fix: group abs_transform should only need to apply transform once

[fundon]

If there is transform on the use element, the abs_transform on the group will be applied transform twice.

This will not cause problems in resvg rendering, but if it is parsed through usvg, the abs_transform obtained is incorrect, which will cause the custom rendering to be incorrect.

The correct scale should be 0.5, not 0.25.

resvg/crates/usvg/src/parser/use_node.rs

Lines 273 to 274 in 3a0fdba

	let old_abs_transform = parent.abs_transform;
	parent.abs_transform = parent.abs_transform.pre_concat(transform);

resvg/crates/usvg/src/parser/converter.rs

Line 768 in 3a0fdba

let abs_transform = parent.abs_transform.pre_concat(transform);

• Original SVG

• Before

• After

[LaurenzV]

This change was explicitly introduced in 09338a1 to solve #722. So I'm not entirely sure whether this is the right fix. It does seem to me like the absolute transform of group2 should be translate(20, 20), since the transform is on the node itself? Or am I missing something?

[LaurenzV]

I agree that a scale of 0.25 does seem wrong here, but I'm not sure if the fix you applied is the right one.

[fundon]

Let me check the context. Thank you.

[RazrFalcon]

If it does not affect resvg then why some tests have changed?

[fundon]

If it does not affect resvg then why some tests have changed?

I have no clue. Is it an error caused by the latest oxipng?

[LaurenzV]

Can you try restoring the old snapshots and see whether tests still pass?

[fundon]

Can you try restoring the old snapshots and see whether tests still pass?

Tried. These use cases all have several pixel differences.

[LaurenzV]

Ah ok. Well, I haven't gotten to reviewing this yet, but if it's just a very small diff it's probably fine and due to some floating-point stuff.