Exposing locking primitives to lua plugins is tricky and may lead to
deadlocks. Instead, if possible, it's better to ensure all the needed
synchonization in micro itself, without leaving this burden to lua code.
Since we've added micro.After() timer API and removed exposing Go timers
directly to lua, now we (probably?) have no cases of lua code possibly
running asynchronously without micro controlling when it is running. So
now we can remove lua.Lock.
This means breaking compatibility, but, until recently lua.Lock wasn't
workable at all (see #2945), which suggests that it has never been
really used by anyone. So it should be safe to remove it.
Directly using Go's time.AfterFunc() from lua is tricky. First, it
requires the lua timer callback to explicitly lock ulua.Lock to prevent
races. Second, it requires the lua timer callback to explicitly redraw
the screen if the callback changes the screen contents (see #2923).
So instead provide micro's own timer API which ensures both
synchronization and redrawing on its own, instead of leaving this burden
to lua code. In fact, its implementation runs the lua timer callback in
the main micro's goroutine (i.e. from micro's perspective it is
synchronous, not asynchronous), so both redrawing and synchronization
are ensured automatically.
Fixes#2923
The lock provided to lua as micro.Lock does not really work: an attempt
to use it via micro.Lock:Lock() results in an error:
Plugin initlua: init:260: attempt to call a non-function object
stack traceback:
init:260: in main chunk
[G]: ?
The reason is that the value that is provided to lua is a copy of the
mutex, not the mutex itself.
Ref #1539
Softwrap implementation enhanced to fix various issues with scrolling,
centering, relocating etc.
The main idea is simple: work not with simple line numbers but
with (Line, Row) pairs, where Line is a line number in the buffer
and Row is a visual line (a row) number within this line.
The logic remains mostly the same, but simple arithmetic operations
on line numbers are replaced with corresponding operations on
(Line, Row) pairs.
Fixes#632, #1657
