[Gecko Bug 1927270] Force fill columns if the current multicol's nested balancing depth exceeds the maximum. #50010
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…xceeds the maximum. Currently, only a maximum of two levels of nested "balancing" multicol are allowed. In the third or deeper levels of a multicol container that uses the balancing behavior (`column-fill: balancing`), we don't honor the balancing request and make it act as if `column-count: 1` is set, for performance reasons [1]. In such scenarios, this patch sets the `mForceAuto` to `true`, allowing the content to be laid out regardless of whether the multicol is at the top of the page or not [2]. This prevents the indefinite creation of columns. This change should have minimal impact on real sites, as nested multicol layouts beyond two levels are rare. WARNING: Opening the testcase in Firefox without this patch applied can hang the browser. [1] https://searchfox.org/mozilla-central/rev/ead020d3989d3e9477b353d3d117f9c0f4b16f53/layout/generic/nsColumnSetFrame.cpp#296-301 [2] https://searchfox.org/mozilla-central/rev/6b61714b224f8cdca1a48ef1c51edab027f2c09f/layout/generic/nsColumnSetFrame.cpp#650-654 Differential Revision: https://phabricator.services.mozilla.com/D233711 bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1927270 gecko-commit: c0d9ef2b735c417769b9caadbb74056846c38e51 gecko-reviewers: dshin
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Currently, only a maximum of two levels of nested "balancing" multicol are
allowed. In the third or deeper levels of a multicol container that uses the
balancing behavior (
column-fill: balancing), we don't honor the balancingrequest and make it act as if
column-count: 1is set, for performance reasons[1].
In such scenarios, this patch sets the
mForceAutototrue, allowing thecontent to be laid out regardless of whether the multicol is at the top of the
page or not [2]. This prevents the indefinite creation of columns.
This change should have minimal impact on real sites, as nested multicol layouts
beyond two levels are rare.
WARNING: Opening the testcase in Firefox without this patch applied can hang the
browser.
[1] https://searchfox.org/mozilla-central/rev/ead020d3989d3e9477b353d3d117f9c0f4b16f53/layout/generic/nsColumnSetFrame.cpp#296-301
[2] https://searchfox.org/mozilla-central/rev/6b61714b224f8cdca1a48ef1c51edab027f2c09f/layout/generic/nsColumnSetFrame.cpp#650-654
Differential Revision: https://phabricator.services.mozilla.com/D233711
bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1927270
gecko-commit: c0d9ef2b735c417769b9caadbb74056846c38e51
gecko-reviewers: dshin