Re: Is there a chance to set an alpha-mask using XOrg?

[Helge Bahmann]

Am Saturday 06 June 2009 21:03:12 schrieb Leif Bergerhoff:
> Peter Harris wrote:
> > It depends on your toolkit. If you're not using any particular toolkit,
> > the easiest way is to set _NET_WM_WINDOW_OPACITY on your window. See
> > http://webcvs.freedesktop.org/xapps/transset/transSet.c?view=markup for
> > an example.
> >
> > Make sure a composite manager is running (many desktops run one by
> > default these days).
>
> No, I don't want to make use of a toolkit if possible.
>
> As I can see I would have to make use of the composite extension.

no, you need "composite" if you want to write your own compositing manager 
(it's unlikely you really want to do that)

> If I remember correctly, I read about this extension supporting max. 2
> output devices. Right?

no

> This would mean, I'll need another way for setting an image as an
> alpha-mask, since I want to make use of 6 output devices.

to *draw* using transparency, you need either the "render" extension (but use 
cairo if you can, as pointed out), or GL (but note that compositing managers 
and direct rendering do not mix well with DRI1)

to *show* a translucent window, you generally need a compositing manager, and 
either set _NET_WM_WINDOW_OPACITY as suggested (if you want uniform opacity), 
or otherwise create your window using an ARGB visual and provide appropriate 
per-pixel alpha while drawing

Helge Bahmann
-- 
Dipl. Math.
Helge Bahmann
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Re: Is there a chance to set an alpha-mask using XOrg?

[Glynn Clements]

Leif Bergerhoff wrote:

> > It depends on your toolkit. If you're not using any particular toolkit,
> > the easiest way is to set _NET_WM_WINDOW_OPACITY on your window. See
> > http://webcvs.freedesktop.org/xapps/transset/transSet.c?view=markup for
> > an example.
> >
> > Make sure a composite manager is running (many desktops run one by
> > default these days).
> 
> No, I don't want to make use of a toolkit if possible.
> 
> As I can see I would have to make use of the composite extension.
> If I remember correctly, I read about this extension supporting max. 2 output 
> devices. Right?
> This would mean, I'll need another way for setting an image as an alpha-mask, 
> since I want to make use of 6 output devices.

If you just want rendering functions which support translucency, use
Cairo (you can use XRender directly, but there's unlikely to be any
advantage to doing so).

The core X protocol doesn't support alpha blending; apart from
anything else, it's only meaningful with StaticGray and TrueColor
visuals.

-- 
Glynn Clements 
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Re: Is there a chance to set an alpha-mask using XOrg?

[Leif Bergerhoff]

Peter Harris wrote:
> It depends on your toolkit. If you're not using any particular toolkit,
> the easiest way is to set _NET_WM_WINDOW_OPACITY on your window. See
> http://webcvs.freedesktop.org/xapps/transset/transSet.c?view=markup for
> an example.
>
> Make sure a composite manager is running (many desktops run one by
> default these days).

No, I don't want to make use of a toolkit if possible.

As I can see I would have to make use of the composite extension.
If I remember correctly, I read about this extension supporting max. 2 output 
devices. Right?
This would mean, I'll need another way for setting an image as an alpha-mask, 
since I want to make use of 6 output devices.

Leif 

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Re: Is there a chance to set an alpha-mask using XOrg?

[Graeme Gill]

Peter Harris wrote:
> It depends on your toolkit. If you're not using any particular toolkit,
> the easiest way is to set _NET_WM_WINDOW_OPACITY on your window. See
> http://webcvs.freedesktop.org/xapps/transset/transSet.c?view=markup for
> an example.

I notice (from finding out the hard way) that this is not documented
in any  formal fashion (ie. it's not in 
).
It would probably be a good idea to document such things, so that
developers might more easily discover them.

cheers,

Graeme Gill.
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Re: Is there a chance to set an alpha-mask using XOrg?

[Peter Harris]

Leif Bergerhoff wrote:
> 
> My intention is to draw a transparent image on a XScreen.
> How can I do this the best way?

It depends on your toolkit. If you're not using any particular toolkit,
the easiest way is to set _NET_WM_WINDOW_OPACITY on your window. See
http://webcvs.freedesktop.org/xapps/transset/transSet.c?view=markup for
an example.

Make sure a composite manager is running (many desktops run one by
default these days).

Peter Harris
-- 
   Open Text Connectivity Solutions Group
Peter Harrishttp://www.opentext.com/connectivity
Research and DevelopmentPhone: +1 905 762 6001
phar...@opentext.comToll Free: 1 877 359 4866
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Is there a chance to set an alpha-mask using XOrg?

[Leif Bergerhoff]

Hi,

My intention is to draw a transparent image on a XScreen.
How can I do this the best way?
The aim would be that I can set different images on different XScreens of a
multi-monitor setup at the same time.

Any help would be greatly appreciated.

Leif
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