Charts completely black when drawn while not visible

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daze507
Posts: 4
Joined: Wed Jul 17, 2019 10:49 am

Charts completely black when drawn while not visible

Post by daze507 » Wed Jul 17, 2019 11:02 am

Hi, I have had a graphical issue after having update from v8.3.1 to v8.4.2:

Basically, whenever data are loaded into the charts (FreeformPointLineSeries and IntensityGridSeries) while they are not visible, they appear to be completely black when the moment they are displayed.
The only way to fix that is to move the mouse cursor over them or to interact with their parent component (for instance when they are inside a Tab).
I tried to call methods like FullRepaint() or UpdateLayout() on the chart to no avail.
Is there a workaround to avoid that?

Thank you

Arction_LasseP
Posts: 50
Joined: Wed Mar 27, 2019 1:05 pm

Re: Charts completely black when drawn while not visible

Post by Arction_LasseP » Wed Jul 17, 2019 1:47 pm

Hello,

We investigated this issue and managed to reproduce it at least partially. In our test, instead of being black the chart didn't show up at all until mouse cursor was moved above it. Why this behaviour happens is still unclear and we have to investigate it further to determine if this is a bug.

One workaround you could try is to somehow make the chart to draw a new frame after they are displayed. There are several ways to do this. For example, if you have a FreeformPointLineSeries in the chart, set it visibility false if the chart is not shown. Set its visibility true right after the chart is shown which forces the chart to render a new frame. Alternatively, you can update some other chart or series property.

daze507
Posts: 4
Joined: Wed Jul 17, 2019 10:49 am

Re: Charts completely black when drawn while not visible

Post by daze507 » Wed Jul 17, 2019 2:29 pm

It's probably due to the fact that I use a black background colour for the components.
Not sure if that can help but I also noticed that if I resize the parent window it is displayed, also, the ZoomToFit() method seems to have the same effect.

FredWatrous
Posts: 3
Joined: Wed May 17, 2017 9:19 am

Re: Charts completely black when drawn while not visible

Post by FredWatrous » Fri Aug 09, 2019 8:50 am

Hi,
I'm having this problem with the Zoom Bar diagram. I'm loading a line diagram, and then allowing the user to change to a Zoom Bar alternative graph with 2 lightning charts. If the Zoom Bar diagram has never been loaded, it will be white in my case, (light gray theme), but nothing visible unless the diagram is shown when the page is first rendered.
ZoomToFit and resizing doesn't seem to help.

Arction_LasseP
Posts: 50
Joined: Wed Mar 27, 2019 1:05 pm

Re: Charts completely black when drawn while not visible

Post by Arction_LasseP » Fri Aug 09, 2019 9:59 am

Hi,

It sounds like the same issue. After investigating, we have found out that this is a bug which was accidentally caused while fixing another bug in LightningChart v8.4.1 release, so it's present only in the newest versions. We have also found a fix to it, which will be included in our next release (some time this autumn).

Meanwhile, you could test if the non-rendered chart becomes visible if you move mouse over the area where it is supposed to be. If this gets the chart rendered, this definitely is the same bug. If ZoomToFit() or resizing doesn't work, you could try modifying some property after the chart is meant to be rendered. For example, set axis range via _chart.ViewXY.XAxes[0].SetRange(axisMinimum, axisMaximum) or set Visible to true for the series which is used in the zoom bar chart (have it false first).

Best regards,
Lasse

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