qemu-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] X support for QXL and SPICE


From: Anthony Liguori
Subject: Re: [Qemu-devel] X support for QXL and SPICE
Date: Fri, 11 Dec 2009 21:31:34 -0600
User-agent: Thunderbird 2.0.0.23 (X11/20090825)

Soeren Sandmann wrote:
Hi,

Here is an overview of what the current QXL driver does and does not
do.  The parts of X rendering that are currently being used by cairo
and Qt are:

- Most of XRender - Image compositing
        - Glyphs

Does anything use Xrender for drawing glyphs these days?

Certainly, with a compositing window manager, nothing is getting rendered by X...

The X driver for the QXL device is not yet very sophisticated. What it
does is basically this:

        - It keeps a separate memory framebuffer uptodate using
          software

        - Solid fills and CopyArea requests are turned into SPICE
          commands.

        - The cursor is drawn using cursor commands

        - For other things, bitmaps are sent across the wire
                - It uses the hashing feature of SPICE to only send
                  hashcodes for those bitmaps if it can get away with
                  it.

Even this simple support provides a better user experience than VNC
because scrolling is accelerated and doesn't result in a huge bitmap
getting sent across the wire.

Scrolling is accelerated in VNC. In the Cirrus adapter, both X and Windows use a video-to-video bitblt, we use this to create a VNC CopyRect which makes scrolling and Window movement smooth.

However, as things stand right now, there is not much point in adding
this support, because X applications essentially always work like
this:

        - render to offscreen pixmap
        - copy pixmap to screen

There is not yet support for offscreen pixmaps in SPICE, so at the
moment, solid fill and CopyArea are the two main things that actually
make a difference.

Okay, that's in line with what my expectations were. So what's the future of Spice for X? Anything clever or is Windows the only target right now?

Regards,

Anthony Liguori




reply via email to

[Prev in Thread] Current Thread [Next in Thread]