As a matter of fact, Chris Campbell from the 2D team
did an initial investigation on XRender pipeline
a while back (I just found an internal wiki page with
the results of that investigation).
I hope he doesn't mind me posting his thoughts here:
It doesn't appear that we can simply extend the existing X11Renderer code. XRender only knows how to fill rectangles,
trapezoids, and triangles, so we'd have to do some restructuring so that we issue other types of primitives in terms of
these operations. Probably need a complete rewrite of X11Renderer.
Also, XRender operations speak to a "Picture", which can be derived from an existing Drawable, so we'd need to somehow
keep a reference to a Picture in the X11SDOps structure.
It appears that XRender operations are not affected by basic Xlib GC state (such as color, clip region, logic op, etc),
so we'd need a separate state validation path in X11SurfaceData (or perhaps a subclass?) that handles things like
setting the current clip region, composite op, etc.
The OpenGLPipeline deviates slightly from the ColorModel? spec in that it treats opaque destinations as premultiplied.
(This is not allowable under the current ColorModel? spec, but so far no one has called us out on it. We were hoping to
relax the spec in Mustang but we never go around to it unfortunately.) We will probably need to do something similar for
this new pipeline, because we will be blending premultiplied components to an opaque destination.
A good place to start would be to try to implement MaskFill using XRender. We could cache a small (32x32) Picture in the
PictStandardA8? format to use as the mask.
And, we have a couple of bugs already filed for the
use of XRender:
* 6307603: [X11] Use RENDER extension for complex operations done in
software
* 5086814: RFE: Java 2D: consider Xrender for anti-aliased text on remote
X11
Thanks,
Dmitri
Java2D Team
Dmitri Trembovetski wrote:
LOUD, Ben wrote:
>> Meanwhile, if instead of "paths" you've actually already got
something
>> tessellated and just need it to be rasterized, then sure, you can
call
>> into XRenderCompositeTrapezoids to do just that if you'd like.
ahh ok this is interesting. I see your point. I've been speaking under
the assumption that X Render wouldnt be involved in this step. I
believe in Java2D, all the work of producing coverage values is always
done in software, and OGL or whatever only does the compositing. I
hadnt considered that Render could accelerate both.
Yes indeed, in Java2D this part is done in software.
However, I think that it would be nice to start out with
just XRender pipeline (may be sitting on top of the
x11 pipeline - the same way the old ddraw pipeline
extends gdi one).
I'm not really familiar with XRender myself so I don't
know if you could mix X11 and Xrender rendering to
the same drawable.
I think we'll need something to address performance issues with
apps using AA rendering and alpha compositing on X.
We've been careful not to use too much of both in our
built-in Swing L&Fs, but with the introductions of
Nimbus that goes out of the window - it is fully vector
graphics driven, with AA and AC everywhere.
The performance on X11 will suck as a result of that,
unfortunately.
I have my doubts about fully integrating Cairo at this
point (just because it would be much more extensive
undertaking) but it should be relatively straightforward to
implement an XRender pipeline.
You can follow the example of x11 and opengl pipelnes.
Unfortunately you don't have access to the new D3D
and opengl pipelines which we're working on for
6uN - we have improved code sharing between the pipelines
(d3d, ogl) a lot, generalized a bunch of stuff, so it might have
been easier to start from there.
We could forward port the shared pieces to openjdk once
we have some breathing time.
Anyway, the I would approach this would be something like this.
You'd need to create a SurfaceData subclass (say, XRSurfaceData) with
appropriate SurfaceType. See OGL/GLXSurfaceData for
the inspiration. Whether your surface type would be a subtype
of X11* surface types depends on whether you can do x11
rendering to XRender surfaces (Pictures?).
Then you'd define the pipes and blits which render to
and from your surfaces (see OGLRenderer, OGLBlitLoops).
You'd need to create appropriate SurfaceManager (Volatile- and
Caching-) so it would create surfaces of your type
for Buffered- and Volatile-images, and BufferStrategy.
(see GLXVolatileSurfaceManager). Also see SurfaceManagerFactory -
this is where SurfaceManagers are created.
Also, you'd need to create your own GraphicsConfiguration
subclass (see GLXGraphicsConfig) so that the window surfaces
of your type can be created.
There's tons more details, of course. But this is a
general direction.
Thanks,
Dmitri
------------------------------------------------------------------------
*From:* [EMAIL PROTECTED] on behalf of Carl Worth
*Sent:* Thu 6/12/2007 4:23 AM
*To:* LOUD, Ben
*Cc:* [email protected]
*Subject:* Re: [OpenJDK 2D-Dev] Best way organizing XRenderadditions
for theX11 pipeline?
On Wed, 5 Dec 2007 21:48:36 +1030, "LOUD, Ben" wrote:
> Wow, Carl Worth himself! Great to see you on the list. Cairo no
> doubt is a wonderful package, a true gem of free software.
Blah, blah, blah...
> All i meant by my "high level" comment was that its a complete top
> to bottom graphics package, when really the only part that OpenJDK
> desperately needs is one part of the pipeline, the part that
> rasterises paths to produce masks.
I don't disagree that cairo is high-level and likely quite similar to
the existing OpenJDK Java2D interfaces.
But as for "rasterizing a path to produce a mask", that isn't an
operation that Render provides at all, and it's also not something
that is hidden in layers inside cairo. You can get at an efficient
means of doing that with Render by calling into existing cairo
interfaces just fine.
Meanwhile, if instead of "paths" you've actually already got something
tessellated and just need it to be rasterized, then sure, you can call
into XRenderCompositeTrapezoids to do just that if you'd like.
But note that there's a big difference between just calling
XRenderCompositeTrapezoids to get rasterization and using Render
efficiently. For one thing, as suggested by its name, that call can do
both rasterization and compositing, (potentially with accelerated
support from the graphics hardware), so you're not winning by using it
only or rasterization.
> I wonder how difficult it would be to factor out Cairo's
> rasterisation and stroking code so we could just use that. We
> wouldnt need its compositng, font support, SVG and PDF backends
> etc. etc. Of course I know zero about Cairo's internals but if its
> feasible, it might be worth a look. I'd love to see it happen.
Here, I'm totally lost. Things like the SVG and PDF backends are the
lightest things in cairo, (no dependencies at all, for example), so
they should be the least of your concerns. Meanwhile for
"rasterization and stroking" the _code_ that is in cairo---the
software implementation in pixman actually---isn't the most
interesting part. It's not the fastest rasterizer around, so you'd
be making a big mistake to do a bunch of work to try to extract
it. Instead, what is interesting about cairo's rasterization is the
interface to get at faster underlying systems. In the current
conversation you only care about one target (X Render) but as above,
calling into cairo for rasterization alone should work fine. There's
no need to factor anything out.
> I doubt we'd need cairo to take advantage of X Render though. That
> doesnt sound to me like the difficult part. I would think it would
> similar to what they've already done for OGL and D3D.
There are parts of using Render that are a fair amount of work. For
example, getting efficient text output through Render requires the
client to manage a server-side cache of glyph images, etc. Maybe
that's similar to what you've done for OGL and D3D as you say. But
there's not strictly any need to write new code for that. But don't
let me get in your way---please write whatever code you enjoy.
So I'm just trying to say that cairo exists, and should still work
well for the _original_ purpose of cairo, (provide a simple interface
for getting at X Render functionality), even if you just ignore
everything else that cairo can also do.
-Carl
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