fdo#61135 New feature in Calc: Stepped Lines graphs - first part of code submitted

Hello everyone,

I have added my first real code for submission to LO :-) It's in gerrit: 
https://gerrit.libreoffice.org/2476.

It took me a while to find my way around the code and also to get used to the 
new possibilities in C++.

I looked on the LO website to find some pointers around in the code, but 
didn't really found it. My main helpers were OpenGrok and gdb. Did I miss a 
nice overview of where to find which functionality ?

Secondly, what would you recommend as a primer on the C++ functionalities used 
in LO code + how they are used ? I didn't do that advanced C++ coding before 
that I know a lot about templates and namespaces.

I also want to add some debug code in what I have done, mainly to print a 
warning if new curve types are fed to LO. What's the best way to do that ? 
From 
https://wiki.documentfoundation.org/Development/How_to_debug#Macros_Controlling_Debug_Code 
I would think to add the code in #ifdef SAL_LOG_WARN or use the SAL_WARN 
macro.

Anyway, I will now create a mock for the UI and discuss this on the UI list. 
Once this is done, what would be the best way to add the new UI functionality 
? A friendly push in the right direction would save me quite some time ;-)

Thanks,

Eric