Buggy layer makes everything invisible until it is hidden (even upper layers)

[2hu4u]

Hi,
Something very strange has happened to my SVG. Luckily I seem to have found a fix but I believe this might be an undocumented bug or at least something worth investigating. I'll likely submit it to bug reporting later.

I was doing something quite normal (like dragging a node handle or something) when suddenly everything - all objects, paths, text, etc - on the working layer ("Layer 2") disappeared. Yes, I have checked the opacity, stroke width, hidden layers, etc. Selecting with the Select tool  shows the objects are still there.

The strange thing is, Layer 2 is "masking" all the layers too (even upper layers) - all the layers are covered as if by a large opaque white object. But the layers are restored when I hide Layer 2. Drawing objects on Layer 2 does not work. Drawing objects on other layers does work but only if Layer 2 is hidden.

Another very strange thing is that when I select all objects on Layer 2 using Ctrl + A, the bounding box dimensions shows a very large number (too large to display), the height and width both show "1000000000..." leading me to believe there is an infinitely large object on Layer 2 "masking" the lower and upper layers. I cannot select the object though, aside from using Ctrl + A. Using Ctrl + A on non-buggy layers yields the correct bounding box dimensions for objects on that layer. When the infinitely large object is selected, resizing the page to selected content causes Inkscape to crash.

Notes and observations:

• Changing the display mode to "Outline", it appears as if there are no objects on Layer 2 even though there are.
• Duplicating Layer 2 does not restore the "missing" objects.
• When I open the SVG in Adobe Illustrator CS6, it loads with an error, and then briefly shows the correct SVG before crashing.
• The SVG displays correctly in Chrome. Saving the SVG in Chrome and opening it in Inkscape does not fix the problem.
• Restarting Inkscape has no effect.
• I am running Inkscape 0.92.

The only solution I have found so far is:
Manually selecting my missing objects on Layer 2 and moving them to a new upper layer restores them (but only after Layer 2 is hidden).

I have searched on Google for similar bugs but I haven't found anything yet.

Attached is the buggy SVG:
"Layer 10" is the fixed Layer that is working correctly.
To reproduce the problem, try Unhiding "Layer 2" or "Layer 2 copy" and Hiding Layer 10. After Layer 10 is Unhidden, it will not reappear until both the Layer 2s are Hidden.

[brynn]

Welcome to the forum!

Before you report a bug, you need to isolate it.  If you were to present developers with this complex and large file, and say "there's a problem on layer 2", they will not like to find the problem.  But hopefully we can help isolate the problem.

So far, I've discovered at least one troublesome object, and when I delete it, Layer 2 displays again.  It's path 3688.  It has hundreds of nodes (500something, iirc), and also has Powerstroke applied to it.  (That might be too many nodes to expect powerstroke to function??)

Here's what I did.

-- hide all layers
-- unhide layer 2
-- Shift + Tab 4 times - normal behavior
-- Shift + Tab the 5th time selects the troublesome object.  I know it's a troublesome object, even though I can't see it, because when it becomes selected, the scrollbars shrink as small as they can go, which means this object is HUGE (1000000.000 mm, which is as high as Inkscape can measure, I think).  It probably is literally covering up everything else!

So I deleted it, refocused the canvas to the page border, and there's all of layer 2!

I don't think we have enough information to know if there is a bug which caused that object to become so large.  Not unless you specifically remember what you did to it.  It would have been the 5th to last object you created (Shift + Tab selects in backwards order, while just Tab select from the first object).

I'm thinking, with everything else you have in the file, losing that one object will not be a huge loss.  I did try to edit it, but it's so huge, I couldn't find any Selection handles or nodes.  Tried using the control bar, but the W and H fields are unresponsive.  Probably you should think about breaking up this file into several separate files, since it really is quite large.  You must be having some performance issues with it anyway?

Ok, I tried one last thing, to edit the object.  But it just won't edit.  I think you may have hit some kind of bug with the powerstroke.  But without being about to provide specific steps which reproduce the problem every time, it won't be helpful to developers, to report it.

Edit
But if you can reproduce it, where there's only one object in the file (or 2 or 3, if needed to create the problem), let us know how, and we can test 

[2hu4u]

Thanks so much for your help, seems like it's mystery solved! That certainly explains a lot - I was having troubles with powerstroke randomly turning itself on. I only used powerstroke for a single path and everything seemed fine until a couple hours later, so I didn't make the connection. Upon re-examining the path where I used powerstroke, I see for some reason it has created a huge amount of nodes - very strange! I shall investivate further. Thanks again (and apologies for the huge file - I will keep bug isolation in mind for next time)

EDIT -

Looks like it is indeed a known bug with powerstroke! Looks like you've encountered this before 
http://forum.inkscapecommunity.com/index.php?topic=596.0

[brynn]

Oh wow!     You know I answer so many messages, it's impossible to remember them all.  But re-reading it, I got a new idea to try with your file.

Ok yes, rather than delete the item, you can just remove the path effect.  Strangely, it's such a tiny object!

And there is much more info in those bug reports mentioned in the other topic.