Inkscape freezes when pulling out retracted node handle

[Cornelius Sicker]

Inkscape 0.48.1 r9760 on Xubuntu 11.04 64bit (standard version from the repositories)

By working through the "Inkscape: Advanced" tutorial I found the following issue:

When trying to pull out a retracted handle on a node in a bezier curve the handle appears close to the node but Inkscape becomes unresponsive, not reacting to any clicks or shortcuts. It still pops up a dialog whether to save the current document when trying to close the window, but the buttons in this dialog are also inactive. One has to forcefully kill it from htop or the like.

Steps to reproduce:
1) draw or select an arbitrary bezier curve
2) retract the handles of a node by Ctrl+clicking on them
3) try to pull the handles out again by Shift+dragging from the node

edit: The system information below is for my 32bit system which shows the same behavior as the 64bit one from which I reported this bug.
---
Architecture: i386
DistroRelease: Ubuntu 11.04
InstallationMedia: Kubuntu 10.10 "Maverick Meerkat" - Release i386 (20101007)
Package: inkscape 0.48.1-2ubuntu2
PackageArchitecture: i386
ProcEnviron:
 LANGUAGE=en_US
 LANG=de_DE.utf8
 LC_MESSAGES=en_US.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Tags: natty
Uname: Linux 2.6.38-8-generic i686
UpgradeStatus: Upgraded to natty on 2011-05-09 (23 days ago)
UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare

[su_v (suv-lp)]

Not reproduced with Inkscape 0.48.1 on OS X 10.5.8 (i386) when retracting and pulling out again the handles of a node (tested with a new path created in a new document, with my usual settings and with default settings (new prefs file)).

Could you attach a sample SVG file with a path that exposes this behavior?

[Cornelius Sicker (ysis)]

As I said, any bezier curve I've drawn so far shows the above-mentioned behavior.
I also tested on my other PC which runs also Xubuntu 11.04, but 32bit, inkscape version is the same, 0.48.1 r9760, and it shows the same issue.

I uploaded a simple SVG with a bezier curve, when I retract the upper handle of the middle node by Ctrl+click and then try to pull it out again by Shift+dragging I get the picture shown in the screenshot.

Thanks for the swift reaction!

Cheers,
Cornelius

[su_v (suv-lp)]

Not reproduced with your example file either (Inkscape 0.48.0, 0.48.1 and 0.48+devel r10244, OS X 10.5.8 (i386), with custom as well as default settings, no tablet).

- Does it also happen if you extract a handle from a cusp node without handles (create a path with the bézier tool using single clicks - without click-dragging) or only when extracting a handle immediately after retracting it?
- Do you use an extended input device (tablet w/ pen)?
- Could you produce a backtrace (with debugging symbols for Inkscape installed)?

[Cornelius Sicker (ysis)]

To answer your questions:
- Yes, it also happens when pulling out from a cusp node.
- I don't use a tablet.
- I can, if you could tell me how to do that on Ubuntu.

[su_v (suv-lp)]

Cornelius Sicker wrote:
>> Could you produce a backtrace (…)
> if you could tell me how to do that on Ubuntu.

@Alex Valavanis - could you assist with creating the backtrace?

[Cornelius Sicker (ysis)]

I played around and found out that this is somehow Xfce related. On both my computers mentioned above which run Xfce the issue is present, but at my friends PC running Kubuntu 11.04 64bit (so KDE, not Xfce) the feature works smoothly.
So I installed KDE on my computer and within KDE the specific inkscape feature works also smoothly; back to Xfce it doesn't. About Gnome I cannot tell, because Gnome nowadays somehow conflicts with Xfce, so I don't want to install it.

Hope that helps.

[su_v (suv-lp)]

> this is somehow Xfce related

Can you check in the Xfce settings if it defines or reserves the shortcut 'Shift+drag'? (According to he Inkscape FAQ, shortcuts like e.g. 'Alt+drag' are often reserved by the window manager for manipulating windows on linux. Possibly Xfce interferes when using 'Shift+drag' instead?)

I failed to find a full documentation on the Xfce web site, but those settings appear to be in
- Settings Manager > Window Manager Settings > Keyboard
- Settings Manager > Keyboard Preferences > Shortcuts

[Cornelius Sicker (ysis)]

> - Settings Manager > Window Manager Settings > Keyboard
> - Settings Manager > Keyboard Preferences > Shortcuts
I looked in the places you mentioned (which are also the only places I know of where one can set keyboard shortcuts), but there's nothing related. Actually Shift+Drag would rather be a mouse shortcut. The only other mouse shortcut I know of is where you can define a key which enables moving (left drag) and resizing (right drag) of windows while this key is pressed. But this is configured to be Alt by default (I edited this to use the Windows a.k.a. Super key), so I don't see a connection.
Also, when I Shift+Drag for example with the selector tool to get the rubberband selection, everything works.

It would be interesting if others can reproduce this with Xfce or Gnome, and to actually produce some backtrace for you experts to take a look. Any help is appreciated.

[Alex Valavanis (valavanisalex)]

Hi Cornelius,

Please could you do the following to help with the debugging?

1) run the following command in a terminal to gather extra information about your system:

apport-collect 790677

2) Add debug symbol repositories by running the following five commands (as described at https://wiki.edubuntu.org/DebuggingProgramCrash):

echo "deb http://ddebs.ubuntu.com $(lsb_release -cs) main restricted universe multiverse" | \
sudo tee -a /etc/apt/sources.list.d/ddebs.list

echo "deb http://ddebs.ubuntu.com $(lsb_release -cs)-updates main restricted universe multiverse
deb http://ddebs.ubuntu.com $(lsb_release -cs)-security main restricted universe multiverse
deb http://ddebs.ubuntu.com $(lsb_release -cs)-proposed main restricted universe multiverse" | \
sudo tee -a /etc/apt/sources.list.d/ddebs.list

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 428D7C01

sudo apt-get update

sudo apt-get install inkscape-dbgsym

3) Follow the instructions at https://wiki.edubuntu.org/Backtrace to gather a backtrace of the crash

[Alex Valavanis (valavanisalex)]

Also, note that you can install Ubuntu alongside Xubuntu by installing the "ubuntu-desktop" package from your package manager

[Cornelius Sicker (ysis)]

apport information

[Cornelius Sicker (ysis)]

Hi Alex,

I followed your instructions to enable the debugging symbols and generate the backtrace. You find it attached.
Note that this is the same computer as where the apport information was gathered (32bit), but not the same where I first noticed the bug (64bit), though the symptoms are the same.

On the side issue of installing ubuntu-desktop alongside Xfce:
This gives me conflicts when running "sudo aptitude install ubuntu-desktop" with the following suggestion:
"Remove the following packages:
1) libsdl1.2debian-alsa
2) xfce4-notifyd
3) xubuntu-desktop "
Since I don't want to break Xfce, I'll refrain from this.

Hope, that the backtrace will give some insights.

[Alex Valavanis (valavanisalex)]

Hi Cornelius, Thanks for providing the information.

@upstream - Any thoughts about the cause?

[elclanrs (elclanrs)]

I'm experiencing exactly the same problem.
I think Inkscape is not refreshing when pulling the handle with shift. But I also noticed that inkscape doesn't actually hang. It looks like it doesn't respond but if you minimize and restore the windows it should work fine again.
I'm not sure if this is Inkscape or xfce related.

[elclanrs (elclanrs)]

I just found a workaround.
If you're not using a tabled go to File > Input Devices and uncheck "Use pressure-sensitive tablet" at the bottom.
Now restart inkscape and it should work fine.
I'm guessing it's some sort of conflict between the way xfce4 handles tablets devices and inkscape.

[Cornelius Sicker (ysis)]

I never tried minimizing and restoring the windows, but it works! Your other solution regarding "Use pressure-sensitive tablet" also works for me. Since I don't use a tablet, I'll leave this disabled.

But it would still be nice to fix this properly. Thanks elclanrs for the workaround!

[mray (mrayyyy)]

Closing because could not reproduce on Ubuntu in Inkscape 1.0alpha (1:0.92.0+devel+201904052254+98d368e).

Closed by: https://gitlab.com/mray