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        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - Potential _cairo_bentley_ottmann_tessellate_rectangular_traps bug"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=90984">90984</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Potential _cairo_bentley_ottmann_tessellate_rectangular_traps bug
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>cairo
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>unspecified
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>Other
          </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>medium
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>general
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>chris@chris-wilson.co.uk
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>twointofive@gmail.com
          </td>
        </tr>

        <tr>
          <th>QA Contact</th>
          <td>cairo-bugs@cairographics.org
          </td>
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        <pre>Created <span class=""><a href="attachment.cgi?id=116523" name="attach_116523" title="_cairo_bentley_ottmann_tessellate_rectangular_traps patch">attachment 116523</a> <a href="attachment.cgi?id=116523&action=edit" title="_cairo_bentley_ottmann_tessellate_rectangular_traps patch">[details]</a></span>
_cairo_bentley_ottmann_tessellate_rectangular_traps patch

This is being reported with reference to firefox bug 853889:
<a href="https://bugzilla.mozilla.org/show_bug.cgi?id=853889">https://bugzilla.mozilla.org/show_bug.cgi?id=853889</a>

As explained in that bug, using firefox's old version of cairo, there's a bug
related to _cairo_bentley_ottmann_tessellate_rectangular_traps:
if more than one trap is passed in then it's guaranteed that the returned traps
will have their left edge to the left of their right edge, but if only one trap
is passed in then the function always returns without doing anything.

I don't think that bug is reproducible with current cairo code (all current
calls to _cairo_bentley_ottmann_tessellate_rectangular_traps appear to be
guarded by traps.has_intersections checks, which I think implies more than one
trap), but it seems like it's still a potential hole for a future bug, and I
see a similar hole in _cairo_bentley_ottmann_tessellate_boxes has been fixed
already.</pre>
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