In main.c file, we create some buttons and attach event handler to it. I modify it from IUP hello world sample to show how we access other controls from a event handler that only has reference to the control sending the event.
IUP is a cross platform GUI library. Last time tried to figure out how to compile an IUP hello world program using codeblocks IDE. After some searching on internet finally managed to compile it. Here is the linker setting used.