<BackPath> images do not scale or tile to the effective size of a widget, only to the base size

[jus]

<KnobComposed>
  <Size>40f,40f</Size>
  <BackPath scalemode="STRETCH">backdrop.svg</BackPath>
  <Knob>knob.svg</Knob>
  <MinAngle>-230</MinAngle>
  <MaxAngle>50</MaxAngle>
  <Connection>
    <ConfigKey><Variable name="group"/>,<Variable name="control"/></ConfigKey>
  </Connection>
</KnobComposed>

In my example, knob.svg & backdrop.svg both have a base size of 30x30.
knob.svg is scaled as foreground image to 40x40. backdrop.svg as background image should scale as well to 40x40, but instead sits lonely in the corner.

Workaround is to make the backdrop.svg the same size as the actual <KnobComposed> widget size (40x40). This removes the flexibility the tiling/stretching <BackPath> promise to offer.

PS. Scaling works fine with <BackPath> of <WidgetGroup>. Probably other widgets supporting <BackPath> are affected (untested).

See recent conversation: https://github.com/mixxxdj/mixxx/commit/a1de569348b4f91eb28c079bb07164a81eb800bf
Commit history: https://github.com/mixxxdj/mixxx/commits/master/src/widget/wknobcomposed.cpp

[RJ Skerry-Ryan (rryan)]

Hopefully an improvement:
https://github.com/mixxxdj/mixxx/pull/426

[ronso0 (ronso0)]

Found this old bug while I was struggling to resize EQ Knobs in my remix of LateNight to 34x34px.
Initial sizes were: Knob 40x40px, Backpath 50x42.5px
Resizing or cropping the Backpath.svg with Inkscape while keeping the original aspect ratio always resulted in offset or squeezing, scalemode setting didn't have any effect.
Saving as Inkscape SVG or plain SVG didn't matter either.
What DID work was to manually delete the viewBox="0 0 X Y" line from the BackPath.svg.
I don't know which app wrote this attribute, Inkscape doesn't when I edit/save the corrected files.
Hope this helps.

[RJ Skerry-Ryan (rryan)]

Due to lack of progress, marking Triaged and clearing assignee. Feel free to revert if it is in fact still in progress :).

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/7706