Previously, we were collapsing whitespace in Layout::TextNode and then
passed the resulting string for further processing through ChunkIterator
-> InlineLevelIterator -> InlineFormattingContext -> LineBuilder ->
LineBoxFragment -> PaintableFragment. Our painting tree is where we deal
with things like range offsets into the underlying text nodes, but since
we modified the original string, the offsets were wrong.
This changes the way we generate fragments:
* Layout::TextNode no longer collapses whitespace as part of its
stored "text for rendering", but moves this logic to ChunkIterator
which splits up this text into separate views whenever whitespace
needs to be collapsed.
* Layout::LineBox now only extends the last fragment if its end offset
is equal to the new fragment's start offset. Otherwise, there's a
gap caused by collapsing whitespace and we need to generate a
separate fragment for that in order to have a correct start offset.
Some tests need new baselines because of the fixed start offsets.
Fixes#566.
Inline nodes in our layout tree have a position, so let's show it. By
centralizing the logic for this, block nodes now lose their redundant
'content-size' dump info which is already part of the box model dump.
`BlockFormattingContext::compute_width()` stores the left and right
margins in the layout state at the very end of the function. However,
before doing so, it calls `FormattingContext::calculate_inner_width()`
which ends up calling `FormattingContext::calculate_stretch_fit_width()`
if the current box has `width: fit-content`.
Due to this, `calculate_stretch_fit_width()` would always see the
margins from the layout state as zero and therefore not take them into
account. Subsequently, the calculated width ended up being wrong.
Saving margins on the layout state earlier, before calling
`calculate_inner_width()`, makes sure that the width is calculated
correctly.
