1915096 - CSS zoom property doesn't change font size when font-size is specified by keywords

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, defect, P3)

Description

[6k64x4ma]

Attachment: test.html

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:130.0) Gecko/20100101 Firefox/130.0

Steps to reproduce:

Load the attached file.

Actual results:

The first line is not zoomed on Firefox.
Both lines are the same size on Microsoft Edge.

Expected results:

Firefox should match Edge.

Comment 1

[6k64x4ma]

Attachment: Edge vs Firefox

Comment 2

[Michał Gołębiowski-Owczarek [:mgol]]

What's also interesting in this test case is that getComputedStyle($0).fontSize on the first element returns "8px" in Firefox & "16px" in Chrome. The second one returns "16px" in both browsers. If you remove the zoom: 2 declaration, suddenly even Firefox reports "16px" everywhere.

It looks as if Firefox didn't apply zoom properly here but then in another piece of the code it assumed zoom has been applied & it tried to compensate by dividing the resolved value by zoom.

Comment 3

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:jfkthame, could you have a look please?

For more information, please visit BugBot documentation.

Comment 4

[Emilio Cobos Álvarez [:emilio]]

This is because this line isn't applying the effective zoom, and it probably should.

Comment 5

[6k64x4ma]

Attachment: testcase

FYI font-size: initial and deprecated font elements also have this issue.

Comment 6

[Swarup Ukil]

Hi, could I work on this bug?

Comment 7

[Emilio Cobos Álvarez [:emilio]]

Sure, no need to ask for permission, just follow the docs in here. Once you submit the patch the bug gets auto-assigned to you :)

Comment 8

[majaharding]

Attachment: scratch.html

I've also came across this incompatibility, and I've worked out that the font set by font-family can also disable the zoom property. I'm attaching my test case, try opening the devtools and disabling zoom on the centre-content div.

Comment 9

[David McV]

Hi, I'm an aspiring new contributor here, since this says its unassigned I wanted to state my intention to look into this matter. I take it I could just add another comment here if any help is needed?

Comment 10

[Emilio Cobos Álvarez [:emilio]]

Yes, either here or ping me on the introduction or css matrix rooms :)

Comment 11

[Swarup Ukil]

Attachment: Bug 1915096 - Ensure CSS Zoom (effective_zoom) is applied correctly when font-size is specified by keywords. r=emilio

Comment 12

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/9c7c326be95a
Ensure CSS Zoom (effective_zoom) is applied correctly when font-size is specified by keywords. r=emilio

Comment 13

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/51462 for changes under testing/web-platform/tests

Comment 14

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/9c7c326be95a

Comment 15

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Upstream PR merged by moz-wptsync-bot

Comment 16

[6k64x4ma]

Thanks to Swarup's patch, the problem is mostly fixed.
What remains is the font-family: initial case mentioned in comment 5.
Should I file another bug or reopen this?

Comment 17

[Emilio Cobos Álvarez [:emilio]]

Separate bug please. Though initial is a tricky one, much like inherit, see bug 1887627.

Comment 18

[6k64x4ma]

Okay, I filed bug 1955571.

(In comment 16, I meant font-size, not font-family.)