In https://github.com/atom/atom/pull/15503 we mistakenly assumed
`marker.isValid` accounted only for the validity of the marker. However,
that method returns `false` also for markers that are valid but have
been destroyed. As a result, the editor component was mistakenly not
removing block decorations associated with such markers.
With this commit we will rely on the local `wasValid` variable instead.
If its value is `true`, it means that the block decoration has been
accounted for in the `lineTopIndex` and must, as a result, be cleaned up
in case the marker or the decoration gets destroyed.
This prevents the dummy scrollbars from resetting their position to `0`
when the editor element is moved elsewhere in the DOM (e.g. when
splitting a pane item).
Previously, when trying to use block decorations on non-empty markers,
Atom could sometimes throw an error if such markers ended or started at
a position that was not currently rendered.
In fact, even if we already restricted the decoration query to markers
that intersected the visible row range, markers that were only partially
visible would still be considered for rendering. If, depending on the
`reversed` property, we decided to render the tail or head of the marker
in question and this was outside the viewport, Atom would throw the
aforementioned exception.
This commit addresses the above issue by explicitly ignoring block
decorations that are located on rows that are not yet rendered.
Previously, we were hiding scrollbars when their height/width was 0. On
macOS, however, users can decide to only show scrollbars while
scrolling, which causes Atom to detect scrollbars as being invisible
during measurements. As a result, we were mistakenly setting the
visibility property to `hidden` when this setting was on, thus
preventing users from seeing the scrollbar on scroll.
With this commit we are changing the dummy scrollbar components to only
become invisible when the content is not scrollable rather than when the
scrollbars have zero width or height.
As part of this, we have also renamed the
`is{Horizontal,Vertical}ScrollbarVisible` functions to
`canScroll{Horizontally,Vertically}`, to better express their intent.
Previously, when a marker became invalid we would delete the
corresponding block decoration from the DOM, without however removing it
from the `lineTopIndex`. Also, we had a similar issue when decorating a
marker that was already invalid: we would account for it in the index
without adding it to the DOM.
This commit addresses the above problems by ensuring that block
decorations are never added for invalid markers. At the same time, the
editor component will still keep track of changes on the marker that was
decorated, so that it can detect when its validity changes and render it
appropriately.
This commit introduces a change in the way we respond to mousewheel
events. In particular, if `delta * scrollSensitivity` is less than 1 or
greater than -1, we will round it up or down in an attempt to honor the
user's scroll intent.
As a consequence of https://github.com/atom/atom/pull/15378, we are now
able to render highlight decorations in a separate div, as opposed to
having an highlight container for each tile.
Code-wise this is much simpler, because highlights spanning multiple
tiles can be represented via a single region and don't need to be split
across the tiles they span anymore. As a byproduct, performance should
improve as well, because the number of nodes that need to be managed
should decrease significantly.
This also fixes https://github.com/atom/atom/issues/15449, and other
similar rendering artifacts, because highlight decoration DOM nodes
won't need to move between tiles anymore when their position changes.
