inconsistent scaling behavior of LPE PatternAlongPath

[Alvin Penner]

I believe this bug is a duplicate of Bug 1354339, but that report is marked as Fix Released, so I thought I would issue a new report.
If one subjects a LPE Pattern Along Path to a uniform scaling operation, the LPE does not scale uniformly, while other LPE's, such as Bend, do scale uniformly.

Attached is a demo file, demo.svg. It was produced with Inkscape 0.91+devel r13954 (Feb 28 2015) with the preferences:
- Visual bbox
- Scale Stroke Width
- Store Transformation Optimized

- select the bottom object, which has an LPE Bend
- hold down the Ctrl key and drag a corner to produce uniform scaling
- note that the uniform scaling is kept intact after releasing the mouse

- select the top object, which has an LPE Pattern Along Path
- hold down the Ctrl key and drag a corner to produce uniform scaling
- note that the scaling is uniform while the drag is being performed
- now release the mouse and note that the scaling becomes non-uniform, the horizontal scale keeps the new applied scale, but the vertical scale appears to revert back to the original scale.
- similar behavior occurs if one tries to vertically resize the height with the mouse
- similar behavior occurs if one attempts to use the Transform Dialog to perform a perfectly uniform scaling of 200%

- reproduced on Inkscape 0.47pre1 (Jul 3 2009)
- not reproduced on Inkscape 0.46 + devel rev 20418, Dec 30, 2008

[Alvin Penner (apenner)]

I believe this change was introduced in rev 7691

http://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/revision/7691/src/live_effects/lpe-patternalongpath.cpp

[Alvin Penner (apenner)]

- just writing to confirm that reverting rev 7691 does indeed fix this bug.
- the same change also fixes Bug 1354339 as well, details given at that bug report comment 8

- any objections if I proceed with this change, any comments?

[su_v (suv-lp)]

@Johan - any chance you could comment on the proposed reverting of 7691?
http://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/revision/7691/src/live_effects/lpe-patternalongpath.cpp

[su_v (suv-lp)]

AFAICT this report is related to (or a duplicate of)
* Bug #172137 “LPEs must be affected by the "scale stroke width" switch”
  https://bugs.launchpad.net/inkscape/+bug/172137

As mentioned in bug #172137, the behavior depends on the path effect setting "Width in units of length". In the provided test case, the path with the Pattern-along-Path' effect does scale uniformly after turning that setting on.

[Alvin Penner (apenner)]

thanks, I think that fixes it!