The device is a generic method for accessing the underlying interface
with the native graphics subsystem, typically the X connection or
perhaps the GL context. By exposing a cairo_device_t on a surface and
its various methods we enable finer control over interoperability with
external interactions of the device by applications. The use case in
mind is, for example, a multi-threaded gstreamer which needs to serialise
its own direct access to the device along with Cairo's across many
threads.
Secondly, the cairo_device_t is a unifying API for the mismash of
backend specific methods for controlling creation of surfaces with
explicit devices and a convenient hook for debugging and introspection.
The principal components of the API are the memory management of:
cairo_device_reference(),
cairo_device_finish() and
cairo_device_destroy();
along with a pair of routines for serialising interaction:
cairo_device_acquire() and
cairo_device_release()
and a method to flush any outstanding accesses:
cairo_device_flush().
The device for a particular surface may be retrieved using:
cairo_surface_get_device().
The device returned is owned by the surface.
As a simple step to ensure that we do not inadvertently modify (or at least
generate compiler warns if we try) user data, mark the incoming style
and matrices as constant.
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.
is_rectangle() is far stricter than is_box(), and is only required for a
very limited set of operations (essentially were the rectangle must
conform to the motion as described by cairo_rectangle). For the general
case where we just want to know whether we have a single rectangular path
that covers a certain area, is_box() is sufficient.
A typo, I missed converting the user over to the freshly sorted list,
leaving it iterating over original but checking the sorted for termination
conditions.
A very simple surface that produces a hierarchical DAG in a simple XML
format. It is intended to be used whilst debugging, for example with the
automatic regression finding tools of cairo-sphinx, and with test suites
that just want to verify that their code made a particular Cairo call.
As we set the size of the surface to fit the ink extents of the meta
surface, we also need to ensure that the origin of the script lies at the
origin of the ink extents.
This is a simple variation on cairo-trace that wraps records the last 16
contexts by wrapping the target surface inside a tee surface, along with a
meta/recording surface. Then on receipt of a SIGUSR1, those last 16
contexts are played via a script-surface into /tmp/fdr.trace.
Mostly proof-of-concept, it seems to be causing a number of rendering
glitches whilst testing with firefox -- otherwise, it seems to works.
Previously the contexts were permanently associated with the surface and
only destroyed along with the final reference to the surface. This meant
that we kept a large number of unwanted contexts in memory. Most
applications only have a few contexts active at any time, so remove
inactive contexts from the operand stack every time we perform an
operation on a different context.
cairo_script_context_t is an encapsulation object for interfacing with the
output - multiple surfaces can share the same context, meaning that they
write to the same destination file/stream.
Kerning is quite frequent, that is to apply a horizontal but no vertical
offset to a glyph. For instance by discarding the vertical coordinate
where it remains the same and only encoding the horizontal offset we
reduce the file size by ~12.5% when tracing poppler.
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
▏
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.
Remove some redundant defining of surfaces and contexts and of setting
defaults. In order to reduce the number of defines, we need to operate on
the operand stack more frequently - though in practice those operations
are quite rare.
If we are dithering on the Xlib backend we can not simply repaint the
surface used for a solid pattern and must recreate it from scratch.
However, for ordinary XRender usage we do not want to have to pay that
price - so query the backend to see if we can reuse the surface.
A surface will have the chance to use span rendering at cairo_fill()
time by creating a renderer for a specific combination of
pattern/dst/op before the path is scan converted. The protocol is to
first call check_span_renderer() to see if the surface wants to render
with spans and then later call create_span_renderer() to create the
renderer for real once the extents of the path are known.
No backends have an implementation yet.
A new meta-surface backend for serialising drawing operations to a
CairoScript file. The principal use (as currently envisaged) is to provide
a round-trip testing mechanism for CairoScript - i.e. we can generate
script files for every test in the suite and check that we can replay them
with perfect fidelity. (Obviously this does not provide complete coverage
of CairoScript's syntax, but should give reasonable coverage over the
operators.)
