P3 Speller optical error?

Known Issues and Problems with BCI2000
Posts: 18
Joined: 23 Jul 2010, 05:53

P3 Speller optical error?

Post by OKI » 14 Jun 2011, 08:52


i have a question about the P3Speller Interface, i used the P3Speller Code to write new applications with it. In some applications, there is "sometimes" a misstake in the interface, the letters 'Q' and 'G' sometimes look like they have a second line.

I already debugged the whole thing down to the TextField.cpp data, and researched in the Qt docs for any reason of this behaviour but i still have no idea.

The uploaded pic shows the second line. The line is not there every time, but sometimes after loading the Parameters.

Does anyone of you have the same behaviour?

Thanks for answers,
speller fehler 1.JPG

Posts: 1114
Joined: 12 Feb 2003, 11:06

Re: P3 Speller optical error?

Post by mellinger » 15 Jun 2011, 15:20

Hi Stefan,

I have observed this behavior as well. It appears quite rarely, so it is difficult to analyze.
Today, I was able to "play" with it for some time, and made the following observations:
1) The artifact appeared below the letter "Q", and seems to be the top of a "K".
2) The artifact was stable while P3Speller was running, i.e. SetConfig/Start/Resume did not make it disappear.
3) It would only appear for a certain text size. Changing the TextSize parameter by any amount would make it disappear, but it would reappear when the text size was changed back.
4) The artifact was displayed with every "Q" displayed on the screen, and it was highlighted in the same manner as the "Q" was.

From these observations, I tend to see it as a Qt problem rather than a BCI2000 bug.


Edit: I just found a number of related bug reports in the Qt bug tracking database, so it is a known issue with Qt:


Who is online

Users browsing this forum: Bing [Bot] and 1 guest