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Improve JS-side event handling code. Fixes #433
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4 changes: 2 additions & 2 deletions
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src/Microsoft.AspNetCore.Blazor.Browser.JS/src/Interop/InternalRegisteredFunction.ts
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,12 +1,12 @@ | ||
| import { invokeWithJsonMarshalling } from './InvokeWithJsonMarshalling'; | ||
| import { attachComponentToElement, renderBatch } from '../Rendering/Renderer'; | ||
| import { attachRootComponentToElement, renderBatch } from '../Rendering/Renderer'; | ||
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| /** | ||
| * The definitive list of internal functions invokable from .NET code. | ||
| * These function names are treated as 'reserved' and cannot be passed to registerFunction. | ||
| */ | ||
| export const internalRegisteredFunctions = { | ||
| attachComponentToElement, | ||
| attachRootComponentToElement, | ||
| invokeWithJsonMarshalling, | ||
| renderBatch, | ||
| }; |
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156 changes: 156 additions & 0 deletions
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src/Microsoft.AspNetCore.Blazor.Browser.JS/src/Rendering/EventDelegator.ts
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,156 @@ | ||
| import { EventForDotNet, UIEventArgs } from './EventForDotNet'; | ||
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| export interface OnEventCallback { | ||
| (event: Event, componentId: number, eventHandlerId: number, eventArgs: EventForDotNet<UIEventArgs>): void; | ||
| } | ||
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| // Responsible for adding/removing the eventInfo on an expando property on DOM elements, and | ||
| // calling an EventInfoStore that deals with registering/unregistering the underlying delegated | ||
| // event listeners as required (and also maps actual events back to the given callback). | ||
| export class EventDelegator { | ||
| private static nextEventDelegatorId = 0; | ||
| private eventsCollectionKey: string; | ||
| private eventInfoStore: EventInfoStore; | ||
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| constructor(private onEvent: OnEventCallback) { | ||
| const eventDelegatorId = ++EventDelegator.nextEventDelegatorId; | ||
| this.eventsCollectionKey = `_blazorEvents_${eventDelegatorId}`; | ||
| this.eventInfoStore = new EventInfoStore(this.onGlobalEvent.bind(this)); | ||
| } | ||
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| public setListener(element: Element, eventName: string, componentId: number, eventHandlerId: number) { | ||
| // Ensure we have a place to store event info for this element | ||
| let infoForElement: EventHandlerInfosForElement = element[this.eventsCollectionKey]; | ||
| if (!infoForElement) { | ||
| infoForElement = element[this.eventsCollectionKey] = {}; | ||
| } | ||
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| if (infoForElement.hasOwnProperty(eventName)) { | ||
| // We can cheaply update the info on the existing object and don't need any other housekeeping | ||
| const oldInfo = infoForElement[eventName]; | ||
| this.eventInfoStore.update(oldInfo.eventHandlerId, eventHandlerId); | ||
| } else { | ||
| // Go through the whole flow which might involve registering a new global handler | ||
| const newInfo = { element, eventName, componentId, eventHandlerId }; | ||
| this.eventInfoStore.add(newInfo); | ||
| infoForElement[eventName] = newInfo; | ||
| } | ||
| } | ||
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| public removeListener(eventHandlerId: number) { | ||
| // This method gets called whenever the .NET-side code reports that a certain event handler | ||
| // has been disposed. However we will already have disposed the info about that handler if | ||
| // the eventHandlerId for the (element,eventName) pair was replaced during diff application. | ||
| const info = this.eventInfoStore.remove(eventHandlerId); | ||
| if (info) { | ||
| // Looks like this event handler wasn't already disposed | ||
| // Remove the associated data from the DOM element | ||
| const element = info.element; | ||
| if (element.hasOwnProperty(this.eventsCollectionKey)) { | ||
| const elementEventInfos: EventHandlerInfosForElement = element[this.eventsCollectionKey]; | ||
| delete elementEventInfos[info.eventName]; | ||
| if (Object.getOwnPropertyNames(elementEventInfos).length === 0) { | ||
| delete element[this.eventsCollectionKey]; | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| private onGlobalEvent(evt: Event) { | ||
| if (!(evt.target instanceof Element)) { | ||
| return; | ||
| } | ||
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| // Scan up the element hierarchy, looking for any matching registered event handlers | ||
| let candidateElement = evt.target as Element | null; | ||
| let eventArgs: EventForDotNet<UIEventArgs> | null = null; // Populate lazily | ||
| while (candidateElement) { | ||
| if (candidateElement.hasOwnProperty(this.eventsCollectionKey)) { | ||
| const handlerInfos = candidateElement[this.eventsCollectionKey]; | ||
| if (handlerInfos.hasOwnProperty(evt.type)) { | ||
| // We are going to raise an event for this element, so prepare info needed by the .NET code | ||
| if (!eventArgs) { | ||
| eventArgs = EventForDotNet.fromDOMEvent(evt); | ||
| } | ||
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| const handlerInfo = handlerInfos[evt.type]; | ||
| this.onEvent(evt, handlerInfo.componentId, handlerInfo.eventHandlerId, eventArgs); | ||
| } | ||
| } | ||
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| candidateElement = candidateElement.parentElement; | ||
| } | ||
| } | ||
| } | ||
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| // Responsible for adding and removing the global listener when the number of listeners | ||
| // for a given event name changes between zero and nonzero | ||
| class EventInfoStore { | ||
| private infosByEventHandlerId: { [eventHandlerId: number]: EventHandlerInfo } = {}; | ||
| private countByEventName: { [eventName: string]: number } = {}; | ||
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| constructor(private globalListener: EventListener) { | ||
| } | ||
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| public add(info: EventHandlerInfo) { | ||
| if (this.infosByEventHandlerId[info.eventHandlerId]) { | ||
| // Should never happen, but we want to know if it does | ||
| throw new Error(`Event ${info.eventHandlerId} is already tracked`); | ||
| } | ||
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| this.infosByEventHandlerId[info.eventHandlerId] = info; | ||
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| const eventName = info.eventName; | ||
| if (this.countByEventName.hasOwnProperty(eventName)) { | ||
| this.countByEventName[eventName]++; | ||
| } else { | ||
| this.countByEventName[eventName] = 1; | ||
| document.addEventListener(eventName, this.globalListener); | ||
| } | ||
| } | ||
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| public update(oldEventHandlerId: number, newEventHandlerId: number) { | ||
| if (this.infosByEventHandlerId.hasOwnProperty(newEventHandlerId)) { | ||
| // Should never happen, but we want to know if it does | ||
| throw new Error(`Event ${newEventHandlerId} is already tracked`); | ||
| } | ||
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| // Since we're just updating the event handler ID, there's no need to update the global counts | ||
| const info = this.infosByEventHandlerId[oldEventHandlerId]; | ||
| delete this.infosByEventHandlerId[oldEventHandlerId]; | ||
| info.eventHandlerId = newEventHandlerId; | ||
| this.infosByEventHandlerId[newEventHandlerId] = info; | ||
| } | ||
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| public remove(eventHandlerId: number): EventHandlerInfo { | ||
| const info = this.infosByEventHandlerId[eventHandlerId]; | ||
| if (info) { | ||
| delete this.infosByEventHandlerId[eventHandlerId]; | ||
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| const eventName = info.eventName; | ||
| if (--this.countByEventName[eventName] === 0) { | ||
| delete this.countByEventName[eventName]; | ||
| document.removeEventListener(eventName, this.globalListener); | ||
| } | ||
| } | ||
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| return info; | ||
| } | ||
| } | ||
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| interface EventHandlerInfosForElement { | ||
| // Although we *could* track multiple event handlers per (element, eventName) pair | ||
| // (since they have distinct eventHandlerId values), there's no point doing so because | ||
| // our programming model is that you declare event handlers as attributes. An element | ||
| // can only have one attribute with a given name, hence only one event handler with | ||
| // that name at any one time. | ||
| // So to keep things simple, only track one EventHandlerInfo per (element, eventName) | ||
| [eventName: string]: EventHandlerInfo | ||
| } | ||
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| interface EventHandlerInfo { | ||
| element: Element; | ||
| eventName: string; | ||
| componentId: number; | ||
| eventHandlerId: number; | ||
| } |
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