Qt 5.5 + Oscilloscope example

[agarny]

As part of figuring out what was going wrong with my application and my use of QwtPlotDirectPainter (see here), I thought I would try Qwt's Oscilloscope example and there does indeed seem to be an issue of sorts with QwtPlotDirectPainter. Here is a screenshot that illustrates what I mean:



As can be seen, the background is black wherever QwtPlotDirectPainter draws a series of points. I don't remember ever seeing this using previous versions of Qt.

[Uwe]

Which platform - also on the Mac ?

Uwe

[agarny]

Yes, the above screenshot was taken on a MacBook Pro running OS X 10.10 (Yosemite).

[Uwe]

Native or also over VNC only ?

Uwe

[agarny]

The screenshot was taken natively, although I believe I also tried it through VNC a couple of days ago (I won't be able to try it through VNC again before this weekend).

[Uwe]

To be honest I'm not that much interested in the VNC issues - as this is out of the scope of what I can work on - the problems with Qt 5.5 native on the Mac are way more of interest.
Could you please do some tests with comparing between Qt 5.5 and Qt 5.4 - maybe also having a look at what has changed in the implementation of Qt 5.5 ?

Uwe

[agarny]

To be honest I'm not that much interested in the VNC issues - as this is out of the scope of what I can work on - the problems with Qt 5.5 native on the Mac are way more of interest.

This is perfectly understandable.

Could you please do some tests with comparing between Qt 5.5 and Qt 5.4 - maybe also having a look at what has changed in the implementation of Qt 5.5 ?

I will see what I can do...

[agarny]

Ok, I have just got a chance to try the oscilloscope example with both Qt 5.4.2 and Qt 5.5. With Qt 5.5, I can confirm that I do get the result mentioned above (i.e. the background is black wherever QwtPlotDirectPainter draws a series of points). However, using Qt 5.4.2, everything works as expected. In other words, I get:



Now, I must confess that I don't really have the time to compare Qt 5.4.2's code with that of Qt 5.5, not to mention that I don't know enough about the inner workings of QwtPlot to know exactly what I should be comparing...

[Uwe]

Now, I must confess that I don't really have the time to compare Qt 5.4.2's code with that of Qt 5.5

And I don't even have a Mac - so I'm afraid the story ends with knowing that Qt 5.5 is broken on the Mac, but we are not able to file a bug report ...

Uwe