Normally, we don't autoscroll to a cursor when the buffer changes. But
this is a change caused by the cursor itself, so it makes sense to
keep it in view.
When the font size changes and the editor is detached, it schedules
itself to be redrawn the next time we're reattached rather than
updating the display in a detached state.
Detached display updates worked in the past because we didn't need to
be on the DOM to determine horizontal and vertical positions once we
had calculated dimensions once. So it worked to temporarily attach
the editor when calculating new dimensions, and then continue updates
even when it was detached. That now breaks because we can't ask for
pixel positions if we aren't on the DOM.
When translating a logical screen position (columns/rows) to a pixel
position, the editor now builds a temporary version of the line for the
given row. It then uses the DOM range API to insert an empty range
at the correct text node and offset for the given column and determines
the left position based on its clientRect.
Depending on the speed impact, we may want to optimize this by
recycling the existing line node if it exists on screen rather than
building a new one every time. We will still have to build one if the
line we're moving to isn't on screen yet. We could also increase the
chances of the line being on screen by autoscrolling to the vertical
position first, and *then* calculating the horizontal position. Lots
to explore here.
- EditSessions destroy their Selections when they are destroyed
- Editors destroy their EditSessions when they are destroyed
- Editors unsubscribe from the document and window when they are
removed from the DOM.
- When an EditSession is destroyed via any code path, the Editor with
that EditSession removes it.
- Selections no longer trigger 'destroyed' events if their parent
EditSession has already been destroyed.
These are all really intertwined, so I'm doing them as one commit
since that was the only way to keep the specs green.
This commit makes autoscroll a 3-valued property on the cursor. If it
is set to true or false, that setting will stick until the cursor's
next visual update. That means we can explicitly move the cursor with
autoscroll set to false, but also still autoscroll by default when the
cursor's anchor moves on its own.
