Easing test

assets/cutscenes/MoveCubeCutscene.js

@@ -1,31 +1,32 @@
-var PHASE_LEFT = 0;
-var PHASE_RIGHT = 1;
-
 var SPEED = 3.0;
 var DURATION = 2.0;
 
 function MoveCubeCutscene(params) {
   Cutscene.call(this);
   this.cube = params.cube;
-  this.phase = PHASE_LEFT;
+
-  this.timer = 0.0;
+  var startX = this.cube.position.position.x;
+
+  this.animLeft = new Animation([
+    { time: 0.0, value: startX,             easing: Easing.outQuad },
+    { time: DURATION, value: startX - SPEED * DURATION }
+  ]);
+
+  this.animRight = new Animation([
+    { time: 0.0, value: startX - SPEED * DURATION, easing: Easing.inOutQuad },
+    { time: DURATION, value: startX }
+  ]);
 }
 
 MoveCubeCutscene.prototype = Object.create(Cutscene.prototype);
 MoveCubeCutscene.prototype.constructor = MoveCubeCutscene;
 
 MoveCubeCutscene.prototype.update = function() {
-  this.timer += TIME.delta;
+  if(!this.animLeft.complete) {
-
+    this.cube.position.position.x = this.animLeft.update(TIME.delta);
-  if(this.phase === PHASE_LEFT) {
+  } else {
-    this.cube.position.position.x -= SPEED * TIME.delta;
+    this.cube.position.position.x = this.animRight.update(TIME.delta);
-    if(this.timer >= DURATION) {
+    if(this.animRight.complete) {
-      this.phase = PHASE_RIGHT;
-      this.timer = 0.0;
-    }
-  } else if(this.phase === PHASE_RIGHT) {
-    this.cube.position.position.x += SPEED * TIME.delta;
-    if(this.timer >= DURATION) {
       Cutscene.finish();
     }
   }

src/dusk/CMakeLists.txt

@@ -54,6 +54,7 @@ target_sources(${DUSK_BINARY_TARGET_NAME}
 )
 
 # Subdirs
+add_subdirectory(animation)
 add_subdirectory(assert)
 add_subdirectory(asset)
 add_subdirectory(cutscene)

src/dusk/animation/CMakeLists.txt

@@ -0,0 +1,10 @@
+# Copyright (c) 2026 Dominic Masters
+#
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+target_sources(${DUSK_LIBRARY_TARGET_NAME}
+  PUBLIC
+    easing.c
+    animation.c
+)

src/dusk/animation/animation.c

@@ -0,0 +1,75 @@
+// Copyright (c) 2026 Dominic Masters
+//
+// This software is released under the MIT License.
+// https://opensource.org/licenses/MIT
+
+#include "animation.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+#include <math.h>
+
+void animationInit(animation_t *anim) {
+  memoryZero(anim, sizeof(animation_t));
+}
+
+void animationAddKeyframe(
+  animation_t *anim,
+  float_t time,
+  float_t value,
+  easingtype_t easing
+) {
+  assertTrue(
+    anim->keyframeCount < ANIMATION_KEYFRAME_COUNT_MAX,
+    "Keyframe count exceeds ANIMATION_KEYFRAME_COUNT_MAX"
+  );
+  uint8_t i = anim->keyframeCount++;
+  anim->keyframes[i].time = time;
+  anim->keyframes[i].value = value;
+  anim->keyframes[i].easing = easing;
+  if(time > anim->duration) anim->duration = time;
+}
+
+float_t animationGetValue(const animation_t *anim) {
+  if(anim->keyframeCount == 0) return 0.0f;
+
+  uint8_t last = anim->keyframeCount - 1;
+
+  if(anim->keyframeCount == 1) return anim->keyframes[0].value;
+  if(anim->time <= anim->keyframes[0].time) return anim->keyframes[0].value;
+  if(anim->time >= anim->keyframes[last].time) {
+    return anim->keyframes[last].value;
+  }
+
+  for(uint8_t i = 0; i < last; i++) {
+    const keyframe_t *a = &anim->keyframes[i];
+    const keyframe_t *b = &anim->keyframes[i + 1];
+    if(anim->time < a->time || anim->time >= b->time) continue;
+    float_t t = (anim->time - a->time) / (b->time - a->time);
+    t = easingApply(a->easing, t);
+    return a->value + (b->value - a->value) * t;
+  }
+
+  return anim->keyframes[last].value;
+}
+
+float_t animationUpdate(animation_t *anim, float_t delta) {
+  if(anim->complete && !anim->loop) return animationGetValue(anim);
+
+  anim->time += delta;
+
+  if(anim->duration > 0.0f && anim->time >= anim->duration) {
+    if(anim->loop) {
+      anim->time = fmodf(anim->time, anim->duration);
+    } else {
+      anim->time = anim->duration;
+      anim->complete = true;
+    }
+  }
+
+  return animationGetValue(anim);
+}
+
+void animationReset(animation_t *anim) {
+  anim->time = 0.0f;
+  anim->complete = false;
+}

src/dusk/script/module/animation/moduleanimation.h

@@ -0,0 +1,293 @@
+// Copyright (c) 2026 Dominic Masters
+//
+// This software is released under the MIT License.
+// https://opensource.org/licenses/MIT
+
+#pragma once
+#include "script/module/modulebase.h"
+#include "script/scriptproto.h"
+#include "animation/animation.h"
+#include "util/memory.h"
+
+static scriptproto_t MODULE_ANIMATION_PROTO;
+
+static inline animation_t *moduleAnimationGet(
+  const jerry_call_info_t *callInfo
+) {
+  return (animation_t *)scriptProtoGetValue(
+    &MODULE_ANIMATION_PROTO, callInfo->this_value
+  );
+}
+
+// Extracts an easingtype_t from a JS value. Accepts either a plain number
+// or an Easing.xxx function (which has a .type numeric property).
+static easingtype_t moduleAnimationReadEasing(
+  const jerry_value_t val
+) {
+  if(jerry_value_is_number(val)) {
+    return (easingtype_t)(uint32_t)jerry_value_as_number(val);
+  }
+  if(jerry_value_is_object(val) || jerry_value_is_function(val)) {
+    jerry_value_t key = jerry_string_sz("type");
+    jerry_value_t typeVal = jerry_object_get(val, key);
+    jerry_value_free(key);
+    easingtype_t result = EASING_LINEAR;
+    if(jerry_value_is_number(typeVal)) {
+      result = (easingtype_t)(uint32_t)jerry_value_as_number(typeVal);
+    }
+    jerry_value_free(typeVal);
+    return result;
+  }
+  return EASING_LINEAR;
+}
+
+// Fires onReach callbacks for any keyframes crossed between prevTime and
+// newTime. Returns an exception value on error, or jerry_undefined().
+static jerry_value_t moduleAnimationFireKeyframes(
+  const jerry_value_t thisVal,
+  float_t prevTime,
+  float_t newTime
+) {
+  jerry_value_t kfKey = jerry_string_sz("_keyframes");
+  jerry_value_t kfArr = jerry_object_get(thisVal, kfKey);
+  jerry_value_free(kfKey);
+
+  if(!jerry_value_is_array(kfArr)) {
+    jerry_value_free(kfArr);
+    return jerry_undefined();
+  }
+
+  jerry_length_t len = jerry_array_length(kfArr);
+  for(jerry_length_t i = 0; i < len; i++) {
+    jerry_value_t kfObj = jerry_object_get_index(kfArr, i);
+
+    jerry_value_t tKey = jerry_string_sz("time");
+    jerry_value_t tVal = jerry_object_get(kfObj, tKey);
+    jerry_value_free(tKey);
+    float_t kfTime = (float_t)jerry_value_as_number(tVal);
+    jerry_value_free(tVal);
+
+    if(prevTime < kfTime && newTime >= kfTime) {
+      jerry_value_t cbKey = jerry_string_sz("onReach");
+      jerry_value_t cb = jerry_object_get(kfObj, cbKey);
+      jerry_value_free(cbKey);
+
+      if(jerry_value_is_function(cb)) {
+        jerry_value_t r = jerry_call(cb, thisVal, NULL, 0);
+        jerry_value_free(cb);
+        if(jerry_value_is_exception(r)) {
+          jerry_value_free(kfObj);
+          jerry_value_free(kfArr);
+          return r;
+        }
+        jerry_value_free(r);
+      } else {
+        jerry_value_free(cb);
+      }
+    }
+
+    jerry_value_free(kfObj);
+  }
+
+  jerry_value_free(kfArr);
+  return jerry_undefined();
+}
+
+// Fires onComplete once. Returns an exception on error or jerry_undefined().
+static jerry_value_t moduleAnimationFireComplete(
+  const jerry_value_t thisVal
+) {
+  jerry_value_t firedKey = jerry_string_sz("_completeFired");
+  jerry_value_t firedVal = jerry_object_get(thisVal, firedKey);
+  bool_t alreadyFired = jerry_value_is_true(firedVal);
+  jerry_value_free(firedVal);
+
+  if(alreadyFired) {
+    jerry_value_free(firedKey);
+    return jerry_undefined();
+  }
+
+  jerry_value_t trueVal = jerry_boolean(true);
+  jerry_object_set(thisVal, firedKey, trueVal);
+  jerry_value_free(firedKey);
+  jerry_value_free(trueVal);
+
+  jerry_value_t cbKey = jerry_string_sz("onComplete");
+  jerry_value_t cb = jerry_object_get(thisVal, cbKey);
+  jerry_value_free(cbKey);
+
+  if(jerry_value_is_function(cb)) {
+    jerry_value_t r = jerry_call(cb, thisVal, NULL, 0);
+    jerry_value_free(cb);
+    if(jerry_value_is_exception(r)) return r;
+    jerry_value_free(r);
+  } else {
+    jerry_value_free(cb);
+  }
+
+  return jerry_undefined();
+}
+
+moduleBaseFunction(moduleAnimationConstructor) {
+  animation_t *anim = (animation_t *)memoryAllocate(sizeof(animation_t));
+  animationInit(anim);
+
+  if(argc > 0 && jerry_value_is_boolean(args[argc - 1])) {
+    anim->loop = jerry_value_is_true(args[argc - 1]);
+  }
+
+  if(argc > 0 && jerry_value_is_array(args[0])) {
+    jerry_length_t len = jerry_array_length(args[0]);
+    for(jerry_length_t i = 0; i < len; i++) {
+      jerry_value_t kf = jerry_object_get_index(args[0], i);
+
+      jerry_value_t tKey = jerry_string_sz("time");
+      jerry_value_t vKey = jerry_string_sz("value");
+      jerry_value_t eKey = jerry_string_sz("easing");
+
+      float_t t = (float_t)jerry_value_as_number(
+        jerry_object_get(kf, tKey)
+      );
+      float_t v = (float_t)jerry_value_as_number(
+        jerry_object_get(kf, vKey)
+      );
+      jerry_value_t eVal = jerry_object_get(kf, eKey);
+      easingtype_t e = moduleAnimationReadEasing(eVal);
+
+      jerry_value_free(tKey);
+      jerry_value_free(vKey);
+      jerry_value_free(eKey);
+      jerry_value_free(eVal);
+      jerry_value_free(kf);
+
+      animationAddKeyframe(anim, t, v, e);
+    }
+
+    // Store the JS keyframes array for onReach callback detection.
+    jerry_value_t kfKey = jerry_string_sz("_keyframes");
+    jerry_object_set(callInfo->this_value, kfKey, args[0]);
+    jerry_value_free(kfKey);
+  }
+
+  jerry_value_t firedKey = jerry_string_sz("_completeFired");
+  jerry_value_t falseVal = jerry_boolean(false);
+  jerry_object_set(callInfo->this_value, firedKey, falseVal);
+  jerry_value_free(firedKey);
+  jerry_value_free(falseVal);
+
+  jerry_object_set_native_ptr(
+    callInfo->this_value, &MODULE_ANIMATION_PROTO.info, anim
+  );
+  return jerry_undefined();
+}
+
+moduleBaseFunction(moduleAnimationUpdate) {
+  animation_t *anim = moduleAnimationGet(callInfo);
+  if(!anim) return moduleBaseThrow("Invalid Animation instance");
+  if(argc < 1 || !jerry_value_is_number(args[0])) {
+    return moduleBaseThrow("update() expects a number delta");
+  }
+
+  float_t prevTime = anim->time;
+  float_t delta = (float_t)jerry_value_as_number(args[0]);
+  float_t value = animationUpdate(anim, delta);
+
+  jerry_value_t kfResult = moduleAnimationFireKeyframes(
+    callInfo->this_value, prevTime, anim->time
+  );
+  if(jerry_value_is_exception(kfResult)) return kfResult;
+  jerry_value_free(kfResult);
+
+  if(anim->complete) {
+    jerry_value_t cResult = moduleAnimationFireComplete(
+      callInfo->this_value
+    );
+    if(jerry_value_is_exception(cResult)) return cResult;
+    jerry_value_free(cResult);
+  }
+
+  return jerry_number((double)value);
+}
+
+moduleBaseFunction(moduleAnimationGetValue) {
+  animation_t *anim = moduleAnimationGet(callInfo);
+  if(!anim) return moduleBaseThrow("Invalid Animation instance");
+  return jerry_number((double)animationGetValue(anim));
+}
+
+moduleBaseFunction(moduleAnimationReset) {
+  animation_t *anim = moduleAnimationGet(callInfo);
+  if(!anim) return moduleBaseThrow("Invalid Animation instance");
+  animationReset(anim);
+
+  jerry_value_t key = jerry_string_sz("_completeFired");
+  jerry_value_t falseVal = jerry_boolean(false);
+  jerry_object_set(callInfo->this_value, key, falseVal);
+  jerry_value_free(key);
+  jerry_value_free(falseVal);
+
+  return jerry_undefined();
+}
+
+moduleBaseFunction(moduleAnimationGetComplete) {
+  animation_t *anim = moduleAnimationGet(callInfo);
+  return anim ? jerry_boolean(anim->complete) : jerry_boolean(false);
+}
+
+moduleBaseFunction(moduleAnimationGetLoop) {
+  animation_t *anim = moduleAnimationGet(callInfo);
+  return anim ? jerry_boolean(anim->loop) : jerry_boolean(false);
+}
+
+moduleBaseFunction(moduleAnimationSetLoop) {
+  animation_t *anim = moduleAnimationGet(callInfo);
+  if(!anim) return moduleBaseThrow("Invalid Animation instance");
+  if(argc < 1) return moduleBaseThrow("Expected boolean");
+  anim->loop = jerry_value_is_true(args[0]);
+  return jerry_undefined();
+}
+
+moduleBaseFunction(moduleAnimationGetTime) {
+  animation_t *anim = moduleAnimationGet(callInfo);
+  return anim ? jerry_number((double)anim->time) : jerry_number(0.0);
+}
+
+moduleBaseFunction(moduleAnimationGetDuration) {
+  animation_t *anim = moduleAnimationGet(callInfo);
+  return anim ? jerry_number((double)anim->duration) : jerry_number(0.0);
+}
+
+static void moduleAnimation(void) {
+  scriptProtoInit(
+    &MODULE_ANIMATION_PROTO,
+    "Animation",
+    sizeof(animation_t),
+    moduleAnimationConstructor
+  );
+
+  scriptProtoDefineFunc(
+    &MODULE_ANIMATION_PROTO, "update", moduleAnimationUpdate
+  );
+  scriptProtoDefineFunc(
+    &MODULE_ANIMATION_PROTO, "getValue", moduleAnimationGetValue
+  );
+  scriptProtoDefineFunc(
+    &MODULE_ANIMATION_PROTO, "reset", moduleAnimationReset
+  );
+  scriptProtoDefineProp(
+    &MODULE_ANIMATION_PROTO, "complete",
+    moduleAnimationGetComplete, NULL
+  );
+  scriptProtoDefineProp(
+    &MODULE_ANIMATION_PROTO, "loop",
+    moduleAnimationGetLoop, moduleAnimationSetLoop
+  );
+  scriptProtoDefineProp(
+    &MODULE_ANIMATION_PROTO, "time",
+    moduleAnimationGetTime, NULL
+  );
+  scriptProtoDefineProp(
+    &MODULE_ANIMATION_PROTO, "duration",
+    moduleAnimationGetDuration, NULL
+  );
+}

src/dusk/script/module/animation/moduleeasing.h

@@ -0,0 +1,70 @@
+// Copyright (c) 2026 Dominic Masters
+//
+// This software is released under the MIT License.
+// https://opensource.org/licenses/MIT
+
+#pragma once
+#include "script/module/modulebase.h"
+#include "script/scriptproto.h"
+#include "animation/easing.h"
+
+static scriptproto_t MODULE_EASING_PROTO;
+
+// Generate one handler per easing curve.
+#define EASING_MODULE_TABLE \
+  X(Linear,      "linear",      EASING_LINEAR,       easingLinear) \
+  X(InSine,      "inSine",      EASING_IN_SINE,      easingInSine) \
+  X(OutSine,     "outSine",     EASING_OUT_SINE,     easingOutSine) \
+  X(InOutSine,   "inOutSine",   EASING_IN_OUT_SINE,  easingInOutSine) \
+  X(InQuad,      "inQuad",      EASING_IN_QUAD,      easingInQuad) \
+  X(OutQuad,     "outQuad",     EASING_OUT_QUAD,     easingOutQuad) \
+  X(InOutQuad,   "inOutQuad",   EASING_IN_OUT_QUAD,  easingInOutQuad) \
+  X(InCubic,     "inCubic",     EASING_IN_CUBIC,     easingInCubic) \
+  X(OutCubic,    "outCubic",    EASING_OUT_CUBIC,    easingOutCubic) \
+  X(InOutCubic,  "inOutCubic",  EASING_IN_OUT_CUBIC, easingInOutCubic) \
+  X(InQuart,     "inQuart",     EASING_IN_QUART,     easingInQuart) \
+  X(OutQuart,    "outQuart",    EASING_OUT_QUART,    easingOutQuart) \
+  X(InOutQuart,  "inOutQuart",  EASING_IN_OUT_QUART, easingInOutQuart) \
+  X(InBack,      "inBack",      EASING_IN_BACK,      easingInBack) \
+  X(OutBack,     "outBack",     EASING_OUT_BACK,     easingOutBack) \
+  X(InOutBack,   "inOutBack",   EASING_IN_OUT_BACK,  easingInOutBack)
+
+#define X(CName, jsName, type, fn) \
+  moduleBaseFunction(moduleEasing##CName) { \
+    if(argc < 1 || !jerry_value_is_number(args[0])) { \
+      return moduleBaseThrow("Expected number t"); \
+    } \
+    float_t t = (float_t)jerry_value_as_number(args[0]); \
+    return jerry_number((double)fn(t)); \
+  }
+EASING_MODULE_TABLE
+#undef X
+
+// Adds a callable easing function with a .type property to the Easing object.
+static void moduleEasingRegister(
+  const char_t *jsName,
+  uint8_t type,
+  jerry_external_handler_t fn
+) {
+  jerry_value_t fnVal = jerry_function_external(fn);
+
+  jerry_value_t typeKey = jerry_string_sz("type");
+  jerry_value_t typeVal = jerry_number((double)type);
+  jerry_object_set(fnVal, typeKey, typeVal);
+  jerry_value_free(typeKey);
+  jerry_value_free(typeVal);
+
+  jerry_value_t nameKey = jerry_string_sz(jsName);
+  jerry_object_set(MODULE_EASING_PROTO.prototype, nameKey, fnVal);
+  jerry_value_free(nameKey);
+  jerry_value_free(fnVal);
+}
+
+static void moduleEasing(void) {
+  scriptProtoInit(&MODULE_EASING_PROTO, "Easing", sizeof(uint8_t), NULL);
+
+  #define X(CName, jsName, type, fn) \
+    moduleEasingRegister(jsName, type, moduleEasing##CName);
+  EASING_MODULE_TABLE
+  #undef X
+}

src/dusk/script/module/module.h

@@ -17,6 +17,8 @@
 #include "script/module/display/modulescreen.h"
 #include "script/module/display/modulespritebatch.h"
 #include "script/module/display/moduletext.h"
+#include "script/module/animation/moduleeasing.h"
+#include "script/module/animation/moduleanimation.h"
 #include "script/module/scene/modulescene.h"
 #include "script/module/cutscene/modulecutscene.h"
 #include "script/module/console/moduleconsole.h"
@@ -36,6 +38,8 @@ static void moduleRegister(void) {
   moduleScreen();
   moduleSpriteBatch();
   moduleText();
+  moduleEasing();
+  moduleAnimation();
   moduleScene();
   moduleCutscene();
   moduleConsole();