event system

src/main/kotlin/com/neptuneclient/voidui/VoidUI.kt

@@ -1,5 +1,6 @@
 package com.neptuneclient.voidui
 
+import com.neptuneclient.voidui.event.EventHandler
 import com.neptuneclient.voidui.rendering.Renderer
 import com.neptuneclient.voidui.themes.Theme
 import org.slf4j.Logger
@@ -19,6 +20,11 @@ class VoidUI
  */
 constructor(val renderer: Renderer, var theme: Theme) {
 
+    /**
+     * The event handler which handles all events in the instance.
+     */
+    val eventHandler = EventHandler()
+
     companion object {
         val LOGGER: Logger = LoggerFactory.getLogger("VoidUI")
     }

src/main/kotlin/com/neptuneclient/voidui/event/Event.kt

@@ -0,0 +1,17 @@
+package com.neptuneclient.voidui.event
+
+import com.neptuneclient.voidui.VoidUI
+
+/**
+ * The base class for events in VoidUI.
+ */
+abstract class Event {
+
+    /**
+     * Calls the event.
+     *
+     * @param void The instance of VoidUI in which the event will be called.
+     */
+    fun call(void: VoidUI) = void.eventHandler.eventCalled(this)
+
+}

src/main/kotlin/com/neptuneclient/voidui/event/EventHandler.kt

@@ -0,0 +1,72 @@
+package com.neptuneclient.voidui.event
+
+import kotlin.reflect.KClass
+
+/**
+ * Handles all event calls of the library.
+ */
+class EventHandler {
+
+    /**
+     * A table of all actions which are registered.
+     *
+     * See [ActionRegistry] for more info.
+     */
+    private val actions = mutableListOf<ActionRegistry>()
+
+    /**
+     * Register a new action.
+     *
+     * @param action The action which will be invoked at the event call.
+     * @param event The class of the event which will trigger the action.
+     * @param key An optional key which will identify an action when it gets unregistered, keys don't need to be unique but
+     * in case of a duplicate key all actions with this key will get unregistered.
+     */
+    fun <T : Event> register(event: KClass<T>, key: Any? = null, action: (T) -> Unit) {
+        actions.add(ActionRegistry(action as (Event) -> Unit, event as KClass<Event>, key))
+    }
+
+    /**
+     * Invokes all actions which are registered with the provided event.
+     */
+    fun eventCalled(event: Event) {
+        for ((action, eventClass, _) in actions) {
+            if (event::class != eventClass) continue
+            action(event)
+        }
+    }
+
+    /**
+     * Unregisters all actions with the provided key.
+     */
+    fun unregister(key: Any) {
+        val indexCache = mutableListOf<Int>()
+
+        // fuck you ConcurrentModificationException
+        for ((index, data) in actions.withIndex()) {
+            if (key != data.key) continue
+            indexCache.add(index)
+        }
+
+        for (index in indexCache)
+            actions.removeAt(index)
+    }
+
+    /**
+     * Unregisters all actions.
+     */
+    fun unregisterAll() {
+        actions.clear()
+    }
+
+}
+
+/**
+ * Stores information about an event action.
+ *
+ * @param action The action which will be invoked at the event call.
+ * @param event The class of the event which will trigger the action.
+ * @param key An optional key which will identify an action when it gets unregistered, keys don't need to be unique but
+ * in case of a duplicate key all actions with this key will get unregistered.
+ */
+private data class ActionRegistry(val action: (Event) -> Unit, val event: KClass<Event>, val key: Any?)

src/main/kotlin/com/neptuneclient/voidui/event/events.kt

@@ -0,0 +1,3 @@
+package com.neptuneclient.voidui.event
+
+class TestEvent(val test: String) : Event()

src/main/kotlin/com/neptuneclient/voidui/widgets/Screen.kt

@@ -18,6 +18,11 @@ abstract class Screen
  */
 constructor(val void: VoidUI) {
 
+    /**
+     * A shortcut to [VoidUI.eventHandler].
+     */
+    protected val eventHandler = void.eventHandler
+
     /**
      * The size of the screen.
      */

src/main/kotlin/com/neptuneclient/voidui/widgets/Widget.kt

@@ -3,7 +3,6 @@ package com.neptuneclient.voidui.widgets
 import com.neptuneclient.voidui.widgets.objects.BoxConstraints
 import com.neptuneclient.voidui.widgets.objects.Offset
 import com.neptuneclient.voidui.widgets.objects.Size
-import java.awt.Rectangle
 import kotlin.math.round
 import kotlin.properties.Delegates
 

src/test/kotlin/com/neptuneclient/voidui/tests/ScreenTest.kt

@@ -3,6 +3,8 @@
 package com.neptuneclient.voidui.tests
 
 import com.neptuneclient.voidui.VoidUI
+import com.neptuneclient.voidui.event.EventHandler
+import com.neptuneclient.voidui.event.TestEvent
 import com.neptuneclient.voidui.widgets.*
 import com.neptuneclient.voidui.widgets.objects.EdgeInsets
 import org.junit.jupiter.api.condition.DisabledIfEnvironmentVariable
@@ -54,13 +56,21 @@ class TestScreen(void: VoidUI) : Screen(void) {
 val voidUI = VoidUI(TestRenderer(), TestTheme())
 
 fun main() {
+    val handler = EventHandler()
+    handler.register(TestEvent::class, "ok") {  // normally you would use `this` as a proper key
+        println(it.test)
+    }
+
     val screen = TestScreen(voidUI)
     screen.init()
 
     val renderer = voidUI.renderer as TestRenderer
     while (!GLFW.glfwWindowShouldClose(renderer.window)) {
         screen.render()
+        TestEvent("lululu").call(voidUI)
     }
+
+    handler.unregister("ok")
 
     renderer.destroy()
 }