LPE - Envelope deformation 'Link to path' allows self reference

[uwesch]

Win XP SP3
Inkscape REV Inkscape21627-0906200405

1. Create a shape
2. use Envelope deforming
3. select path
4. copy path via icon
5. click on icon link to path

Result: Program is closing without any error messages.

[uwesch (uwesch)]

There is another bug in this effect.

1. Write some text
2. convert the text into a path
3. use LPE Envelope Deformation
4. click on any icon to deform a side
5. select a character so that it's shown as a bundle of nodes
6. set Envelope Deformation again with the character

Result: The program crashes with an undefined error message.

[jazzynico (jazzynico)]

Confirmed on Windows XP, Inkscape rev. 21627.
For the first one, gdb only returns "Program exited normally".
For the second, gdb returns "How to handle helperpaths for non-shapes?" several times while playing with the shape's nodes, and "WARNING: Requested update while update in progress, counter = 1" just before activating an emergency save and crashing.

[Steren (steren-giannini)]

I don't understand action number 5 of the first report.

Concerning the second report, I can confirm it in rev 21718 under Linux. Here are some more info :

- It is not related to text because you can reproduce it with a group of path.
- It is indeed related to the "Envelope Deformation" LPE because we can't reproduce the bug with "Bend" (which is a LPE very similar to "Envelope" in its code)

I'm the author of "Envelope", I will try to investigate the issue.

[Steren (steren-giannini)]

I was wrong. the second report is not related to "Envelope".

Follow these steps :
- create a path
- double click on it to show its nodes (enter Edit mode)
- apply "Bend"
crash

We can also notice that is doesn't crash if we apply "Sketch" for example.

I will create a new bug report, because we moved far away from report #1.

[Steren (steren-giannini)]

Report #1 is still unconfirmed, report #2 has moved to https://bugs.launchpad.net/inkscape/+bug/394899

[jazzynico (jazzynico)]

Steren, I've confirmed both bugs in comment 2.
The second crash could also be linked to Bug #387298.

[Johan Engelen (johanengelen)]

This bug still present after the fix for bug #387298?

[su_v (suv-lp)]

@Johan - of the two bugs that have been mixed in this report:

1) crash when using 'link to path' in the path editor dialog
not reproduced with Inkscape 0.47+devel r9186 on OS X 10.5.8

2) crash when applying LPE while in node-editing mode
duplicate of bug #304018 “Crash when using LPE with node tool selected” (Fix Released in 0.47)

@UweSch - can you reproduce your initially reported crash (link to path) with a current devel snapshot on Windows?

[su_v (suv-lp)]

I misunderstood the original report: it describes using the path which has the 'Envelope' LPE applied to as source for one of the bend paths (copy path -> link to path) - creating kind of a self-reference (?). This no longer crashes Inkscape (0.47+devel r9192) but still yields unexpected results from a users perspective (no green highlighted editable bend path visible after linking one of the bend paths to a copy of the object itself, the other bend paths no longer deform the object - as if they have been disabled).

AFAIU linked bend paths (aka control paths) are meant to be separate paths from the object itself. What is the expected result from a developers perspective when the control path links to the original object itself?

[Johan Engelen (johanengelen)]

> What is the expected result from a developers perspective when the control path links to the original object itself?

Don't do it! I think it doesn't make much sense to have a path bend along itself, right? And the code probably doesn't expect you to do so. Perhaps Inkscape should check whether a path refers to itself... But perhaps it can be useful for some effects.
In any case, if I remember correctly, the path link is to the 'd' attribute, so not to the 'original' path, but to the output of the path after LPE. I can see that this goes wrong when referring to itself.

If it doesn't crash anymore, please remove the crash tag.

[Jabiertxof (jabiertxof)]

Fixed in 0.92.x and master not sure when