WPF ProgressBar loses its glow when it updates too quickly - bug?

2
votes

Ok, so I found some rather weird behaviour while messing around with the WPF ProgressBar control. This control is located in a column of a ListView control and the general situation differs little from this question & answer in its essence.

I bind Progressbar to a class by means of several properties (Min, Max, Value), all OneWay Bindings obviously. This other class is updated from another thread and regularly uses the INotifyPropertyChanged interface to let the ProgressBar know the status is progressing. And this all works just great!

But here is where it gets odd. My ProgressBar loses its glow.. right upto the moment it reaches the Max (=100%) value. Then it suddenly starts pulsing its white glowy stuff all over the green bar, and this is very annoying. I am showing progress with a reason, and the lack of a pulse is actually pretty distracting once you start to notice it not being there.

Thus, I set off to debug. I found that with Thread.Sleep(1000) in my threads processing, it still hid the glow, but if I bump it to Thread.Sleep(1500) the glow comes back at all times with a crazy vigour. After that, I tried translating my progress units to smaller numbers so the integer values would take longer to change. Min 0, Max 100 still has the lack of the glow. Min 0, Max 10 had the glow come back in its full vigor. In all cases, it is the same amount of work and time spent to reach 100%, but it is a very visible binary YES/NO effect with regards to the glow showing. The only thing I have not tested is whether it also happens when the ProgressBar is not placed inside of this ListView control.

I know myself well enough that I can't make sense of the deep WPF innards of the (XAML involved with the) ProgressBar control. So I was hoping anyone here knows whether this is a known bug, something they stumbled into, or something they might even know how to work around/fix.

My machine runs Windows 7, and I'm developing in VS2010 targeting .NET Framework 4 Client Profile.

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c#wpflistviewanimationprogress-bar

1 Answers

0
votes

I would take a guess and say that you lose the glow because you are updating your progress bar to often. Every time you set a new value the progress bar restarts its glowing animation (I think - I haven't tested this, I'm writing off the top of my head).

It seems that you have perhaps thought of the same thing and tried to work around it, but I'm not sure you have fully exhausted all possibilities:

  1. Try creating a check that if (progressbar.Value == newValue) don't do progressbar.Value = newValue;
  2. Progressbar should be using Decimals for Min, Max, Value. Make sure you don't do updates for every decimal point, eg. - 10,1; 10,2; 10,3; etc... (use progressbar.Value = (int)newValue;)
  3. Try setting the progressbar value in bigger increments, instead of increment = 1, use increment = 10;
  4. You could try taking a progressbar outside of ListView, maybe there is a rendering bug with progressbar being inside it.

PS! If you update your progressbar very rapidly, then it is OK for the glow animation not to run. Remember that the glow animiation's purpose is only to show that the application is still running (machine hasn't frozen), despite the fact that the progress(bar) hasn't moved.
If the progress is moving quickly, then that on its own is a visual effect for the user, so there is no need to have the glow animation at that moment...