Prior to this change, SVGs were following the CSS painting order, which
means SVG boxes could have established stacking context and be sorted by
z-index. There is a section in the spec that defines what kind of SVG
boxes should create a stacking context
https://www.w3.org/TR/SVG2/render.html#EstablishingStackingContex
Although this spec is marked as a draft and rendering order described in
this spec does not match what other engines do.
This spec issue comment has a good summary of what other engines
actually do regarding painting order
https://github.com/w3c/svgwg/issues/264#issuecomment-246432360
"as long as you're relying solely on the default z-index (which SVG1
does, by definition), nothing ever changes order when you apply
opacity/filter/etc".
This change aligns our implementation with other engines by forbidding
SVGs to create a formatting context and painting them in order they are
defined in tree tree.
We were overly aggressive in clipping SVG roots, which effectively made
them behave as if they always had `overflow: hidden`.
This fixes incorrect clipping of the logo on https://basecamp.com/
A display list should not contain coordinates shifted by scroll offset.
Instead, "scroll frame id" needs to be used. In the future it's going to
allow us reuse a display list in cases when only scroll offsets need to
be updated.
The SVGContext is a leftover from when SVG properties were more ad-hoc.
All properties are now (for better or worse) treated as CSS properties
(or handled elsewhere). This makes the SVGContext's fill/stroke
inheritance handling unnecessary.
This simplifies the ownership model between DOM/layout/paint nodes
immensely by deferring to the garbage collector for figuring out what's
live and what's not.
This fixes a few sizing issues too. The page size is now correct in most
cases! \o/
We get to remove some of the `to_type<>()` shenanigans, though it
reappears in some other places.
Since handling overflow: hidden in PaintableBox::before_children_paint
while following paint traversal order can't result in correctly computed
clip rectangle for elements that create their own stacking context
(because before_children_paint is called only for parent but overflow:
hidden can be set somewhere deeper but not in direct ancestor), here
introduced new function PaintableBox::clip_rect() that computes clip
rectangle by looking into containing block.
should_clip_overflow flag that disables clip for absolutely positioned
elements in before_children_paint and after_children_paint is removed
because after changing clip rectangle to be computed from not parent
but containing block it is not needed anymore (absolutely positioned
item is clipped if it's containing block has hidden overflow)
This makes SVG-in-HTML behave quite a bit better by following general
replaced layout rules. It also turns <svg> elements into inline-level
boxes instead of block-level boxes.
This patch adds a bunch of Paintable subclasses, each corresponding to
the Layout::Node subclasses that had a paint() override. All painting
logic is moved from layout nodes into their corresponding paintables.
Paintables are now created by asking a Layout::Box to produce one:
static NonnullOwnPtr<Paintable> Layout::Box::create_paintable()
Note that inline nodes still have their painting logic. Since they
are not boxes, and all paintables have a corresponding box, we'll need
to come up with some other solution for them.
