OpenTTD
Modules
Here is a list of all modules:
 DirtyHandles the repaint of some part of the screen
 Snowline functions and data structures
 Rows and columns in the viewportColumns are vertical sections of the viewport that are half a tile wide
 Hierarchical widgetsHierarchical widgets, also known as nested widgets, are widgets stored in a tree
 Hierarchical widget partsTo make nested widgets easier to enter, nested widget parts have been created