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
