A problem that does not present itself whilst using spans to intermediate
masks is that the tor-span-convertor did not emit the empty rows. When
compositing directly using spans with an unbounded operator this was
causing rendering artefacts, for overlapping-glyphs and the gl backend.
Prior to introduction of the buggy members to the surface, we obviously
cannot set them. However, the boilerplate code is meant to compile against
older revisions of the library so we need to check for the existence prior
to use.
We can offload creation of gradients to server that support RENDER 0.10
and later. This greatly reduces the amount of traffic we need to send over
our display connection as the gradient patterns are much smaller than the
full image. Even if the server fallbacks to using pixman, performance
should be improved by the reduced transport overhead. Furthermore this is a
requisite to enable hardware accelerated gradients with the xlib backend.
Running cairo-perf-trace on tiny, Celeron/i915:
before: firefox-20090601 211.585
after: firefox-20090601 270.939
and on tiger, CoreDuo/nvidia:
before: firefox-20090601 70.143
after: firefox-20090601 87.326
where linear gradients are used extensively throughout the GTK+ theme.
Not quite the result I was expecting!
In particular, looking at tiny:
xlib-rgba paint-with-alpha_linear-rgba_over-512 47.11 (47.16 0.05%) -> 123.42 (123.72 0.13%): 2.62x slowdown
█▋
xlib-rgba paint-with-alpha_linear3-rgba_over-512 47.27 (47.32 0.04%) -> 123.78 (124.04 0.13%): 2.62x slowdown
█▋
xlib-rgba paint-with-alpha_linear-rgb_over-512 47.19 (47.21 0.02%) -> 123.37 (123.70 0.13%): 2.61x slowdown
█▋
xlib-rgba paint-with-alpha_linear3-rgb_over-512 47.30 (47.31 0.04%) -> 123.52 (123.62 0.09%): 2.61x slowdown
█▋
xlib-rgba paint_linear3-rgb_over-512 47.29 (47.32 0.05%) -> 118.95 (119.60 0.29%): 2.52x slowdown
█▌
xlib-rgba paint_linear-rgba_over-512 47.14 (47.17 0.06%) -> 116.76 (117.06 0.16%): 2.48x slowdown
█▌
xlib-rgba paint_linear3-rgba_over-512 47.32 (47.34 0.04%) -> 116.85 (116.98 0.05%): 2.47x slowdown
█▌
xlib-rgba paint_linear-rgb_over-512 47.15 (47.19 0.03%) -> 114.08 (114.55 0.20%): 2.42x slowdown
█▍
xlib-rgba paint-with-alpha_radial-rgb_over-512 117.25 (119.43 1.21%) -> 194.36 (194.73 0.09%): 1.66x slowdown
▋
xlib-rgba paint-with-alpha_radial-rgba_over-512 117.22 (117.26 0.02%) -> 193.81 (194.17 0.11%): 1.65x slowdown
▋
xlib-rgba paint_radial-rgba_over-512 117.23 (117.26 0.02%) -> 186.35 (186.41 0.03%): 1.59x slowdown
▋
xlib-rgba paint_radial-rgb_over-512 117.23 (117.27 0.02%) -> 184.14 (184.62 1.51%): 1.57x slowdown
▋
Before 1.10, we may choose to disable server-side gradients for the
current crop of Xorg servers, similar to the extended repeat modes.
[Updated by Chris Wilson. All bugs are his.]
The extended repeat modes were only introduced in RENDER 0.10, so disable
them if the server reports an earlier version. This is in addition to
disabling the repeat modes if we know (guess!) the server to have a buggy
implementation.
As the change and ranking is based on the min_ticks, and as this can
sometimes deviate wildly from median_ticks, include min_ticks in the
output.
In particular it helps to explain cases like:
xlib-rgba rectangles_similar-rgba-mag_source-512 10.13 88.41% -> 5.77 0.19%: 1.50x slowdown
which becomes
xlib-rgba rectangles_similar-rgba-mag_source-512 3.83 (10.13 88.41%) -> 5.75 (5.77 0.19%): 1.50x slowdown
(Considering the poor standard deviation on the initial measurement, this
is more likely a sampling error than a true regression.)
More the large slowdowns to the end. This has two pleasing effects:
1. There is symmetry between large speedups at the top, and large
slowdowns at the bottom, with long bars -> short bars -> long bars.
2. After a cairo-perf-diff run the largest slowdowns are immediately
visible on the console. What better way to flag performance
regressions?
Add a CAIRO_PERF_OUTPUT environment variable to cause cairo-perf to first
generate an output image in order to manually check that the test is
functioning correctly. This needs to be automated, so that we have
absolute confidence that the performance tests are not broken - but isn't
that the role of the test suite? If we were ever to publish cairo-perf
results, I would want some means of verification that the test-suite had
first been passed.
The warning is repeated in the error message if we fail to find any
traces, and now that we search a path it is likely that some elements do
not exist. Thus we annoy the user with irrelevant, non-fatal warnings.
Still looking for suggestions for the most appropriate home for the system
wide cairo-traces dir...
The original stroke only contains a single subpath. Self-intersection
removal particularly affects strokes with multiple curved segments, so add
a path that encompasses both straight edges and rounded corners.
Andrea Canciani (ranma42) found another instance of my broken 'degenerate'
curve-to as line-to optimisation. All I can say is when I do something
wrong, at least I'm consistent!
This test case highlights the bug in the rel-curve-to path.
There are many common scenarios, mostly involving overlapping glyphs,
for which to guarantee correct rendering we have to composite the glyphs
via an explicit mask. That is instead of just blending the glyphs on to
the destination, we have to add the glyphs to a mask, and then composite
that mask+source with the destination.
By performing the check on whether the operator is supported prior to
acquiring the context, we do not need to handle the error part way
through the context setup. This makes the code much cleaner, and save
some work for the unsupported cases.
In order to catch infinite loops whilst replaying and converting vector
surfaces to images (via external renderers) we need to also install
alarms around the calls to finish() and get_image().
The stroker code is liable to wedge when passed
dash patterns which don't advance the dash offset
due to limited precision arithmetic. This test
attempts to hit all the places in the stroker where
that can happen.
Reported on the cairo mailing list by Hans Breuer:
http://lists.cairographics.org/archives/cairo/2009-June/017506.html
As pointed out by Andrea, and now tested by test/degenerate-curve-to, a
curve-to that begins and ends on the same point may extend further due to
its control points. It can not be simply replaced with a degenerate
line-to. In order to do so we will need more extensive degeneracy
checking, ala _cairo_spline_init().
Andrea Canciani (ranma42) pointed out a second bug in the curve-to as
line-to optimisation, that is a curve starting and finishing on the same
point is not necessarily degenerate. This test case exercises 5 different
curves that start and end on the same point.
Looks like ghostscript has a similar buggy optimization like we
just fixed in cairo. I'm just waiting on a new bugzilla account
from bugs.ghostscript.com after which I plan to report the bug
there.
