flickering string

[TINGELS]

I have a string indicator that I'm updating with a count down timer.  It's pretty large (350 pt application font).  If I run this with a laptop resolution of 1024X768 or less, it blinks on every update.  If I run it at 1600*1260, it doesn't blink at all or it blinks very little.

It happens with a numerical indicator as well.

is there any way to combat this issue?

[Megan B.]

Hi TINGELS,

What version of LabVIEW are you using?  I downloaded the VI you attached but it is missing a subVI, "update by ref.vi" so I just deleted this missing VI and its wire input.  However, I wasn't able to replicate the blinking you described.  I ran the VI on several resolutions (from 800x600 to 1400x1050), and also on LabVIEW 8.0 and 7.1, but the controls didn't blink. 

Are you using an older version of LabVIEW, or do you think the missing subVI is part of the problem?

Megan B.
National Instruments

[TINGELS]

thanks for your reply.  I've attached a verison without the call by ref.vi that it still happens on.  ON my laptop, the flicker doesn't happen all the time and is very hard to see (a very quick, almost imperceptable flicker) but on slower processors, it's much easier to see.  All you will see is a VERY brief flick, almost imperceptable. 

[Megan B.]

Hi TINGELS,

Does your second machine meet the system requirements for LabVIEW?  You can see those here:  http://ni.com/labview/requirements.htm.  I've done some research and I haven't seen any reports on this behavior.  Does the flickering change if you increase the refresh rate on your monitor?

Megan B.
National Instrument

[TINGELS]

Hi Megan,
Thanks for your response.  All machines I've tried it on meet the system requirments.  The monitor is set to default monitor, (it came that way on the laptop) at 60 htz (I can't change it on these laptops).  The flicker doesn't seem to change if I make the delay longer or shorter for the execution of the vi. 
If I shrink the string font, the flicker isn't there, it just is there if the fonts are large (around 350). 
Like I said, on the faster laptop, its hard to see, but its definitely there.
I may try it on a desktop when I can, but I mostly work on laptops.

Thanks
T

[Megan B.]

Hi TINGELS,

I'm afraid there doesn't seem to be a good workaround since it's just taking the OS and LabVIEW a while to complete the update for these very large fonts.  You may find some helpful workarounds, however, in this post on a flickering picture:  http://forums.ni.com/ni/board/message?board.id=170&message.id=22891&view=by_date_ascending&page=1.  You could try delaying the front panel updates link Ben suggests, but I think that when dealing with such large fonts, there is going to be some overhead in the monitor updating no matter what.

Megan B.
National Instruments

[TINGELS]

Thanks Megan. 
That thread actually did help.  I used the invoke method to get the image of the indicators. 
this stopped the flicker when I chose smooth updates on the front panel.

I've attached the code that worked.

Thanks again!
Tyson