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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 - [GTK] BadDamage X Window System error in WebKit::AcceleratedBackingStoreX11::update when called from WebPageProxy::exitAcceleratedCompositingMode"
   href="https://bugs.webkit.org/show_bug.cgi?id=164303">164303</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>[GTK] BadDamage X Window System error in WebKit::AcceleratedBackingStoreX11::update when called from WebPageProxy::exitAcceleratedCompositingMode
          </td>
        </tr>

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

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

        <tr>
          <th>Version</th>
          <td>Other
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux
          </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>WebKit Gtk
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>mcatanzaro&#64;igalia.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>bugs-noreply&#64;webkitgtk.org
          </td>
        </tr></table>
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        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=293621" name="attach_293621" title="Backtrace with breakpoint set on gdk_x_error()">attachment 293621</a> <a href="attachment.cgi?id=293621&amp;action=edit" title="Backtrace with breakpoint set on gdk_x_error()">[details]</a></span>
Backtrace with breakpoint set on gdk_x_error()

With Epiphany master, if you close the browser with Ctrl+C, about half the time you will receive this:

(epiphany:28727): Gdk-ERROR **: The program 'epiphany' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadDamage (invalid Damage parameter)'.
  (Details: serial 83341 error_code 149 request_code 142 (DAMAGE) minor_code 2)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the GDK_SYNCHRONIZE environment
   variable to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)

I think you can reproduce it with a stable version of Epiphany by using Ctrl+Q or the Quit app menu item.

Detailed backtrace attached.</pre>
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