Performance regression related to gnomeTheme.hideSingleTab

[piousdeer]

Performance regression related to gnomeTheme.hideSingleTab

[piousdeer]

I haven't dove into DOM to look for simpler selectors, but simply consolidating those using :is fixes the lag while keeping the intended behavior.

@media (-moz-bool-pref: "gnomeTheme.hideSingleTab") {
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) :is(
		tab,
		tab ~ toolbarbutton,
		tab ~ #tabbrowser-arrowscrollbox-periphery
	) {
		visibility: collapse;
	}
}

[piousdeer]

In fact, I've noticed my context menus open quicker with this tweak. To see if it's placebo, I exaggerated the problematic rule into

@media (-moz-bool-pref: "gnomeTheme.hideSingleTab") {
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab ~ toolbarbutton,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab ~ #tabbrowser-arrowscrollbox-periphery,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab ~ toolbarbutton,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab ~ #tabbrowser-arrowscrollbox-periphery,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab ~ toolbarbutton,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab ~ #tabbrowser-arrowscrollbox-periphery,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab ~ toolbarbutton,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab ~ #tabbrowser-arrowscrollbox-periphery,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab ~ toolbarbutton,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab ~ #tabbrowser-arrowscrollbox-periphery,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab ~ toolbarbutton,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab ~ #tabbrowser-arrowscrollbox-periphery,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab ~ toolbarbutton,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab ~ #tabbrowser-arrowscrollbox-periphery,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab ~ toolbarbutton,
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) tab ~ #tabbrowser-arrowscrollbox-periphery{
		visibility: collapse;
	}
}

and indeed, opening a context menu or doing pretty much anything slowed everything down to a crawl. So, this is not limited to Ctrl+Tab.

[rafaelmardojai]

I haven't dove into DOM to look for simpler selectors, but simply consolidating those using :is fixes the lag while keeping the intended behavior.

@media (-moz-bool-pref: "gnomeTheme.hideSingleTab") {
	#tabbrowser-tabs:not(:has(tab:not([hidden="true"]) ~ tab:not([hidden="true"]))) :is(
		tab,
		tab ~ toolbarbutton,
		tab ~ #tabbrowser-arrowscrollbox-periphery
	) {
		visibility: collapse;
	}
}

Thanks for the detailed examination, are you willing to send a patch with these changes?

[piousdeer]

Sure, a bit later today