These exceptions break specs when simulateDomAttachment is used. They
were only present to ensure correct sequencing during development of the
react editor, so it's safe to remove them for now.
CSS has a line-height property with values like '1.3', but we also have
a measured pixel value for line height. It's important to keep these
separate conceptually.
This entailed quite a few changes to dial in scrollbars. The scrollbars
are now adjusted in size to account for the width of the opposite
scrollbar. If the width or height are not explicitly constrained and we
are scrollable in the opposite direction that is constrained, we account
for the width of the opposite scrollbar in assigning a natural height
or width based on the content.
We set overflow to hidden in the opposite scroll direction only if we
can't actually scroll in that direction, causing the white square where
neither scrollbar overlaps to appear at the lower right corner.
This assumes the scrollbar is 15px high, which is incorrect when using
overlay scrollbars or when the scrollbar is styled to have a different
height. We'll need to measure it in a subsequent commit.
This commit breaks the initial render of the editor component into two
stages.
The first stage just renders the shell of the editor so the height,
width, line height, and default character width can be measured. Nothing
that depends on these values is rendered on the first render pass.
Once the editor component is mounted, all these values are measured and
we force another update, which fills in the lines, line numbers,
selections, etc.
We also refrain from assigning an explicit height and width on the
model if these values aren't explicitly styled in the DOM, and just
assume the editor will stretch to accommodate its contents.
This preserves the original behavior of the editor model with respect
to scroll position and autoscroll unless it's being used by the react
component, which flips the ::manageScrollPosition flag to true.
