Bug 7578

Summary: Drawing huge lines has hefty memory usage
Product: cairo Reporter: Simon Budig <simon>
Component: generalAssignee: Carl Worth <cworth>
Status: RESOLVED FIXED QA Contact: cairo-bugs mailing list <cairo-bugs>
Severity: normal    
Priority: high    
Version: 1.2.0   
Hardware: x86 (IA32)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:
Attachments: Testcase for the "freezing computer" problem.

Description Simon Budig 2006-07-20 10:14:48 UTC 
When stumbeling on the limits of the internal 16.16 format and trying to figure
out when it fails I noticed, that drawing lines that come near to this limit
have a short but hefty impact on the memory usage - typically my computer
freezes for a second or so.

A testcase program is attached.

cworth mentioned that this might be a problem of the X-Server.

This is with the debian-testing package of libcairo, version 1.2.0-2  and the
X.Org version 7.0.0 (debian-testing package 1:7.0.22).
Comment 1 Simon Budig 2006-07-20 10:16:53 UTC 
Created attachment 6289 [details]
Testcase for the "freezing computer" problem.
Comment 2 Owen Taylor 2006-07-20 10:54:15 UTC 
Hmm, I vaguely thought this had already been dealt with. There are two
basic ways of attacking this:

 - Make sure that X server limits the size of any temporary surfaces
   created for XRenderCompositeTrapezoids to the size of the destination
   picture.

 - Have cairo create the temporary surfaces itself and use XRenderAddTraps
   rather than XRenderCompositeTrapezoids.

In fact, I thought we had already done *both*.
Comment 3 Chris Wilson 2012-04-03 14:04:46 UTC 
We now do geometric clipping of the lines prior to computing mask extents.

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