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Rendering order of region backgrounds

From: Michael Foster <foster@PacketVideo.COM>
Date: Thu, 19 Jun 2003 09:40:32 -0700
Message-ID: <72263E8E8622D611975C0002B32C19D84A368A@MISTY>
To: "'www-smil@w3.org'" <www-smil@w3.org>

I tried to post this message on May 30. Not sure if it got through (did not
receive any responses). Here it is again
............................................................................
..
Hi everyone,

I have a couple of questions about the rendering order of region
backgrounds. I have searched the newsgroup archives and SMIL spec, but can't
find any discussion of these issues.

Here is the first question. In the following SMIL file, all regions have the
same z-index. Two media elements share the same region ('full'). At t=8s,
according to the z-index processing described in the spec, 'img1' will be
rendered first, followed by 'img2' and then 'img3'. The question is when
will the background of region 'full' be rendered? Will it be rendered before
rendering 'img1' and then again before rendering 'img3'? If so, no portion
of 'img1' would be visible if 'img3' were smaller than 'img1'. Or will it be
rendered only once before either 'img1' or 'img3' is rendered? If it were
only rendered before 'img1', then 'img3' could be rendered on top of 'img2'
without its background.
......................................
<smil>
    <head>
        <layout>
            <root-layout width="100" height="100" z-index="1"
background-color="#000000" />
            <region id="full" top="0%" left="0%" width="100%" height="100%"
z-index="1" background-color="#0000FF" />
            <region id="top_right" top="0%" left="50%" width="50%"
height="50%" z-index="1" background-color="#FF0000" />
        </layout>
    </head>
    <body>
        <par dur="10s">
            <img id="img1" begin="0s" region="full" type="image/gif"
src="img1.gif" />
            <img id="img2" begin="4s" region="top_right" type="image/gif"
src="img2.gif" />
            <img id="img3" begin="6s" region="full" type="image/gif"
src="img3.gif" />
        </par>
    </body>
</smil>
......................................


Here is the second question. In the following SMIL file, all regions have
the same z-index. Region 'top_right' does not have any media elements
associated with it, however since the default value of the showBackground
attribute is always, this region background will be rendered. At t=6s,
according to the z-index processing described in the spec, 'img1' will be
rendered first, followed by 'img2'. The question is when will the background
of region 'top_right' be rendered? The z-index processing described in the
spec cannot be used to determine the rendering order for this region
background because there is no media element associated with it. 
......................................
<smil>
    <head>
        <layout>
            <root-layout width="100" height="100" z-index="1"
background-color="#000000" />
            <region id="full" top="0%" left="0%" width="100%" height="100%"
z-index="1" background-color="#0000FF" />
            <region id="top_right" top="0%" left="50%" width="50%"
height="50%" z-index="1" background-color="#FF0000" />
        </layout>
    </head>
    <body>
        <par dur="10s">
            <img id="img1" begin="0s" region="full" type="image/gif"
src="img1.gif" />
            <img id="img2" begin="4s" region="full" type="image/gif"
src="img2.gif" />
        </par>
    </body>
</smil>
......................................


Thanks for any help you can provide


Mike

_________________________________________________
Michael Foster  *  PacketVideo  *  (858) 731-5543
Senior Member of Technical Staff
foster@pv.com  *  www.packetvideo.com   
Received on Thursday, 19 June 2003 12:40:47 GMT

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