how to get the popup UILayout feedback message?

I want to get the popup UILayout feedback message(or event) ,when my mouse hover to the list item and it will popup a discription window,how can I use this function in MY addon? it there an api or not?
for example when my mouse is hovering to one of the custom list item, I want It feedback a message for me so the I can popup the custom icon(instead of tooltip) for this item using opengl api.

like this

That’s called a tooltip. You add it between three pairs of quotes in your operator, like this:

class SimpleOperator(bpy.types.Operator):
    <b>"""Add your tooltip here"""</b>    
    bl_idname = "object.simple_operator"
    bl_label = "Simple Object Operator"    

thanks ,I want to popup my custom icon instead of tooltip,I know how to make custom icon,but I don’t know how to make it popup like the tooltip does.
actually,I want to get a feedback message when the mouse is hovering to the item,so that I can draw my custom icon with opengl api.