Spiro path effect makes other paths invisible

[Hachmann]

I've been able to reproduce this twice, with Inkscape 0.91 from official repo on LM17.3 (64bit).

I'm not at all clear about which specific action caused this, but this is what I did, and what I got as a result:

- Used the pencil tool in spiro path mode
- drew a few random paths with it, in rapid sequence
- changed width of last drawn, selected path (a few times)
- changed miter limit of last drawn, selected path (a few times)
- added arrow markers
- changed smoothing a few times
- changed stroke dashes, too (but not each time, so this is probably not causing it)

At some point, the path I drew started to look as if I was using the eraser on the drawing - the other parts below became invisible.
The path itself then also became invisible.

The file has also got a problem with the coordinates.
The page borders were displayed at the left of the canvas when I tabbed through the paths (first zoom in a bit beside the page, then hit tab repeatedly when you do not see the full page anymore), and then suddenly, the numbers displayed in the ruler became huge and while the page borders are still visible, I'm really far away from the page. This is reproducible with the attached file.

When I reopen the file and start drawing in it, new paths are also still invisible (also when I open with ppa trunk version).

What fixes it is *removing the path effect from the path with id path7882*.

(and just in case you wonder why I drew all this nonsense: It was because of a forum message about weird behaviour of the pen tool, see https://www.youtube.com/watch?v=bGruR4Ce3d0 - no idea if this is related, though)

[jazzynico (jazzynico)]

Reproduced on Windows 7, Inkscape 0.91 and trunk rev. 14761 (32-bit).

Steps:
1. Open the file attached comment #1.
2. Select path 7882.
3. Move the path to the left or the bottom of the page. After 2 or 3 moves, the whole canvas become invisible.
4. Remove (or hide) the LPE in the LPE editor and the drawing is visible again.

Note that it seems to depend on the object position (everything shows correctly when first opening the file) and on the zoom level (try to zoom out when the canvas disappears).

[su_v (suv-lp)]

Based on tests with archived builds (on OS X 10.7.5):
- not reproduced with Inkscape 0.48.5 r10040,
- not reproduced with lp:inkscape rev <= 10578,
- reproduced with lp:inkscape rev >= 10579,
- reproduced with Inkscape 0.91 r13725,
- reproduced with lp:inkscape/0.92.x rev 15301;
the reported symptom (blank canvas triggered by geometry/computed dimension of a single element) seems to have been exposed with the merge of the rendering cache branch in r10579:
http://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/changes/10579
http://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/revision/10579

Similar symptoms have been reported in: bug #1475875, bug #1653694.

[Jonathan Hofinger (jhofinger)]

Hi, the issue of the blank rendering has been reported to Gitlab: https://gitlab.com/inkscape/inkscape/-/issues/1446. The part about the spiro path effect has been migrated to https://gitlab.com/inkscape/inbox/-/issues/2693.

I've copied the relevant info and the example file.

Closed by: htps://gitlab.com/jhofinger