From 455f71d2fda82bf70f2522f3573162286f09c62b Mon Sep 17 00:00:00 2001
From: Morgan Rae Reschenberg <mreschenberg@mozilla.com>
Date: Thu, 12 Jan 2023 19:10:12 +0000
Subject: [PATCH] Bug 1808828: Compute ancestor transform for continuations
 that span multiple subtrees r=Jamie

Differential Revision: https://phabricator.services.mozilla.com/D166485
---
 accessible/generic/LocalAccessible.cpp        | 19 +++++
 .../e10s/browser_caching_text_bounds.js       | 81 ++++++++++++++++++-
 accessible/tests/mochitest/layout.js          |  2 +-
 3 files changed, 97 insertions(+), 5 deletions(-)

diff --git a/accessible/generic/LocalAccessible.cpp b/accessible/generic/LocalAccessible.cpp
index 5800bd4e92ef..96cc7ae6ca9d 100644
--- a/accessible/generic/LocalAccessible.cpp
+++ b/accessible/generic/LocalAccessible.cpp
@@ -3399,9 +3399,27 @@ already_AddRefed<AccAttributes> LocalAccessible::BundleFieldsForCache(
         nsTArray<int32_t> charData;
 
         if (nsTextFrame* currTextFrame = do_QueryFrame(frame)) {
+          nsTextFrame* prevTextFrame = currTextFrame;
           nsRect frameRect = currTextFrame->GetRect();
+          nsIFrame* nearestAccAncestorFrame =
+              LocalParent() ? LocalParent()->GetFrame() : nullptr;
           while (currTextFrame) {
             nsRect contRect = currTextFrame->GetRect();
+            if (prevTextFrame->GetParent() != currTextFrame->GetParent() &&
+                nearestAccAncestorFrame) {
+              // Continuations can span multiple frame tree subtrees,
+              // particularly when multiline text is nested within both block
+              // and inline elements. In addition to using the position of this
+              // continuation to offset our char rects, we'll need to offset
+              // this continuation from the continuations that occurred before
+              // it. We don't know how many there are or what subtrees they're
+              // in, so we use a transform here. This also ensures our offset is
+              // accurate even if the intervening inline elements are not
+              // present in the a11y tree.
+              contRect = frameRect;
+              nsLayoutUtils::TransformRect(currTextFrame,
+                                           nearestAccAncestorFrame, contRect);
+            }
             nsTArray<nsRect> charBounds;
             currTextFrame->GetCharacterRectsInRange(
                 currTextFrame->GetContentOffset(),
@@ -3422,6 +3440,7 @@ already_AddRefed<AccAttributes> LocalAccessible::BundleFieldsForCache(
               charData.AppendElement(charRect.width);
               charData.AppendElement(charRect.height);
             }
+            prevTextFrame = currTextFrame;
             currTextFrame = currTextFrame->GetNextContinuation();
           }
         }
diff --git a/accessible/tests/browser/e10s/browser_caching_text_bounds.js b/accessible/tests/browser/e10s/browser_caching_text_bounds.js
index e16e10d31d7b..0f505992938f 100644
--- a/accessible/tests/browser/e10s/browser_caching_text_bounds.js
+++ b/accessible/tests/browser/e10s/browser_caching_text_bounds.js
@@ -34,13 +34,24 @@ async function testTextRange(accDoc, browser, id, start, end) {
         // ignore whitespace, but not embedded elements
         let isEmbeddedElement = false;
         if (element.length == undefined) {
-          if (!element.firstChild) {
-            continue;
-          } else {
+          let potentialTextContainer = element;
+          while (
+            potentialTextContainer &&
+            potentialTextContainer.length == undefined
+          ) {
+            potentialTextContainer = element.firstChild;
+          }
+          if (potentialTextContainer && potentialTextContainer.length) {
+            // If we can reach some text from this container, use that as part
+            // of our range. This is important when testing with intervening inline
+            // elements. ie. <pre><code>ab%0acd
+            element = potentialTextContainer;
+          } else if (element.firstChild) {
             isEmbeddedElement = true;
+          } else {
+            continue;
           }
         }
-
         if (element.length + traversed < _start) {
           // If our start index is not within this
           // node, keep looking.
@@ -431,6 +442,68 @@ addAccessibleTask(
   { chrome: true, topLevel: !isWinNoCache }
 );
 
+/**
+ * Test character bounds in an intervening inline element with non-br line breaks
+ */
+addAccessibleTask(
+  `
+  <style>
+    @font-face {
+      font-family: Ahem;
+      src: url(${CURRENT_CONTENT_DIR}e10s/fonts/Ahem.sjs);
+    }
+    pre {
+      font: 20px/20px Ahem;
+    }
+  </style>
+  <pre id="t"><code>XX
+XXX
+XX
+X</pre>`,
+  async function(browser, docAcc) {
+    await testChar(docAcc, browser, "t", 0);
+    await testChar(docAcc, browser, "t", 3);
+    await testChar(docAcc, browser, "t", 7);
+    await testChar(docAcc, browser, "t", 10);
+  },
+  {
+    chrome: true,
+    topLevel: !isWinNoCache,
+    iframe: !isWinNoCache,
+  }
+);
+
+// XXX: There's a fuzziness here of about 8 pixels, implying we aren't taking into
+// account some kind of margin or padding. See bug 1809695.
+// /**
+//  * Test character bounds in an intervening inline element with margins
+//  * and with non-br line breaks
+//  */
+// addAccessibleTask(
+//   `
+//   <style>
+//     @font-face {
+//       font-family: Ahem;
+//       src: url(${CURRENT_CONTENT_DIR}e10s/fonts/Ahem.sjs);
+//     }
+//   </style>
+//   <div>hello<pre id="t" style="margin-left:100px;margin-top:30px;background-color:blue;">XX
+// XXX
+// XX
+// X</pre></div>`,
+//   async function(browser, docAcc) {
+//     await testChar(docAcc, browser, "t", 0);
+//     await testChar(docAcc, browser, "t", 3);
+//     await testChar(docAcc, browser, "t", 7);
+//     await testChar(docAcc, browser, "t", 10);
+//   },
+//   {
+//     chrome: true,
+//     topLevel: !isWinNoCache,
+//     iframe: !isWinNoCache,
+//   }
+// );
+
 /**
  * Test text bounds in a textarea after scrolling.
  */
diff --git a/accessible/tests/mochitest/layout.js b/accessible/tests/mochitest/layout.js
index f10c14bad10e..1467d5fe7fa8 100644
--- a/accessible/tests/mochitest/layout.js
+++ b/accessible/tests/mochitest/layout.js
@@ -170,7 +170,7 @@ function testTextPos(aID, aOffset, aPoint, aCoordOrigin) {
     "Wrong x coordinate at offset " + aOffset + " for " + prettyName(aID)
   );
   ok(
-    yObj.value - expectedY < 2 && expectedY - yObj.value < 2,
+    yObj.value - expectedY <= 2 && expectedY - yObj.value <= 2,
     "Wrong y coordinate at offset " +
       aOffset +
       " for " +