Previously, text selection always used the system highlight color. This
implements support for the ::selection pseudo-element's background-color
and color properties.
For form controls like <input> and <textarea>, the selection style is
looked up on the shadow host element, since the actual text lives inside
their shadow DOM.
The text painting logic has been refactored to split fragments into
styled spans (before selection, selected, after selection) so that each
portion can be rendered with its appropriate colors, taking care not to
allocate in 99%+ of fragment rendering cases.
When rendering selections, we want to extend the selection rect for
wrapped lines to show that there is whitespace present. We don't
actually store this whitespace in the fragments; it's purely a visual
clue.
This reflects how both Chrome and Firefox deal with selection ranges
over wrapped lines.
This migrates TextNode::text_for_rendering() to Utf16String and deals
with the fallout. As a consequence, this effectively reverts commit
3df83dade8.
The layout test expecation file updates are because we now express text
lengths and offsets in UTF-16 code units.
The selection-over-multiple-code-units expectation file update actually
represents a correctness fix. Our result now matches Firefox.
This change fixes at least two issues:
- `update_associated_selection()` is responsible for selectionchange
dispatch, and we were incorrectly dispatching this event on ranges
that were not associated with a selection.
- `Range::get_client_rects()` was using `update_associated_selection()`
to refresh the selection state in the paintable tree for the current
range, but since a range might not be associated with a selection,
this could make the painted selection reflect the state of an
arbitrary range instead of the actual selection range.
Fixes a bug on Discord where any text typed into the message input would
get selected.
We generated `PaintableFragment`s with a start and length represented in
UTF-8 byte offsets, but failed to consider that the offsets in a
`DOM::Range` are actually expressed in UTF-16 code units.
This is a bit of a mess: almost all web specs use UTF-16 code units as
the unit for indexing into text nodes, but we almost exclusively use
UTF-8 in our code base. Arguably the best thing would for us to use
UTF-16 everywhere as well: it prevents these mismatches in our
implementations for the price of a bit more memory usage - and even that
could potentially be optimized for.
But for now, try to do the correct thing and lazily allocate UTF-16 data
in a `PaintableFragment` whenever we need to index into it or if we're
asked to determine the code unit offset of a pixel position.
Fixes underinvalidation caused by resolving text-decoration-thickness
during layout commit, while this property can be invalidated
independently of layout.
This reduces the number of `.cpp` files that need to be recompiled when
one of the below header files changes as follows:
Painting/Command.h: 1030 -> 61
Painting/DisplayList.h: 1030 -> 60
Painting/DisplayListRecorder.h: 557 -> 59
Resulting in a massive rename across almost everywhere! Alongside the
namespace change, we now have the following names:
* JS::NonnullGCPtr -> GC::Ref
* JS::GCPtr -> GC::Ptr
* JS::HeapFunction -> GC::Function
* JS::CellImpl -> GC::Cell
* JS::Handle -> GC::Root
