Avoid inheriting transparency when it's set to 0.

[Guillermo Espertino (Gez)]

It's common to see here reports about "broken" tools that are, actually, a misinterpretation of a feature.
Transparency=0 should be avoided when creating new shapes. It's confusing and prone to leave transparent shapes lost in the canvas.
An elegant solution for the shape tools would be to set the transparency to 100% if the inherited value is 0, and leave it as is if it has a visible opacity.

[prkos (prkos)]

I'd also find this feature useful, maybe an option in preferences to inherit opacity

[Guillermo Espertino (Gez) (gespertino-gmail)]

Here's an example of a common situation caused by that "feature" :-)
https://answers.launchpad.net/inkscape/+question/66551
That was caused by an invisible object with a filter. It's quite difficult to address the origin of this kind of problems for the novice user.
I think we should change the importance of this report from "wishlist" to "bug". Technnically it's not a bug, but it brings several problems and no advantages.
I'd add that an object with 0% opacity should have filters de-activated if its opacity is 0. It's pointless to include an object in the redrawing if it isn't visible.

[Guillermo Espertino (Gez) (gespertino-gmail)]

Another report about a misinterpretation of the style inheritance feature: #358563
Inheriting opacity in new shapes seems to make more harm than good.
I think a fast and elegant solution would be to disable it as default and make it available via preferences.
I mean, color and stroke can be inherited, but the user should have to explicitly activate the opacity inheritance in features to get it.
That would eliminate the recurring bug report about tools that have not effect and disappearing objects. Or, in this last case I mention, about "pale" objects.
Of course it's ok to inherit opacity when pasting the style in another object, but inheriting it in new shapes proved to be quite problematic.

Again, I'd change this to BUG.