Bug 1670541 - Return the parent line end offset if an embedded character contains a line break, r=Jamie

If the offset for an embedded character is queried, and it is an inline element, such as a link, and it contains a line break, return the full parent line.

Likewise, if querying character offsets before that embedded character, include its line break in the end offset.

Differential Revision: https://phabricator.services.mozilla.com/D94024

accessible/generic/HyperTextAccessible.cpp

@@ -745,9 +745,51 @@ uint32_t HyperTextAccessible::FindLineBoundary(
       // Move to begin of the next line if any (arrow down and home keys),
       // otherwise end of the current line (arrow down only).
       uint32_t tmpOffset = FindOffset(aOffset, eDirNext, eSelectLine);
-      if (tmpOffset == CharacterCount()) return tmpOffset;
+      uint32_t characterCount = CharacterCount();
+      if (tmpOffset == characterCount) {
+        return tmpOffset;
+      }
 
-      return FindOffset(tmpOffset, eDirPrevious, eSelectBeginLine);
+      // Now, simulate the Home key on the next line to get its real offset.
+      uint32_t nextLineBeginOffset =
+          FindOffset(tmpOffset, eDirPrevious, eSelectBeginLine);
+      // Sometimes, there are line breaks inside embedded characters. If this
+      // is the case, the cursor is after the line break, but the offset will
+      // be that of the embedded character, which points to before the line
+      // break. We definitely want the line break included.
+      if (IsCharAt(nextLineBeginOffset, kEmbeddedObjectChar)) {
+        // We can determine if there is a line break by pressing End from
+        // the queried offset. If there is a line break, the offset will be 1
+        // greater, since this line ends with the embed. If there is not, the
+        // value will be different even if a line break follows right after the
+        // embed.
+        uint32_t thisLineEndOffset =
+            FindOffset(aOffset, eDirNext, eSelectEndLine);
+        if (thisLineEndOffset == nextLineBeginOffset + 1) {
+          // If we're querying the offset of the embedded character, we want
+          // the end offset of the parent line instead. Press End
+          // once more from the current position, which is after the embed.
+          if (nextLineBeginOffset == aOffset) {
+            uint32_t thisLineEndOffset2 =
+                FindOffset(thisLineEndOffset, eDirNext, eSelectEndLine);
+            // The above returns an offset exclusive the final line break, so we
+            // need to add 1 to it to return an inclusive end offset. Make sure
+            // we don't overshoot if we've started from another embedded
+            // character that has a line break, or landed on another embedded
+            // character, or if the result is the very end.
+            return (thisLineEndOffset2 == characterCount ||
+                    (IsCharAt(thisLineEndOffset, kEmbeddedObjectChar) &&
+                     thisLineEndOffset2 == thisLineEndOffset + 1) ||
+                    IsCharAt(thisLineEndOffset2, kEmbeddedObjectChar))
+                       ? thisLineEndOffset2
+                       : thisLineEndOffset2 + 1;
+          }
+
+          return thisLineEndOffset;
+        }
+      }
+
+      return nextLineBeginOffset;
     }
 
     case eNextLineEnd: {

accessible/tests/mochitest/text/test_lineboundary.html

@@ -171,6 +171,41 @@
                        [ [ 0, 0, kEmbedChar, 0, 1 ],
                          [ 1, 1, kEmbedChar, 1, 2 ] ]);
 
+      // Embedded char containing a line break breaks line offsets in parent.
+      testTextAtOffset([ "brInEmbed" ], BOUNDARY_LINE_START,
+                       [ [0, 1, "a " + kEmbedChar, 0, 3],
+                         [2, 2, "a " + kEmbedChar + " d", 0, 5],
+                         [3, 5, kEmbedChar + " d", 2, 5] ]);
+      testTextAtOffset([ "brInEmbedAndBefore" ], BOUNDARY_LINE_START,
+                       [ [0, 1, "a\n", 0, 2],
+                         [2, 3, "b " + kEmbedChar, 2, 5],
+                         [4, 4, "b " + kEmbedChar + " e", 2, 7],
+                         [5, 7, kEmbedChar + " e", 4, 7] ]);
+      testTextAtOffset([ "brInEmbedAndAfter" ], BOUNDARY_LINE_START,
+                       [ [0, 1, "a " + kEmbedChar, 0, 3],
+                         [2, 2, "a " + kEmbedChar + " d\n", 0, 6],
+                         [3, 5, kEmbedChar + " d\n", 2, 6],
+                         [6, 7, "e", 6, 7] ]);
+      testTextAtOffset([ "brInEmbedAndBlockElementAfter" ], BOUNDARY_LINE_START,
+                       [ [0, 2, "a " + kEmbedChar, 0, 3],
+                         [3, 4, kEmbedChar, 3, 4] ]);
+      testTextAtOffset([ "brInEmbedThenTextThenBlockElement" ], BOUNDARY_LINE_START,
+                       [ [0, 1, "a " + kEmbedChar, 0, 3],
+                         [2, 2, "a " + kEmbedChar + " d", 0, 5],
+                         [3, 4, kEmbedChar + " d", 2, 5],
+                         [5, 6, kEmbedChar, 5, 6] ]);
+      testTextAtOffset([ "noBrInEmbedButOneBefore" ], BOUNDARY_LINE_START,
+                       [ [0, 1, "a\n", 0, 2],
+                         [2, 7, "b " + kEmbedChar + " d", 2, 7] ]);
+      testTextAtOffset([ "noBrInEmbedButOneAfter" ], BOUNDARY_LINE_START,
+                       [ [0, 3, "a " + kEmbedChar + "\n", 0, 4],
+                         [4, 5, "c", 4, 5] ]);
+      testTextAtOffset([ "twoEmbedsWithBRs" ], BOUNDARY_LINE_START,
+                       [ [0, 1, "a " + kEmbedChar, 0, 3],
+                         [2, 2, "a " + kEmbedChar + kEmbedChar, 0, 4],
+                         [3, 3, kEmbedChar + kEmbedChar + " f", 2, 6],
+                         [4, 6, kEmbedChar + " f", 3, 6] ]);
+
       SimpleTest.finish();
     }
 
@@ -270,6 +305,13 @@ two words
     <p>Block</p>
     <ul><li>Li</li></ul>
   </div>
-  </body>
+  <div id="brInEmbed" contenteditable>a <a href="https://mozilla.org/">b<br>c</a> d</div>
+  <div id="brInEmbedAndBefore">a<br>b <a href="https://mozilla.org/">c<br>d</a> e</div>
+  <div id="brInEmbedAndAfter">a <a href="https://mozilla.org/">b<br>c</a> d<br>e</div>
+  <div id="brInEmbedAndBlockElementAfter">a <a href="https://mozilla.org/">b<br>c</a><p>d</p></div>
+  <div id="brInEmbedThenTextThenBlockElement">a <a href="https://mozilla.org/">b<br>c</a> d<p>e</p></div>
+  <div id="noBrInEmbedButOneBefore">a<br>b <a href="https://mozilla.org/">c</a> d</div>
+  <div id="noBrInEmbedButOneAfter">a <a href="https://mozilla.org/">b</a><br>c</div>
+  <div id="twoEmbedsWithBRs">a <a href="https://mozilla.org">b<br>c</a><a href="https://mozilla.org">d<br>e</a> f</div>
 </body>
 </html>