feat(player): add option to disable or override double-click handling. (#5611)

`userActions.doubleClick` can be set to false to disable double click to fullscreen. Can be set to a function to override behavior.

Fixes #5604.

docs/guides/options.md

@@ -36,6 +36,7 @@
   * [techCanOverridePoster](#techcanoverrideposter)
   * [techOrder](#techorder)
   * [userActions](#useractions)
+  * [userActions.doubleClick](#useractions.doubleclick)
   * [userActions.hotkeys](#useractions.hotkeys)
   * [userActions.hotkeys.fullscreenKey](#useractions.hotkeys.fullscreenkey)
   * [userActions.hotkeys.muteKey](#useractions.hotkeys.mutekey)
@@ -376,6 +377,28 @@ Defines the order in which Video.js techs are preferred. By default, this means
 
 > Type: `Object`
 
+### `userActions.doubleClick`
+
+> Type: `boolean|function`
+
+Controls how double-clicking on the player/tech operates. If set to `false`, double-clicking is disabled. If undefined or set to
+`true`, double-clicking is enabled and toggles fullscreen mode. To override the default double-click handling, set `userActions.doubleClick`
+to a function which accepts a `dblclick` event:
+
+```js
+function myDoubleClickHandler(event) = {
+  // `this` is the player in this context
+
+  this.pause();
+};
+
+videojs('my-player', {
+  userActions: {
+    doubleClick: myDoubleClickHandler
+  }
+});
+```
+
 ### `userActions.hotkeys`
 
 > Type: `boolean|function|object`

src/js/player.js

@@ -1855,10 +1855,33 @@ class Player extends Component {
     );
 
     if (!inAllowedEls) {
-      if (this.isFullscreen()) {
-        this.exitFullscreen();
-      } else {
-        this.requestFullscreen();
+      /*
+       * options.userActions.doubleClick
+       *
+       * If `undefined` or `true`, double-click toggles fullscreen if controls are present
+       * Set to `false` to disable double-click handling
+       * Set to a function to substitute an external double-click handler
+       */
+      if (
+        this.options_ === undefined ||
+        this.options_.userActions === undefined ||
+        this.options_.userActions.doubleClick === undefined ||
+        this.options_.userActions.doubleClick !== false
+      ) {
+
+        if (
+          this.options_ !== undefined &&
+          this.options_.userActions !== undefined &&
+          typeof this.options_.userActions.doubleClick === 'function'
+        ) {
+
+          this.options_.userActions.doubleClick.call(this, event);
+
+        } else if (this.isFullscreen()) {
+          this.exitFullscreen();
+        } else {
+          this.requestFullscreen();
+        }
       }
     }
   }