transparent object vs object in invisible layer?

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brynn
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transparent object vs object in invisible layer?

Postby brynn » Fri Jul 31, 2009 1:28 am

Hi Friends,
In a project I'm working on, I just learned the hard way that objects whose layer is invisible can't be selected, and therefore, can't be manipulated. And I'm surprised to learn that, because I know that objects that are fully transparent (effectively invisible, but not technically invisible) CAN be selected and edited at will (even though itcan be a bit tricky).

I'm sure there must be something about the way Inkscape handles objects in invisible layers vs fully transparent objects, that explains this....well, it's almost a paradox, I guess (maybe more of a conumdrum).

Can someone explain it for me, so that hopefully I won't have to learn it the hard way twice? Thanks for your help :D

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prkos
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Re: transparent object vs object in invisible layer?

Postby prkos » Fri Jul 31, 2009 3:34 am

Look under Inkscape preferences, you can choose whether to ignore hidden objects and layers ;)
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brynn
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Re: transparent object vs object in invisible layer?

Postby brynn » Fri Jul 31, 2009 11:46 am

Um, yeah, I saw that. But I thought hidden objects were something else (not on an invisible layer and not fully transparent). I have not gone into Object Properties and checked Hide (or Lock).

Ok, I changed that setting, and it does allow the object in the invisible layer to be selected and edited. But now I have some new issues. First, the reason I thought objects in invisible layers could not be selected or edited, is because I found this in the tavmjong Guide


Also, hiding a layer is apparently synonymous with making it not visible. But hiding an object is just hiding an object. Wouldn't it make more sense to use the little eye icon for both, or a Hide checkbox for both? I have seen that setting, but thought hiding a layer was something else entirely (something like hiding an object)(which I have thus far found no use for).

Thanks for your help prkos.

~suv
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Re: transparent object vs object in invisible layer?

Postby ~suv » Fri Jul 31, 2009 1:21 pm

Maybe the discussion in the comments of this bug report (“items with 0% opacity are not click-sensitive”) helps to (un-)clarify the issue...? (AFAIU visibility vs. opacity/transparency vs. select-ability)

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brynn
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Re: transparent object vs object in invisible layer?

Postby brynn » Mon Aug 03, 2009 8:48 am

Well, I can see where the issues are related, but you're right, it more UN-clarifies things for me.

I'm not sure what you mean by this. I'm not sure how you mean the slash (/) to be used here.
visibility vs. opacity/transparency vs. select-ability

I mean, I understand the issue about transparent objects not being readily selectable; it's almost like a transparent object doesn't exist....but it does.

Are you saying that an object in an invisible layer is the same thing as a fully transparent object? I don't think that's so. In the sense that neither is readily selectable, yes, they are alike. But in the end, one can still select a fully transparent object, while one can never select an object in an invisible layer (unless one changes the setting in Inks. Prefs.)

At this point, all I would like to clarify is the info in the tavmjong Guide (Objects in locked or invisible Layers cannot be selected or changed.). I have solved my problem by changing the setting to show hidden objects or layers. But that would imply the Guide is wrong on this point......

And if the Guide is wrong (or maybe slightly outdated on that point), does this mean that the bug you referenced is not really a bug, because the user need simply change that setting for showing hidden objects and layers? I never finished reading all the comments in the bug report, because it was dragging on and repeating the same arguments over and over. So I don't know if in the end, someone posted the info about the setting for showing hidden things.....or whether someone should post the info, as a solution to the "bug"?

Thanks for your help ~suv :D

~suv
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Re: transparent object vs object in invisible layer?

Postby ~suv » Mon Aug 03, 2009 9:28 am

brynn wrote:it's almost like a transparent object doesn't exist....but it does.
I guess I meant to point to the endless discussion to show there's no such clarity even among the developers, and I doubt this issue was solved…

Now I have to go back and reread the whole thread of comments… ;-)

CarlCravens
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Re: transparent object vs object in invisible layer?

Postby CarlCravens » Tue Aug 04, 2009 4:18 am

There's a big difference between 0% opacity (nothing in the object needs to be drawn because it's 100% transparent) and hidden (the object is not displayed, and therefore Inkscape does not need to evaluate any other properties).

You're right, hiding a layer should be the same as hiding an object... a layer is nothing but a group with a special inkscape-specific flag on it so Inkscape knows to treat it a little differently. Clicking the "eye" icon mark's a layer as hidden. Setting a layer's opacity to zero makes it transparent.

These are two separate values an object's style attribute in the SVG code... "display" and "opacity" and they refer to very different things, even if, from the user's point of view, each of them causes an object to not be visible on the canvas.

The use of the word "invisible" confounds the issue, as "invisible" does not clearly refer to either of these style attributes. Discussions would be easier if we stuck to discussing "hidden" and "transparent", as these more clearly refer to concrete settings... hidden (style="display:none") versus transparent (style="display:inline; opacity:0").

Bugs in selecting transparent objects and the option to select objects within hidden layers further confounds the issue. So making sure we're talking about exactly the same thing would make things easier.

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brynn
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Re: transparent object vs object in invisible layer?

Postby brynn » Tue Aug 04, 2009 1:16 pm

Oh, sorry about using the wrong terminology. I thought the proper terminology must be "disabling the visibility" which I shortened to 'invisible'. Plus the use of the eye icon sort of invokes words about vision. Maybe it would be better to use the 'Hide' checkbox everywhere?

I never meant to get involved in the whole bug debate. As far as I'm concerned, the setting for displaying hidden layers and objects should be a "fix" for the "bug". I just want to know about quote from the tavmjong Guide about not being able to select or edit objects in hidden (or locked) layers. Is that just outdated info, or am I still misunderstanding these issues?


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