Bug 248693

Summary:

[GTK][cairo] overflow-x: clip on html and body causes content to be invisible unless zoomed in

Product:

WebKit

Reporter:

two

Component:

CSS

Assignee:

Nobody <webkit-unassigned>

Status:

RESOLVED DUPLICATE

Severity:

Normal

CC:

alicem, fujii.hironori

Priority:

Version:

WebKit Nightly Build

Hardware:

Unspecified

OS:

Unspecified

See Also:

https://bugs.webkit.org/show_bug.cgi?id=256139

Attachments:

Description	Flags
2 windows with the same code (as described above, plus a background) & an html preview buffer: the 1st one shows a page with only the background visible, the 2nd shows the page with also visible text	none
test case	none
WIP patch	none
WIP patch of changing kLayoutUnitFractionalBits	none

two

Reported 2022-12-02 15:52:45 PST

Created attachment 463861 [details] 2 windows with the same code (as described above, plus a background) & an html preview buffer: the 1st one shows a page with only the background visible, the 2nd shows the page with also visible text one website wasn't rendering correctly in epiphany, all the text was invisible, but it became visible after i zoomed in on the page. after poking some css rules in the inspector, it turned out that having `overflow-x: clip` on both `<head>` and `<body>` is what's causing it. a minimal document to reproduce: ```html <html> <head> <style> html { overflow-x: clip; } body { overflow-x: clip; } </style> </head> <body> <p>some text blabla</p> </body> </html> ``` here are some screenshots with a background to show the zoom clearer:

Attachments
2 windows with the same code (as described above, plus a background) & an html preview buffer: the 1st one shows a page with only the background visible, the 2nd shows the page with also visible text (1015.58 KB, image/png) 2022-12-02 15:52 PST, two	no flags	Details
test case (188 bytes, text/html) 2023-04-30 13:33 PDT, Fujii Hironori	no flags	Details
WIP patch (1.05 KB, patch) 2023-04-30 14:53 PDT, Fujii Hironori	no flags	Details Formatted Diff Diff
WIP patch of changing kLayoutUnitFractionalBits (644 bytes, patch) 2023-05-09 23:48 PDT, Fujii Hironori	no flags	Details Formatted Diff Diff
View All Add attachment proposed patch, testcase, etc.

two

Comment 1 2022-12-02 16:00:41 PST

reproducible on 16 Technology Preview too

Fujii Hironori

Comment 2 2023-04-30 13:33:19 PDT

Created attachment 466150 [details] test case

Fujii Hironori

Comment 3 2023-04-30 14:50:04 PDT

RenderBox::overflowClipRect expands the clip rect to inifinite in Y axis. if (style().overflowX() == Overflow::Clip && style().overflowY() == Overflow::Visible) clipRect.expandToInfiniteY(); https://github.com/WebKit/WebKit/blob/aad6f77b647edba28f9e192346076d2922841a0d/Source/WebCore/rendering/RenderBox.cpp#L2132-L2133

Fujii Hironori

Comment 4 2023-04-30 14:53:36 PDT

Created attachment 466152 [details] WIP patch

Fujii Hironori

Comment 5 2023-05-09 00:43:52 PDT

LayoutUnit is using 26.6 fixed point number while cairo is using 24.8 fixed point number internally. _cairo_fixed_from_double returns 0 for large numbers.

Fujii Hironori

Comment 6 2023-05-09 23:48:49 PDT

Created attachment 466304 [details] WIP patch of changing kLayoutUnitFractionalBits I tried another approach of changing kLayoutUnitFractionalBits to match with cairo. However, some tests fail due to the maximum value change and the precision change. Regressions: Unexpected text-only failures (20) css1/formatting_model/vertical_formatting.html [ Failure ] css1/text_properties/vertical_align.html [ Failure ] css2.1/t080301-c411-vt-mrgn-00-b.html [ Failure ] css3/flexbox/flex-algorithm.html [ Failure ] css3/flexbox/flex-flow-auto-margins-no-available-space-assert.html [ Failure ] fast/css-grid-layout/grid-auto-repeat-huge-grid.html [ Failure ] fast/css/calc-parsing-limits.html [ Failure ] fast/css/calc-parsing.html [ Failure ] fast/css/getComputedStyle/getComputedStyle-margin-percentage.html [ Failure ] fast/css/large-number-round-trip.html [ Failure ] fast/css/large-numbers.html [ Failure ] fast/css/percentage-non-integer.html [ Failure ] fast/css/word-space-extra.html [ Failure ] fast/dom/HTMLMeterElement/meter-optimums.html [ Failure ] fast/dom/HTMLMeterElement/meter-styles.html [ Failure ] fast/events/constructors/mouse-event-constructor.html [ Failure ] fast/events/constructors/wheel-event-constructor.html [ Failure ] fast/text/text-letter-spacing.html [ Failure ] fast/text/whitespace/024.html [ Failure ] fast/visual-viewport/client-rects-relative-to-layout-viewport-zoomed.html [ Failure ]

Fujii Hironori

Comment 7 2023-05-10 13:01:00 PDT

I'm goint to fix this bug in bug#228920. *** This bug has been marked as a duplicate of bug 228920 ***

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