Several of our newer meters have merged coding concerns in terms
of extracting values and displaying those values. This commit
rectifies that for the SysArch and Hostname meters, allowing use
of this code with alternative front/back ends. The SysArch code
is also refined to detect whether the platform has an os-release
file at all and/or the sys/utsname.h header via configure.ac.
Reasoning:
- implementation was unsound -- broke down when I added a fairly
basic macro definition expanding to a struct initializer in a *.c
file.
- made it way too easy (e.g. via otherwise totally innocuous git
commands) to end up with timestamps such that it always ran
MakeHeader.py but never used its output, leading to overbuild noise
when running what should be a null 'make'.
- but mostly: it's just an awkward way of dealing with C code.
Rationale (copied from htop issue #471):
The function name "setValues" is misleading. For most OOP (object-
oriented programming) contexts, setXXX functions mean they will change
some member variables of an object into something specified in
function arguments. But in the *Meter_setValues() case, the new values
are not from the arguments, but from a hard-coded source. The caller
is not supposed to change the values[] to anything it likes, but
rather to "update" the values from the source. Hence, updateValues is
a better name for this family of functions.
Two changes in this commit:
- All meters now explicitly specify "maxItems" property, even for just
1 item. (Exception is "container" CPU meter classes, which use
CUSTOM_METERMODE.)
- "maxItems" being 0 is now allowed. This will let bar meters and graph
meters render an empty meter.
