<html>
<head>
<base href="https://bugs.freedesktop.org/" />
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Priority</th>
<td>medium
</td>
</tr>
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Broken line drawing with cairo graphics using SNA and UXA"
href="https://bugs.freedesktop.org/show_bug.cgi?id=84115">84115</a>
</td>
</tr>
<tr>
<th>Assignee</th>
<td>chris@chris-wilson.co.uk
</td>
</tr>
<tr>
<th>Summary</th>
<td>Broken line drawing with cairo graphics using SNA and UXA
</td>
</tr>
<tr>
<th>QA Contact</th>
<td>intel-gfx-bugs@lists.freedesktop.org
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux (All)
</td>
</tr>
<tr>
<th>Reporter</th>
<td>maurizio.berti@gmail.com
</td>
</tr>
<tr>
<th>Hardware</th>
<td>x86 (IA32)
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Version</th>
<td>7.4 (2008.09)
</td>
</tr>
<tr>
<th>Component</th>
<td>Driver/intel
</td>
</tr>
<tr>
<th>Product</th>
<td>xorg
</td>
</tr></table>
<p>
<div>
<pre>As reported on cairo graphics mailing list (here:
<a href="http://lists.cairographics.org/archives/cairo/2014-September/025623.html">http://lists.cairographics.org/archives/cairo/2014-September/025623.html</a> ), it
looks like that the accelerated line drawing is broken while drawing arcs with
cairo, and this is visible when the line width is way bigger than 1 pixel.
Using UXA the beginning of the arc is not straight, as shown here:
<a href="http://jidesk.net/sypy/strangearc2.jpg">http://jidesk.net/sypy/strangearc2.jpg</a>
Using SNA there is also a seaming issue as shown here:
<a href="http://jidesk.net/sypy/strangearc-bryce.png">http://jidesk.net/sypy/strangearc-bryce.png</a>
After consulting users on #cairo on FreeNode, the issue is confirmed, and they
suggested me to report here, since it looks like it is related to intel's X
acceleration on newer drivers. I am using a i5-3570K for graphics too, which is
an Ivy Bridge architecture, but I suppose that the problem affects Sandy Bridge
architectures also.
Unfortunally I am no programmer, so I am just supposing a lot of things
figuring out techno-babble I barely understand. I'm pretty sure that you could
find the source of this issue anyway, and eventually bounce back to cairo
developers if you find out that this is only a cairo related bug.
Thanks,
Maurizio</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are the QA Contact for the bug.</li>
</ul>
</body>
</html>