Introduce a set of Constructor traits which are implemented on
integer of float depending on the formatted values. This traits
allows building formatted values using expressions such as:
```rust
let buffer_nb = 20.buffers();
let size = 42.k_bytes();
let duration = 15.minutes() + 30.seconds();
let quantity = 42.default_format();
let progress = 20.percent();
let progress = 0.2.percent_ratio();
```
Previous proposition for constructing specific formatted values was
to use an operation such as `42 * Default::ONE` which, in retrospect,
doesn't seem idiomatic.
This commit adds `from_u64` and `from_usize` constructors for most
formatted values. Having `from_usize` is convenient when dealing with
quantities related to containers indices or length.
This also fixes the `Percent` from float constructors from which was
derived the `ONE` constant as well as previous display implementation.
Also removed the `pub` specifier for `Undefined` inner value. It wasn't
removed in a previous commit as `Undefined` can use the full range of
the inner type. But now, it seems preferable not to expose the inner
value for proper encapsulation and so as to reduce the differences with
other formatted values (kind of least astonishment principle).
... users would be able to bypass the range checks and build a
defined Rust value which would be interpreted as `None` in C code.
Added format module examples for formatted values constructions.
The trait FormattedValue was only implemented on types which
could implement the full range of values for a Format. In order
to declare a function which could take both the intrinsic type
of any Format (e.g. `ClockTime`) as well the full range of values
(e.g. `Option<ClockTime>`), the argument was declared:
```rust
impl Into<GenericFormattedValue>,
```
This commit implements `FormattedValue` for any type representing
a format. E.g.: both `ClockTime` and `Option<ClockTime>` will now
implement `FormattedValue`. The trait `FormattedValueFullRange`
is implemented on types which can be built from any raw value.
These changes are intended to help for the implementation of a
means to enforce format conformity at compilation time for
functions with multiple formatted value arguments.
The following signatures were found to be incorrect and are fixed:
- `message::StepDone`: forced the type for `amount` and `duration`
to be of the same type, when `duration` is expected to be of the
`Time` format.
- `query::Convert::set`: the two arguments were forced to the same
type, so potentialy the same format, unless a
`GenericFormattedValue` was used.
See https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/merge_requests/1059
