Debugging and the execution path

Alex Tweedly alex at
Wed Dec 21 20:52:40 EST 2005

Jerry Daniels wrote:

> Dick,
> I threw together a quick Var Watcher last night that puts the calling  
> path into a pop up menu above the vars, much like Rev's Var Watcher  
> does. Each item in the menu looks like this:
>     stack "save test"/button "Button"/handler "mouseUp"/line: 7
I find that a bit verbose.

> The label of the pop up menu is the current execution context.  
> Clicking the menu displays the calling path in order from last to  
> first in the format you see above. The format is easy to change if  
> you think it would look better some other way. I also thought of  
> making more like the transcript syntax:
>     line "7" of handler "mouseUp" of button "button" of stack "save  
> test"
> Not sure which approach more clearly delineates that item as part of  
> the calling path.
And that even more verbose :-)

I'd consider suppressing the stack name unless it is different from the 
breakpoint's stack name.

I would like to see it as brief as possible, with an easy way to get the 
full version (such as pop-up text like a tooltip for the full info, with 
only object / handler / line shown normally).

> Funtionality: I made the menu switch execution contexts upon picking  
> another menu item. In terms of the list of vars, upon clicking they  
> are editable.
> What puzzles me is the fact that every one wanted the calling path  
> when, as far as I can tell, it's already in the Rev Var Watcher. They  
> call it the "execution contexts." Please tell me if I'm missing  
> something.
Rev VW has only partial info - it's missing the handler name which is 
one of the the most important parts.

> Conclusion: I'm not sure that the watcher I built would offer much  
> new, other than the fact that it would reside in the upper two panes  
> of Constellation where the props and previews sit ordinarily. I could  
> make the array elements editable, I suppose.
There is lots of value waiting to be added :-)

 - currently you can only see data in an array by clicking on that 
variable to see each element in the "extended" display area; you could 
display the first few elements in the "line per variable" display.
 - same issue for multi-line variables; you could (as an option) display 
e.g. "\n" or "\r\n" for the newlines, and hence show a few lines 
directly in "line per var" mode
 - make it an expression watcher - i.e. allow the user to specify an 
expression to evaluate & display
 - allow user-selection of variables to hide or display (and hence 
eliminate scrolling back and forwards to see the two or three variables 
that are most interesting).
 - highlight values changed since last display
 - allow display of variables from another context

That's enough for a (good) start :-)

Alex Tweedly

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