Line Numbers in Text Editor

Justin Sloan sloan.justin at gmail.com
Sat Jun 26 14:36:57 CDT 2010


Richard,

Fantastic primer on handling line numbers in Rev! Thank you!  It's amazing how something seemingly so simple can have such a huge impact.

That is what I love about programming, the elegance of creative solutions.


 - Justin


On Jun 26, 2010, at 7:23 PM, Richard Gaskin wrote:

> Justin Sloan wrote:
> > I am planning to implement line numbers in a proprietary text editor
> > that I wrote for in-house use.  Problem is, I don't know how I am
> > going to implement it. I thought about using a parallel text field,
> > but there has to be an easier way.  Any of you genius devs have any
> > ideas?
> 
> I forked the MC IDE's script editor many years ago to add, among other things, line numbers.  It was at the time the only script editor for Rev which had line numbers, and having implemented this "advanced technology" <g> I can share with you a couple tips I learned:
> 
> The line numbers are displayed in a separate field to the left of the editor field, kept in synch with scrollbardrag handlers in each.  Being a script editor I also have another field in between them for marking breakpoints, but you probably won't need that for other types of editing.
> 
> I chose a separate field for the line numbers because it seemed a more with-the-grain approach than attempting to put anything in the editor field except for the script itself.  In Rev, a script is just a block of text, so my mandate for my editor was to maintain as close a relationship as possible between what you see and what the engine expects.  So the script is dumped into a field, with no caches or other intermediaries to complicate the scripter's relationship with the engine. WYGIWE - what you got is what exists. ;)  I have a McCabe algo for Rev (see note on RevCloud below) so I'm sensitive to the impact of complexity in a code base.
> 
> At first I went the route most other text editors use, in which the line number field is populated dynamically to show only the lines present in the editor field.  But I found that when I got beyond a few thousand lines the time it takes the engine to render the line number field became a performance drag on my typing.  So I went with having pre-populated numbers, which isn't so bad since you can still see how many lines you have in your script by just scrolling to the end and look at the last line number across from the last line of script.
> 
> But even pre-populating the line number field was not without some challenge, since putting in 10,000 lines of numbers would not be sufficient for some scripts, and added a lot of bulk to the editor stack file.
> 
> So the final solution I went with was leaving the field blank when the stack is saved, and populating it on preOpenStack with the number of lines of the script + 5000.  Since this is a one-time performance hit when the stack opens, the impact on performance isn't nearly as noticeable as it was when I was appending that list with each carriage return (has anyone younger than 40 even seen an actual typewriter carriage? Odd nomenclature in the 21st century, but I digress).
> 
> This keeps the stack file small enough to be extremely portable (I'm migrating a lot of tools to cloud storage - look for RevCloud coming soon to RevNet this summer; think devolution on serious steroids and focused on collaborative workflows), and it's unlikely that a person will type more than 5000 lines during a given session with the editor open.
> 
> But what if they paste more than 5k lines?  I've trapped for that in the Paste item and add another block of lines numbers beyond the number already in the field + the number in the clipboard, so we stay a few thousand lines ahead of the scripter.
> 
> HTH -
> 
> -- 
> Richard Gaskin
> Fourth World
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