updating cairo drawing area

["Pierre Benz" <benz pierre gmail com>]

I have successfully managed to use cairo to draw a simple little grid on my application. But I'm now at a loss in order to update the whole drawing when I draw something on top of it ( in this case, a dot to represent movement in the map). Now, I have noticed that when I change the the pane width or height, it manages to update the whole drawing, so it does draw. I am, however at a loss of how to go about updating the drawing area when , example, I click a button on the UI to indicate the the next drawing must occur. 

ui_mainwindow.cpp http://docs.google.com/Doc?id=dkqjxd7_7dktb4z
ui_mainwindow.h      http://docs.google.com/Doc?id=dkqjxd7_8gm9cqr
ui_mapdraw.cpp       http://docs.google.com/Doc?id=dkqjxd7_92vwrkj
ui_mapdraw.h            http://docs.google.com/Doc?id=dkqjxd7_10vqbvzr

the ui_mainwindow.* basically houses the main UI, where there are buttons etc etc. My drawing object is housed in a HPane. The main drawing happens in UI_MapDraw, but in the program I'm going to need a way in which the ui_mainwindow* updates the mapdraw functions.

Basically, if you look at the files above, from ui_mainwindow.cpp, when I click the ViewNext button or insert a placement from action_placement (which gives me a location on the map), i want to be able to place a circle on the map which will then be displayed on the screen. 

Is there anyway that when those functions are called (eg. UI_MainWindow::on_action_placement() UI_MainWindow::on_view_next()) the map will be able to refresh itself? I've tried looking into writing my own signals, but was not very successful. 

Any help would be appreciated
  

thanks

Pierre Benz