New Reactive system (#89)

Simplify

Move out shared code

Wrap render functions and event functions in transactions

Rename

Basalt/libraries/reactivePrimitives.lua

@@ -0,0 +1,165 @@
+local NodeStatus = {
+    CURRENT = 0,
+    STALE = 1,
+    MAYBE_STALE = 2
+}
+
+local Node = {}
+
+Node.new = function()
+    return {
+        fn = nil,
+        value = nil,
+        status = NodeStatus.STALE,
+        parents = {},
+        children = {},
+
+        cleanup = function(self)
+            for _, parentNode in ipairs(self.parents) do
+                for index, childNode in ipairs(parentNode.children) do
+                    if (childNode == self) then
+                        table.remove(parentNode.children, index)
+                        break
+                    end
+                end
+            end
+            self.parents = {}
+        end
+    }
+end
+
+local ReactiveState = {
+    listeningNode = nil,
+    sourceNodes = {},
+    effectNodes = {},
+    transaction = false
+}
+
+local Reactive = {}
+
+Reactive.pushUpdates = function()
+    for _, sourceNode in ipairs(ReactiveState.sourceNodes) do
+        Reactive.pushSourceNodeUpdate(sourceNode)
+    end
+    Reactive.pullUpdates()
+end
+
+Reactive.pushSourceNodeUpdate = function(sourceNode)
+    if (sourceNode.status == NodeStatus.CURRENT) then
+        return
+    end
+    Reactive.pushNodeUpdate(sourceNode)
+    for _, childNode in ipairs(sourceNode.children) do
+        childNode.status = NodeStatus.STALE
+    end
+    sourceNode.status = NodeStatus.CURRENT
+end
+
+Reactive.pushNodeUpdate = function(node)
+    if (node == nil) then
+        return
+    end
+    node.status = NodeStatus.MAYBE_STALE
+    for _, childNode in ipairs(node.children) do
+        Reactive.pushNodeUpdate(childNode)
+    end
+end
+
+Reactive.pullUpdates = function()
+    for _, effectNode in ipairs(ReactiveState.effectNodes) do
+        Reactive.pullNodeUpdates(effectNode)
+    end
+end
+
+Reactive.pullNodeUpdates = function(node)
+    if (node.status == NodeStatus.CURRENT) then
+        return
+    end
+    if (node.status == NodeStatus.MAYBE_STALE) then
+        for _, parentNode in ipairs(node.parents) do
+            Reactive.pullNodeUpdates(parentNode)
+        end
+    end
+    if (node.status == NodeStatus.STALE) then
+        node:cleanup()
+        local prevListeningNode = ReactiveState.listeningNode
+        ReactiveState.listeningNode = node
+        local oldValue = node.value
+        node.value = node.fn()
+        ReactiveState.listeningNode = prevListeningNode
+        for _, childNode in ipairs(node.children) do
+            if (oldValue == node.value) then
+                childNode.status = NodeStatus.CURRENT
+            else
+                childNode.status = NodeStatus.STALE
+            end
+        end
+    end
+    node.status = NodeStatus.CURRENT
+end
+
+Reactive.subscribe = function(node)
+    local listeningNode = ReactiveState.listeningNode
+    if (listeningNode ~= nil) then
+        table.insert(node.children, listeningNode)
+        table.insert(listeningNode.parents, node)
+    end
+end
+
+Reactive.observable = function(initialValue)
+    local node = Node.new()
+    node.value = initialValue
+    node.status = NodeStatus.CURRENT
+    local get = function()
+        Reactive.subscribe(node)
+        return node.value
+    end
+    local set = function(newValue)
+        if (node.value == newValue) then
+            return
+        end
+        node.value = newValue
+        node.status = ReactiveState.STALE
+        if (not ReactiveState.transaction) then
+            Reactive.pushUpdates()
+        end
+    end
+    table.insert(ReactiveState.sourceNodes, node)
+    return get, set
+end
+
+Reactive.derived = function(fn)
+    local node = Node.new()
+    node.fn = fn
+    return function()
+        if (node.status ~= NodeStatus.CURRENT) then
+            Reactive.pullNodeUpdates(node)
+        end
+        Reactive.subscribe(node)
+        return node.value
+    end
+end
+
+Reactive.effect = function(fn)
+    local node = Node.new()
+    node.fn = fn
+    table.insert(ReactiveState.effectNodes, node)
+    Reactive.pushUpdates()
+end
+
+Reactive.transaction = function(fn)
+    ReactiveState.transaction = true
+    fn()
+    ReactiveState.transaction = false
+    Reactive.pushUpdates()
+end
+
+Reactive.untracked = function(fn)
+    local prevListeningNode = ReactiveState.listeningNode
+    ReactiveState.listeningNode = nil
+    local value = fn()
+    ReactiveState.listeningNode = prevListeningNode
+    return value
+end
+
+return Reactive

Basalt/plugins/reactiveXml.lua

@@ -1,72 +1,6 @@
+local Reactive = require("reactivePrimitives")
 local XMLParser = require("xmlParser")
 
-local Reactive = {}
-
-Reactive.currentEffect = nil
-
-Reactive.observable = function(initialValue)
-    local value = initialValue
-    local observerEffects = {}
-    local get = function()
-        if (Reactive.currentEffect ~= nil) then
-            table.insert(observerEffects, Reactive.currentEffect)
-            table.insert(Reactive.currentEffect.dependencies, observerEffects)
-        end
-        return value
-    end
-    local set = function(newValue)
-        value = newValue
-        local observerEffectsCopy = {}
-        for index, effect in ipairs(observerEffects) do
-            observerEffectsCopy[index] = effect
-        end
-        for _, effect in ipairs(observerEffectsCopy) do
-            effect.execute()
-        end
-    end
-    return get, set
-end
-
-Reactive.untracked = function(getter)
-    local parentEffect = Reactive.currentEffect
-    Reactive.currentEffect = nil
-    local value = getter()
-    Reactive.currentEffect = parentEffect
-    return value
-end
-
-Reactive.effect = function(effectFn)
-    local effect = {dependencies = {}}
-    local execute = function()
-        Reactive.clearEffectDependencies(effect)
-        local parentEffect = Reactive.currentEffect
-        Reactive.currentEffect = effect
-        effectFn()
-        Reactive.currentEffect = parentEffect
-    end
-    effect.execute = execute
-    effect.execute()
-end
-
-Reactive.derived = function(computeFn)
-    local getValue, setValue = Reactive.observable();
-    Reactive.effect(function()
-        setValue(computeFn())
-    end)
-    return getValue;
-end
-
-Reactive.clearEffectDependencies = function(effect)
-    for _, dependency in ipairs(effect.dependencies) do
-        for index, backlink in ipairs(dependency) do
-            if (backlink == effect) then
-                table.remove(dependency, index)
-            end
-        end
-    end
-    effect.dependencies = {};
-end
-
 local Layout = {
     fromXML = function(text)
         local nodes = XMLParser.parseText(text)
@@ -91,7 +25,9 @@ end
 
 local registerFunctionEvent = function(object, event, script, env)
     event(object, function(...)
-        local success, msg = pcall(load(script, nil, "t", env))
+        local success, msg = pcall(function()
+            Reactive.transaction(load(script, nil, "t", env))
+        end)
         if not success then
             error("XML Error: "..msg)
         end
@@ -116,11 +52,10 @@ return {
                 if (attribute:sub(1, 2) == "on") then
                     registerFunctionEvent(object, object[attribute], expression .. "()", env)
                 else
-                    local update = function()
+                    Reactive.effect(function()
                         local value = load("return " .. expression, nil, "t", env)()
                         object:setProperty(attribute, value)
-                    end
+                    end)
-                    basalt.effect(update)
                 end
             end
             for _, child in ipairs(node.children) do
@@ -134,9 +69,10 @@ return {
 
         local object = {
             observable = Reactive.observable,
-            untracked = Reactive.untracked,
-            effect = Reactive.effect,
             derived = Reactive.derived,
+            effect = Reactive.effect,
+            transaction = Reactive.transaction,
+            untracked = Reactive.untracked,
 
             layout = function(path)
                 if (not fs.exists(path)) then
@@ -163,7 +99,9 @@ return {
                     end
                 })
                 if (layout.script ~= nil) then
-                    executeScript(layout.script, env)
+                    Reactive.transaction(function()
+                        executeScript(layout.script, env)
+                    end)
                 end
                 local objects = {}
                 for _, node in ipairs(layout.nodes) do