Bug 75720 - Zero length, zero width lines drawn inconsistently as nothing or one pixel depending on backend.
Summary: Zero length, zero width lines drawn inconsistently as nothing or one pixel de...
Status: RESOLVED DUPLICATE of bug 54168
Alias: None
Product: xorg
Classification: Unclassified
Component: Server/General (show other bugs)
Version: unspecified
Hardware: Other All
: medium normal
Assignee: Xorg Project Team
QA Contact: Xorg Project Team
URL:
Whiteboard:
Keywords:
Depends on:
Blocks:
 
Reported: 2014-03-03 15:46 UTC by Michal Srb
Modified: 2018-07-17 09:59 UTC (History)
1 user (show)

See Also:
i915 platform:
i915 features:

Attachments
Minimal test case. (631 bytes, text/plain)
2014-04-28 13:03 UTC, Michal Srb 		no flags Details
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Description Michal Srb 2014-03-03 15:46:17 UTC 
When a zero-width (default GC) line is drawn with the same starting and ending point using PolySegment the results differ based on current backend.

When the fbGCOps functions are used, like in Xephyr, nothing is drawn.
For example with EXA and nouveau or UXA and intel, 1 pixel is drawn.

Shouldn't it be consistent?

This has real-life impact; libgdk_pixbuf is (bit stupidly) rendering masks using lines and it expects one pixel to be drawn in this case. If it isn't drawn it leads to missing title bars in icewm. (https://bugzilla.novell.com/show_bug.cgi?id=856931)
Comment 1 Adam Jackson 2014-04-10 14:59:02 UTC 
(In reply to comment #0)
> When a zero-width (default GC) line is drawn with the same starting and
> ending point using PolySegment the results differ based on current backend.
> 
> When the fbGCOps functions are used, like in Xephyr, nothing is drawn.
> For example with EXA and nouveau or UXA and intel, 1 pixel is drawn.
> 
> Shouldn't it be consistent?

I believe it should, yeah.  Is there an xts test that triggers this?
Comment 2 Michal Srb 2014-04-28 13:03:57 UTC 
Created attachment 98127 [details]
Minimal test case.

(In reply to comment #1)
> I believe it should, yeah.  Is there an xts test that triggers this?

Sorry, I am not so familiar with xts. It looks like some of the lines drawn in Xlib9/XDrawLine could reproduce this, but I don't know for sure.

I attach minimal program that can be used for reproducing. It shows window that is either whole white (e.g. in Xephyr) or has one black pixel in top left corner (e.g. with EXA/nouveau and many others).
Comment 3 Stefan Dirsch 2014-12-17 13:28:47 UTC 
Probably duplicate of https://bugs.freedesktop.org/show_bug.cgi?id=54168.
Comment 4 Stefan Dirsch 2018-07-17 09:59:18 UTC 
(In reply to Stefan Dirsch from comment #3)
> Probably duplicate of https://bugs.freedesktop.org/show_bug.cgi?id=54168.

Let's assume so. Otherwise, Michal, please reopen!

*** This bug has been marked as a duplicate of bug 54168 ***

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