AD2.1.1: Scale transform incorrectly computed in presence of viewBox

[purplie]

Summary: An SVG file containing a group element with a simple "scale" transform causes a shape to be incorrectly placed.  The bug may be related to incorrectly using a coordinate system based on the viewBox.  

Application:  Affinity Designer 2.1.1

OS: MacOS 13.5

Reproducible: Yes.

Detail:

The attached SVG file describes two concentric circles, centered at (0,0), one red and the other blue.  

The file renders correctly in Inkscape, Safari, Chrome, and Intellij, thus:

But when opened in Affinity Designer, the blue circle is centered at (500,500) while the red circle is centered at (25000, 25000):

If the viewBox is deleted from the SVG file, the result is then correct. I suspect that the "transform" is being applied relative to the corner of the viewBox; but that is incorrect. Transforms apply in the "user coordinate system", not the viewBox coordinate system.

Here's a wild guess:  perhaps, in an effort to avoid showing unsightly negative coordinates in the UI, AD incorrectly handles the case of the viewBox having negative coordinates: it simply added a "translate(+500,+500)", and the scale() transform got applied after that.  But as you can see, that would be incorrect behavior.

bug-6.svg

[Callum]

Hi Purple,

I have logged this with our developers to be fixed in a future update

Thanks
C