In order to update the printed progress string the code tried to move
the cursor N cells to the left, where N is the number of written bytes,
and then clear the remaining part of the line.
This strategy has two main issues:
- Is only valid if the number of characters is equal to the number of
written bytes,
- Is only valid if the line doesn't get too long.
The second point is the main motivation for this change, when the line
becomes too long the terminal wraps it to a new physical line. This
means that moving the cursor to the left won't be enough anymore as once
the left border is reached it cannot move anymore.
The wrapped line is still stored by the terminal as a single line,
despite now taking more than a single one when displayed. If you try to
resize the terminal you'll notice how the contents are reflowed and are
essentially illegible.
Querying the cursor position on non-Windows systems (plot twist,
Microsoft suggests using VT escape sequences on newer systems) is
extremely cumbersome so let's do something different.
Before printing anything let's save the cursor position and clear the
screen below the cursor, this way we ensure there's absolutely no trace
of stale data on screen, and after the message is printed we simply
restore it.
* move concurrency primitives that always operate on kernel threads to
the std.Thread namespace
* remove std.SpinLock. Nobody should use this in a non-freestanding
environment; the other primitives are always preferable. In
freestanding, it will be necessary to put custom spin logic in there,
so there are no use cases for a std lib version.
* move some std lib files to the top level fields convention
* add std.Thread.spinLoopHint
* add std.Thread.Condition
* add std.Thread.Semaphore
* new implementation of std.Thread.Mutex for Windows and non-pthreads Linux
* add std.Thread.RwLock
Implementations provided by @kprotty
We generally get away with atomic primitives, however a lock is required
around the refresh function since it traverses the Node graph, and we
need to be sure no references to Nodes remain after end() is called.
