fix: using existing canvas option (#2017)

* refactor: document cleanup to DocumentCloner

* fix: using existing canvas option

* fix: lint errors

* fix: preview transform origin

src/__tests__/index.ts

@@ -0,0 +1,91 @@
+import html2canvas from '../index';
+
+import {CanvasRenderer} from '../render/canvas/canvas-renderer';
+import {DocumentCloner} from '../dom/document-cloner';
+import {COLORS} from '../css/types/color';
+
+jest.mock('../core/logger');
+jest.mock('../css/layout/bounds');
+jest.mock('../dom/document-cloner');
+jest.mock('../dom/node-parser', () => {
+    return {
+        isBodyElement: () => false,
+        isHTMLElement: () => false,
+        parseTree: jest.fn().mockImplementation(() => {
+            return {styles: {}};
+        })
+    };
+});
+
+jest.mock('../render/stacking-context');
+jest.mock('../render/canvas/canvas-renderer');
+
+describe('html2canvas', () => {
+    // eslint-disable-next-line @typescript-eslint/no-object-literal-type-assertion
+    const element = {
+        ownerDocument: {
+            defaultView: {
+                pageXOffset: 12,
+                pageYOffset: 34
+            }
+        }
+    } as HTMLElement;
+
+    it('should render with an element', async () => {
+        DocumentCloner.destroy = jest.fn().mockReturnValue(true);
+        await html2canvas(element);
+        expect(CanvasRenderer).toHaveBeenLastCalledWith(
+            expect.objectContaining({
+                backgroundColor: 0xffffffff,
+                scale: 1,
+                height: 50,
+                width: 200,
+                x: 0,
+                y: 0,
+                scrollX: 12,
+                scrollY: 34,
+                canvas: undefined
+            })
+        );
+        expect(DocumentCloner.destroy).toBeCalled();
+    });
+
+    it('should have transparent background with backgroundColor: null', async () => {
+        await html2canvas(element, {backgroundColor: null});
+        expect(CanvasRenderer).toHaveBeenLastCalledWith(
+            expect.objectContaining({
+                backgroundColor: COLORS.TRANSPARENT
+            })
+        );
+    });
+
+    it('should use existing canvas when given as option', async () => {
+        // eslint-disable-next-line @typescript-eslint/no-object-literal-type-assertion
+        const canvas = {} as HTMLCanvasElement;
+        await html2canvas(element, {canvas});
+        expect(CanvasRenderer).toHaveBeenLastCalledWith(
+            expect.objectContaining({
+                canvas
+            })
+        );
+    });
+
+    it('should not remove cloned window when removeContainer: false', async () => {
+        DocumentCloner.destroy = jest.fn();
+        await html2canvas(element, {removeContainer: false});
+        expect(CanvasRenderer).toHaveBeenLastCalledWith(
+            expect.objectContaining({
+                backgroundColor: 0xffffffff,
+                scale: 1,
+                height: 50,
+                width: 200,
+                x: 0,
+                y: 0,
+                scrollX: 12,
+                scrollY: 34,
+                canvas: undefined
+            })
+        );
+        expect(DocumentCloner.destroy).not.toBeCalled();
+    });
+});