Marker/line opacity unaffected by restyle when fill=toself

[cpsievert]

http://codepen.io/cpsievert/pen/ZOdVOk

[rreusser]

Not fixed by the big changes in animations: http://codepen.io/rsreusser/pen/ozNkEv

[rreusser]

Seems like perhaps an issue with restyle figuring out what needs to update, in which case this shouldn't be affected by the animation PR. (otherwise wouldn't recommend fixing before merge)

[etpinard]

After some investigation:

• this issue has nothing to do with toself, all fill values behave the same
• I believe this is the desired behavior. Trace opacity does not impact fillcolor. See the current logic fillcolor default logic here.

In brief, fillcolor defaults to:

• line.color with 0.5 alpha channel,
• if line.color isn't set, marker.color with 0.5 alpha channel,
• if line.color and marker.color aren't set, marker.line.color with 0.5 alpha channel,
• if line.color, marker.color and marker.line.color aren't set, the default trace color with 0.5 alpha channel.

But, as discussed with @cpsievert , trace opacity should really impact the fill color. The fact that plotly.js doesn't do that at the moment is a design flaw - that unfortunately cannot be easily fixed in a backward-compatible way.

We should consider making opacity impact fill color in the v2.0.0 release. Changing the issue title accordingly.

[etpinard]

Oops. I didn't read the issue title correctly.

There is in fact a bug here - where we explicitly remove trace opacity from traces that have a non-none fill value to avoid edge-case inconsistencies. Please refer to this 2015 issue for the details.

But, the aforementioned inconsistency does not apply to toself traces. Fix is coming up.

[tsando]

Sorry, I was a bit lost by the thread comments and links but is there a workaround or fix for this yet? I wan to make the opacity apply to the fill area color. Is there any way to do this using toself? Thanks.