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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 - WebGL: drawingBuffer problems with Ultra HD Resolutions"
   href="https://bugs.webkit.org/show_bug.cgi?id=162604">162604</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>WebGL: drawingBuffer problems with Ultra HD Resolutions
          </td>
        </tr>

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

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

        <tr>
          <th>Version</th>
          <td>Safari 10
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>Macintosh
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>OS X 10.11
          </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>WebGL
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>michael.herzog&#64;human-interactive.org
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>dino&#64;apple.com
          </td>
        </tr></table>
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        <pre>Steps to reproduce the problem:

1. First you need a high resolution monitor (e.g. iMac 5K)
2. Start Safari and maximize your window
3. Go to <a href="http://threejs.org/examples/webgl_interactive_cubes.html">http://threejs.org/examples/webgl_interactive_cubes.html</a>

What is the expected behavior?

When you position your mouse exactly over a cube, it should be highlighted.

What went wrong?

On ultrad HD resolutions the application is not able to determine the correct cube. This problem only occurs when Safari exceeds a specific resolution. On smaller monitors (e.g.FullHD), everything works fine.

Did this work before? 

No 

Details:

I assume that Webkit must be limiting the maximum drawing buffer width/height which leads to incorrect canvas sizes.

My recommendation is to change the backbuffer limit from e.g. 4k per dimension to 4k x 4k total area like Blink does (see <a href="https://bugs.chromium.org/p/chromium/issues/detail?id=445542">https://bugs.chromium.org/p/chromium/issues/detail?id=445542</a>)</pre>
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