Highlights toolbar to give an idea of what it would look like
if item was added to toolbar at the position indicated by index_.
If item is NULL, highlighting is turned off. In that case index_
is ignored.
The tool_item passed to this function must not be part of any widget
hierarchy. When an item is set as drop highlight item it can not
added to any widget hierarchy or used as highlight item for another
toolbar.
Highlights toolbar to give an idea of what it would look like if item was added to toolbar at the position indicated by index_. If item is NULL, highlighting is turned off. In that case index_ is ignored.
The tool_item passed to this function must not be part of any widget hierarchy. When an item is set as drop highlight item it can not added to any widget hierarchy or used as highlight item for another toolbar.