[rohanjariwala03]

Text x, y, dx and dy values in em were treated as pixels. For example, dy=".35em" with font-size="425px" moved the text down by 0.35 pixels instead of about 149, so text centered this way was drawn too high.

DoubleOrPercentage.fromString stripped the unit with parseDouble, so an em value ended up the same as a plain number. Now it remembers that the value is in em, and computeTextPosition multiplies it by the element's font size, including one inherited from a parent. Without a font size it uses kDefaultFontSize (16), the same default computeTextConfig uses when drawing the text. The bug is in vector_graphics_compiler, which flutter_svg uses to parse SVGs.

Fixes flutter/flutter#158758

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Code Review

This pull request introduces support for 'em' units in SVG text positions (x, y, dx, dy) by updating the DoubleOrPercentage class to parse and calculate values relative to the font size. Feedback suggests converting the parsed string to lowercase to ensure case-insensitive matching of the 'em' unit.

[rohanjariwala03]

@gaaclarke Thanks for the review! Merged upstream. Since 1.3.3 is now the coordinate list change, I moved this entry to 1.3.4.

[gaaclarke]

@flar can you be a second review on this please?

[flar]

Mostly LGTM, but there's a nit that I'd like to hear back about...

[flar]

This feels weak in that it seems to need to exclude rem but it doesn't otherwise ensure that the value is #####em rather than #####somethingsomethingelseem. It leaves me wondering why rem was specifically chosen to be excluded, but nothing else was done to make sure the em was just an em...?

[flar]

Also, there appears to be an isPercentage method somewhere, should there be something like an isEm method?

[rohanjariwala03]

Fair point, rem was only excluded because it's the other unit ending in "em". I added isEm/parseEm next to the percentage helpers. isEm only matches a number followed by em, so the special case is gone. Added tests too.