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LibWeb: Return early during viewport scrolling if nothing changes

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I noticed that when performing a smooth scroll up or down, we would
repeatedly enter `Navigable::perform_a_scroll_of_the_viewport()` when
the top or bottom (respectively) of the page was reached. Optimize this
case by returning early when we've reached the intended target scroll
position and we're not performing any vertical or horizontal scrolling.
This commit is contained in:
Jelle Raaijmakers 2026-01-28 23:29:02 +01:00 committed by Andreas Kling
parent d50ab3015e
commit 887ed85877
1 changed files with 6 additions and 0 deletions
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6
Libraries/LibWeb/HTML/Navigable.cpp
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@ -2891,6 +2891,12 @@ GC::Ref<WebIDL::Promise> Navigable::perform_a_scroll_of_the_viewport(CSSPixelPoi
// NOTE: Clamp to the scrolling area.
new_viewport_scroll_offset.set_x(max(0.0, min(new_viewport_scroll_offset.x(), scrolling_area.width() - viewport_size().width().to_double())));
new_viewport_scroll_offset.set_y(max(0.0, min(new_viewport_scroll_offset.y(), scrolling_area.height() - viewport_size().height().to_double())));
// AD-HOC: If the scroll position would not change, return early to avoid unnecessary display invalidation
// and event loop scheduling (e.g. during momentum scrolling against a boundary).
if (new_viewport_scroll_offset.to_type<CSSPixels>() == m_viewport_scroll_offset && visual_dx == 0.0 && visual_dy == 0.0)
return WebIDL::create_resolved_promise(doc->realm(), JS::js_undefined());
// FIXME: Get a Promise from this.
perform_scroll_of_viewport_scrolling_box(new_viewport_scroll_offset.to_type<CSSPixels>());