gridstack · adumesny · Feb 21, 2022 · Feb 20, 2022
diff --git a/README.md b/README.md
@@ -33,6 +33,7 @@ Join us on Slack: https://gridstackjs.troolee.com
   - [Requirements](#requirements)
   - [API Documentation](#api-documentation)
   - [Extend Library](#extend-library)
+  - [Extend Engine](#extend-engine)
   - [Change grid columns](#change-grid-columns)
   - [Custom columns CSS](#custom-columns-css)
   - [Override resizable/draggable options](#override-resizabledraggable-options)
@@ -186,6 +187,27 @@ let grid = GridStack.init();
 grid.printCount();
 ```
 
+## Extend Engine
+
+You can now (5.1+) easily create your own layout engine to further customize you usage. Here is a typescript example
+
+```ts
+import { GridStack, GridStackEngine, GridStackNod, GridStackMoveOpts } from 'gridstack';
+
+class CustomEngine extends GridStackEngine {
+
+  /** refined this to move the node to the given new location */
+  public moveNode(node: GridStackNode, o: GridStackMoveOpts): boolean {
+    // keep the same original X and Width and let base do it all...
+    o.x = node.x;
+    o.w = node.w;
+    return super.moveNode(node, o);
+  }
+}
+
+GridStack.registerEngine(CustomEngine); // globally set our custom class
+```
+
 ## Change grid columns
 
 GridStack makes it very easy if you need [1-12] columns out of the box (default is 12), but you always need **2 things** if you need to customize this:

diff --git a/demo/custom-engine.html b/demo/custom-engine.html
@@ -0,0 +1,75 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <meta http-equiv="X-UA-Compatible" content="IE=edge">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <title>Custom Engine</title>
+
+  <link rel="stylesheet" href="demo.css"/>
+  <!-- <script src="../dist/gridstack-h5.js"></script> -->
+  <script src="events.js"></script>
+</head>
+<body>
+  <div class="container-fluid">
+    <h1>Custom Engine</h1>
+    <p>shows a custom engine subclass in Typescript that only allows objects to move vertically.</p>
+    <div>
+      <a class="btn btn-primary" onClick="addNewWidget()" href="#">Add Widget</a>
+      <a class="btn btn-primary" onclick="toggleFloat()" id="float" href="#">float: true</a>
+    </div>
+    <br><br>
+    <div class="grid-stack"></div>
+  </div>
+
+  <script type="module" > // so we can use import
+    // get CORS error in Chrome...need to have http://localhost/ URL - see https://stackoverflow.com/questions/50197495/javascript-modules-and-cors
+    import { GridStack, GridStackEngine } from '../dist/gridstack-h5.js';
+
+    /**
+     * Custom engine class that only allows vertical movement and resizing
+     */
+    class CustomEngine extends GridStackEngine {
+      /** refined this to move the node to the given new location */
+      moveNode(node, o) {
+        // keep the same original X and Width and let base do it all...
+        o.x = node.x;
+        o.w = node.w;
+        return super.moveNode(node, o);
+      }
+    }
+    GridStack.registerEngine(CustomEngine); // globally set our custom class
+
+    let count = 0;
+    let items = [
+      {x: 0, y: 0},
+      {x: 1, y: 0},
+      {x: 1, y: 2, w: 3},
+    ];
+    items.forEach(n => n.content = String(count++));
+
+    let grid = GridStack.init({
+      float: true, 
+      disableOneColumnMode: true,
+      cellHeight: 70
+    }).load(items);
+    addEvents(grid);
+
+    let addNewWidget = function() {
+      let n = items[count] || {
+        x: Math.round(12 * Math.random()),
+        y: Math.round(5 * Math.random()),
+        w: Math.round(1 + 3 * Math.random()),
+        h: Math.round(1 + 3 * Math.random())
+      };
+      n.content = n.content || String(count++);
+      grid.addWidget(n);
+    };
+
+    let toggleFloat = function() {
+      grid.float(! grid.getFloat());
+      document.querySelector('#float').innerHTML = 'float: ' + grid.getFloat();
+    };
+  </script>
+</body>
+</html>
diff --git a/doc/CHANGES.md b/doc/CHANGES.md
@@ -69,6 +69,7 @@ Change log
 
 
 ## 5.0.0-dev (TBD)
+* add `GridStack.registerEngine()` to let user use their own custom layout engine subclass. Thank you [Thomas] for sponsoring it.
 
 ## 5.0.0 (2022-01-10)
 * add [#992](https://github.com/gridstack/gridstack.js/issues/992) support dragging into and out of nested grids from parents! Thank you [@arclogos132](https://github.com/arclogos132) for sponsoring it.

diff --git a/doc/README.md b/doc/README.md
@@ -27,6 +27,7 @@ gridstack.js API
   - [`initAll(options: GridStackOptions = {}, selector = '.grid-stack'): GridStack[]`](#initalloptions-gridstackoptions---selector--grid-stack-gridstack)
   - [`addGrid(parent: HTMLElement, opt: GridStackOptions = {}): GridStack `](#addgridparent-htmlelement-opt-gridstackoptions---gridstack-)
   - [`setupDragIn(dragIn?: string, dragInOptions?: DDDragInOpt)`](#setupdragindragin-string-draginoptions-dddraginopt)
+  - [`GridStack.registerEngine(engineClass: typeof GridStackEngine)`](#gridstackregisterengineengineclass-typeof-gridstackengine)
 - [API](#api)
   - [`addWidget(el?: GridStackWidget | GridStackElement, options?: GridStackWidget)`](#addwidgetel-gridstackwidget--gridstackelement-options-gridstackwidget)
   - [`batchUpdate()`](#batchupdate)
@@ -100,6 +101,7 @@ gridstack.js API
   * **Note2**: instead of 'clone' you can also pass your own function (get passed the event).
 - `draggable` - allows to override draggable options. (default: `{handle: '.grid-stack-item-content', scroll: false, appendTo: 'body', containment: null}`)
 - `dragOut` to let user drag nested grid items out of a parent or not (default false) See [example](http://gridstackjs.com/demo/nested.html)
+- `engineClass` - the type of engine to create (so you can subclass) default to GridStackEngine
 - `float` - enable floating widgets (default: `false`) See [example](http://gridstackjs.com/demo/float.html)
 - `handle` - draggable handle selector (default: `'.grid-stack-item-content'`)
 - `handleClass` - draggable handle class (e.g. `'grid-stack-item-content'`). If set `handle` is ignored (default: `null`)
@@ -321,6 +323,10 @@ Called during `GridStack.init()` as options, but can also be called directly (la
 * @param dragInOptions options - see `DDDragInOpt`. (default: `{revert: 'invalid', handle: '.grid-stack-item-content', scroll: false, appendTo: 'body'}`
 but you will probably also want `helper: 'clone'` or your own callback function).
 
+
+### `GridStack.registerEngine(engineClass: typeof GridStackEngine)`
+
+* call to specify global custom engine subclass - see instead `GridStackOptions.engineClass` if you only need to replace just one instance.
 ## API
 
 ### `addWidget(el?: GridStackWidget | GridStackElement, options?: GridStackWidget)`

diff --git a/src/gridstack-engine.ts b/src/gridstack-engine.ts
@@ -622,14 +622,8 @@ export class GridStackEngine {
     if (Utils.samePos(node, o)) return false;
     let prevPos: GridStackPosition = Utils.copyPos({}, node);
 
-    // during while() collisions make sure to check entire row so larger items don't leap frog small ones (push them all down)
-    let area = nn;
-    // if (this._useEntireRowArea(node, nn)) {
-    //   area = {x: 0, w: this.column, y: nn.y, h: nn.h};
-    // }
-
     // check if we will need to fix collision at our new location
-    let collides = this.collideAll(node, area, o.skip);
+    let collides = this.collideAll(node, nn, o.skip);
     let needToMove = true;
     if (collides.length) {
       // now check to make sure we actually collided over 50% surface area while dragging

diff --git a/src/gridstack.ts b/src/gridstack.ts
@@ -179,6 +179,14 @@ export class GridStack {
     return grid;
   }
 
+  /** call this method to register your engine instead of the default one.
+   * See instead `GridStackOptions.engineClass` if you only need to
+   * replace just one instance.
+   */
+  static registerEngine(engineClass: typeof GridStackEngine) {
+    GridStack.engineClass = engineClass;
+  }
+
   /** scoping so users can call GridStack.Utils.sort() for example */
   public static Utils = Utils;
 
@@ -194,6 +202,8 @@ export class GridStack {
   /** grid options - public for classes to access, but use methods to modify! */
   public opts: GridStackOptions;
 
+  protected static engineClass: typeof GridStackEngine;
+
   /** @internal create placeholder DIV as needed */
   public get placeholder(): HTMLElement {
     if (!this._placeholder) {
@@ -321,7 +331,8 @@ export class GridStack {
 
     this._setStaticClass();
 
-    this.engine = new GridStackEngine({
+    let engineClass = this.opts.engineClass || GridStack.engineClass || GridStackEngine;
+    this.engine = new engineClass({
       column: this.getColumn(),
       float: this.opts.float,
       maxRow: this.opts.maxRow,

diff --git a/src/types.ts b/src/types.ts
@@ -4,6 +4,7 @@
  */
 
 import { GridStack } from './gridstack';
+import { GridStackEngine } from './gridstack-engine';
 
 
 /** different layout options when changing # of columns,
@@ -105,6 +106,9 @@ export interface GridStackOptions {
   /** let user drag nested grid items out of a parent or not (default false) */
   dragOut?: boolean;
 
+  /** the type of engine to create (so you can subclass) default to GridStackEngine */
+  engineClass?: typeof GridStackEngine;
+
   /** enable floating widgets (default?: false) See example (http://gridstack.github.io/gridstack.js/demo/float.html) */
   float?: boolean;