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.
The first iteration of COW snapshotting always made an initial copy when
the snapshot was requested (and reused that copy until the surface was
modified). However, in a few circumstances we can avoid even that copy
so long as the surface is still alive and unmodified between the
snapshotting and its use. In order to do so, we need a new proxy surface
that can automatically perform the copy if the target should disappear
prior to use.
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.
A nasty surprise whilst profiling is that performing redundant clear
operations is extremely painful. We can mitigate this somewhat by
tracking the cleared state of surfaces and skipping repeated attempts to
clear a surface.
Previously target device offsets were applied in cairo-surface.c which
could cause bugs when paths were taken as fallbacks, as for example
pointed out by ade55037ff and quick-fixed
by 79190d8985. The quick-fix is now
unnecessary and was removed.
Gah, that was a horrible mistake. It was a flawed hack to create Pixmaps
of the correct depth when cloning patterns for blitting to the xlib
backend. However, it had the nasty side-effect of discarding alpha when
targeting Window surfaces. The correct solution is to simply correct the
Pixmap of the desired depth and render a matching pattern onto the
surface - i.e. a reversal the current acquire -> clone. See the
forthcoming revised xcb backend on how I should have done it originally.
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.
Gah! I had believed that the dst extents and the clip were correct to
enable unbounded fixup for the unbounded trapezoids. I was wrong, so I
need to requery the trapezoid extents. As this information is already
known, I should update the interface to pass along all relevant
information.
Fill a region using IN and a white source is a frequent reduction of a
complex clip (viz a path that covers the whole operation extents will be
reduced to a single rectangle), and we can simply discard the fill (as it
always has bounded semantics).
If we have to rasterise a pattern for use by PS/PDF (for example, to
satisfy CAIRO_EXTENT_PAD) then only generate an image large enough to
cover the operation extents. We ensure tight coverage by computing the
extents afresh - we could do this lazily in the future, but we can not
rely on the bounds as computed by the analysis surface as for native
operations they may not be tight.
Always use spans, even for unaligned boxes. In the future (given a new
interface) we may want to emit the common unaligned box code more
efficient than a per-scanline computation -- but for now simply avoid the
requirements to write a temporary CPU buffer.
Add a new surface type that multiplies it input onto several output
surfaces. The only limitation is that it requires a master surface that is
used whenever we need to query surface options, such as font options and
extents.
Bug 23067 -- using clear drawing operator crashes printing
http://bugs.freedesktop.org/show_bug.cgi?id=23067
Here we were hitting an assert within the paginated surface after creating
a zero sized fallback image, due to the paginated surface being created
with an x fallback resolution of 0 dpi (by
_gtk_printer_create_cairo_surface(), gtk/gtkprinter.c:924).
Avoid the bug by guarding against bad input to
cairo_surface_set_fallback_resolution() which also allows us to identity
the invalid caller.
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
▏
Use the cow-snapshotting mechanism to store the meta surface replay (either
to an image inside acquire_source_image() or to a similar surface during
clone_similar()).
Fixes Bug 17971 -- Extreme slowdown for manual convolutions in most
vector backends.
https://bugs.freedesktop.org/show_bug.cgi?id=17971
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.
Explicitly handle a region clip which represents that the
entire surface is clipped out by passing in a temporary
empty region to the backend set_clip_region() method.
Previously the passed in region may have been NULL even
when clip->all_clipped = TRUE.
Fixes a bug tickled by the clip-all test case which was
brought to light by 394e139213.
Previously the reference to the newly created snapshot was owned by the
containing pattern. The consequence of this was that when the pattern was
destroyed the snapshot was cleaned up which prevent reuse of the snapshot
across multiple pages. Transferring ownership upon attachment of the
snapshot to the target means that the snapshot stays in existence until
the target itself is destroyed or modified *and* the containing pattern
is consumed. Obvious in hindsight.
Provide a mechanism for backends to attach and remove snapshots. This can
be used by backends to provide a cache for _cairo_surface_clone_similar(),
or by the meta-surfaces to only emit a single pattern for each unique
snapshot.
In order to prevent stale data being returned upon a snapshot operation,
if the surface is modified (via the 5 high level operations, and on
notification of external modification) we break the association with any
current snapshot of the surface and thus preserve the current data for
their use.
The number of mime-types attached to a surface is usually small,
typically zero. Therefore it is quicker to do a strcmp() against
each key in the private mime-data array than it is to intern the
string (i.e. compute a hash, search the hash table, and do a final
strcmp).
If the backend cannot create a similar surface to hold the image, then
report back the failure before embarking upon an infinite recursion.
The UNSUPPORTED return should percolate up through the call stack and
trigger a fallback.
As an aide to tracking down the source of uninitialised reads, run
VALGRIND_CHECK_MEM_IS_DEFINED() over the contents of image surfaces at the
boundary between backends, e.g. upon setting a glyph image or acquiring
a source image.
Damian Frank noted
[http://lists.cairographics.org/archives/cairo/2009-May/017095.html]
a performance problem with an older XServer with an
unaccelerated composite - similar problems will be seen with non-XRender
servers which will trigger extraneous fallbacks. The problem he found was
that painting an ARGB32 image onto an RGB24 destination window (using
SOURCE) was going via the RENDER protocol and not core. He was able to
demonstrate that this could be worked around by declaring the pixel data as
an RGB24 image. The issue is that the image is uploaded into a temporary
pixmap of matching depth (i.e. 32 bit for ARGB32 and 24 bit for RGB23
data), however the core protocol can only blit between Drawables of
matching depth - so without the work-around the Drawables are mismatched
and we either need to use RENDER or fallback.
This patch adds a content mask to _cairo_surface_clone_similar() to
provide the extra bit of information to the backends for when it is
possible for them to drop channels from the clone. This is used by the
xlib backend to only create a 24 bit source when blitting to a Window.
Specifically,
cairo_region_union_rect -> cairo_region_union_rectangle
cairo_region_create_rect -> cairo_region_create_rectangle
Also delete cairo_region_clear() which is not that useful.
Usually, rectangles are more useful than boxes, so regions should only
expose rectangles in their public API.
Specifically,
_cairo_region_num_boxes becomes _cairo_region_num_rectangles
_cairo_region_get_box becomes _cairo_region_get_rectangle
Remove the cairo_box_int_t type
The _cairo_region_get_boxes() interface was difficult to use and often
caused unnecessary memory allocation. With _cairo_region_get_box() it
is possible to access the boxes of a region without allocating a big
temporary array.
Move the mime-data into its own array so that it cannot be confused with
user-data and we do not need to hard-code the copy list during
snapshotting. The copy-on-snapshotting code becomes far simpler and will
accommodate all future mime-types.
Keeping mime-data separate from user-data is important due to the
principle of least surprise - the API is different and so it would be
surprising if you queried for user-data and were returned an opaque
mime-data pointer, and vice versa. (Note this should have been prevented
by using interned strings, but conceptually it is cleaner to make the
separation.) Also it aides in trimming the user data arrays which are
linearly searched.
Based on the original patch by Adrian Johnson:
http://cgit.freedesktop.org/~ajohnson/cairo/commit/?h=metadata&id=37e607cc777523ad12a2d214708d79ecbca5b380
Adds an error code replacing CAIRO_STATUS_NO_MEMORY in one case where it
is not really appropriate. CAIRO_STATUS_INVALID_SIZE is used by several
backends that do not support image sizes beyond 2^15 pixels on each side.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
