This new painter is written with a virtual interface from the start,
and we begin with a Skia backend.
This patch adds enough to support our basic 2D HTML canvas usecase.
...if only the scroll offset is updated.
Currently, on any document with a large amount of content, the process
of building a display list is often more expensive than its
rasterization. This is because the amount of work required to build a
display list is proportional to the size of the paintable tree, whereas
rasterization only occurs for the portion visible in the viewport.
This change is the first step toward improving this process by caching
the display list across repaints when neither style nor layout requires
invalidation. This means that repainting while scrolling becomes
significantly less expensive, as we only need to reapply the scroll
offsets to the existing display list.
The performance improvement is especially visible on pages like
https://ziglang.org/documentation/master/ or
https://www.w3.org/TR/css-grid-2/
Copy a display list item and apply scroll offset instead of mutating
display list directly.
It's a preparation for upcoming changes where a display list will be
cached across repaints and used multiple times with different scroll
offsets.
This factory forced callers to make a list of GC-allocated FileAPI::File
objects. This isn't safe - this opens a window for these files to be
garbage collected before the FileList object stores / visits the list.
Instead, only allow creating an empty FileList and incrementally adding
files to that list.
This allows us to use HeapFunction all of the way down, allowing us
to remove the Handle usage in after_session_callback for
create_new_child_navigable.
...For the completion steps. This is quite nice, as we can simply
capture this in the heap function where it is used instead of
needing to establish a new root.
Note that with these changes, to represent 'an empty algorithm', we now
use a null HeapFunction and do not invoke the steps.
For a long time, we've used two terms, inconsistently:
- "Identifier" is a spec term, but refers to a sequence of alphanumeric
characters, which may or may not be a keyword. (Keywords are a
subset of all identifiers.)
- "ValueID" is entirely non-spec, and is directly called a "keyword" in
the CSS specs.
So to avoid confusion as much as possible, let's align with the spec
terminology. I've attempted to change variable names as well, but
obviously we use Keywords in a lot of places in LibWeb and so I may
have missed some.
One exception is that I've not renamed "valid-identifiers" in
Properties.json... I'd like to combine that and the "valid-types" array
together eventually, so there's no benefit to doing an extra rename
now.
If given, the spec expects the input URL to be manipulated on the fly
as it is being parsed, and may ignore any errors thrown by the URL
parser.
Previously, we were not exactly following the specs assumption here
which resulted in us needed to make awkward copies of the URL in these
situations.
For most cases this is not an issue. But it does cause problems for
situations where URL parsing would result in a failure (which is
ignored by the caller), and the URL is _partially_ updated
while parsing.
Such a situation can occur when setting the host of an href alongside a
port number which is not valid. It is expected that this situation will
result in the host being updates - but not the port number.
Adjust the URL parser API so that it mutates the URL given (if any), and
adjust the callers accordingly.
Fixes two tests on https://wpt.live/url/url-setters-a-area.window.html
This change causes the viewport to be treated as a "scroll frame,"
similar to how it already works for boxes with "overflow: scroll."
This means that, instead of encoding the viewport translation into a
display list, the items will be assigned the scroll frame id of the
viewport and then shifted by the scroll offset before execution. In the
future it will allow us to reuse a display list for repainting if only
scroll offset has changed.
As a side effect, it also removes the need for special handling of
"position: fixed" because compensating for the viewport offset while
painting or hit-testing is no longer necessary. Instead, anything
contained within a "position: fixed" element is simply not assigned
a scroll frame id, which means it is not shifted by the scroll offset.
