improve initialization strategy and begin with scrollbars

package.json

@@ -60,7 +60,7 @@
     "rollup-plugin-typescript2": "^0.27.1",
     "should": "^13.2.3",
     "tslib": "^2.2.0",
-    "typescript": "^4.2.4",
+    "typescript": "^4.3.2",
     "utf-8-validate": "^5.0.2"
   },
   "scripts": {

packages/overlayscrollbars/src/classnames.ts

@@ -17,3 +17,9 @@ export const classNameSizeObserverListenerItem = `${classNameSizeObserverListene
 export const classNameSizeObserverListenerItemFinal = `${classNameSizeObserverListenerItem}-final`;
 
 export const classNameTrinsicObserver = 'os-trinsic-observer';
+
+export const classNameScrollbar = 'os-scrollbar';
+export const classNameScrollbarHorizontal = `${classNameScrollbar}-horizontal`;
+export const classNameScrollbarVertical = `${classNameScrollbar}-vertical`;
+export const classNameScrollbarTrack = 'os-scrollbar-track';
+export const classNameScrollbarHandle = 'os-scrollbar-handle';

packages/overlayscrollbars/src/environment.ts

@@ -25,12 +25,40 @@ import {
   classNameViewportScrollbarStyling,
 } from 'classnames';
 import { OSOptions, defaultOptions } from 'options';
+import { OSTargetElement } from 'typings';
 
-export interface InitializationStrategy {
-  _padding: boolean;
-  _content: boolean;
+type StructureInitializationElementFn<T> = ((target: OSTargetElement) => HTMLElement | T) | T;
+
+type ScrollbarsInitializationElementFn<T> = ((target: OSTargetElement, host: HTMLElement, viewport: HTMLElement) => HTMLElement | T) | T;
+
+/**
+ * A Static element is an element which MUST be generated.
+ * If null (or the returned result is null), the initialization function is generatig the element, otherwise
+ * the element returned by the function acts as the generated element.
+ */
+export type StructureInitializationStaticElement = StructureInitializationElementFn<null>;
+
+/**
+ * A Dynamic element is an element which CAN be generated.
+ * If null (or the returned result is null), then the default behavior is used.
+ * If boolean (or the returned result is boolean), the generation of the element is forced (or not).
+ * If the function returns and element, the element returned by the function acts as the generated element.
+ */
+export type StructureInitializationDynamicElement = StructureInitializationElementFn<boolean | null>;
+
+export interface StructureInitializationStrategy {
+  _host: StructureInitializationStaticElement;
+  _viewport: StructureInitializationStaticElement;
+  _padding: StructureInitializationDynamicElement;
+  _content: StructureInitializationDynamicElement;
 }
 
+export interface ScrollbarsInitializationStrategy {
+  _scrollbarsSlot: ScrollbarsInitializationElementFn<null | undefined>;
+}
+
+export interface InitializationStrategy extends StructureInitializationStrategy, ScrollbarsInitializationStrategy {}
+
 export type OnEnvironmentChanged = (env: Environment) => void;
 export interface Environment {
   _nativeScrollbarSize: XY;
@@ -132,9 +160,13 @@ const getWindowDPR = (): number => {
   return window.devicePixelRatio || dDPI / sDPI;
 };
 
+// init function decides for all values
 const getDefaultInitializationStrategy = (nativeScrollbarStyling: boolean): InitializationStrategy => ({
-  _padding: !nativeScrollbarStyling,
-  _content: false,
+  _host: null,
+  _viewport: null,
+  _padding: null,
+  _content: null,
+  _scrollbarsSlot: null,
 });
 
 const createEnvironment = (): Environment => {

packages/overlayscrollbars/src/lifecycles/lifecycleHub.ts

@@ -7,6 +7,7 @@ import { createTrinsicLifecycle } from 'lifecycles/trinsicLifecycle';
 import { createPaddingLifecycle } from 'lifecycles/paddingLifecycle';
 import { createOverflowLifecycle } from 'lifecycles/overflowLifecycle';
 import { StyleObject } from 'typings';
+import { ScrollbarsSetup } from 'setups/scrollbarsSetup';
 
 export type LifecycleCheckOption = <T>(path: string) => LifecycleOptionInfo<T>;
 
@@ -99,7 +100,7 @@ const lifecycleCommunicationFallback: LifecycleCommunication = {
   },
 };
 
-export const createLifecycleHub = (options: OSOptions, structureSetup: StructureSetup): LifecycleHubInstance => {
+export const createLifecycleHub = (options: OSOptions, structureSetup: StructureSetup, scrollbarsSetup: ScrollbarsSetup): LifecycleHubInstance => {
   let lifecycleCommunication = lifecycleCommunicationFallback;
   const { _viewport } = structureSetup._targetObj;
   const {
@@ -201,6 +202,9 @@ export const createLifecycleHub = (options: OSOptions, structureSetup: Structure
     _destroy() {
       destroyObservers();
       removeEnvironmentListener(envUpdateListener);
+
+      structureSetup._destroy();
+      scrollbarsSetup._destroy();
     },
   };
 };

packages/overlayscrollbars/src/overlayscrollbars.ts

@@ -1,12 +1,13 @@
-import { OSTarget, OSTargetObject } from 'typings';
+import { OSTarget, OSInitializationObject } from 'typings';
 import { PartialOptions, validateOptions, assignDeep, isEmptyObject } from 'support';
 import { createStructureSetup, StructureSetup } from 'setups/structureSetup';
+import { createScrollbarsSetup, ScrollbarsSetup } from 'setups/scrollbarsSetup';
 import { createLifecycleHub } from 'lifecycles/lifecycleHub';
 import { OSOptions, optionsTemplate } from 'options';
 import { getEnvironment } from 'environment';
 
 export interface OverlayScrollbarsStatic {
-  (target: OSTarget | OSTargetObject, options?: PartialOptions<OSOptions>, extensions?: any): OverlayScrollbars;
+  (target: OSTarget | OSInitializationObject, options?: PartialOptions<OSOptions>, extensions?: any): OverlayScrollbars;
 }
 
 export interface OverlayScrollbars {
@@ -14,12 +15,13 @@ export interface OverlayScrollbars {
   options(newOptions?: PartialOptions<OSOptions>): OSOptions;
 
   update(force?: boolean): void;
+  destroy(): void;
 
   state(): any;
 }
 
 export const OverlayScrollbars: OverlayScrollbarsStatic = (
-  target: OSTarget | OSTargetObject,
+  target: OSTarget | OSInitializationObject,
   options?: PartialOptions<OSOptions>,
   extensions?: any
 ): OverlayScrollbars => {
@@ -30,7 +32,9 @@ export const OverlayScrollbars: OverlayScrollbarsStatic = (
     validateOptions(options || ({} as PartialOptions<OSOptions>), optionsTemplate, null, true)._validated
   );
   const structureSetup: StructureSetup = createStructureSetup(target);
-  const lifecycleHub = createLifecycleHub(currentOptions, structureSetup);
+  const scrollbarsSetup: ScrollbarsSetup = createScrollbarsSetup(target, structureSetup);
+  const lifecycleHub = createLifecycleHub(currentOptions, structureSetup, scrollbarsSetup);
+
   const instance: OverlayScrollbars = {
     options(newOptions?: PartialOptions<OSOptions>) {
       if (newOptions) {
@@ -47,6 +51,7 @@ export const OverlayScrollbars: OverlayScrollbarsStatic = (
     update(force?: boolean) {
       lifecycleHub._update(null, force);
     },
+    destroy: () => lifecycleHub._destroy(),
   };
 
   instance.update(true);

packages/overlayscrollbars/src/setups/scrollbarsSetup.ts

@@ -0,0 +1,70 @@
+import { appendChildren, createDiv, removeElements, isFunction } from 'support';
+import {
+  classNameScrollbar,
+  classNameScrollbarHorizontal,
+  classNameScrollbarVertical,
+  classNameScrollbarTrack,
+  classNameScrollbarHandle,
+} from 'classnames';
+import { getEnvironment, ScrollbarsInitializationStrategy } from 'environment';
+import { OSTarget, ScrollbarsInitialization } from 'typings';
+import { StructureSetup } from 'setups/structureSetup';
+
+export interface ScrollbarStructure {
+  _scrollbar: HTMLElement;
+  _track: HTMLElement;
+  _handle: HTMLElement;
+}
+
+export interface ScrollbarsSetup {
+  _horizontalScrollbarStructure: ScrollbarStructure;
+  _verticalScrollbarStructure: ScrollbarStructure;
+  _destroy: () => void;
+}
+
+const generateScrollbarDOM = (scrollbarClassName: string): ScrollbarStructure => {
+  const scrollbar = createDiv(`${classNameScrollbar} ${scrollbarClassName}`);
+  const track = createDiv(classNameScrollbarTrack);
+  const handle = createDiv(classNameScrollbarHandle);
+
+  appendChildren(scrollbar, track);
+  appendChildren(track, handle);
+
+  return {
+    _scrollbar: scrollbar,
+    _track: track,
+    _handle: handle,
+  };
+};
+
+export const createScrollbarsSetup = (target: OSTarget | ScrollbarsInitialization, structureSetup: StructureSetup): ScrollbarsSetup => {
+  const { _getInitializationStrategy } = getEnvironment();
+  const { _scrollbarsSlot: environmentScrollbarSlot } = _getInitializationStrategy() as ScrollbarsInitializationStrategy;
+  const { _targetObj, _targetCtx } = structureSetup;
+  const { _target, _host, _viewport } = _targetObj;
+  const initializationScrollbarSlot = !_targetCtx._targetIsElm && (target as ScrollbarsInitialization).scrollbarsSlot;
+  const initializationScrollbarSlotResult = isFunction(initializationScrollbarSlot)
+    ? initializationScrollbarSlot(_target, _host, _viewport)
+    : initializationScrollbarSlot;
+  const evaluatedScrollbarSlot =
+    initializationScrollbarSlotResult ||
+    (isFunction(environmentScrollbarSlot) ? environmentScrollbarSlot(_target, _host, _viewport) : environmentScrollbarSlot) ||
+    _host;
+
+  const horizontalScrollbarStructure = generateScrollbarDOM(classNameScrollbarHorizontal);
+  const verticalScrollbarStructure = generateScrollbarDOM(classNameScrollbarVertical);
+
+  const { _scrollbar: horizontalScrollbar } = horizontalScrollbarStructure;
+  const { _scrollbar: verticalScrollbar } = verticalScrollbarStructure;
+
+  appendChildren(evaluatedScrollbarSlot, horizontalScrollbar);
+  appendChildren(evaluatedScrollbarSlot, verticalScrollbar);
+
+  return {
+    _horizontalScrollbarStructure: horizontalScrollbarStructure,
+    _verticalScrollbarStructure: verticalScrollbarStructure,
+    _destroy() {
+      removeElements([horizontalScrollbar, verticalScrollbar]);
+    },
+  };
+};

packages/overlayscrollbars/src/setups/structureSetup.ts

@@ -7,7 +7,7 @@ import {
   insertAfter,
   addClass,
   parent,
-  isUndefined,
+  indexOf,
   removeElements,
   removeClass,
   push,
@@ -15,6 +15,8 @@ import {
   insertBefore,
   attr,
   isBoolean,
+  isFunction,
+  keys,
 } from 'support';
 import {
   classNameHost,
@@ -24,8 +26,13 @@ import {
   classNameContent,
   classNameViewportScrollbarStyling,
 } from 'classnames';
-import { getEnvironment } from 'environment';
-import { OSTarget, OSTargetObject, OSTargetElement } from 'typings';
+import {
+  getEnvironment,
+  StructureInitializationStaticElement,
+  StructureInitializationDynamicElement,
+  StructureInitializationStrategy,
+} from 'environment';
+import { OSTarget, OSTargetElement, StructureInitialization } from 'typings';
 
 export interface OSTargetContext {
   _isTextarea: boolean;
@@ -34,15 +41,16 @@ export interface OSTargetContext {
   _bodyElm: HTMLBodyElement;
   _windowElm: Window;
   _documentElm: HTMLDocument;
+  _targetIsElm: boolean;
 }
 
 export interface PreparedOSTargetObject {
   _target: OSTargetElement;
   _host: HTMLElement;
   _viewport: HTMLElement;
-  _padding: HTMLElement | false | null;
-  _content: HTMLElement | false | null;
-  _viewportArrange: HTMLStyleElement | false | null;
+  _padding: HTMLElement | false;
+  _content: HTMLElement | false;
+  _viewportArrange: HTMLStyleElement | false;
 }
 
 export interface StructureSetup {
@@ -51,60 +59,113 @@ export interface StructureSetup {
   _destroy: () => void;
 }
 
+let contentArrangeCounter = 0;
+
 const unwrap = (elm: HTMLElement | false | null | undefined) => {
   appendChildren(parent(elm), contents(elm));
   removeElements(elm);
 };
 
-let contentArrangeCounter = 0;
-const createUniqueViewportArrangeElement = (): HTMLStyleElement => {
-  const elm = document.createElement('style');
+const createUniqueViewportArrangeElement = (): HTMLStyleElement | false => {
+  const { _nativeScrollbarStyling, _nativeScrollbarIsOverlaid, _cssCustomProperties } = getEnvironment();
+  /* istanbul ignore next */
+  const create = !_cssCustomProperties && !_nativeScrollbarStyling && (_nativeScrollbarIsOverlaid.x || _nativeScrollbarIsOverlaid.y);
+  const result = create ? document.createElement('style') : false;
 
-  attr(elm, 'id', `${classNameViewportArrange}-${contentArrangeCounter}`);
-  contentArrangeCounter++;
-
-  return elm;
-};
-const evaluateCreationFromStrategy = (initializationValue: HTMLElement | boolean | undefined, strategy: boolean): HTMLElement | false | undefined => {
-  const isBooleanValue = isBoolean(initializationValue);
-  if (isBooleanValue || isUndefined(initializationValue)) {
-    return (isBooleanValue ? initializationValue : strategy) && undefined;
+  if (result) {
+    attr(result, 'id', `${classNameViewportArrange}-${contentArrangeCounter}`);
+    contentArrangeCounter++;
   }
-  return initializationValue as HTMLElement;
+
+  return result;
 };
 
-export const createStructureSetup = (target: OSTarget | OSTargetObject): StructureSetup => {
-  const { _getInitializationStrategy, _nativeScrollbarStyling, _nativeScrollbarIsOverlaid, _cssCustomProperties } = getEnvironment();
-  const { _padding: paddingNeeded, _content: contentNeeded } = _getInitializationStrategy();
+const staticCreationFromStrategy = (
+  target: OSTargetElement,
+  initializationValue: HTMLElement | undefined,
+  strategy: StructureInitializationStaticElement,
+  elementClass: string
+): HTMLElement => {
+  const result = initializationValue ? initializationValue : isFunction(strategy) ? strategy(target) : (strategy as null);
+  return result ? result : createDiv(elementClass);
+};
+
+const dynamicCreationFromStrategy = (
+  target: OSTargetElement,
+  initializationValue: HTMLElement | boolean | undefined,
+  strategy: StructureInitializationDynamicElement,
+  elementClass: string,
+  defaultValue: boolean
+): HTMLElement | false => {
+  const takeInitializationValue = isBoolean(initializationValue) || initializationValue;
+  const result = takeInitializationValue ? (initializationValue as boolean | HTMLElement) : isFunction(strategy) ? strategy(target) : strategy;
+
+  if (result === null) {
+    return defaultValue ? createDiv(elementClass) : false;
+  }
+
+  return result === true ? createDiv(elementClass) : result;
+};
+
+export const createStructureSetup = (target: OSTarget | StructureInitialization): StructureSetup => {
+  const { _getInitializationStrategy, _nativeScrollbarStyling } = getEnvironment();
+  const {
+    _host: hostInitializationStrategy,
+    _viewport: viewportInitializationStrategy,
+    _padding: paddingInitializationStrategy,
+    _content: contentInitializationStrategy,
+  } = _getInitializationStrategy() as StructureInitializationStrategy;
   const targetIsElm = isHTMLElement(target);
-  const osTargetObj: Partial<PreparedOSTargetObject> = targetIsElm
-    ? ({} as Partial<PreparedOSTargetObject>)
-    : {
-        _host: (target as OSTargetObject).host,
-        _target: (target as OSTargetObject).target,
-        _viewport: (target as OSTargetObject).viewport,
-        _padding: evaluateCreationFromStrategy((target as OSTargetObject).padding, paddingNeeded),
-        _content: evaluateCreationFromStrategy((target as OSTargetObject).content, contentNeeded),
-      };
-
-  if (targetIsElm) {
-    const viewport = createDiv(classNameViewport);
-    const padding = paddingNeeded && createDiv(classNamePadding);
-    const content = contentNeeded && createDiv(classNameContent);
-
-    osTargetObj._target = target as OSTargetElement;
-    osTargetObj._padding = padding;
-    osTargetObj._viewport = viewport;
-    osTargetObj._content = content;
-  }
-
-  let { _target, _padding, _viewport, _content } = osTargetObj;
+  const targetStructureInitialization = target as StructureInitialization;
+  const targetElement = targetIsElm ? (target as OSTargetElement) : targetStructureInitialization.target;
+  const isTextarea = is(targetElement, 'textarea');
+  const isBody = !isTextarea && is(targetElement, 'body');
+  const ownerDocument: HTMLDocument = targetElement!.ownerDocument;
+  const bodyElm = ownerDocument.body as HTMLBodyElement;
+  const wnd = ownerDocument.defaultView as Window;
+  const evaluatedTargetObj: PreparedOSTargetObject = {
+    _target: targetElement,
+    _host: isTextarea
+      ? staticCreationFromStrategy(targetElement, targetStructureInitialization.host, hostInitializationStrategy, classNameHost)
+      : (targetElement as HTMLElement),
+    _viewport: staticCreationFromStrategy(targetElement, targetStructureInitialization.viewport, viewportInitializationStrategy, classNameViewport),
+    _padding: dynamicCreationFromStrategy(
+      targetElement,
+      targetStructureInitialization.padding,
+      paddingInitializationStrategy,
+      classNamePadding,
+      !_nativeScrollbarStyling // default value for padding
+    ),
+    _content: dynamicCreationFromStrategy(
+      targetElement,
+      targetStructureInitialization.content,
+      contentInitializationStrategy,
+      classNameContent,
+      false // default value for content
+    ),
+    _viewportArrange: createUniqueViewportArrangeElement(),
+  };
+  const ctx: OSTargetContext = {
+    _windowElm: wnd,
+    _documentElm: ownerDocument,
+    _htmlElm: parent(bodyElm) as HTMLHtmlElement,
+    _bodyElm: bodyElm,
+    _isTextarea: isTextarea,
+    _isBody: isBody,
+    _targetIsElm: targetIsElm,
+  };
+  const generatedElements = keys(evaluatedTargetObj).reduce((arr, key: string) => {
+    const value = evaluatedTargetObj[key];
+    return push(arr, value && !parent(value) ? value : false);
+  }, [] as HTMLElement[]);
+  const elementIsGenerated = (elm: HTMLElement | false) => (elm ? indexOf(generatedElements, elm) > -1 : null);
+  const { _target, _host, _padding, _viewport, _content, _viewportArrange } = evaluatedTargetObj;
   const destroyFns: (() => any)[] = [];
-  const isTextarea = is(_target, 'textarea');
-  const isBody = !isTextarea && is(_target, 'body');
-  const _host = (isTextarea ? osTargetObj._host || createDiv() : _target) as HTMLElement;
-  const getTargetContents = (contentSlot: HTMLElement) => (isTextarea ? (_target as HTMLTextAreaElement) : contents(contentSlot as HTMLElement));
-  const isTextareaHostGenerated = isTextarea && _host !== osTargetObj._host;
+  const isTextareaHostGenerated = isTextarea && elementIsGenerated(_host);
+  const targetContents = isTextarea
+    ? _target
+    : contents([_content, _viewport, _padding, _host, _target].find((elm) => elementIsGenerated(elm) === false));
+  const contentSlot = _content || _viewport;
 
   // only insert host for textarea after target if it was generated
   if (isTextareaHostGenerated) {
@@ -116,88 +177,48 @@ export const createStructureSetup = (target: OSTarget | OSTargetObject): Structu
     });
   }
 
-  if (targetIsElm) {
-    const contentSlot = _content || _viewport;
-    appendChildren(contentSlot, getTargetContents(_target!));
-    appendChildren(_host, _padding);
-    appendChildren(_padding || _host, _viewport);
-    appendChildren(_viewport, _content);
-
-    push(destroyFns, () => {
-      appendChildren(_host, contents(contentSlot));
-      removeElements(_padding || _viewport);
-      removeClass(_host, classNameHost);
-    });
-  } else {
-    const contentContainingElm = _content || _viewport || _padding || _host;
-    const createPadding = isUndefined(_padding);
-    const createViewport = isUndefined(_viewport);
-    const createContent = isUndefined(_content);
-    const targetContents = getTargetContents(contentContainingElm);
-
-    _padding = osTargetObj._padding = createPadding ? createDiv() : _padding;
-    _viewport = osTargetObj._viewport = createViewport ? createDiv() : _viewport;
-    _content = osTargetObj._content = createContent ? createDiv() : _content;
-
-    appendChildren(_host, _padding);
-    appendChildren(_padding || _host, _viewport);
-    appendChildren(_viewport, _content);
-
-    const contentSlot = _content || _viewport;
-    appendChildren(contentSlot, targetContents);
-
-    push(destroyFns, () => {
-      if (createContent) {
-        unwrap(_content);
-      }
-      if (createViewport) {
-        unwrap(_viewport);
-      }
-      if (createPadding) {
-        unwrap(_padding);
-      }
-      removeClass(_host, classNameHost);
-      removeClass(_padding, classNamePadding);
-      removeClass(_viewport, classNameViewport);
-      removeClass(_content, classNameContent);
-    });
-  }
+  appendChildren(contentSlot, targetContents);
+  appendChildren(_host, _padding);
+  appendChildren(_padding || _host, _viewport);
+  appendChildren(_viewport, _content);
 
   addClass(_host, classNameHost);
   addClass(_padding, classNamePadding);
   addClass(_viewport, classNameViewport);
   addClass(_content, classNameContent);
 
-  const ownerDocument: HTMLDocument = _target!.ownerDocument;
-  const bodyElm = ownerDocument.body as HTMLBodyElement;
-  const wnd = ownerDocument.defaultView as Window;
-  const ctx: OSTargetContext = {
-    _windowElm: wnd,
-    _documentElm: ownerDocument,
-    _htmlElm: parent(bodyElm) as HTMLHtmlElement,
-    _bodyElm: bodyElm,
-    _isTextarea: isTextarea,
-    _isBody: isBody,
-  };
-  // @ts-ignore
-  const obj: PreparedOSTargetObject = {
-    ...osTargetObj,
-    _host,
-  };
+  push(destroyFns, () => {
+    if (targetIsElm) {
+      appendChildren(_host, contents(contentSlot));
+      removeElements(_padding || _viewport);
+      removeClass(_host, classNameHost);
+    } else {
+      if (elementIsGenerated(_content)) {
+        unwrap(_content);
+      }
+      if (elementIsGenerated(_viewport)) {
+        unwrap(_viewport);
+      }
+      if (elementIsGenerated(_padding)) {
+        unwrap(_padding);
+      }
+      removeClass(_host, classNameHost);
+      removeClass(_padding, classNamePadding);
+      removeClass(_viewport, classNameViewport);
+      removeClass(_content, classNameContent);
+    }
+  });
 
   if (_nativeScrollbarStyling) {
     push(destroyFns, removeClass.bind(0, _viewport, classNameViewportScrollbarStyling));
-  } else if (!_cssCustomProperties && (_nativeScrollbarIsOverlaid.x || _nativeScrollbarIsOverlaid.y)) {
-    const viewportArrangeElm = createUniqueViewportArrangeElement();
-
-    insertBefore(_viewport, viewportArrangeElm);
-    push(destroyFns, removeElements.bind(0, viewportArrangeElm));
-
-    obj._viewportArrange = viewportArrangeElm;
+  }
+  if (_viewportArrange) {
+    insertBefore(_viewport, _viewportArrange);
+    push(destroyFns, removeElements.bind(0, _viewportArrange));
   }
 
   return {
-    _targetObj: obj,
+    _targetObj: evaluatedTargetObj,
     _targetCtx: ctx,
     _destroy: () => {
       runEach(destroyFns);

packages/overlayscrollbars/src/styles/overlayscrollbars.scss

@@ -1,5 +1,6 @@
 @import './sizeobserver.scss';
 @import './trinsicobserver.scss';
+@import './scrollbars.scss';
 
 .os-environment {
   --os-custom-prop: -1;

packages/overlayscrollbars/src/support/utils/types.ts

@@ -32,7 +32,7 @@ export function isBoolean(obj: any): obj is boolean {
   return typeof obj === 'boolean';
 }
 
-export function isFunction(obj: any): obj is (...args: Array<unknown>) => unknown {
+export function isFunction(obj: any): obj is (...args: any[]) => any {
   return typeof obj === 'function';
 }
 

packages/overlayscrollbars/src/typings.ts

@@ -1,3 +1,5 @@
+
+
 export type PlainObject<T = any> = { [name: string]: T };
 
 export type StyleObject<CustomCssProps = ''> = {
@@ -10,6 +12,19 @@ export type InternalVersionOf<T> = {
 
 export type OSTargetElement = HTMLElement | HTMLTextAreaElement;
 
+/**
+ * Static elements MUST be present.
+ */
+type StructureInitializationStaticElement = HTMLElement;
+
+/**
+ * Dynamic element CAN be present.
+ * If its a element the element will be handled as the repsective element.
+ * True means that the respective dynamic element is forced to be generated.
+ * False means that the respective dynamic element is forced NOT to be generated.
+ */
+type StructureInitializationDynamicElement = HTMLElement | boolean;
+
 /**
  * Object for special initialization.
  * 
@@ -18,19 +33,29 @@ export type OSTargetElement = HTMLElement | HTMLTextAreaElement;
  * If element is provided, the provided element takes all its responsibilities. 
  * DOM hierarchy isn't checked in this case, its assumed that hieararchy is correct in such a case.
  * 
- * Undefined means that the plugin decides whether the respective element needs to be added or can be savely omitted.
- * True means that even if the plugin would decide to not generate the element, the element is still generated.
- * False means that event if the plugin would decide to generate the element, the element won't be generated.
+ * Undefined means that the environment initialization strategy for the respective element is used.
  */
-export interface OSTargetObject {
+ export interface StructureInitialization {
   target: OSTargetElement;
-  host?: HTMLElement;
-  padding?: HTMLElement | boolean;
-  viewport?: HTMLElement;
-  content?: HTMLElement | boolean;
+  host?: StructureInitializationStaticElement; // only relevant for textarea
+  viewport?: StructureInitializationStaticElement;
+  padding?: StructureInitializationDynamicElement;
+  content?: StructureInitializationDynamicElement;
 }
 
-export type OSTarget = OSTargetElement | OSTargetObject;
+/**
+ * Object for special initialization.
+ * 
+ * scrollbarsSlot is the element to which the scrollbars are applied to. If null or undefined the plugin decides by itself whats the scrollbars slot.
+ */
+export interface ScrollbarsInitialization {
+  scrollbarsSlot?: null | HTMLElement | ((target: OSTargetElement, host: HTMLElement, viewport: HTMLElement) => null | HTMLElement);
+}
+
+export interface OSInitializationObject extends StructureInitialization, ScrollbarsInitialization {
+}
+
+export type OSTarget = OSTargetElement | OSInitializationObject;
 
 /*
 export namespace OverlayScrollbars {

yarn.lock

@@ -8790,10 +8790,10 @@ typescript@^3.9.3:
   resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.9.7.tgz#98d600a5ebdc38f40cb277522f12dc800e9e25fa"
   integrity sha512-BLbiRkiBzAwsjut4x/dsibSTB6yWpwT5qWmC2OfuCg3GgVQCSgMs4vEctYPhsaGtd0AeuuHMkjZ2h2WG8MSzRw==
 
-typescript@^4.2.4:
-  version "4.2.4"
-  resolved "https://registry.yarnpkg.com/typescript/-/typescript-4.2.4.tgz#8610b59747de028fda898a8aef0e103f156d0961"
-  integrity sha512-V+evlYHZnQkaz8TRBuxTA92yZBPotr5H+WhQ7bD3hZUndx5tGOa1fuCgeSjxAzM1RiN5IzvadIXTVefuuwZCRg==
+typescript@^4.3.2:
+  version "4.3.2"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-4.3.2.tgz#399ab18aac45802d6f2498de5054fcbbe716a805"
+  integrity sha512-zZ4hShnmnoVnAHpVHWpTcxdv7dWP60S2FsydQLV8V5PbS3FifjWFFRiHSWpDJahly88PRyV5teTSLoq4eG7mKw==
 
 unicode-canonical-property-names-ecmascript@^1.0.4:
   version "1.0.4"