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