GNOME Bugzilla – Bug 661872
When drawing in Gimp with a tablet the line breaks outside the canvas
Last modified: 2014-02-21 23:22:41 UTC
Hi, When I use my Wacom tablet to draw in Gimp, the line drawn breaks outside the canvas for no apparent reason. Please see the attached screencast for an illustration of the problem. I use Gimp 2.6.11 in Gnome Shell 3.2 as provided by Ubuntu 11.10. I think that Gimp is not responsible since I did not have the problem with Gimp 2.6.11 and Gnome 2.x from Ubuntu 11.04.
Created attachment 199093 [details] Screencast of the bug
Actually I have the same problem when using Unity. I move the bug to Gimp until I do more testing.
Most likely not a gimp bug. There is one spot in there, that manipulates the coords as they come in 2.6, but it happens almost all events and would manifest all the time and not on particular installs. My suspects would be either GTK or the wacom driver assuming that the tablet itself is tested to be okay on another machine. X and/or y coordinate is hitting zero randomly. If the bug goes away when you disable it as an extended device its most likely a gtk(or in one specific case driver) bug. I suggest testing the recent development build first tho. Updating your wacom driver cant hurt either.
(In reply to comment #3) > Most likely not a gimp bug. There is one spot in there, that manipulates the > coords as they come in 2.6, but it happens almost all events and would manifest > all the time and not on particular installs. My suspects would be either GTK or > the wacom driver assuming that the tablet itself is tested to be okay on > another machine. The tablet worked fine with Gimp 2.6.11 before updating to Ubuntu 11.10. I do not know if they have made any changes in their package for their update. Also I have tested it with MyPaint and it worked fine too, pressure included. > X and/or y coordinate is hitting zero randomly. If the bug > goes away when you disable it as an extended device its most likely a gtk(or in > one specific case driver) bug. I suggest testing the recent development build > first tho. Updating your wacom driver cant hurt either. Indeed, the bug goes away when the tablet is disabled in the extended devices. The drawing is correct but the pressure is not handled. Thus gtk seems to be the cause of the bug. I would like to reproduce the bug in an other software than Gimp to confirm this.
Ive had a confirmation from another source that this bug indeed does not manifest in 2.7. That pinpoints it to a specific feature in X/GTK, namely the event history buffer used to get more exact event info. Its broken very often and can be broken by both GTK and the driver. There are drivers out there that fill it wrong as matter of course. Nothing but gimp out there uses the event history buffer as far as I know and at 2.7 we silently disable its use because it crops up bugs more often than its of use. So you could try updating the driver as first step. if it breaks there, reporting a bug against the driver is appropriate.
Indeed I do not have the problem with Gimp 2.7. I have installed an older version of the driver, the one from the previous version of Ubuntu, and the problem was still here. Since Gimp is clearly not the cause of the problem, I have reported the bug at Ubuntu for further investigations: http://bugs.launchpad.net/ubuntu/+source/xf86-input-wacom/+bug/881821
*** Bug 663000 has been marked as a duplicate of this bug. ***
*** Bug 665451 has been marked as a duplicate of this bug. ***
From ubuntu bug is clear that this is not driver specific and may be caused by X.
So, according to https://bugs.launchpad.net/ubuntu/+source/gimp/+bug/863154, should we resolve this as NOTGNOME?
Resolving as notgnome, as GIMP was impacted by a bug in X. Additionally, use of history buffer is off by default in master and has been so for a while. Recommended workaround for distributors is back-porting this commit from master: http://git.gnome.org/browse/gimp/commit/?id=dbf844c012894166e312470f0d98560d5e426613 The trade off is minimal amount of quality in pen strokes, the gain is usable gimp.
*** Bug 667179 has been marked as a duplicate of this bug. ***
*** Bug 673261 has been marked as a duplicate of this bug. ***