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https://github.com/RGBCube/serenity
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ac6b3c989d
With this change, instead of applying scroll offsets during the recording of the painting command list, we do the following: 1. Collect all boxes with scrollable overflow into a PaintContext, each with an id and the total amount of scrolling offset accumulated from ancestor scrollable boxes. 2. During the recording phase assign a corresponding scroll_frame_id to each command that paints content within a scrollable box. 3. Before executing the recorded commands, translate each command that has a scroll_frame_id by the accumulated scroll offset. This approach has following advantages: - Implementing nested scrollables becomes much simpler, as the recording phase only requires the correct assignment of the nearest scrollable's scroll_frame_id, while the accumulated offset from ancestors is applied subsequently. - The recording of painting commands is not tied to a specific offset within scrollable boxes, which means in the future, it will be possible to update the scrolling offset and repaint without the need to re-record painting commands.
78 lines
2.7 KiB
C++
78 lines
2.7 KiB
C++
/*
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* Copyright (c) 2023, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <LibWeb/Layout/Viewport.h>
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#include <LibWeb/Painting/StackingContext.h>
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#include <LibWeb/Painting/ViewportPaintable.h>
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namespace Web::Painting {
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JS::NonnullGCPtr<ViewportPaintable> ViewportPaintable::create(Layout::Viewport const& layout_viewport)
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{
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return layout_viewport.heap().allocate_without_realm<ViewportPaintable>(layout_viewport);
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}
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ViewportPaintable::ViewportPaintable(Layout::Viewport const& layout_viewport)
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: PaintableWithLines(layout_viewport)
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{
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}
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ViewportPaintable::~ViewportPaintable() = default;
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void ViewportPaintable::build_stacking_context_tree_if_needed()
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{
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if (stacking_context())
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return;
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build_stacking_context_tree();
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}
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void ViewportPaintable::build_stacking_context_tree()
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{
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set_stacking_context(make<StackingContext>(*this, nullptr, 0));
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size_t index_in_tree_order = 1;
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for_each_in_subtree_of_type<PaintableBox>([&](PaintableBox const& paintable) {
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auto& paintable_box = const_cast<PaintableBox&>(paintable);
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paintable_box.invalidate_stacking_context();
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if (!paintable_box.layout_box().establishes_stacking_context()) {
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VERIFY(!paintable_box.stacking_context());
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return TraversalDecision::Continue;
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}
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auto* parent_context = paintable_box.enclosing_stacking_context();
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VERIFY(parent_context);
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paintable_box.set_stacking_context(make<Painting::StackingContext>(paintable_box, parent_context, index_in_tree_order++));
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return TraversalDecision::Continue;
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});
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stacking_context()->sort();
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}
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void ViewportPaintable::paint_all_phases(PaintContext& context)
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{
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build_stacking_context_tree_if_needed();
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context.recording_painter().translate(-context.device_viewport_rect().location().to_type<int>());
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stacking_context()->paint(context);
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}
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void ViewportPaintable::collect_scroll_frames(PaintContext& context) const
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{
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i32 next_id = 0;
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for_each_in_subtree_of_type<PaintableBox>([&](auto const& paintable_box) {
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if (paintable_box.has_scrollable_overflow()) {
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auto offset = paintable_box.scroll_offset();
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auto ancestor = paintable_box.parent();
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while (ancestor) {
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if (ancestor->is_paintable_box() && static_cast<PaintableBox const*>(ancestor)->has_scrollable_overflow())
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offset.translate_by(static_cast<PaintableBox const*>(ancestor)->scroll_offset());
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ancestor = ancestor->parent();
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}
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context.scroll_frames().set(&paintable_box, { .id = next_id++, .offset = -offset });
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}
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return TraversalDecision::Continue;
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});
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}
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}
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