Because the scrollbar now spans the entire editor but the scrollable
area does not include the gutter, we need to add the current width of
the gutter to the scroll width of the horizontal scrollbar to allow
it to scroll to the end of the longest lines.
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.
When the target of a mousewheel event is removed, it breaks velocity
scrolling.
Previously, we were preserving the entire screen range when scrolling
with the mouse wheel, which caused a lot of DOM nodes to accumulate. Now
we only preserve the individual line and line number associated with the
target of the mousewheel event, moving them just off screen below all
the on-screen lines and line numbers. This keeps the number of DOM nodes
limited while retaining velocity effects.
During the transition to React, it will be easier if the EditorComponent
assumes it's rendered inside the ReactEditorView. This will make it
easier to test compatibility with existing editor APIs.
