Changing the default unit scales paths with Pattern along the path LPE applied

[jazzynico]

Follow-up to Bug #1351651 "pattern along path scaling issues".
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Inkscape Version: Inkscape 0.48+devel r custom built from trunk revno: 13454
Linux 3.14-1-amd64 #1 SMP Debian 3.14.12-1 (2014-07-11) x86_64 GNU/Linux (debian testing)

Changing the default units of a document should not affect it at all, it's just a different way of thinking about it.
See attached svg file for demonstration.

[jazzynico (jazzynico)]

Reproduced on Windows XP, Inkscape trunk revision 13502.
Not reproduced with 0.48.5.

[LucaDC (lucadc)]

> jazzynico wrote:
> Changing the default units of a document should not affect it at all, it's just a different way of thinking about it.

Personally I do not completely agree, at least in the very specific case where I expect dimensions of the drawing to be stored in the specified document unit.
If only, a distinction should be made between the unit displayed in the toolboxes and in input fields, that when changed should not have any impact in the document but only "change the way of thinking it"; and the unit used to store coordinates of objects, that should be deeply tied to the document, preferably determined at the beginning of the work because when changed triggers a recalculation of all internally stored numbers to reflect the new preference.

I wouldn't mind having a pop-up saying that the whole document will be recalculated and asking for confirmation as the operation could be not so easily undoable.
In my mind, changing the document unit is like changing font in a wordprocessor textual document: what is written is unchanged but some aspects of the layout will probably need to be fixed: you usually think before doing it and expect some consequences (but in this case, it's easily undoable).

Of course, it's absolutely out of the question that the changes should be minimal: the program must do the best it can to convert from one unit to another with the highest available precision.
The posted example shows a clear bug: this is not expected to happen in any case.

I have to admit that the direction Inskcape is taking with regards to how to address this problem is unclear to me. There are still too many little bugs related to units handling that make me think it's being underestimate and set aside, somewhat.

[su_v (suv-lp)]

Reproduced with 0.48+devel r13502 and experimental r13464 on OS X 10.7.5 (default prefs, default new doc based on locale en_US).

[David Mathog (mathog)]

A related problem I think.

1. new (pixels document units)
2. draw three rectangles.
3. select the first one and fill with stripes 1:1
4. change document units to mm.
5. select the 2nd rectangle and fill with stripes 1:1
6. change the document units to in.
7. select the 3rd rectangle and fill with stripes 1:1

Result, the stripe pattern is different in all 3 rectangles. Click on any one
of the rectangles and the fill and stroke dialog will show "stripes 1:1". Try changing
them to other fill patterns and they are all big black blobs (for most patterns) because
in the attached example, after the "in" change the widths and heights are about 1 inch, but
the defs for the patterns are in pixels, and they are mostly bigger than 1.

This is, I believe, another manifestation of a document unit problem. These come about because
on document unit changes all lengths and coordinates are transformed recursively, that is, the actual values are changed ( it isn't that a single transform at the top is changed, doing that doesn't break links to objects in defs), but <defs> isn't similarly modified. So things break, like here, and bugs #1348417 and #1302857.

[su_v (suv-lp)]

Please clarify: is this report meant to handle "Changing the default units of a document should not affect it at all" in general, or to track the specific issue with the 'Pattern along Path' path effect?

[su_v (suv-lp)]

On 2014-08-08 10:51 (+0100), jazzynico wrote:
> Changing the default units of a document should not affect it at all,
> it's just a different way of thinking about it.

The earlier change in trunk which caused that 'Default units' affected the document scale (internally) was reverted in 0.91.x as well as trunk - default units are now again just display units, and do not affect the scale of the drawing.

Closing as 'Fix released' without milestone - the originally reported issue does no longer reproduce, and the underlying change was never part of a stable release version.

Discussions about the scope of the 'Default units' (0.91) aka 'Display units' (0.91+devel) should be moved to the inkscape-devel mailing list.

[Alvin Penner (apenner)]

there is one aspect of this bug report that has not yet been addressed. It is in the second line of text in the file bugreport.svg where it says:

Path (a) using the above shape as pattern along path
Scale (a) to 10% of original width and height

Previously the object in the third line of this svg file was wrongly scaled.
A fix for this has been proposed in Bug 1432762
https://bugs.launchpad.net/inkscape/+bug/1432762/comments/3

any comments?