Standard text LCD menu system

The pattern I use for menu systems in C is something like this:

struct menuitem
{
  const char *name; // name to be rendered
  functionPointer handlerFunc; // handler for this leaf node (optionally NULL)
  struct menu *child; // pointer to child submenu (optionally NULL)
};

struct menu
{
  struct menu *parent; // pointer to parent menu
  struct **menuitem; // array of menu items, NULL terminated
};

I then declare an array of menus each containing menuitems and pointers to child submenus. Up and down moves through the currently selected array of menuitems. Back moves to the parent menu and forward/select either moves to a child submenu or calls a handlerFunc for a leaf node.

Rendering a menu just involves iterating through its items.

The advantage of this scheme is that it's fully data driven, the menu structures can be statically declared in ROM independent of the renderer and handler functions.

Toby's answer is a very good starting point. The structures mentioned assume that the menus are static and you just navigate through them.

If you want dymanic menus (e.g. displaying certain values, such as temperature, time, etc), then you need to be able to generate that.

One way could be to have register a function to build your string.

struct menuitem
{
  const char *name; // name to be rendered
  const char * (*builderFunc)( const char *name );  // callback to generate string, if not null.
  functionPointer handlerFunc; // handler for this leaf node (optionally NULL)
  struct menu *child; // pointer to child submenu (optionally NULL)
};