Bug 206161

Summary: getComputedStyle(img).height returns string of a rounded int not a float
Product: WebKit Reporter: cathiechen <cathiechen>
Component: CSSAssignee: Sammy Gill <sgill26>
Status: RESOLVED FIXED    
Severity: Normal CC: bfulgham, emilio, esprehn+autocc, ews-watchlist, fred.wang, glenn, kondapallykalyan, pdr, sabouhallawa, simon.fraser, webkit-bug-importer, yurys, zalan
Priority: P2 Keywords: InRadar
Version: WebKit Nightly Build   
Hardware: Unspecified   
OS: Unspecified   
Bug Depends on:    
Bug Blocks: 201641, 242079    
Attachments:
Description Flags
testcase
none
testcase
none
Add_img_test_cases
none
Add_img_test_cases
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Patch none

Description cathiechen 2020-01-12 21:04:34 PST 
According to the spec getComputedStyle(img).height should return the "Used Value" if img isn't display:none.
The "Used Value" of height is (used width) / (intrinsic ratio). So it can be a float, while WebKit always returns rouned int. (https://www.w3.org/TR/CSS21/visudet.html#propdef-height)

The related test: LayoutTests/imported/w3c/web-platform-tests/html/rendering/replaced-elements/attributes-for-embedded-content-and-images/img-aspect-ratio.html
Comment 1 Frédéric Wang (:fredw) 2020-01-14 02:25:45 PST 
These are the relevant spec definitions:

getComputedStyle(): https://drafts.csswg.org/cssom/#extensions-to-the-window-interface

CSS declaration block: https://drafts.csswg.org/cssom/#css-declaration-block

CSS declaration: https://drafts.csswg.org/cssom/#css-declaration

Serialize a CSS declaration: https://drafts.csswg.org/cssom/#serialize-a-css-declaration

Serialize a CSS value: https://drafts.csswg.org/cssom/#serialize-a-css-value

Serialize a CSS component value: https://drafts.csswg.org/cssom/#serialize-a-css-component-value

<length>
    The <number> component serialized as per <number> followed by the unit in its canonical form as defined in its respective specification.
    ISSUE 12: Probably should distinguish between specified and computed / resolved values.

<number>
    A base-ten number using digits 0-9 (U+0030 to U+0039) in the shortest form possible, using "." to separate decimals (if any), rounding the value if necessary to not produce more than 6 decimals, preceded by "-" (U+002D) if it is negative.
    Note: scientific notation is not used.

<percentage>
    The <number> component serialized as per <number> followed by the literal string "%" (U+0025).
Comment 2 Frédéric Wang (:fredw) 2020-01-14 02:26:58 PST 
Created attachment 387638 [details]
testcase

Serialization seems to happen as expected in Gecko/Blink/WebKit with the attached testcase.
Comment 3 Frédéric Wang (:fredw) 2020-01-14 02:28:37 PST 
Created attachment 387639 [details]
testcase
Comment 4 cathiechen 2020-01-15 04:07:58 PST 
Created attachment 387775 [details]
Add_img_test_cases

Hi Fred,

This issue seems only related to RenderReplaced, i.e, use intrinsic aspect-ratio to compute width / height. In RenderReplaced::computeReplacedLogicalWidth and RenderReplaced::computeReplacedLogicalHeight, roundToInt is called.

PS: Append <img> test to your case.
Comment 5 cathiechen 2020-01-15 05:55:25 PST 
Created attachment 387784 [details]
Add_img_test_cases
Comment 6 cathiechen 2020-01-17 07:03:15 PST 
Created attachment 388035 [details]
Patch
Comment 7 Radar WebKit Bug Importer 2022-05-24 15:00:17 PDT 
<rdar://problem/93860607>
Comment 8 Sammy Gill 2022-05-31 14:16:52 PDT 
Pull request: https://github.com/WebKit/WebKit/pull/1191
Comment 9 EWS 2022-06-21 16:29:20 PDT 
Committed r295701 (251706@main): <https://commits.webkit.org/251706@main>

Reviewed commits have been landed. Closing PR #1191 and removing active labels.
Comment 10 Sammy Gill 2022-06-29 10:34:49 PDT 
Re-opening for pull request https://github.com/WebKit/WebKit/pull/1902
Comment 11 EWS 2022-06-29 10:47:31 PDT 
Committed 251955@main (5d047d546dd9): <https://commits.webkit.org/251955@main>

Reviewed commits have been landed. Closing PR #1902 and removing active labels.
Comment 12 Sammy Gill 2022-06-30 13:32:20 PDT 
Patch has been reverted due to regression reported in 242079. Reopening.
Comment 13 Sammy Gill 2022-07-06 14:25:43 PDT 
Pull request: https://github.com/WebKit/WebKit/pull/2138
Comment 14 EWS 2022-07-18 15:56:06 PDT 
Committed 252583@main (e2c4f937d459): <https://commits.webkit.org/252583@main>

Reviewed commits have been landed. Closing PR #2138 and removing active labels.