Second line appearing when using the brush component via Pavlovia

URL of experiment:

Description of the problem:

Hello all,

I was hoping to get some ideas and/or advice about an issue I’m having with Pavlovia.

Currently working on producing an online experiment. One of my tasks is the Trail Making Test, and it involves connecting a series of circles. We intend to measure time taken to complete.

A colleague of mine (Rebecca_dw: Getting the start and end timing for a brush component) had previously posted on the forum to design the task. It is now working for her, but I am having an error when I try to upload it to my own Pavlovia account.

OS Win10
PsychoPy3 2020.2.10 win64
Standard standalone

Currently, the task works fine on PsychoPy. However, when I sync it to Pavlovia and try to run it on there, the brush component creates two lines. One line is the one that the participant would produce, which moves along with the mouse. However, there is another line that originates from where the mouse first clicks on the screen, and then follows the cursor.

Ideally, we need to get rid of this additional line as it would be distracting for the participant. I believe one of the reasons for this is due to having an updated version of PsychoPy. Does anybody have any ideas on how this could be solved? If so, that would be greatly appreciated!

Many thanks,


Hi There,

Please can you confirm if your issue is similar to the one reported here? Brush tool closes automatically in psychojs/online, despite closeShape : false.

If so, a permanent fix is on the way, but there may be some JS tweaks we can add to fix this temporarily.


Hi Becca,

Thanks for the reply! The question you sent does sound like a similar type of issue, although the brush tool doesn’t force close. Instead, it seems to create an additional line from the point of origin to wherever the mouse is moving. So there are two lines appearing at the same time. However, the line doesn’t close automatically at the end.

However, perhaps this could be something that would be addressed from the fixes being made, as it does seem like it may be slightly related to the previous question/discussion.

Many thanks,