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      <base href="https://bugs.webkit.org/" />
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    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - Ensure that RenderMathMLOperator::stretchTo functions are called with stretchy operators that have the correct direction"
   href="https://bugs.webkit.org/show_bug.cgi?id=156542">156542</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Ensure that RenderMathMLOperator::stretchTo functions are called with stretchy operators that have the correct direction
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>WebKit
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>WebKit Nightly Build
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>Normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P2
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>MathML
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>webkit-unassigned&#64;lists.webkit.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>fred.wang&#64;free.fr
          </td>
        </tr>

        <tr>
          <th>Blocks</th>
          <td>152244
          </td>
        </tr></table>
      <p>
        <div>
        <pre>I'm extracting this change from <a class="bz_bug_link 
          bz_status_ASSIGNED "
   title="ASSIGNED - Add separate module for selection/measuring/drawing of stretchy operators"
   href="show_bug.cgi?id=152244">bug 152244</a>.

This has already been done for horizontal stretchy operators in the RenderMathMLUnderOver refactoring (<a href="http://trac.webkit.org/changeset/199293">http://trac.webkit.org/changeset/199293</a>)
Let's do that for RenderMathMLRow and vertical stretchy operators too.
We can then add appropriate ASSERT in the RenderMathMLOperator::stretchTo functions.

Note that this change causes test failures for the following dynamic DOM/style tests, probably because some relayout that used to be forced by useless stretchTo called is not done anymore.

mathml/presentation/mo-lspace-rspace-dynamic.html
mathml/presentation/style-changed.html

So the solution from <a class="bz_bug_link 
          bz_status_ASSIGNED "
   title="ASSIGNED - Add separate module for selection/measuring/drawing of stretchy operators"
   href="show_bug.cgi?id=152244">bug 152244</a> was to be a bit more aggressive with updates, until we better manage such things in the MathML code (<a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - [meta] Move MathML attribute parsing from the renderer classes to the element classes"
   href="show_bug.cgi?id=156536">bug 156536</a>).</pre>
        </div>
      </p>
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