From 2d66d5cee9bf3ed5779f65d8a99b40ee5181bf30 Mon Sep 17 00:00:00 2001
From: cbdev <cb@cbcdn.com>
Date: Fri, 20 Mar 2020 21:50:33 +0100
Subject: Implement Lua threading

---
 backends/lua.md | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

(limited to 'backends/lua.md')

diff --git a/backends/lua.md b/backends/lua.md
index 96e53c8..05509b6 100644
--- a/backends/lua.md
+++ b/backends/lua.md
@@ -19,24 +19,41 @@ The following functions are provided within the Lua interpreter for interaction
 | `output_value(string)`	| `output_value("bar")`		| Get the last output value on a channel |
 | `input_channel()`		| `print(input_channel())`	| Returns the name of the input channel whose handler function is currently running or `nil` if in an `interval`'ed function (or the initial parse step) |
 | `timestamp()`			| `print(timestamp())`		| Returns the core timestamp for this iteration with millisecond resolution. This is not a performance timer, but intended for timeouting, etc |
+| `thread(function)`		| `thread(run_show)`		| Run a function as a Lua thread (see below) |
+| `sleep(number)`		| `sleep(100)`			| Suspend current thread for time specified in milliseconds |
 
 Example script:
-```
+```lua
 function bar(value)
-	output("foo", value / 2)
+	output("foo", value / 2);
 end
 
 step = 0
 function toggle()
-	output("bar", step * 1.0)
+	output("bar", step * 1.0);
 	step = (step + 1) % 2;
 end
 
+function run_show()
+	while(true) do
+		sleep(1000);
+		output("narf", 0);
+		sleep(1000);
+		output("narf", 1.0);
+	end
+end
+
 interval(toggle, 1000)
+thread(run_show)
 ```
 
 Input values range between 0.0 and 1.0, output values are clamped to the same range.
 
+Threads are implemented as Lua coroutines, not operating system threads. This means that
+cooperative multithreading is required, which can be achieved by calling the `sleep(number)`
+function from within a running thread. Calling that function from any other context is
+not supported.
+
 #### Global configuration
 
 The `lua` backend does not take any global configuration.
@@ -61,9 +78,10 @@ lua1.foo > lua2.bar
 
 #### Known bugs / problems
 
-Using any of the interface functions (`output`, `interval`, `input_value`, `output_value`, `input_channel`,
-`timestamp`) as an input channel name to a Lua instance will not call any handler functions.
-Using these names as arguments to the output and value interface functions works as intended.
+Using any of the interface functions (`output`, `interval`, etc.) as an input channel name to a
+Lua instance will not call any handler functions. Using these names as arguments to the output and
+value interface functions works as intended. When using a default handler, the default handler will
+be called.
 
 Output values will not trigger corresponding input event handlers unless the channel is mapped
 back in the MIDIMonster configuration. This is intentional.
-- 
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