Need Script Debugger Tutorial

[Sarah]

As others have said, Rev 2 will have an entirely different debugger, 
however I expect some functionality while remain the same and you 
probably want information now, so here is a brief explanation:

The 3 popups just allow you to select which handler to debug. The first 
selects the stack, the second allows you to select any object that has 
a script, and the third allows you to choose a handler.

When you have chosen your handler, click on a line to turn it red - 
this is where the debugger will kick in. You can now either click "Send 
message" to start that handler running from within the debugger, or 
leave the debug window open and do whatever you do to get to that 
handler e.g. click a button, type in a field, select a menu item).

When the script gets to your red line, it will stop and wait for you to 
tell it what to do next. The difference between step over & step into 
only shows up when your handler calls another handler or function. 
Suppose you were debugging a script like this:

on mouseUp
	put 3 into myVar
	put myFunction(myVar) into newVar
	answer newVar
end mouseUp

You put the red line on the "put 3 into myVar" line so that is where it 
stops. Click "Step over" once - you will see the hilite move one line 
down and in the variable list, you will see that myVar is now 3. The 
next line to be processed is the one that calls another function. 
Clicking "Step over" will show you the result of that function only. 
Clicking "Step into" will take you into the separate function so you 
can track your way through it as well.

Trace effectively clicks "Step into" about twice a second, so you can 
see where your script is going. The Send message button has now become 
Run which goes to the next red line (you can have more than one) or to 
the end of the handler.

While stopped on a line, you can click on any variable name to see that 
variable in the field at the bottom right. From there, you can edit the 
variable on the fly. This can be very useful if you have detected an 
error, but still want to go on and check the rest of the script.

The other function of the debugger is it's ability to time your 
scripts. The debugger slows everything down a lot but the timer at 
least gives you an idea of which parts of your scripts are slowing you 
down and how many times each line is used. Select your handler as 
before but clear any red lines by clicking on them again. Then click 
"Start timing", followed by "Send message". The script field will be 
divided into 3 columns showing the number of calls to each line and the 
taken spent on each line. Click "Stop timing" and "Clear timing" to 
revert to the usual display.

A word of warning: the debugger can be so slow with large handlers that 
it feels like the program has crashed. There is also no way to button a 
handler running although the usual command/control period will usually 
work. If you only need to check the value of a couple of variables, you 
will often be better off using an "answer" or "put" command to check 
them.

Cheers,
Sarah

On Thursday, January 16, 2003, at 09:25  pm, Graham Samuel wrote:

> I have tried to search the usual sources, but I have not found a 
> detailed description of the way the Script Debugger works in 1.1.1. 
> For example, what do the 'run', 'trace', 'step into' and 'step over' 
> buttons do - the last two seem to do the same thing, which is to 
> execute the highlighted line of script. What do the other buttons and 
> pull-downs do - I have not found out what the pull-down lists are for, 
> for example. Why do some steps not get shown, as in some repeat loops, 
> etc?
>
> What I'm trying to do is to trace the path thro a quite long program 
> in the most intelligent way possible - I already know from a thread of 
> last October that there is no path trace as such. I feel that if I 
> knew everything the Script Debugger can do, I'd be in a better 
> position to work on my scripting problems.
>
> I'd be glad to find I'd missed a tutorial on debugging - if anyone 
> knows of one, please say.
>
> TIA
>
> Graham
> -- 
> -------------------------------------------------------------------
>          Graham Samuel / The Living Fossil Co. / UK & France
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