Feat/struct subscr - Githubissues

Summary so far:

Structs now have "subscript operator" that allows them to behave as C arrays.
The "subscript operator" is equivalent to Python's __getitem__, __setitem__, __delitem__
When creating a Struct, the user can specify the array size by providing an integer in the constructor to specify the number of elements. Default is 1.
Structs can be accessed either directly (s.field = 1) or through the "subscript operator" (s[17].field = 1).
The following are always True for Structs: s == s[0], s[0] != s[1], s[10][20] == s[30], etc.
char ** are converted to C_Pointer Struct which provides str_val and therefore provides a string array (with the subscript operator)
Arrays of C Native Types are supported only for int types (8bit, 16bit, 32bit and 64bit). They are represented by a new C_Array type which implements the "subscript operator" to access the integer values. Native arrays can be created from Python lists. Native arrays, as Structs, are convertible to Pointer (Blob).
On all these new Array conversions, size is not maintained and no bound checking is performed. Therefore len operator is not implemented and the array don't provide iterator (since we don't know when to stop).
Element deletion (del arr[17]) simply memsets the array element at that position to 0.
Currently C_Array constructor is not provided explicitly. The user would usually works with Python lists, which would be converted to C_Array when needed. On the other direction, a C array usually cannot be converted to Python list because its size is not known, therefore either a Struct or a C_Array are returned instead of a Python list when accessing a C pointer.

lvgl / lv_binding_micropython

Feat/struct subscr #179