Added IDEAS file to docs as a place to collect ideas as I have them.

docs/IDEAS.md

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+Ideas
+=====
+
+This file is simply a collection of ideas for future capabilities of glabels.
+The ideas may or may not be very well thought out -- it simply a scratchpad.
+
+
+Merge Fields
+------------
+
+Currently substitution fields are specified simply by `${field-name}`. Here, I
+am exploring ideas to extend this to be a richer substitution language.
+Some of the criteria to consider are:
+
+ - A rich formatting capability probably cannot be done through GUI controls alone.
+ - It should be simple and easy to understand, but also powerful.
+ - Is there an existing language that can be used in whole or in part.
+ 
+
+## Format Control
+It is desirable to control the format of the fields -- e.g. decimal, hex,
+number of digits, leading zeros, fixed width, left or right justification,
+etc.  Perhaps something like `${NAME:%-10s}`, i.e.
+`${field-name:printf-style-format}`.
+
+
+## Default Values
+It would also be desirable to specify a default value.  (Or an initial value
+in the event of a counter, see Label Counter below.)  Perhaps, something like
+`${field-name:=value}`
+
+
+## Possible Syntax
+This is the first stab at a syntax specification.  It is roughly based on
+the parameter substitution of the Bourne shell.
+
+```
+<field>     ::= "${" <field_name> [ ":" _modifiers_ ] "}"
+<modifiers> ::= <modifier> [ ":" <modifiers> ]
+<modifier>  ::= { "%" <format_spec> | "=" <value> }
+```
+
+Need a way to quote "`:`" in value.  Perhaps "`\:`" or maybe string values
+should always be in quotes (you would still need to quote out quotes.
+
+
+## Special Builtin Fields
+
+### Label Counter
+
+It would be nice if there was a label counter field.  Maybe something like
+`${#}` or `${label#}`.  Also desirable would be the ability to set the start
+value.  Possibly even reading it from a file and updating the file each time.
+You would want to control if the value is repeated for copies or every copy
+would be unique -- perhaps two different fields.  It would also be desirable to
+control the format of the counter -- e.g. decimal, hex, number of digits, or
+leading zeros.
+
+### Date and Time Fields
+
+Date and time fields would need to be able to be formatted much like strftime.
+
+
+## Examples
+Just some examples of the type of thing I am thinking.
+
+```
+${1}       /// CSV column 1
+${addr1}   /// Field named "addr1"
+${n:%09d}  /// Field named "n", format as 9 decimal digits with leading zeros
+${MI:=NMI} /// Field named "MI", with default value of "NMI"
+${#:%06d:=1000} /// Label counter, format as 6 decimal digits with leading zeros, starting at 1000
+${#:%06d:<count.txt:>count.txt}  /// Perhaps a way to read and write the starting and ending value
+
+```
+