Re: There should be an option to set the display size of an image to zero

[Marc Feeley]

On 2013-09-17, at 10:02 AM, Eli Zaretskii <address@hidden> wrote:

>> From: Marc Feeley <address@hidden>
>> Date: Tue, 17 Sep 2013 08:50:45 -0400
>> Cc: "Stephen J. Turnbull" <address@hidden>,
>> address@hidden
>> 
>> Let me explain the context so that you better understand my specific needs.  
>> I want to use emacs as a programming tool to display the result of some 
>> program analyses of the code currently in the buffer.  Specifically I want 
>> to display arrows that indicate how data flows in the program.  For example, 
>> what are all the places in the code where the value resulting from a given 
>> constructor are referenced, or inversely, what are all the calls to 
>> constructors whose resulting value can flow to a particular point in the 
>> code.
> 
> I vaguely understand, but it is still not clear enough how you would
> achieve those goals with "arrows".  Where will the arrows originate,
> and where will they point?  Perhaps you could show a screenshot?

Here's a screenshot showing the type of annotation I'm trying to implement:

http://planet.racket-lang.org/package-source/mflatt/scribble-paper.plt/2/1/planet-docs/scribble/collatz.png

The screenshot is from the racket Scheme implementation which supports arrow 
annotations.

>> My plan is to display arrows indicating these relationships and to overlay 
>> them on top of the program source code.  It would be ideal if it was 
>> possible to place an image on top of the text that scrolls with the text.  
>> The arrows would only appear if the cursor (or mouse) is placed on top of a 
>> constructor or accessor, so it must be efficient to change the image 
>> dynamically.  An SVG image would be ideal because the image can easily be 
>> constructed and takes little space.
> 
> Did you consider using display margins?  Emacs can show display
> strings and images in the display margins, to the left or right of the
> text.  These display strings and images are "pinned" to specific
> buffer positions, so they scroll with the text.

But can the image in a margin overflow the margin to overlay the main text?  I 
assume not.

Marc