Bug 287749

Summary:	Impossible to move a selection accurately. Selection jumps a pixel in arbitrary & consistent direction when releasing the mouse. Compensation is futile, always jumps the unintended way.
Product:	[Applications] kolourpaint	Reporter:	Andreas Nordal <andreas_nordal_4>
Component:	general	Assignee:	kolourpaint-support
Status:	RESOLVED NOT A BUG
Severity:	normal	CC:	kollix
Priority:	NOR
Version:	unspecified
Target Milestone:	---
Platform:	openSUSE
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description Andreas Nordal 2011-11-28 13:56:34 UTC

Version: unspecified (using KDE 4.7.2)
OS: Linux

This bug happens every time, but not for every point in the drawing - roughly half of the points are affected. These points are impossible to move a selection on top of. Depending on the point, the selection will jump consistently a pixel up, down, sideways or diagonally when releasing the left mouse button.

This is a regression between KDE 4.6.0 and 4.7.2. Specifically, Kolourpaint works in the version of KDE in OpenSUSE 11.4 and Tumbleweed, but after dist-upgrading to OpenSUSE 12.1, Kolourpaint is (for all my purposes) useless.

Reproducible: Always

Steps to Reproduce:
1) Draw a cross.
2) Select the cross, using the selection tool. The selection tool has 2 modes, use the one that treats the background color as transparent.
3) Copy and paste (Ctrl-C, Ctrl-V) the selection.
4) Click and drag the copied cross exactly on top of the original.

Actual Results:
If you drew the cross on an unfortunate point, it will be impossible to place the copy on top of it! Apparently, some pixel borders are hilltops (unstable points); a ball placed nearby will always roll away from it, and no matter how you compensate, it must roll down on one side or another. Strangely, this is irrespective of where you are holding the selection and the amount selected. Rather, it appears as if a troll knows there is a cross in your selection, and in no way are you going to place it on top of the original cross!

Expected Results:
The selection should not jump away from the moved-to position when releasing the left mouse button.

Unlike bug 277408 (incorrectly closed, how to reopen?), this problem does not go away by downgrading Kolourpaint back to version 4.6.0 (the good old OpenSUSE 11.4 package) while running KDE 4.7.2. The Help->About Kolourpaint dialog says «Using KDE 4.7.2», so I guess this is a library bug.

Comment 1 Martin Koller 2011-11-28 19:03:02 UTC

I can not reproduce this. Could you create an image where you see this problem and attach it here, please ?
I also can not understand why this should happen. The only thing which comes to my mind is: check your mouse resolution settings or the pointer acceleration setting.
Your description sounds like that kolourpaint simply does not get all mouse move events, but I would not know why. I doubt that this has to do with a change in the kolourpaint code ... but who knows ;-)

Comment 2 Andreas Nordal 2011-11-30 20:58:13 UTC

You are absolutely correct, Martin! Using a proper mouse solves it.

Something is wrong with my touchpad. The pointer jumps when releasing the fixed buttons on my touchpad, even without any physical contact with the pointer plate.

Sorry for the false alarm.