feat(RenderWindow): Add sharing of GPU resources accross render windows

To share resources accross render windows, they need to share a common context
To do so, the render windows can now have a parent that will contain the shared context
The child render windows will proxy some methods of their parent to do the rendering
The content of the parent canvas is then copied to the child canvas using a 2D context

Sources/Rendering/Core/RenderWindow/index.d.ts

@@ -9,6 +9,7 @@ export interface IRenderWindowInitialValues {
 	interactor?: any,
 	neverRendered?: boolean,
 	numberOfLayers?: number
+	childRenderWindows?: vtkRenderWindow[],
 }
 
 interface IStatistics {
@@ -42,6 +43,12 @@ export interface vtkRenderWindow extends vtkObject {
 	 */
 	addRenderer(renderer: vtkRenderer): void;
 
+	/**
+	 * Add a child render window
+	 * @param {vtkRenderWindow} renderWindow The vtkRenderWindow instance.
+	 */
+	addRenderWindow(renderWindow: vtkRenderWindow): void;
+
 	/**
 	 * Add renderer
 	 * @param view 
@@ -87,6 +94,16 @@ export interface vtkRenderWindow extends vtkObject {
 	 */
 	getRenderersByReference(): vtkRenderer[];
 
+	/**
+	 * 
+	 */
+	getChildRenderWindows(): vtkRenderWindow[];
+
+	/**
+	 * 
+	 */
+	getChildRenderWindowsByReference(): vtkRenderWindow[];
+
 	/**
 	 * 
 	 */

Sources/Rendering/Core/RenderWindow/index.js

@@ -143,6 +143,15 @@ function vtkRenderWindow(publicAPI, model) {
       )
       .filter((i) => !!i);
   };
+
+  publicAPI.addRenderWindow = (child) => {
+    if (model.childRenderWindows.includes(child)) {
+      return false;
+    }
+    model.childRenderWindows.push(child);
+    publicAPI.modified();
+    return true;
+  };
 }
 
 // ----------------------------------------------------------------------------
@@ -156,6 +165,7 @@ const DEFAULT_VALUES = {
   interactor: null,
   neverRendered: true,
   numberOfLayers: 1,
+  childRenderWindows: [],
 };
 
 // ----------------------------------------------------------------------------
@@ -173,7 +183,7 @@ export function extend(publicAPI, model, initialValues = {}) {
     'defaultViewAPI',
   ]);
   macro.get(publicAPI, model, ['neverRendered']);
-  macro.getArray(publicAPI, model, ['renderers']);
+  macro.getArray(publicAPI, model, ['renderers', 'childRenderWindows']);
   macro.moveToProtected(publicAPI, model, ['views']);
   macro.event(publicAPI, model, 'completion');
 

Sources/Rendering/OpenGL/RenderWindow/index.d.ts

@@ -18,6 +18,7 @@ export interface IOpenGLRenderWindowInitialValues {
 	shaderCache?: null;
 	initialized?: boolean;
 	context?: WebGLRenderingContext | WebGL2RenderingContext;
+	context2D?: CanvasRenderingContext2D;
 	canvas?: HTMLCanvasElement;
 	cursorVisibility?: boolean;
 	cursor?: string;
@@ -40,13 +41,6 @@ export interface ICaptureOptions {
 	scale?: number
 }
 
-export interface I3DContextOptions {
-    preserveDrawingBuffer?: boolean;
-    depth?: boolean;
-    alpha?: boolean;
-    powerPreference?: string;
-}
-
 type vtkOpenGLRenderWindowBase = vtkObject & Omit<vtkAlgorithm,
 	| 'getInputData'
 	| 'setInputData'
@@ -228,9 +222,44 @@ export interface vtkOpenGLRenderWindow extends vtkOpenGLRenderWindowBase {
 
 	/**
 	 *
-	 * @param {I3DContextOptions} options
+	 * @param {WebGLContextAttributes} options
+	 */
+	get3DContext(options: WebGLContextAttributes): Nullable<WebGLRenderingContext>;
+
+	/**
+	 *
+	 * @param {CanvasRenderingContext2DSettings} options
+	 */
+	get2DContext(options: CanvasRenderingContext2DSettings): Nullable<CanvasRenderingContext2D>;
+
+	/**
+	 * Copy the content of the root parent, if there is one, to the canvas
+	 */
+	copyParentContent(): void;
+
+	/**
+	 * Resize this render window using the size of its children
+	 * The new size of the renderwindow is the size of the bounding box
+	 * containing all the child render windows
+	 */
+	resizeFromChildRenderWindows(): void;
+
+	/**
+	 * Returns the last ancestor of type vtkOpenGLRenderWindow if there is one
+	 * If there is no parent vtkOpenGLRenderWindow, returns undefined
+	 */
+	getRootOpenGLRenderWindow(): vtkOpenGLRenderWindow | undefined;
+
+	/**
+	 * The context 2D is created during initialization instead of the WebGL context
+	 * when there is a parent render window
+	 */
+	getContext2D(): CanvasRenderingContext2D | undefined;
+
+	/**
+	 *
 	 */
-	get3DContext(options: I3DContextOptions): Nullable<WebGLRenderingContext>;
+	setContext2D(context2D: CanvasRenderingContext2D | undefined): boolean;
 
 	/**
 	 *