Add ability to add MouseListeners to Gutter

[bobbylight]

Copied over from SourceForge:

There is no easy way to add a popup menu to the Gutter component. Perhaps allow adding a MouseListener to the (package private) IconRowHeader. This would provide maximum flexibility, but it might be just as useful to provide a custom event/listener API (something like "LineHeaderMouseListener/LineHeaderMouseEvent", but better named) that add easy methods to return line number clicked and other useful info.

Comment: "I needed the same functionality and used a workaround by installing listener on all components returned by gutter.getComponents(). It will be nice if gutter exposes listener interfaces and installs them on all visible components."

[matthew11]

I have created a right side panel (like netbeans have) that indicates if there is any warning/error/bookmark/world occurrence in the document and indicates it's approximate location. The component works fine, but I have to notify the component about the collapse/expand event in order to rearrange it's indicators. It would be really nice if the events would exists mentioned above. Install listener to every component in the Gutter (even if install on only for the FoldIndicators) is messy, and I have to handle the newly created, and destroyed Folds.

[bobbylight]

@matthew11, the component you're creating already exists in RSyntaxTextArea, and is called ErrorStrip.