Graphical indication of overflow

[rrdtool@…]

When --rigid is used, peaks that go "off the chart" are truncated with a line straight across the top of the graph. They are indistinguishable from peaks that just happen to go right to the top of the graph.

I'd like to see some visual indicator of truncation. The usual convention is a jagged line, something like this:

|----~~~~~~----------                                                                                
|    |    |                                                                                          
|    |    |    ____                                                                                  
|    |    |    |  |                                                                                  
|____|    |____|  |__                                                                                
---------------------                                                                                

That would make it much easier to see at a glance what was going on.