add before/after preload and setup

contributor_docs/creating_libraries.md

@@ -92,6 +92,10 @@ Method names you can register and unregister include the following list. Note th
   * **post** — Called at the end of `draw()`.
   * **remove** — Called when `remove()` is called.
   * **init** — Called when the sketch is first initialized, just before the sketch initialization function (the one that was passed into the `p5` constructor) is executed. This is also called before any global mode setup, so your library can add anything to the sketch and it will automatically be copied to `window` if global mode is active.
+  * **beforePreload** — Called before the `preload()` function is executed.
+  * **afterPreload** — Called after the `preload()` function is executed.
+  * **beforeSetup** — Called before the `setup()` function is executed.
+  * **afterSetup** — Called after the `setup()` function is executed.
 
 More to come shortly, lining up roughly with this list:
 https://GitHub.com/processing/processing/wiki/Library-Basics#library-methods

src/core/main.js

@@ -231,6 +231,20 @@ class p5 {
       this._events.devicemotion = null;
     }
 
+    // Function to invoke registered hooks before or after events such as preload, setup, and pre/post draw.
+    p5.prototype.callRegisteredHooksFor = function (hookName) {
+      const target = this || p5.prototype;
+      const context = this._isGlobal ? window : this;
+      if (target._registeredMethods.hasOwnProperty(hookName)) {
+        const methods = target._registeredMethods[hookName];
+        for (const method of methods) {
+          if (typeof method === 'function') {
+            method.call(context);
+          }
+        }
+      }
+    };
+
     this._start = () => {
       // Find node if id given
       if (this._userNode) {
@@ -241,6 +255,7 @@ class p5 {
 
       const context = this._isGlobal ? window : this;
       if (context.preload) {
+        this.callRegisteredHooksFor('beforePreload');
         // Setup loading screen
         // Set loading screen into dom if not present
         // Otherwise displays and removes user provided loading screen
@@ -286,6 +301,7 @@ class p5 {
         if (loadingScreen) {
           loadingScreen.parentNode.removeChild(loadingScreen);
         }
+        this.callRegisteredHooksFor('afterPreload');
         if (!this._setupDone) {
           this._lastTargetFrameTime = window.performance.now();
           this._lastRealFrameTime = window.performance.now();
@@ -322,6 +338,7 @@ class p5 {
     };
 
     this._setup = () => {
+      this.callRegisteredHooksFor('beforeSetup');
       // Always create a default canvas.
       // Later on if the user calls createCanvas, this default one
       // will be replaced
@@ -369,6 +386,7 @@ class p5 {
       if (this._accessibleOutputs.grid || this._accessibleOutputs.text) {
         this._updateAccsOutput();
       }
+      this.callRegisteredHooksFor('afterSetup');
     };
 
     this._draw = () => {

src/core/structure.js

@@ -6,7 +6,6 @@
  */
 
 import p5 from './main';
-
 /**
  * Stops p5.js from continuously executing the code within <a href="#/p5/draw">draw()</a>.
  * If <a href="#/p5/loop">loop()</a> is called, the code in <a href="#/p5/draw">draw()</a>
@@ -471,9 +470,6 @@ p5.prototype.redraw = function(n) {
     if (typeof context.setup === 'undefined') {
       context.scale(context._pixelDensity, context._pixelDensity);
     }
-    const callMethod = f => {
-      f.call(context);
-    };
     for (let idxRedraw = 0; idxRedraw < numberOfRedraws; idxRedraw++) {
       context.resetMatrix();
       if (this._accessibleOutputs.grid || this._accessibleOutputs.text) {
@@ -483,14 +479,14 @@ p5.prototype.redraw = function(n) {
         context._renderer._update();
       }
       context._setProperty('frameCount', context.frameCount + 1);
-      context._registeredMethods.pre.forEach(callMethod);
+      this.callRegisteredHooksFor('pre');
       this._inUserDraw = true;
       try {
         context.draw();
       } finally {
         this._inUserDraw = false;
       }
-      context._registeredMethods.post.forEach(callMethod);
+      this.callRegisteredHooksFor('post');
     }
   }
 };