gEDA-user: gEDA attributes -- why not in this simple way

[Stefan Salewski <mail@xxxxxxxxxxxx>]

I wonder why gEDA attribute handling works not in this simple manner:

- attributes can be defined in symbols

- gschem takes these attributes from symbols and allows overwriting.

(For each attribute of the form a=v the position (relative to the symbol
reference point) and visibility is stored.)

If a symbol is inserted in a schematic gschem has only to store the path
to that symbol file and the position in the schematic.

All attributes are accessible in gschems attribute editor, and the
visible attributes are displayed and printed.

Now the user can redefine arbitrary attributes -- they overwrite/shadow
the attributes from the symbol. And of course the user can define new
additional symbols.

Example:
Attributes of a symbol:
a1=v1
a2=v2
a3=v3
a4=v4
a5=v5

For the first instance of this symbol in the schematic the user
overwrites the content of a1 in gschem:
a1=vx

To display, print or present the list of attributes in an attribute
editor gschem takes all attributes from the symbols and replaces some of
it resulting in

a1=vx
a2=v2
a3=v3
a4=v4
a5=v5

Only a1=vx needs to be stored in the schematic.

Similar to the second instance of this symbol, a1=vy, a6=v6 and position
or visibility of a2=v2 in modified. So gschem has to store

a1=vy
a6=v6
a2=v2 (position/visibility)
in the schematic. The complete set is

a1=v1 replaced by a1=vy
a2=v2 replaced by a2=v2 (position/visibility)
a3=v3
a4=v4
a5=v5
a6=v6 added.



Where is the problem by this simple approach?



Best regards

Stefan Salewski




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