We should use the Gtk+ 2.4 themable icons API to add icons for the
standard markers, and make the view fallback to using stock icons if
no pixbuf is provided through gtk_source_view_set_marker_pixbuf().

I agree
Could anyone provide the icons?

Ok, here is a quick off-the-top-of-my-head list of icons we should 
get:

- Compiler Error (can we use the dialogerror stock?)
- Compiler Warning (use dialogwarning?)
- Bookmark/Flag (VS.net uses a cyan rounded rectangle, however i am 
open to other suggestions)
- Search result (Should we use one of the existing search icons? 
would there be enough detail for the limited amount of space in the 
icon margin?)
- General Warning (For example, "the name DoFoo does not follow the 
GTK+ coding convention. Try using a name like do_foo". Maybe this 
should be the same as Compiler Warning)
- Breakpoint (a red circle is typical here. However, we have to be 
careful that it is distinct from the Error icon).

Also, I think we should have functionality to add a tooltip to the 
icon. Examples:

Compiler error -- Show the error
Break Point -- show if there are any conditions to break on the point.

It would be nice as well to have functionality to detect a click on 
the icon margin built in (for example, in VS.net if you click on the 
margin, you toggle a breakpoint). Same goes for right clicking on an 
icon. Maybe you can do this with existing code, but having hooks 
would be nice.

Is this following summary correct?

- Allow stock icon names (char *) for markers instead of just GdkPixbufs
- Provide tooltip for marker
- Generalize the click-in-gutter by adding a signal to GtkSourceView when the
user clicks in the marker gutter.

I'm against adding specific icons to GtkSourceView. Isn't it enough if the app
using GtkSourceView registers a stock icon with GtkIconFactory (or whatever it's
called) and pass the stock icon name to GtkSourceView?

We have way to set source marks images from pixbuf, icon names and gicon these days, and api to set tooltips and handle clicks. What would be still missing are the icon themselves, but I think icon shipped in libraries quickly become obsolete when the surrounding icon theme changes. Beside we do not have the skills to maintain good icons, so I am closing this as fixed.