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Message-ID:	<55A95B75.9080306@sbcglobal.net>
Date:	Fri, 17 Jul 2015 12:45:57 -0700
From:	"Girvin R. Herr (gherr375 AT sbcglobal DOT net) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
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To:	geda-user AT delorie DOT com
Subject:	Re: [geda-user] Difference between attached and detached attributes
References:	<55A813B5 DOT 4040609 AT sbcglobal DOT net> <20150716210154 DOT GD14931 AT localhost DOT localdomain>
In-Reply-To:	<20150716210154.GD14931@localhost.localdomain>
Reply-To:	geda-user AT delorie DOT com

On 07/16/2015 02:01 PM, Vladimir Zhbanov (vzhbanov AT gmail DOT com) [via 
geda-user AT delorie DOT com] wrote:
> On Thu, Jul 16, 2015 at 01:27:33PM -0700, Girvin R. Herr (gherr375 AT sbcglobal DOT net) [via geda-user AT delorie DOT com] wrote:
>> Greetings,
>> I have been doing some symbol work in gschem and I got confused again about
>> attached attributes vs detached attributes.  The manuals do not go into
>> detail about usage.  Hint, hint.  Can someone tell me what is the difference
>> between them and where I should apply one vs the other?
>>
> I believe nothing changed since the creation of this document:
>    http://wiki.geda-project.org/geda:master_attributes_list
>
> I don't see any ambiguous statements there.
>
>> Right now, I am using attached attributes for everything except the pin
>> attributes in my symbols. But the fact that there is that detached option
> Brrr,
> pin attributes must be attached to their pins,
> general symbol attributes must be detached/floating in the symbol
>
>> there makes me wonder if I am using the correct type.  In other words, what
>> is detached used for?  Then there is the "attribute promotion" issue.  Is
> What is the issue with promotion?
>
>> there any impact on attribute promotion when using one or the other?
> Detached/floating attributes are promoted when the symbol is
> instantiated.
>
>> Any other "gotchas" when using one or the other?
>> Is there any problem with changing the attribute value after symbol
>> instantiation from one or the other?
> The floating attribute value within the symbol can be thought of as the
> default. If you remove a promoted attribute of an instance of the symbol
> then this value will be used. Otherwise nothing changes.
>
> HTH,
>    Vladimit
>
Vladimir,
So, if I understand you correctly, the short answer is that all 
attributes are detached except for pin attributes, which are attached to 
the pin.  That seems logical.  I was thinking along the lines of all 
attributes are "attached" to the symbol, not "attached" to the pin in 
the symbol.  Now I see the error of my thinking.

Is it possible to edit the pin number attribute value after symbol 
instantiation?
Example: I would like to create a generic symbol whose part has 
insulated wire leads of arbitrary colors.  It would be nice to create a 
single symbol with placeholder pin numbers which can be changed to the 
wire color after instantiation.  Yes, I suppose I could hand edit the 
schematic file, but that is crude.

My issue with promotion was based on my past experience of not being 
able to change the DEVICE attribute value after symbol instantiation.  I 
was wondering if this was due to my use of the wrong attachment 
(attached vs detached).  I am sure I had problems with this in past 
gschem versions.  However, I just ran a test with 1.8.2 and I was able 
to change DEVICE whether it was attached or detached.  I also now see 
that the DEVICE attribute was promoted upon instantiation and I was able 
to edit the promoted version, but not the unpromoted version.  Either 
what I was doing in the past was wrong or there has been a change in the 
way gschem promotes attributes.  In any case, this issue is no longer a 
problem for me - other than now going back and changing all of my 
library symbols to get rid of the work-arounds.

Thanks for your help.
Girvin Herr

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