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CoreWebView2Frame Class

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CoreWebView2Frame provides direct access to the iframes information and handling. You can get a CoreWebView2Frame by handling the CoreWebView2.FrameCreated event.

Summary

Members Description
FrameId The unique identifier of the current frame. It's the same kind of ID as with the CoreWebView2.FrameId and CoreWebView2FrameInfo.FrameId.
Name The value of iframe's window.name property. The default value equals to iframe html tag declaring it.
ExecuteScriptAsync Runs JavaScript code from the javaScript parameter in the current frame.
IsDestroyed Check whether a frame is destroyed. Returns true during the CoreWebView2Frame.Destroyed event.
PostSharedBufferToScript Share a shared buffer object with script of the iframe in the WebView.
PostWebMessageAsJson Posts the specified webMessageAsJson to the current frame.
PostWebMessageAsString Posts a message that is a simple string rather than a JSON string representation of a JavaScript object.
RemoveHostObjectFromScript Remove the host object specified by the name so that it is no longer accessible from JavaScript code in the iframe.
ContentLoading ContentLoading is raised before any content is loaded, including scripts added with CoreWebView2.AddScriptToExecuteOnDocumentCreatedAsync. ContentLoading is not raised if a same page navigation occurs.
DOMContentLoaded DOMContentLoaded is raised when the initial HTML document has been parsed.
Destroyed Destroyed event is raised when the iframe corresponding to this CoreWebView2Frame object is removed or the document containing that iframe is destroyed.
NameChanged NameChanged is raised when the iframe changes its window.name property.
NavigationCompleted NavigationCompleted is raised when the current frame has completely loaded (body.onload has been raised) or loading stopped with error.
NavigationStarting NavigationStarting is raised when the current frame is requesting permission to navigate to a different URI.
PermissionRequested PermissionRequested is raised when content in an iframe or any of its descendant iframes requests permission to access some privileged resources.
ScreenCaptureStarting ScreenCaptureStarting event is raised when the Screen Capture API is requested by the user using getDisplayMedia().
WebMessageReceived WebMessageReceived is raised when the CoreWebView2Settings.IsWebMessageEnabled setting is set and the iframe runs window.chrome.webview.postMessage.

Properties

FrameId

readonly uint32_t FrameId

The unique identifier of the current frame. It's the same kind of ID as with the CoreWebView2.FrameId and CoreWebView2FrameInfo.FrameId.

Name

readonly string Name

The value of iframe's window.name property. The default value equals to iframe html tag declaring it.

Methods

ExecuteScriptAsync

IAsyncOperation<string> ExecuteScriptAsync(string javaScript)

Runs JavaScript code from the javaScript parameter in the current frame. A function that has no explicit return value returns undefined. If the script that was run throws an unhandled exception, then the result is also null. This method is applied asynchronously. If the method is run before CoreWebView2Frame.ContentLoading, the script will not be executed and the JSON null will be returned. This operation works even if CoreWebView2Settings.IsScriptEnabled is set to false.

IsDestroyed

int IsDestroyed()

Check whether a frame is destroyed. Returns true during the CoreWebView2Frame.Destroyed event.

PostSharedBufferToScript

void PostSharedBufferToScript(CoreWebView2SharedBuffer sharedBuffer, CoreWebView2SharedBufferAccess access, string additionalDataAsJson)

Share a shared buffer object with script of the iframe in the WebView. The script will receive a sharedbufferreceived event from chrome.webview. The event arg for that event will have the following methods and properties.

Property Description
getBuffer() A method that returns an ArrayBuffer object with the backing content from the shared buffer.
additionalData An object as the result of parsing additionalDataAsJson as JSON string. This property will be undefined if additionalDataAsJson is nullptr or empty string.
source With a value set as chrome.webview object.

If access is CoreWebView2SharedBufferAccess.ReadOnly, the script will only have read access to the buffer. If the script tries to modify the content in a read only buffer, it will cause an access violation in WebView renderer process and crash the renderer process.

If the shared buffer is already closed, the API throws COMException with error code of RO_E_CLOSED. The script code should call chrome.webview.releaseBuffer with the shared buffer as the parameter to release underlying resources as soon as it does not need access to the shared buffer any more.

The application can post the same shared buffer object to multiple web pages or iframes, or post to the same web page or iframe multiple times. Each PostSharedBufferToScript will create a separate ArrayBuffer object with its own view of the memory and is separately released. The underlying shared memory will be released when all the views are released.

Sharing a buffer to script has security risk. You should only share buffer with trusted site. If a buffer is shared to a untrusted site, possible sensitive information could be leaked. If a buffer is shared as modifiable by the script and the script modifies it in an unexpected way, it could result in corrupted data that might even crash the application.

The example code shows how to send data to script for one time read only consumption.

PostWebMessageAsJson

void PostWebMessageAsJson(string webMessageAsJson)

Posts the specified webMessageAsJson to the current frame. The event args is an instance of MessageEvent. The CoreWebView2Settings.IsWebMessageEnabled setting must be true or the message will not be sent. The event arg's data property of the event arg is the webMessageAsJson string parameter parsed as a JSON string into a JavaScript object. The event arg's source property of the event arg is a reference to the window.chrome.webview object. For information about sending messages from the iframe to the host, navigate to CoreWebView2Frame.WebMessageReceived. The message is sent asynchronously. If a navigation occurs before the message is posted to the iframe, the message is not be sent. Runs the message event of the window.chrome.webview of the iframe. JavaScript in that document may subscribe and unsubscribe to the event using the following code:

window.chrome.webview.addEventListener('message', handler)
window.chrome.webview.removeEventListener('message', handler)

PostWebMessageAsString

void PostWebMessageAsString(string webMessageAsString)

Posts a message that is a simple string rather than a JSON string representation of a JavaScript object. This behaves in exactly the same manner as CoreWebView2Frame.PostWebMessageAsJson, but the data property of the event arg of the window.chrome.webview message is a string with the same value as webMessageAsString. Use this instead of CoreWebView2Frame.PostWebMessageAsJson if you want to communicate using simple strings rather than JSON objects.

RemoveHostObjectFromScript

void RemoveHostObjectFromScript(string name)

Remove the host object specified by the name so that it is no longer accessible from JavaScript code in the iframe. While new access attempts are denied, if the object is already obtained by JavaScript code in the iframe, the JavaScript code continues to have access to that object. Calling this method for a name that is already removed or was never added fails. If the iframe is destroyed this method will return fail also.

Events

ContentLoading

ContentLoading is raised before any content is loaded, including scripts added with CoreWebView2.AddScriptToExecuteOnDocumentCreatedAsync. ContentLoading is not raised if a same page navigation occurs. This operation follows the CoreWebView2Frame.NavigationStarting event and precedes the CoreWebView2Frame.DOMContentLoaded and CoreWebView2Frame.NavigationCompleted events.

Type: TypedEventHandler<CoreWebView2Frame, CoreWebView2ContentLoadingEventArgs>

DOMContentLoaded

DOMContentLoaded is raised when the initial HTML document has been parsed. This aligns with the the document's DOMContentLoaded event in HTML.

Type: TypedEventHandler<CoreWebView2Frame, CoreWebView2DOMContentLoadedEventArgs>

Destroyed

Destroyed event is raised when the iframe corresponding to this CoreWebView2Frame object is removed or the document containing that iframe is destroyed.

Type: TypedEventHandler<CoreWebView2Frame, Object>

NameChanged

NameChanged is raised when the iframe changes its window.name property.

Type: TypedEventHandler<CoreWebView2Frame, Object>

NavigationCompleted is raised when the current frame has completely loaded (body.onload has been raised) or loading stopped with error.

Type: TypedEventHandler<CoreWebView2Frame, CoreWebView2NavigationCompletedEventArgs>

NavigationStarting is raised when the current frame is requesting permission to navigate to a different URI. A frame navigation will raise a CoreWebView2Frame.NavigationStarting event and a CoreWebView2.FrameNavigationStarting event. All of the CoreWebView2.FrameNavigationStarting event handlers will be run before the CoreWebView2Frame.NavigationStarting event handlers. All of the event handlers share a common CoreWebView2NavigationStartingEventArgs object. Whichever event handler is last to change the CoreWebView2NavigationStartingEventArgs.Cancel property will decide if the frame navigation will be cancelled. Redirects raise this event as well, and the navigation id is the same as the original one. You may block corresponding navigations until the event handler returns.

Type: TypedEventHandler<CoreWebView2Frame, CoreWebView2NavigationStartingEventArgs>

PermissionRequested

PermissionRequested is raised when content in an iframe or any of its descendant iframes requests permission to access some privileged resources. This relates to the PermissionRequested event on the CoreWebView2. Both these events will be raised in the case of an iframe requesting permission. The CoreWebView2Frame's event handlers will be invoked before the event handlers on the CoreWebView2. If the Handled property of the PermissionRequestedEventArgs is set to TRUE within the CoreWebView2Frame event handler, then the event will not be raised on the CoreWebView2, and it's event handlers will not be invoked. In the case of nested iframes, the PermissionRequested event will be raised from the top level iframe. If a deferral is not taken on the event args, the subsequent scripts are blocked until the event handler returns. If a deferral is taken, the scripts are blocked until the deferral is completed.

Type: TypedEventHandler<CoreWebView2Frame, CoreWebView2PermissionRequestedEventArgs>

ScreenCaptureStarting

ScreenCaptureStarting event is raised when the Screen Capture API is requested by the user using getDisplayMedia(). This relates to the ScreenCaptureStarting event on the CoreWebView2. Both these events will be raised in the case of an iframe requesting screen capture. The CoreWebView2Frame's event handlers will be invoked before the event handlers on the CoreWebView2. If the Handled property of the ScreenCaptureStartingEventArgs is set to TRUE within the CoreWebView2Frame event handler, then the event will not be raised on the CoreWebView2, and it's event handlers will not be invoked. In the case of nested iframes, the ScreenCaptureStarting event will be raised from the top level iframe. If a deferral is not taken on the event args, the subsequent scripts are blocked until the event handler returns. If a deferral is taken, the scripts are blocked until the deferral is completed.

Type: TypedEventHandler<CoreWebView2Frame, CoreWebView2ScreenCaptureStartingEventArgs>

WebMessageReceived

WebMessageReceived is raised when the CoreWebView2Settings.IsWebMessageEnabled setting is set and the iframe runs window.chrome.webview.postMessage. The postMessage function is void postMessage(object) where object is any object supported by JSON conversion. When postMessage is called, the handler's Invoke method will be called with the object parameter postMessage converted to a JSON string.

Type: TypedEventHandler<CoreWebView2Frame, CoreWebView2WebMessageReceivedEventArgs>

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