[directfb-dev] Re: Request for new DFBDisplayLayerOptions flag

[Ville Syrjälä <syrjala@sci.fi>]

On Sun, Nov 02, 2003 at 01:51:28PM +0100, Andreas Robinson wrote:
> Hi,
> 
> I have a feature request:
> 
> The video layer in the CLE266 can be blended with the graphics layer on a
> per-pixel basis. It reads the alpha channel in the graphics layer and use it
> as its own.

There was a message from Simon Glass where he wrote that the alpha channel
is inverted ie. 255 == video layer transparent, 0 == video layer opaque.
Is that true?

If that is the case then the video layer is an underlay not an overlay and
the alpha really belongs to the graphics layer. You should just move the
opacity handling to the primary layer and hook it in with
dfb_layers_hook_primary(). See the cyber5k driver for an existing underlay
implementation.

AFAICS we don't have anything besides the layer name that an application
can use to identify an underlay. Maybe we should add a flag to the layer
description? Or maybe a number indicating the layer's position in
the stack for hardware with multiple overlays and/or underlays?

-- 
Ville Syrjälä
syrjala@sci.fi
http://www.sci.fi/~syrjala/


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