Bug 4165

Summary:	A few pixels wrong in some tests on PPC
Product:	cairo	Reporter:	Billy Biggs <billy.biggs>
Component:	image backend	Assignee:	Billy Biggs <billy.biggs>
Status:	RESOLVED FIXED	QA Contact:	cairo-bugs mailing list <cairo-bugs>
Severity:	normal
Priority:	high	CC:	cworth
Version:	0.9.3
Hardware:	x86 (IA32)
OS:	Linux (All)
Whiteboard:
i915 platform:		i915 features:
Attachments:	pixels-off.c Patch

Description Billy Biggs 2005-08-20 21:48:35 UTC

The following tests all have a bunch of incorrect pixels using the image backend
on my PowerBook G4 running OS X (freetype not ATSUI).  These failures are not
reproducable on Linux/x86, so I suspect they are more endian issues:

  clip-operator
  fill-and-stroke
  linear-gradient
  operator-clear
  operator-source
  unantialiased-shapes
  unbounded-operator

Comment 1 Billy Biggs 2005-08-20 22:13:30 UTC

Created attachment 2954 [details]
pixels-off.c

Attached is a minimal failing test case.  The problem seems to be the mask
created for the path.  Here is the mask on x86:

00 00 00 00 00 00 00 00 00 00 00 00 
00 00 0a 68 c4 f5 f5 c4 68 0a 00 00 
00 2b dd ff ff ff ff ff ff dd 2b 00 
0a e0 ff c5 3d 0a 0a 3d c5 ff e0 0a 
70 ff c2 06 00 00 00 00 06 c2 ff 70 
c7 ff 3a 00 00 00 00 00 00 3a ff c7 
f4 ff 0b 00 00 00 00 00 00 0b ff f4 
f4 ff 0b 00 00 00 00 00 00 0b ff f4 
c7 ff 3a 00 00 00 00 00 00 3a ff c7 
70 ff c2 06 00 00 00 00 06 c2 ff 70 
0a e0 ff c5 3d 0a 0a 3d c5 ff e0 0a 
00 2b dd ff ff ff ff ff ff dd 2b 00 
00 00 0a 68 c4 f5 f5 c4 68 0a 00 00 

And here is the mask on PPC:

00 00 00 00 00 00 00 00 00 00 00 00
00 00 0a 68 c4 f5 f5 c4 68 0a 00 00
00 2b dd ff ff ff ff ff ff dd 2b 00
0a e0 ff c5 3d 0a 0a 3d c5 ff e0 0a
70 ff c2 06 00 00 00 00 06 c2 ff 70
c7 ff 3a 00 00 00 00 00 00 3a ff c7
f4 ff 0b 00 00 00 00 00 00 0b ff f4
bf 76 00 00 00 00 00 00 00 0b ca 50
c7 ff 2d 00 00 00 00 00 00 3a ff a0
70 ff c2 06 00 00 00 00 06 c2 ff 66
0a e0 ff c5 3d 0a 0a 3d c5 ff e0 0a
00 2b dd ff ff ff ff ff ff dd 2b 00
00 00 0a 68 c4 f5 f5 c4 68 0a 00 00

Comment 2 Billy Biggs 2005-08-20 22:43:59 UTC

The list of trapezoids returned by _cairo_path_fixed_stroke_to_traps differs
between my two systems.

Comment 3 Billy Biggs 2005-08-21 11:08:50 UTC

Created attachment 2965 [details] [review]
Patch

The differences are due to a behaviour difference between qsort() on my two
machines.  The attached patch modifies the qsort vertex comparision function in
cairo-hull.c to handle coincident points.  This makes the output of all of the
above tests equal (except for linear-gradient, which seems to also have a
different problem).

When this patch is applied, the output for all of those tests will also need to
be updated.

Comment 4 Billy Biggs 2005-08-21 11:42:24 UTC

2005-08-21  Billy Biggs  <vektor@dumbterm.net>

        Fix for bug #4165:

        * src/cairo-hull.c: (_cairo_hull_vertex_compare): Use pointer
        comparison for coincident points to ensure a well-defined
        ordering, and avoid setting discard on both points.  This fixes
        problems with my Mac's implementation of qsort.  Final patch by
        Bertram Felgenhauer.

        * test/clip-operator-ref.png:
        * test/linear-gradient-ref.png:
        * test/operator-clear-ref.png:
        * test/operator-source-ref.png:
        * test/unantialiased-shapes-ref.png:
        * test/unbounded-operator-ref.png: Update reference images after
        the change.

Comment 5 Carl Worth 2005-08-22 17:14:22 UTC

Move bugs against "cvs" version to "0.9.3" so we can remove the "cvs" version.

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