In `RasterImageView` events related to `AbstractRasterImageViewTool` are
propagated to the parent class in case they have not been accepted. In
case a tool derived from `AbstractRasterImageViewTool` does not
implement its own handler for an event, the empty handler of
`AbstractRasterImageViewTool` is used. Since "by default `isAccepted()`
is set to true" according to the `QEvent` docs, this then results in
events not being propagated.
This can lead to issues, as demonstrated in D14286. As a follow-up to
that and to D14755, let's `ignore()` events by default in
`AbstractRasterImageViewTool`, so they are passed on.