[text-autospace] Extract getCharAdvances

This patch extracts a JavaScript function from
`text-autospace-001.html`and share it with
`text-spacing-trim-combinations-001.html`.

Bug: 1463890, 1463891
Change-Id: I509fc6948d5242e970674f9e65ada48d27ab408c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4835287
Auto-Submit: Koji Ishii <[email protected]>
Reviewed-by: Lingqi Chi <[email protected]>
Commit-Queue: Lingqi Chi <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1191928}

css/css-text/support/get-char-advances.js

@@ -0,0 +1,25 @@
+'use strict';
+
+/**
+ * Returns an array of advances (widths) for all characters in the descendants
+ * of the specified element.
+ */
+function getCharAdvances(element) {
+  const range = document.createRange();
+  let advances = [];
+  for (const node of element.childNodes) {
+    const nodeType = node.nodeType;
+    if (nodeType === Node.TEXT_NODE) {
+      const text = node.nodeValue;
+      for (let i = 0; i < text.length; ++i) {
+        range.setStart(node, i);
+        range.setEnd(node, i + 1);
+        const bounds = range.getBoundingClientRect();
+        advances.push(bounds.width);
+      }
+    } else if (nodeType === Node.ELEMENT_NODE) {
+      advances = advances.concat(getCharAdvances(node));
+    }
+  }
+  return advances;
+}

css/css-text/text-autospace/text-autospace-001.html

@@ -4,6 +4,7 @@
 <link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
+<script src="../support/get-char-advances.js"></script>
 <style>
 .test {
   font-family: Ahem;
@@ -17,28 +18,6 @@
 <div class="test" expect="3">国。XX国</div>
 <div class="test first-line" expect="1,3,6,8">国国XX国<br>国国XX国</div>
 <script>
-const range = document.createRange();
-
-// Get advances of all characters in the descendants.
-function getCharAdvances(element) {
-  let advances = [];
-  for (const node of element.childNodes) {
-    const nodeType = node.nodeType;
-    if (nodeType === Node.TEXT_NODE) {
-      const text = node.nodeValue;
-      for (let i = 0; i < text.length; ++i) {
-        range.setStart(node, i);
-        range.setEnd(node, i + 1);
-        const bounds = range.getBoundingClientRect();
-        advances.push(bounds.width);
-      }
-    } else if (nodeType === Node.ELEMENT_NODE) {
-      advances = advances.concat(getCharAdvances(node));
-    }
-  }
-  return advances;
-}
-
 for (const element of document.getElementsByClassName('test')) {
   const advances = getCharAdvances(element);
 

css/css-text/text-spacing-trim/text-spacing-trim-combinations-001.html

@@ -3,6 +3,7 @@
 <link rel="help" href="https://drafts.csswg.org/css-text-4/#text-spacing-trim-property">
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
+<script src="../support/get-char-advances.js"></script>
 <style>
 #container {
   /* This test prefers fonts with the `halt` feature. */
@@ -17,25 +18,17 @@
 <script>
 const range = document.createRange();
 
-function assertNode(textNode, expect) {
-  const text = textNode.nodeValue;
-  const results = [];
-  for (let i = 0; i < text.length; ++i) {
-    range.setStart(textNode, i);
-    range.setEnd(textNode, i + 1);
-    const rect = range.getBoundingClientRect();
-    results.push(rect.width >= 8 ? 'F' : 'H');
-  }
+function assertNode(element, expect) {
+  const advances = getCharAdvances(element);
+  const results = advances.map(advance => advance >= 8 ? 'F' : 'H');
   const result = results.join('');
   assert_equals(result, expect);
 }
 
 for (const element of document.querySelectorAll('div[expect]')) {
-  const textNode = element.firstChild;
-  const text = textNode.nodeValue;
   test(() => {
     let expect = element.getAttribute('expect');
-    assertNode(textNode, expect);
-  }, `"${text}"`);
+    assertNode(element, expect);
+  }, `"${element.innerHTML}"`);
 }
 </script>