How to limit the GL11 Viewport?

[Bedrock_Miner]

Heyho Guys! I want to create a gui which shows a map with several Icons on it. You are able to move the map within its frame. The problem is: If the Icons come near the edge of the frame they should be only partially visible.  I think the best way to achieve this is to tell GL that it has to hide everything outside of this range. But how can I do this? I already tried out GLviewport() but this does no clipping but zooms out instead.

Have you got any ideas how to do this?

[MultiMote]

glScissor, but I don't know how to use it.

[Bedrock_Miner]

Thanks, this works great!