@ -90,7 +90,7 @@ function focusInitial(direction, container) {
     .filter(hasTabIndex)
     .filter((elem) => elem.tabIndex > 0)
   const markedElement = getMinimumBy(tabindexed, (elem) => elem.tabIndex)
-  if (markedElement != null) {
+  if (markedElement != null && isBeingRendered(markedElement)) {
     applyFocus(direction, makeVirtualOrigin(direction), markedElement)
     return
   }
@@ -137,7 +137,8 @@ function getFocusableElements(container) {
  * - it is a descendant of an element marked with `data-focus-skip`,
  * - it is a descendant of a closed `details` element,
  * - it is `disabled`,
- * - it is `inert`.
+ * - it is `inert`
+ * - it is not being rendered.
  *
  * Otherwise it counts as focusable.
  *
@@ -162,9 +163,53 @@ function isFocusable(element) {
   // Descends from closed details element
   if (hasClosedDetailsAncestor(element)) return false
 
+  return isBeingRendered(element)
+}
+
+/**
+ * Decide whether an element is being rendered or not.
+ *
+ * An element is not being rendered if:
+ * 1. An element has the style "visibility: hidden | collapse" or "display: none". (Note: these are inherited.)
+ * 2. An element has the style "opacity: 0". (Somewhat of a white lie, as it will still affect layout.)
+ * 3. The width or height of an element is explicitly set to 0.
+ * 4. An element's parent is hidden.
+ *
+ * @see {@link https://html.spec.whatwg.org/multipage/rendering.html#being-rendered}
+ * @function isBeingRendered
+ * @param element {Element}
+ * @returns {boolean}
+ */
+
+function isBeingRendered(element) {
+  if (element.parentElement) {
+    const parentStyle = window.getComputedStyle(element.parentElement, null)
+    if (hasHidingStyleProperty(parentStyle)) return false
+  }
+  const elementStyle = window.getComputedStyle(element, null)
+  if (
+    hasHidingStyleProperty(elementStyle) ||
+    elementStyle.getPropertyValue("width") === "0px" ||
+    elementStyle.getPropertyValue("height") === "0px"
+  )
+    return false
   return true
 }
 
+/**
+ * Determine if a style declaration has any properties that make an element hidden.
+ * @function hasHidingStyleProperty
+ * @param style {CSSStyleDeclaration}
+ * @returns {boolean}
+ */
+function hasHidingStyleProperty(style) {
+  return (
+    style.getPropertyValue("display") === "none" ||
+    ["hidden", "collapse"].includes(style.getPropertyValue("visibility")) ||
+    style.getPropertyValue("opacity") === "0"
+  )
+}
+
 /**
  * Tests whether the element is contained within a closed `details` element.
  *