s is misaligned
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	Cmglee
	May 17 2023, 6:13 PM

Description

Steps to replicate the issue (include links if applicable):

Observe the text on https://upload.wikimedia.org/wikipedia/commons/thumb/archive/0/05/20230515045519!Sixth_power_example.svg/400px-Sixth_power_example.svg.png from http://commons.wikimedia.org/wiki/File:Sixth_power_example.svg .
Viewing https://upload.wikimedia.org/wikipedia/commons/archive/0/05/20230515045519%21Sixth_power_example.svg in Firefox or Chrome does not manifest the bug.

What happens?:

The text labels overlap with the shapes.

What should have happened instead?:

There should be no overlap, similar to https://upload.wikimedia.org/wikipedia/commons/thumb/0/05/Sixth_power_example.svg/400px-Sixth_power_example.svg.png?20230515045942 which worked around the issue by using less-preferred Unicode superscript characters.

Software version (skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):

I think what happens is the first <tspan> is middle-aligned, then subsequent ones are appended to its right, instead of treating the multiple <tspan>s as a unit and middle-aligning it.
I tried working around it by enclosing the <tspan>s in another <tspan> in https://upload.wikimedia.org/wikipedia/commons/archive/0/05/20230515045941%21Sixth_power_example.svg but it did not fix the bug.

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Status	Subtype	Assigned	Task
Duplicate	BUG REPORT	None	T336894 librsvg 2.44.10 causes a regression: <text> with text-anchor="middle" and multiple <tspan>s is misaligned
Open		None	T265549 Update librsvg to > 2.44.10
Open		None	T40010 RFC: Re-evaluate librsvg as SVG renderer on Wikimedia wikis
Duplicate		None	T56030 Support PhantomJS as an SVG rasterizer/renderer option
Open		None	T336881 [XL] Upgrade Thumbor to bullseye
Resolved		AntiCompositeNumber	T260285 Use ImageMagick for XCF rendering instead of xcftools

Event Timeline

Cmglee created this task.May 17 2023, 6:13 PM

Restricted Application added a subscriber: Aklapper. · View Herald TranscriptMay 17 2023, 6:13 PM

Cmglee renamed this task from librsvg 2.44.10 causes <text> with text-anchor="middle" and multiple <tspan>s to be misaligned to librsvg 2.44.10 causes a regression: <text> with text-anchor="middle" and multiple <tspan>s is misaligned.May 17 2023, 6:15 PM

JoKalliauer changed the task status from Open to Stalled.May 19 2023, 12:27 PM

JoKalliauer triaged this task as Low priority.

JoKalliauer added projects: Upstream, Thumbor, Commons.

JoKalliauer subscribed.May 19 2023, 12:30 PM

description	SVG-file	librsvg 2.40(svgcheck)	librsvg2.44(Wikimedia)	librsvg2.56(Fedora38)	resvg	inkscape
description	svg-file

Screenshot_20230521_003321.png (758×1 px, 306 KB)

JoKalliauer moved this task from Backlog to Patch merged upstream on the Upstream board.May 21 2023, 4:35 AM

JoKalliauer moved this task from Backlog to Upstream (librsvg) on the Thumbor board.

JoKalliauer moved this task from Backlog to update librsvg on the Wikimedia-SVG-rendering board.

JoKalliauer added a subtask: T265549: Update librsvg to > 2.44.10.May 21 2023, 4:38 AM

Arthur2e5 mentioned this in T265549: Update librsvg to > 2.44.10.May 21 2023, 7:26 AM

A haphazard build of 2.56.0 does not show this issue. See build instructions in https://phabricator.wikimedia.org/T265549#8868748.

Renderer miscalculates the width of a text chunk.

See T97233

Instead of using the width of all constituents of the text chunk, librsvg uses the width of the last constituent.

For OP's first example, text-anchor: end; was in effect for

<text x="340"  y="180"><tspan >4</tspan><tspan dy="-1ex" font-size="80">3</tspan></text>

Width used is just of the second tspan, so the current position is only adjusted by the width the "3" rather than "4" and "3".

More tests are at
*https://commons.wikimedia.org/wiki/File:SVG_Text_Chunk_Test.svg

Gnome fixed this bug two years ago. They apparently fixed it in both the C and Rust versions then. It has reappeared on MW because we went from a recent C version to an old Rust version.

So I see this issue as a dup of T97233

Glrx closed this task as a duplicate of T97233: Incorrect text positioning in SVG with tspan element and text-anchor attribute.Jul 16 2023, 7:26 PM

Glrx mentioned this in T97233: Incorrect text positioning in SVG with tspan element and text-anchor attribute.Aug 9 2023, 3:40 PM

Glrx changed the status of subtask T265549: Update librsvg to > 2.44.10 from Stalled to Open.Oct 22 2023, 6:11 PM

	F37026224: Screenshot_20230521_003321.png
	May 21 2023, 4:35 AM

	F37026216: Sixth power example_Inkscape.png
	May 21 2023, 4:35 AM

	F37026213: Sixth power example_rendersvg.png
	May 21 2023, 4:35 AM

	F37026210: Sixth power example_librsvg.png
	May 21 2023, 4:35 AM

	F37026208: 20230515045519!Sixth_power_example.svg.png
	May 21 2023, 4:35 AM

	F37026222: sixth power example_svgcheck.png
	May 21 2023, 4:35 AM

	F37026519: 1.png
	May 21 2023, 8:13 AM

librsvg 2.44.10 causes a regression: <text> with text-anchor="middle" and multiple <tspan>s is misalignedClosed, DuplicatePublicBUG REPORTActions

Description

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Event Timeline

librsvg 2.44.10 causes a regression: <text> with text-anchor="middle" and multiple <tspan>s is misaligned
Closed, DuplicatePublicBUG REPORT
Actions

Related Objects
Search...