This updates NEWS with items shown by `git log --stat 1.12.8..`
Hopefully I haven't misrepresented any of the work done. For sake of
brevity where there were several changes in one area, I've given a
single general entry to summarize those changes. The division between
features and bug fixes is quite rough.
Replaying a meta surface can be achieved by using it as a source for a
cairo_paint() so exporting a separate API is unnecesary and confusing.
So after consulting Chris and Carl, we decided to remove the function
again.
We refactor the surface fallbacks to convert full strokes and fills to the
intermediate polygon representation (as opposed to before where we
returned the trapezoidal representation). This allow greater flexibility
to choose how then to rasterize the polygon. Where possible we use the
local spans rasteriser for its increased performance, but still have the
option to use the tessellator instead (for example, with the current
Render protocol which does not yet have a polygon image).
In order to accommodate this, the spans interface is tweaked to accept
whole polygons instead of a path and the tessellator is tweaked for speed.
Performance Impact
==================
...
Still measuring, expecting some severe regressions.
...
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.]
Handling clip as part of the surface state, as opposed to being part of
the operation state, is cumbersome and a hindrance to providing true proxy
surface support. For example, the clip must be copied from the surface
onto the fallback image, but this was forgotten causing undue hassle in
each backend. Another example is the contortion the meta surface
endures to ensure the clip is correctly recorded. By contrast passing the
clip along with the operation is quite simple and enables us to write
generic handlers for providing surface wrappers. (And in the future, we
should be able to write more esoteric wrappers, e.g. automatic 2x FSAA,
trivially.)
In brief, instead of the surface automatically applying the clip before
calling the backend, the backend can call into a generic helper to apply
clipping. For raster surfaces, clip regions are handled automatically as
part of the composite interface. For vector surfaces, a clip helper is
introduced to replay and callback into an intersect_clip_path() function
as necessary.
Whilst this is not primarily a performance related change (the change
should just move the computation of the clip from the moment it is applied
by the user to the moment it is required by the backend), it is important
to track any potential regression:
ppc:
Speedups
========
image-rgba evolution-20090607-0 1026085.22 0.18% -> 672972.07 0.77%: 1.52x speedup
▌
image-rgba evolution-20090618-0 680579.98 0.12% -> 573237.66 0.16%: 1.19x speedup
▎
image-rgba swfdec-fill-rate-4xaa-0 460296.92 0.36% -> 407464.63 0.42%: 1.13x speedup
▏
image-rgba swfdec-fill-rate-2xaa-0 128431.95 0.47% -> 115051.86 0.42%: 1.12x speedup
▏
Slowdowns
=========
image-rgba firefox-periodic-table-0 56837.61 0.78% -> 66055.17 3.20%: 1.09x slowdown
▏
Based on the work by Øyvind Kolås and Pierre Tardy -- many thanks to
Pierre for pushing this backend for inclusion as well as testing and
reviewing my initial patch. And many more thanks to pippin for writing the
backend in the first place!
Hacked and chopped by myself into a suitable basis for a backend. Quite a
few issues remain open, but would seem to be ready for testing on suitable
hardware.
The meta-surface is a vital tool to record a trace of drawing commands
in-memory. As such it is used throughout cairo.
The value of such a surface is immediately obvious and should be
applicable for many applications. The first such case is by
cairo-test-trace which wants to record the entire graph of drawing commands
that affect a surface in the event of a failure.
