render: preserve absolute static position
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SGavrl committed
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fb87e87849
commit
f6484f51c8
1 file changed
+103
-12
@@ -667,7 +667,8 @@ pub fn layout_dom_with_images(
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}
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if let Some(taffy_root) = build(tree, root_id, &mut taffy_tree, &mut id_map, &mut words, &mut engine, &mut ifc_items, &styles) {
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reparent_inset_positioned_nodes(tree, &mut taffy_tree, taffy_root, &id_map, &styles);
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let static_position_candidates =
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reparent_inset_positioned_nodes(tree, &mut taffy_tree, taffy_root, &id_map, &styles);
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let available = taffy::Size {
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width: taffy::AvailableSpace::Definite(viewport.0),
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height: taffy::AvailableSpace::Definite(viewport.1),
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@@ -905,10 +906,24 @@ pub fn layout_dom_with_images(
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}
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}
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if !static_position_candidates.is_empty() {
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let _ = taffy_tree.compute_layout_with_measure(taffy_root, available, &mut measure);
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resolve_static_positions_and_reparent(
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&mut taffy_tree,
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&static_position_candidates,
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);
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}
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let _ = taffy_tree.compute_layout_with_measure(taffy_root, available, &mut measure);
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}
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#[cfg(not(feature = "paint"))]
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{
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if !static_position_candidates.is_empty() {
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let _ = taffy_tree.compute_layout(taffy_root, available);
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resolve_static_positions_and_reparent(
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&mut taffy_tree,
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&static_position_candidates,
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);
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}
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let _ = taffy_tree.compute_layout(taffy_root, available);
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}
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compute_absolute_rects(&taffy_tree, taffy_root, 0.0, 0.0, &id_map, &words, &mut rects, &mut text_runs, &mut anon_rects);
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@@ -1235,28 +1250,35 @@ fn compute_absolute_rects(
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}
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}
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/// Attach inset-positioned boxes to their CSS containing block rather than
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/// their immediate DOM parent.
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#[derive(Clone, Copy)]
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struct StaticPositionCandidate {
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child: taffy::NodeId,
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target: taffy::NodeId,
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inline_axis: bool,
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block_axis: bool,
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}
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/// Attach positioned boxes to their CSS containing block rather than their
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/// immediate DOM parent.
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///
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/// Taffy resolves an absolute child's insets against its direct layout-tree
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/// parent. CSS instead uses the nearest positioned or transformed ancestor;
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/// fixed boxes use the nearest transformed ancestor or the initial containing
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/// block. Gecko represents that distinction by reparenting the positioned
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/// frame and leaving a placeholder in normal flow. We can safely do the same
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/// without a placeholder when each axis has at least one specified inset: no
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/// static-position coordinate is needed. Boxes with an entirely auto axis
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/// stay under their DOM parent until the placeholder path is implemented.
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/// block. A box with a fully-auto axis first remains in its original formatting
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/// context so taffy can produce the placeholder-like static coordinate. The
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/// caller harvests that coordinate and reparents it in a bounded second pass.
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fn reparent_inset_positioned_nodes(
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tree: &DomTree,
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taffy_tree: &mut TaffyTree<usize>,
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taffy_root: taffy::NodeId,
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id_map: &HashMap<taffy::NodeId, NodeId>,
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styles: &HashMap<NodeId, crate::LayoutStyle>,
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) {
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) -> Vec<StaticPositionCandidate> {
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let reverse: HashMap<NodeId, taffy::NodeId> =
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id_map.iter().map(|(&taffy_id, &dom_id)| (dom_id, taffy_id)).collect();
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let mut nearest_abs_cb_for_children: HashMap<NodeId, taffy::NodeId> = HashMap::new();
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let mut nearest_fixed_cb_for_children: HashMap<NodeId, taffy::NodeId> = HashMap::new();
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let mut static_candidates = Vec::new();
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for dom_id in tree.descendants(tree.document()) {
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let Some(style) = styles.get(&dom_id) else { continue };
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@@ -1292,9 +1314,6 @@ fn reparent_inset_positioned_nodes(
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}
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let has_block_inset = style.inset[0].is_some() || style.inset[2].is_some();
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let has_inline_inset = style.inset[1].is_some() || style.inset[3].is_some();
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if !has_block_inset || !has_inline_inset {
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continue;
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}
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let Some(&child) = reverse.get(&dom_id) else { continue };
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let target = if style.position_fixed {
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inherited_fixed_cb
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@@ -1305,10 +1324,82 @@ fn reparent_inset_positioned_nodes(
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if current == target {
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continue;
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}
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if !has_block_inset || !has_inline_inset {
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static_candidates.push(StaticPositionCandidate {
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child,
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target,
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inline_axis: !has_inline_inset,
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block_axis: !has_block_inset,
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});
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continue;
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}
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if taffy_tree.remove_child(current, child).is_ok() {
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let _ = taffy_tree.add_child(target, child);
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}
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}
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static_candidates
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}
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fn taffy_global_origin(
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taffy_tree: &TaffyTree<usize>,
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node: taffy::NodeId,
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) -> Option<(f32, f32)> {
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let mut current = Some(node);
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let mut x = 0.0;
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let mut y = 0.0;
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while let Some(id) = current {
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let layout = taffy_tree.layout(id).ok()?;
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x += layout.location.x;
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y += layout.location.y;
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current = taffy_tree.parent(id);
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}
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Some((x, y))
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}
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fn resolve_static_positions_and_reparent(
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taffy_tree: &mut TaffyTree<usize>,
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candidates: &[StaticPositionCandidate],
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) {
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// Harvest every placeholder coordinate before mutating parent links.
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// Otherwise reparenting an outer candidate changes the global-origin walk
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// for a nested candidate while both still contain preliminary-pass layout
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// coordinates.
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let mut resolved = Vec::with_capacity(candidates.len());
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for candidate in candidates {
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let Some(child_origin) = taffy_global_origin(taffy_tree, candidate.child) else { continue };
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let Some(target_origin) = taffy_global_origin(taffy_tree, candidate.target) else { continue };
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let Ok(child_layout) = taffy_tree.layout(candidate.child) else { continue };
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let child_margin = child_layout.margin;
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let Ok(target_layout) = taffy_tree.layout(candidate.target) else { continue };
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let target_border = target_layout.border;
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let Ok(current_style) = taffy_tree.style(candidate.child) else { continue };
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let mut style = current_style.clone();
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if candidate.inline_axis {
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style.inset.left =
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length(child_origin.0 - target_origin.0 - target_border.left - child_margin.left);
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}
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if candidate.block_axis {
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style.inset.top =
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length(child_origin.1 - target_origin.1 - target_border.top - child_margin.top);
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}
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resolved.push((*candidate, style));
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}
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for (candidate, style) in resolved {
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let Some(current) = taffy_tree.parent(candidate.child) else { continue };
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if taffy_tree.remove_child(current, candidate.child).is_err() {
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continue;
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}
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if taffy_tree.add_child(candidate.target, candidate.child).is_err() {
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let _ = taffy_tree.add_child(current, candidate.child);
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continue;
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}
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if taffy_tree.set_style(candidate.child, style).is_err() {
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let _ = taffy_tree.remove_child(candidate.target, candidate.child);
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let _ = taffy_tree.add_child(current, candidate.child);
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}
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}
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}
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/// Does `id` have any direct child that is inline-level (a non-whitespace
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