Sort attributes when exporting SVG

Don't know how to change title to "Enh sort attributes when exporting SVG" which would be easier to read.

It seems (only tested with a minimal rectangle) that File>Save As>Optimized SVG (scour) already sorts the attributes (starting with id). Thus it may be easier to implement the option directly in that extension than in Inkscape directly.

This feature has been implemented by Tavmjong Bah in core Inkscape in rev 14980 and a few follow-up commits (14983, 15007).

* Optionally sort attributes and properties into a canonical order.
  Useful for comparing different versions of an SVG file.
https://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/revision/14980

The new SVG output feature is controlled by a preference setting (which has no GUI yet in the preferences dialog), and is disabled by default. The attribute "sort_attributes" of the group "svgoutput" in preferences.xml controls the output ('0' to disable (default), '1' to enable).

just writing to note that this option works well when applied to linked image attributes.

I applied it to the two files linkBeethoven.svg and linkChopin.svg from Bug 1655613 and it removed the differences in the ordering of the parameters for the lined image.

Would it be considered a new feature if we add the option in the preferences dialog? If not, it should not be too difficult to implement for 0.92.1.
Targeting 0.93 for now.

Why not make it the default, i.e. is there ever a reason not to order attributes?

Eduard Braun wrote:
> Why not make it the default, i.e. is there ever a reason not to order
> attributes?

@Tavmjong - any thoughts on enabling 'sort_attributes' by default, does it affect performance?

No real performance penalty but it might cause files with minimal edits to be completely rewritten (I haven' tested)... which is why I didn't enable it by default.

@Tav: actually, without sorting even files with no modifications (e.g. create an object, delete it, save) are (modified and) rewritten. Moreover, the problem of files being rewritten is going to affect existing unsorted files only and only for their first save (which would happen anyway); subsequently the sorting is going to mitigate it.

I'm +1 for sorting by default and I don't see any reason to have an option to disable it as, FWIU, the unsorted ordering doesn't have any desirable property.

Elaborating my last comment: the unsorted saving could be useful if one doesn't want an existing (unsorted) file to be modified. But the current Inkscape's behavior doesn't permit this as it's not preserving the original ordering anyway.
So the enable/disable option would have sense only if the unordered saving is fixed first.

No comments about the second part of the wish ?

Sorting would be great (for DIFFing) but I'd really really like to be able to preserve the position of some attributes (typically id) so that I don't have to search for it in the middle of "meaningless" other attributes

Having some semantic order in attributes is definitely useful. Actually I just implemented that for Scour (landed in version 0.35), see [1] for some details and thoughts I had on it.

I'm skeptical if it justifies a (user-visible) option in Inkscape (most people probably don't care). Hardcoding an order for the most common attributes (as I ended up doing in Scour) might be worth a thought, though.

Or you could just use Scour. ;-)

[1] https://github.com/scour-project/scour/issues/60