Hi Friends,
Status bar: "An exception occurred during execution of the path effect" I'm thinking I should be able to remove the path effect, then reapply it. Or maybe even redraw the object. So I'm not looking for a fix. (.....unless redoing doesn't fix it, I'll let you know)

I'm just curious exactly what it means. Does anyone know what "exception" means in terms of Inkscape and path effects? If it's a highly technical explanation, don't worry about it. I'm just looking for a general idea, that's a little more informative than 'something went wrong'.

Hhmmm, I wonder if I can learn anything by looking at the XML? I'll post if I find any sort of discrepancy.

If it matters, this was text converted to path, and using Envelope Deformation LPE. I've successfully used the same effect on different text, a short distance away on the same canvas.

Thanks for any comments

Edit
Ah-ha! There IS a difference in XML Editor. On the succesful object, there's an attribute called "inkscape: connector-curvature" with a value of 0. On the one with the "exception" that attribute is missing.

Maybe "exception" means that an attribute wasn't created??

Edit 2
Well, so far, removing the effect and reapplying hasn't solved the problem. But there's another "symptom". After I apply the effect, I can't move the object. Or more precisely, I can move it, but as soon as I release the mouse, it snaps back to it original position! Weird, huh?!! I guess I'll recreate the object, and hope that fixes it

Edit 3
Removing the effect and reapplying it did not fix the problem. I managed to get the effect applied by moving the object to the same part of the canvas where I did the first one. However, now I can't move it to the position where I need it. It acts a lot like a spiro spline when I move it around -- it just goes wacky! I've closed the file, and hope that reopening it will somehow solve the problem. I'll let you know what happens. (I didn't use Pen or Pencil, since the path started out as text, so it's not accidentally a spiro spline.)

Ok, well the Envelope Deform LPE continued to give me enough trouble that I trashed the idea altogether. Next I tried the Envelope Deform extension, but I needed some curves in the deformation, and while I could achieve some curving with the extension, it just wasn't good enough for what I need. So in the end, I used Pattern Along Path.

According to the manual,

"The implementation of LPEs has many bugs....."

so I guess this might be one of them. Although, I have used that ED LPE, with text/paths, in the past with beautiful results; so this current trouble is a bit of a puzzle. I guess consistency isn't necessarily an attribute of bugginess .

Perhaps surprisingly, but definitely happily, yes, I did successfully use the PAP LPE!

I'm still curious about what "exception" means in the sense meant by the status bar though. Could it be the omission of the attribute in the XML? I can see how "exception" could refer to something being left out. I know it says "...during execution..." but I'm not sure if it refers specifically to the the process of the deformation, or to the writing of the XML or both.

Anyway, thanks for listening, and for any comments

An exception, in computing terms, is an "exceptional" event that occurs and takes the CPU out of its normal program flow and into some kind of "exception handler" routine.

In pure microprocessor terms it can be desirable - for example the CPU in your microwave might want to interrupt the normal program flow when the Cancel button is pressed. The pressing of the button is an exceptional event - the CPU can't just sit there waiting for it to happen as it's got to get on with its normal tasks of driving the turntable motor and counting down the timer. So the code for your microwave will include an exception handler that kicks in when the button is pressed and handles this exceptional event.

With PCs it's a bit more complex. The CPU still has the same notion of exceptions and handlers for hardware events (such as some data coming in from the keyboard), but it also allows software exceptions and handlers to be defined. The underlying development framework will use some of these so that if something unexpected happens (i.e. a bug), the code has a chance to do something about it via an exception handler. Of course unless you're being paid to write military grade code, most people don't bother to write exception handlers for every possibility, so you end up with a generic "an exception occurred". Usually it actually means "something went wrong but I don't know what to do about it."

I would say that any such message indicates a bug, but the fact that it's an exceptional event means that they can be hard to track down. If you report it, do try to include a file and clear instructions that can be used to reproduce it.

Oh wow, thanks Xav That is so interesting!

Unless someone thinks I should report it, I probably won't. I don't think it will be always reproducable. I've used that LPE before without any problems, and I have no idea why this is happening in this file. It seems that the location of the object on the canvas has something to do with it (which might indicate a tranform-related issue). But by the way it looks, I might even think it was related to the rendering issues we've seen reported here so much lately....except for the error message, which is pretty much of a red flag, as they say. So I'd have to submit that file, and it's too complex to be used for troubleshooting.

Anyway, thanks for the info Xav -- very helpful