Deactive sliders when canvas loses focus (BabylonJS#8728)

* allow controls to handle canvas blur

* update whatsnew

* reword what's new

* linting fix

* only handle sliders

* fix color pickers

dist/what's new.md

@@ -236,6 +236,7 @@
 - Added `ScrollViewer.freezeControls` property to speed up rendering ([Popov72](https://github.com/Popov72))
 - Added `ImageScrollBar.num90RotationInVerticalMode` property to let the user rotate the pictures when in vertical mode ([Popov72](https://github.com/Popov72))
 - Modified isPointerBlocker to block mouse wheel scroll events. ScrollViewer mouse scroll no longer dependent on scene. ([lockphase](https://github.com/lockphase/))
+- Added `_onCanvasBlur` event for controls to detect when the canvas loses focus. Fixes bug where sliders and color pickers would become stuck when canvas lost focus. ([DarraghBurkeMS](https://github.com/DarraghBurkeMS))
 
 ### Particles
 

gui/src/2D/advancedDynamicTexture.ts

@@ -56,6 +56,7 @@ export class AdvancedDynamicTexture extends DynamicTexture {
     private _pointerMoveObserver: Nullable<Observer<PointerInfoPre>>;
     private _pointerObserver: Nullable<Observer<PointerInfo>>;
     private _canvasPointerOutObserver: Nullable<Observer<PointerEvent>>;
+    private _canvasBlurObserver: Nullable<Observer<Engine>>;
     private _background: string;
     /** @hidden */
     public _rootContainer = new Container("root");
@@ -480,6 +481,9 @@ export class AdvancedDynamicTexture extends DynamicTexture {
         if (this._canvasPointerOutObserver) {
             scene.getEngine().onCanvasPointerOutObservable.remove(this._canvasPointerOutObserver);
         }
+        if (this._canvasBlurObserver) {
+            scene.getEngine().onCanvasBlurObservable.remove(this._canvasBlurObserver);
+        }
         if (this._layerToDispose) {
             this._layerToDispose.texture = null;
             this._layerToDispose.dispose();
@@ -741,6 +745,7 @@ export class AdvancedDynamicTexture extends DynamicTexture {
             }
         });
         this._attachToOnPointerOut(scene);
+        this._attachToOnBlur(scene);
     }
     /** @hidden */
     private onClipboardCopy = (rawEvt: Event) => {
@@ -838,6 +843,7 @@ export class AdvancedDynamicTexture extends DynamicTexture {
         });
         mesh.enablePointerMoveEvents = supportPointerMove;
         this._attachToOnPointerOut(scene);
+        this._attachToOnBlur(scene);
     }
     /**
     * Move the focus to a specific control
@@ -876,6 +882,14 @@ export class AdvancedDynamicTexture extends DynamicTexture {
             }
         });
     }
+    private _attachToOnBlur(scene: Scene): void {
+        this._canvasBlurObserver = scene.getEngine().onCanvasBlurObservable.add((pointerEvent) => {
+            Object.entries(this._lastControlDown).forEach(([key, value]) => {
+                value._onCanvasBlur();
+            });
+            this._lastControlDown = {};
+        });
+    }
     // Statics
     /**
      * Creates a new AdvancedDynamicTexture in projected mode (ie. attached to a mesh)

gui/src/2D/controls/colorpicker.ts

@@ -434,6 +434,11 @@ export class ColorPicker extends Control {
         super._onPointerUp(target, coordinates, pointerId, buttonIndex, notifyClick);
     }
 
+    public _onCanvasBlur() {
+        this._forcePointerUp();
+        super._onCanvasBlur();
+    }
+
     /**
      * This function expands the color picker by creating a color picker dialog with manual
      * color value input and the ability to save colors into an array to be used later in

gui/src/2D/controls/control.ts

@@ -1853,6 +1853,9 @@ export class Control {
         if (canNotify && this.parent != null) { this.parent._onWheelScroll(deltaX, deltaY); }
     }
 
+    /** @hidden */
+    public _onCanvasBlur(): void {}
+
     /** @hidden */
     public _processObservables(type: number, x: number, y: number, pointerId: number, buttonIndex: number, deltaX?: number, deltaY?: number): boolean {
         if (!this._isEnabled) {

gui/src/2D/controls/sliders/baseSlider.ts

@@ -326,4 +326,10 @@ export class BaseSlider extends Control {
         delete this._host._capturingControl[pointerId];
         super._onPointerUp(target, coordinates, pointerId, buttonIndex, notifyClick);
     }
+
+    public _onCanvasBlur(): void {
+        this._forcePointerUp();
+        super._onCanvasBlur();
+    }
+
 }