SysWin WebView2 Events

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WebView2 event handlers

Implements the WebView2 callback interfaces as classes to extend, one per event or result.

Implements the WebView2 callback interfaces as classes to extend, one per event or result.

WebView2 reports events (a navigation finished, the title changed, the page posted a message) and the results of asynchronous calls (a script ran, the environment is ready) by calling back into the program through small COM interfaces. Each class here implements one of them. In every class Invoke does nothing and returns S_OK, so an object of the class itself receives the event and ignores it.

Handling an event. Extend the class and declare Invoke again with exactly the same parameter types; it is virtual, so yours is the one WebView2 calls. Create the object with new and pass it, cast to any ptr, to the CWebView2 method that attaches it, such as AddDocumentTitleChanged, or to the interface method that takes it. The classes extend OBJECT, not the interface types, which is why the cast is needed; their virtual methods are laid out as the interface expects. An Invoke declared with other parameter types is a different method, and WebView2 keeps calling the one that does nothing.

Lifetime. The objects are reference counted the COM way, in the public field refCount as ULONG. It starts at 0 (at 1 in CWebView2ExecuteScriptWithResultCompletedHandler). WebView2 takes a reference when the handler is attached or the call is made, and gives it back when the handler is removed, once a one-time result has been delivered, or when the web view closes; Release deletes the object when the count reaches 0. So never dim one on the stack and never delete one that WebView2 has accepted. If attaching fails, nothing holds the object: delete it yourself.

In Invoke. Invoke runs on the thread that created the web view, while it dispatches messages: in DoEvents or in IsReady. sender and args are borrowed for the call; call AddRef on one to keep it longer. A string read from them is the handler's to free with CoTaskMemFree. args has methods of its own (get_uri, put_Cancel …), listed with each class and on WebView2 interfaces and types.

Removing a handler. The Add methods fill in an EventRegistrationToken. Keep it to detach the handler later with the matching Remove method; WebView2 then gives back its reference.

Importing

#import "sys/win"
#import "sys/win/webview2"
using win, webview2

Example

A browser window whose caption follows the page title and says when a navigation fails. Like every WebView2 program it needs WebView2Loader.dll beside the executable; the WebView2 examples in the toolchain's examples/win64/ folder come with one.

#import "sys/win"
#import "sys/win/gui"
#import "sys/win/webview2"
using win, gui, webview2

declare function WndProc( byval hwnd as HWND, byval uMsg as UINT, byval wParam as WPARAM, byval lParam as LPARAM ) as LRESULT

' // Puts the page title in the caption
type TitleHandler extends CWebView2DocumentTitleChangedEventHandler
    declare constructor( byval hWin as HWND )
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as IUnknown ptr ) as HRESULT
    m_hWin as HWND
end type

constructor TitleHandler( byval hWin as HWND )
    m_hWin = hWin
end constructor

function TitleHandler.Invoke( byval sender as ICoreWebView2 ptr, byval args as IUnknown ptr ) as HRESULT
    dim pwszTitle as LPWSTR
    if sender->get_DocumentTitle( @pwszTitle ) = S_OK then
        SetWindowTextW( m_hWin, pwszTitle )
        CoTaskMemFree( pwszTitle )
    end if
    return S_OK
end function

' // Reports a failed navigation in the caption
type NavHandler extends CWebView2NavigationCompletedEventHandler
    declare constructor( byval hWin as HWND )
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2NavigationCompletedEventArgs ptr ) as HRESULT
    m_hWin as HWND
end type

constructor NavHandler( byval hWin as HWND )
    m_hWin = hWin
end constructor

function NavHandler.Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2NavigationCompletedEventArgs ptr ) as HRESULT
    dim bSuccess as LONG, nStatus as COREWEBVIEW2_WEB_ERROR_STATUS
    args->get_IsSuccess( @bSuccess )
    args->get_WebErrorStatus( @nStatus )
    if bSuccess = 0 then SetWindowText( m_hWin, "Navigation failed, status " & nStatus )
    return S_OK
end function

function main() as long
    SetProcessDpiAwareness( PROCESS_SYSTEM_DPI_AWARE )
    dim pWindow as CWindow = "WebView2Events"
    dim hWin as HWND = pWindow.Create( NULL, "WebView2 events", @WndProc )
    pWindow.SetClientSize( 900, 600 )
    pWindow.Center()
    dim ustrFolder as ustring = GetTempPath() & "tkWebView2"
    dim pWebView2 as CWebView2 = CWebView2( hWin, ustrFolder )
    if pWebView2.IsReady( 10000 ) then
        dim as EventRegistrationToken tokTitle, tokNav
        dim pTitle as TitleHandler ptr = new TitleHandler( hWin )
        if pWebView2.AddDocumentTitleChanged( cast( any ptr, pTitle ), @tokTitle ) <> S_OK then delete pTitle
        dim pNav as NavHandler ptr = new NavHandler( hWin )
        if pWebView2.AddNavigationCompleted( cast( any ptr, pNav ), @tokNav ) <> S_OK then delete pNav
        pWebView2.Navigate( "https://learn.microsoft.com/" )
    end if
    return pWindow.DoEvents( SW_NORMAL )
end function

function WndProc( byval hwnd as HWND, byval uMsg as UINT, byval wParam as WPARAM, byval lParam as LPARAM ) as LRESULT
    select case uMsg
        case WM_SIZE
            dim pWebView2 as CWebView2 ptr = CWebView2Ptr( hwnd )
            if pWebView2 then
                dim rc as RECT
                GetClientRect( hwnd, @rc )
                pWebView2->SetBounds( rc )
            end if
            return 0
        case WM_DESTROY
            PostQuitMessage( 0 )
            return 0
    end select
    return DefWindowProcW( hwnd, uMsg, wParam, lParam )
end function

end main()

The handlers are never deleted by the program: WebView2 releases them when the web view closes, as main ends, and they delete themselves.

Members

Every class has the same QueryInterface, AddRef, Release, a Constructor, Destructor entry and an Invoke that does nothing and returns S_OK. What Invoke receives:

Class	Implements	Invoke receives
CWebView2CreateCoreWebView2EnvironmentCompletedHandler	ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandler	the new environment
CWebView2CreateCoreWebView2ControllerCompletedHandler	ICoreWebView2CreateCoreWebView2ControllerCompletedHandler	the new controller
CWebView2NavigationStartingdEventHandler	ICoreWebView2NavigationStartingEventHandler	the start of a navigation
CWebView2NavigationCompletedEventHandler	ICoreWebView2NavigationCompletedEventHandler	the end of a navigation
CWebView2ContentLoadingEventHandler	ICoreWebView2ContentLoadingEventHandler	the start of loading of a new document
CWebView2SourceChangedEventHandler	ICoreWebView2SourceChangedEventHandler	a change of the address
CWebView2HistoryChangedEventHandler	ICoreWebView2HistoryChangedEventHandler	a change of the back and forward history
CWebView2ScriptDialogOpeningEventHandler	ICoreWebView2ScriptDialogOpeningEventHandler	a JavaScript alert, confirm, prompt or beforeunload dialog
CWebView2PermissionRequestedEventHandler	ICoreWebView2PermissionRequestedEventHandler	a request for a permission
CWebView2ProcessFailedEventHandler	ICoreWebView2ProcessFailedEventHandler	the failure of a browser process
CWebView2WebMessageReceivedEventHandler	ICoreWebView2WebMessageReceivedEventHandler	a message posted by the page
CWebView2NewWindowRequestedEventHandler	ICoreWebView2NewWindowRequestedEventHandler	a request to open a new window
CWebView2DocumentTitleChangedEventHandler	ICoreWebView2DocumentTitleChangedEventHandler	a change of the page title
CWebView2ContainsFullScreenElementChangedEventHandler	ICoreWebView2ContainsFullScreenElementChangedEventHandler	an element entering or leaving full screen
CWebView2WebResourceRequestedEventHandler	ICoreWebView2WebResourceRequestedEventHandler	a request for a resource that matches a filter
CWebView2WindowCloseRequestedEventHandler	ICoreWebView2WindowCloseRequestedEventHandler	a request from the page to close the window
CWebView2ExecuteScriptCompletedHandler	ICoreWebView2ExecuteScriptCompletedHandler	the result of a script
CWebView2AddScriptToExecuteOnDocumentCreatedCompleteHandler	ICoreWebView2AddScriptToExecuteOnDocumentCreatedCompletedHandler	the id of a script added to every document
CWebView2AddCapturePreviewCompletedHandler	ICoreWebView2CapturePreviewCompletedHandler	the end of a screenshot of the page
CWebView2DevToolsProtocolEventReceivedEventHandler	ICoreWebView2DevToolsProtocolEventReceivedEventHandler	a DevTools Protocol event
CWebView2ZoomFactorChangedEventHandler	ICoreWebView2ZoomFactorChangedEventHandler	a change of the zoom factor
CWebView2MoveFocusRequestedEventHandler	ICoreWebView2MoveFocusRequestedEventHandler	a request to move the focus out of the web view
CWebView2FocusChangedEventHandler	ICoreWebView2FocusChangedEventHandler	the web view gaining or losing the focus
CWebView2AcceleratorKeyPressedEventHandler	ICoreWebView2AcceleratorKeyPressedEventHandler	a shortcut key pressed in the web view
CWebView2NewBrowserVersionAvailableEventHandler	ICoreWebView2NewBrowserVersionAvailableEventHandler	the installation of a newer WebView2 runtime
CWebView2CallDevToolsProtocolMethodCompletedHandler	ICoreWebView2CallDevToolsProtocolMethodCompletedHandler	the result of a DevTools Protocol method
CWebView2ExecuteScriptWithResultCompletedHandler	ICoreWebView2ExecuteScriptWithResultCompletedHandler	the result of a script, with any exception

Common members

QueryInterface, AddRef, Release

virtual function QueryInterface( byval riid as REFIID, byval ppvObject as LPVOID ptr ) as HRESULT
virtual function AddRef() as ULONG
virtual function Release() as ULONG

The IUnknown methods, the same in all 27 classes. WebView2 calls them; a program rarely does.

• QueryInterface returns S_OK whatever interface is asked for, and writes nothing to ppvObject. WebView2 does not call it on a handler.
• AddRef adds 1 to refCount and returns the new count.
• Release takes 1 from refCount and, when that leaves 0, deletes the object, running the destructors of your type and of the class. It returns the count; once the object has deleted itself that value is read from the deleted object, so do not rely on it, and do not touch the object again.

Parameter	Meaning
riid	The identifier of the interface asked for.
ppvObject	Where the interface pointer would go; left as it is.

Returns S_OK (QueryInterface); the new reference count (AddRef, Release).

Example

dim pHandler as CWebView2DocumentTitleChangedEventHandler ptr = new CWebView2DocumentTitleChangedEventHandler
print pHandler->AddRef()      ' 1
pHandler->Release()           ' the count is 0 again: the object deletes itself

Microsoft Learn: IUnknown

CWebView2CreateCoreWebView2EnvironmentCompletedHandler

Implements ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandler: the new environment.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim hr as HRESULT = CreateCoreWebView2Environment( cast( any ptr, new CWebView2CreateCoreWebView2EnvironmentCompletedHandler ) )

Invoke

virtual function Invoke( byval errorCode as HRESULT, byval createdEnvironment as ICoreWebView2Environment ptr ) as HRESULT

Called once when an environment requested with CreateCoreWebView2Environment or CreateCoreWebView2EnvironmentWithOptions has been created, or has failed. CWebView2 does this step itself with a handler of its own; use this class to drive WebView2 without it. The usual next step is CreateCoreWebView2Controller on the environment. To keep the environment after Invoke returns, call its AddRef.

Parameter	Meaning
errorCode	S_OK, or why the environment could not be created.
createdEnvironment	The environment, borrowed for the call; NULL on failure.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type EnvironmentReady extends CWebView2CreateCoreWebView2EnvironmentCompletedHandler
    declare function Invoke( byval errorCode as HRESULT, byval createdEnvironment as ICoreWebView2Environment ptr ) as HRESULT
end type
function EnvironmentReady.Invoke( byval errorCode as HRESULT, byval createdEnvironment as ICoreWebView2Environment ptr ) as HRESULT
    if errorCode <> S_OK then return S_OK
    ' // ask for the controller of a web view in the window
    createdEnvironment->CreateCoreWebView2Controller( hwnd, cast( any ptr, new CWebView2CreateCoreWebView2ControllerCompletedHandler ) )
    return S_OK
end function

Microsoft Learn: ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandler

CWebView2CreateCoreWebView2ControllerCompletedHandler

Implements ICoreWebView2CreateCoreWebView2ControllerCompletedHandler: the new controller.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim pEnv as ICoreWebView2Environment ptr = CWebView2Ptr( hwnd )->GetEnvironmentPtr()
pEnv->CreateCoreWebView2Controller( hwnd, cast( any ptr, new CWebView2CreateCoreWebView2ControllerCompletedHandler ) )

Invoke

virtual function Invoke( byval errorCode as HRESULT, byval createdController as ICoreWebView2Controller ptr ) as HRESULT

Called once when a controller requested with the environment's CreateCoreWebView2Controller has been created, or has failed. The controller gives the ICoreWebView2 through get_CoreWebView2. Call AddRef on it to keep it; until a controller is kept, the web view goes away when the call returns.

Parameter	Meaning
errorCode	S_OK, or why the controller could not be created.
createdController	The controller, borrowed for the call; NULL on failure.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

dim shared g_pController as ICoreWebView2Controller ptr
type ControllerReady extends CWebView2CreateCoreWebView2ControllerCompletedHandler
    declare function Invoke( byval errorCode as HRESULT, byval createdController as ICoreWebView2Controller ptr ) as HRESULT
end type
function ControllerReady.Invoke( byval errorCode as HRESULT, byval createdController as ICoreWebView2Controller ptr ) as HRESULT
    if errorCode = S_OK then
        g_pController = createdController
        g_pController->AddRef()
    end if
    return S_OK
end function

Microsoft Learn: ICoreWebView2CreateCoreWebView2ControllerCompletedHandler

CWebView2NavigationStartingdEventHandler

Implements ICoreWebView2NavigationStartingEventHandler: the start of a navigation.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->AddNavigationStarting( cast( any ptr, new CWebView2NavigationStartingdEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2NavigationCompletedEventArgs ptr ) as HRESULT

Called before the web view navigates to a new document, and before each redirect, while the navigation can still be cancelled. Attach it with AddNavigationStarting (the main document) or AddFrameNavigationStarting (iframes).

The class name has a d before EventHandler, and args is declared as ICoreWebView2NavigationCompletedEventArgs ptr although WebView2 passes an ICoreWebView2NavigationStartingEventArgs. Declare your Invoke with the declared types, or it does not replace this one (the base Invoke keeps being called), and cast args to ICoreWebView2NavigationStartingEventArgs ptr to read it, as the example does.

Parameter	Meaning
sender	The web view.
args	The navigation: get_uri, get_IsUserInitiated, get_IsRedirected, get_RequestHeaders, put_Cancel, get_NavigationId.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type NavStarting extends CWebView2NavigationStartingdEventHandler
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2NavigationCompletedEventArgs ptr ) as HRESULT
end type
function NavStarting.Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2NavigationCompletedEventArgs ptr ) as HRESULT
    dim pArgs as ICoreWebView2NavigationStartingEventArgs ptr = cast( any ptr, args )
    dim pwszUri as LPWSTR
    if pArgs->get_uri( @pwszUri ) = S_OK then
        if instr( *pwszUri, "example.org" ) then pArgs->put_Cancel( TRUE )
        CoTaskMemFree( pwszUri )
    end if
    return S_OK
end function

Microsoft Learn: ICoreWebView2NavigationStartingEventHandler

CWebView2NavigationCompletedEventHandler

Implements ICoreWebView2NavigationCompletedEventHandler: the end of a navigation.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->AddNavigationCompleted( cast( any ptr, new CWebView2NavigationCompletedEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2NavigationCompletedEventArgs ptr ) as HRESULT

Called when a navigation has finished, whether it succeeded or failed. Attach it with AddNavigationCompleted or AddFrameNavigationCompleted.

Parameter	Meaning
sender	The web view.
args	get_IsSuccess, get_WebErrorStatus (a COREWEBVIEW2_WEB_ERROR_STATUS) and get_NavigationId.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type NavCompleted extends CWebView2NavigationCompletedEventHandler
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2NavigationCompletedEventArgs ptr ) as HRESULT
end type
function NavCompleted.Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2NavigationCompletedEventArgs ptr ) as HRESULT
    dim bSuccess as LONG, nStatus as COREWEBVIEW2_WEB_ERROR_STATUS
    args->get_IsSuccess( @bSuccess )
    args->get_WebErrorStatus( @nStatus )
    if bSuccess = 0 then SetWindowText( hwnd, "Navigation failed: status " & nStatus )
    return S_OK
end function

Microsoft Learn: ICoreWebView2NavigationCompletedEventHandler

CWebView2ContentLoadingEventHandler

Implements ICoreWebView2ContentLoadingEventHandler: the start of loading of a new document.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->AddContentLoading( cast( any ptr, new CWebView2ContentLoadingEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2ContentLoadingEventArgs ptr ) as HRESULT

Called when the web view begins loading the content of a new document, after NavigationStarting and before NavigationCompleted. Attach it with AddContentLoading.

Parameter	Meaning
sender	The web view.
args	get_IsErrorPage, nonzero when the content is the built-in error page, and get_NavigationId.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type ContentLoading extends CWebView2ContentLoadingEventHandler
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2ContentLoadingEventArgs ptr ) as HRESULT
end type
function ContentLoading.Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2ContentLoadingEventArgs ptr ) as HRESULT
    dim bErrorPage as LONG
    args->get_IsErrorPage( @bErrorPage )
    SetWindowText( hwnd, iif( bErrorPage, "Error page", "Loading..." ) )
    return S_OK
end function

Microsoft Learn: ICoreWebView2ContentLoadingEventHandler

CWebView2SourceChangedEventHandler

Implements ICoreWebView2SourceChangedEventHandler: a change of the address.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->AddSourceChanged( cast( any ptr, new CWebView2SourceChangedEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2SourceChangedEventArgs ptr ) as HRESULT

Called when the web view's source URI changes: on a navigation to a new document, and on a change within the same document such as a fragment. Attach it with AddSourceChanged.

Parameter	Meaning
sender	The web view; get_Source gives the new address.
args	get_IsNewDocument, nonzero when the change loads a new document.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type SourceChanged extends CWebView2SourceChangedEventHandler
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2SourceChangedEventArgs ptr ) as HRESULT
end type
function SourceChanged.Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2SourceChangedEventArgs ptr ) as HRESULT
    dim pwszUri as LPWSTR
    if sender->get_Source( @pwszUri ) = S_OK then
        SetWindowTextW( hwnd, pwszUri )
        CoTaskMemFree( pwszUri )
    end if
    return S_OK
end function

Microsoft Learn: ICoreWebView2SourceChangedEventHandler

CWebView2HistoryChangedEventHandler

Implements ICoreWebView2HistoryChangedEventHandler: a change of the back and forward history.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->GetWebViewPtr()->add_HistoryChanged( cast( any ptr, new CWebView2HistoryChangedEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2 ptr, byval args as IUnknown ptr ) as HRESULT

Called when the navigation history changes, the moment to update Back and Forward buttons. AddHistoryChanged of CWebView2 attaches the handler to the SourceChanged event, not to HistoryChanged; to receive HistoryChanged itself, attach it through the interface with add_HistoryChanged, as the registration example does.

Parameter	Meaning
sender	The web view; get_CanGoBack and get_CanGoForward give the new state.
args	args is not used by this event; WebView2 passes NULL.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type HistoryChanged extends CWebView2HistoryChangedEventHandler
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as IUnknown ptr ) as HRESULT
end type
function HistoryChanged.Invoke( byval sender as ICoreWebView2 ptr, byval args as IUnknown ptr ) as HRESULT
    dim bBack as WINBOOL, bForward as WINBOOL
    sender->get_CanGoBack( @bBack )
    sender->get_CanGoForward( @bForward )
    EnableWindow( GetDlgItem( hwnd, 101 ), bBack )
    EnableWindow( GetDlgItem( hwnd, 102 ), bForward )
    return S_OK
end function

Microsoft Learn: ICoreWebView2HistoryChangedEventHandler

CWebView2ScriptDialogOpeningEventHandler

Implements ICoreWebView2ScriptDialogOpeningEventHandler: a JavaScript alert, confirm, prompt or beforeunload dialog.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->AreDefaultScriptDialogsEnabled = false
CWebView2Ptr( hwnd )->AddScriptDialogOpening( cast( any ptr, new CWebView2ScriptDialogOpeningEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2ScriptDialogOpeningEventArgs ptr ) as HRESULT

Called when the page opens a JavaScript dialog, so that the program can show its own. The event is raised only once the built-in dialogs are turned off with AreDefaultScriptDialogsEnabled. Call Accept to answer OK (and put_ResultText first for a prompt); return without it to answer Cancel. Attach it with AddScriptDialogOpening.

Parameter	Meaning
sender	The web view.
args	get_Kind (a COREWEBVIEW2_SCRIPT_DIALOG_KIND), get_Message, get_DefaultText, put_ResultText, Accept, GetDeferral.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type ScriptDialog extends CWebView2ScriptDialogOpeningEventHandler
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2ScriptDialogOpeningEventArgs ptr ) as HRESULT
end type
function ScriptDialog.Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2ScriptDialogOpeningEventArgs ptr ) as HRESULT
    dim pwszMessage as LPWSTR
    if args->get_Message( @pwszMessage ) = S_OK then
        if MessageBoxW( hwnd, pwszMessage, "The page says", MB_OKCANCEL ) = IDOK then args->Accept()
        CoTaskMemFree( pwszMessage )
    end if
    return S_OK
end function

Microsoft Learn: ICoreWebView2ScriptDialogOpeningEventHandler

CWebView2PermissionRequestedEventHandler

Implements ICoreWebView2PermissionRequestedEventHandler: a request for a permission.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->AddPermissionRequested( cast( any ptr, new CWebView2PermissionRequestedEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2PermissionRequestedEventArgs ptr ) as HRESULT

Called when the page asks for a permission such as the location, the camera or the microphone. Set the answer with put_State; leaving it at COREWEBVIEW2_PERMISSION_STATE_DEFAULT lets WebView2 decide, which usually means asking the user. Attach it with AddPermissionRequested.

Parameter	Meaning
sender	The web view.
args	get_uri, get_PermissionKind (a COREWEBVIEW2_PERMISSION_KIND), get_IsUserInitiated, put_State, GetDeferral.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type PermissionAsked extends CWebView2PermissionRequestedEventHandler
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2PermissionRequestedEventArgs ptr ) as HRESULT
end type
function PermissionAsked.Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2PermissionRequestedEventArgs ptr ) as HRESULT
    dim nKind as COREWEBVIEW2_PERMISSION_KIND
    args->get_PermissionKind( @nKind )
    if nKind = COREWEBVIEW2_PERMISSION_KIND_GEOLOCATION then args->put_State( COREWEBVIEW2_PERMISSION_STATE_DENY )
    return S_OK
end function

Microsoft Learn: ICoreWebView2PermissionRequestedEventHandler

CWebView2ProcessFailedEventHandler

Implements ICoreWebView2ProcessFailedEventHandler: the failure of a browser process.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->AddProcessFailed( cast( any ptr, new CWebView2ProcessFailedEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2ProcessFailedEventArgs ptr ) as HRESULT

Called when one of the browser processes behind the web view exits unexpectedly or stops responding. A failed render process leaves the page blank until it is reloaded; a failed browser process ends the web view, which then has to be created again. Attach it with AddProcessFailed.

Parameter	Meaning
sender	The web view.
args	get_ProcessFailedKind, a COREWEBVIEW2_PROCESS_FAILED_KIND.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type ProcessFailed extends CWebView2ProcessFailedEventHandler
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2ProcessFailedEventArgs ptr ) as HRESULT
end type
function ProcessFailed.Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2ProcessFailedEventArgs ptr ) as HRESULT
    dim nKind as COREWEBVIEW2_PROCESS_FAILED_KIND
    args->get_ProcessFailedKind( @nKind )
    if nKind = COREWEBVIEW2_PROCESS_FAILED_KIND_RENDER_PROCESS_EXITED then sender->Reload()
    return S_OK
end function

Microsoft Learn: ICoreWebView2ProcessFailedEventHandler

CWebView2WebMessageReceivedEventHandler

Implements ICoreWebView2WebMessageReceivedEventHandler: a message posted by the page.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->AddWebMessageReceived( cast( any ptr, new CWebView2WebMessageReceivedEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2WebMessageReceivedEventArgs ptr ) as HRESULT

Called when the page's script calls window.chrome.webview.postMessage. It is the page's way of talking to the program; the other direction is PostWebMessageAsString and PostWebMessageAsJson. Web messages must be enabled, which they are by default. Attach it with AddWebMessageReceived.

Parameter	Meaning
sender	The web view.
args	get_Source (the address of the page that sent it), get_webMessageAsJson, and TryGetWebMessageAsString, which fails unless the message is a string.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type MessageReceived extends CWebView2WebMessageReceivedEventHandler
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2WebMessageReceivedEventArgs ptr ) as HRESULT
end type
function MessageReceived.Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2WebMessageReceivedEventArgs ptr ) as HRESULT
    dim pwszMessage as LPWSTR
    if args->TryGetWebMessageAsString( @pwszMessage ) = S_OK then
        SetWindowTextW( hwnd, pwszMessage )
        CoTaskMemFree( pwszMessage )
    end if
    return S_OK
end function

Microsoft Learn: ICoreWebView2WebMessageReceivedEventHandler

CWebView2NewWindowRequestedEventHandler

Implements ICoreWebView2NewWindowRequestedEventHandler: a request to open a new window.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->AddNewWindowRequested( cast( any ptr, new CWebView2NewWindowRequestedEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2NewWindowRequestedEventArgs ptr ) as HRESULT

Called when the page asks for a new window: window.open, a link with target="_blank", or the user choosing to open a link in a new window. Unless the handler sets put_Handled or supplies a web view with put_NewWindow, WebView2 opens a separate browser window. Attach it with AddNewWindowRequested.

Parameter	Meaning
sender	The web view.
args	get_uri, put_NewWindow, put_Handled, get_IsUserInitiated, GetDeferral, get_WindowFeatures.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type NewWindow extends CWebView2NewWindowRequestedEventHandler
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2NewWindowRequestedEventArgs ptr ) as HRESULT
end type
function NewWindow.Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2NewWindowRequestedEventArgs ptr ) as HRESULT
    ' // open the page in this web view instead
    dim pwszUri as LPWSTR
    if args->get_uri( @pwszUri ) = S_OK then
        args->put_Handled( TRUE )
        sender->Navigate( pwszUri )
        CoTaskMemFree( pwszUri )
    end if
    return S_OK
end function

Microsoft Learn: ICoreWebView2NewWindowRequestedEventHandler

CWebView2DocumentTitleChangedEventHandler

Implements ICoreWebView2DocumentTitleChangedEventHandler: a change of the page title.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->AddDocumentTitleChanged( cast( any ptr, new CWebView2DocumentTitleChangedEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2 ptr, byval args as IUnknown ptr ) as HRESULT

Called when the title of the top-level document changes. Attach it with AddDocumentTitleChanged.

Parameter	Meaning
sender	The web view; get_DocumentTitle gives the new title.
args	args is not used by this event; WebView2 passes NULL.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type TitleChanged extends CWebView2DocumentTitleChangedEventHandler
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as IUnknown ptr ) as HRESULT
end type
function TitleChanged.Invoke( byval sender as ICoreWebView2 ptr, byval args as IUnknown ptr ) as HRESULT
    dim pwszTitle as LPWSTR
    if sender->get_DocumentTitle( @pwszTitle ) = S_OK then
        SetWindowTextW( hwnd, pwszTitle )
        CoTaskMemFree( pwszTitle )
    end if
    return S_OK
end function

Microsoft Learn: ICoreWebView2DocumentTitleChangedEventHandler

CWebView2ContainsFullScreenElementChangedEventHandler

Implements ICoreWebView2ContainsFullScreenElementChangedEventHandler: an element entering or leaving full screen.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->AddContainsFullScreenElementChanged( cast( any ptr, new CWebView2ContainsFullScreenElementChangedEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2 ptr, byval args as IUnknown ptr ) as HRESULT

Called when an element of the page, typically a video, enters or leaves full-screen mode. WebView2 only fills the web view's own bounds; making the window cover the screen is the program's job. Attach it with AddContainsFullScreenElementChanged.

Parameter	Meaning
sender	The web view; get_ContainsFullScreenElement gives the new state.
args	args is not used by this event; WebView2 passes NULL.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type FullScreenChanged extends CWebView2ContainsFullScreenElementChangedEventHandler
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as IUnknown ptr ) as HRESULT
end type
function FullScreenChanged.Invoke( byval sender as ICoreWebView2 ptr, byval args as IUnknown ptr ) as HRESULT
    dim bFullScreen as LONG
    sender->get_ContainsFullScreenElement( @bFullScreen )
    ShowWindow( hwnd, iif( bFullScreen, SW_MAXIMIZE, SW_RESTORE ) )
    return S_OK
end function

Microsoft Learn: ICoreWebView2ContainsFullScreenElementChangedEventHandler

CWebView2WebResourceRequestedEventHandler

Implements ICoreWebView2WebResourceRequestedEventHandler: a request for a resource that matches a filter.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->AddWebResourceRequestedFilter( "*", COREWEBVIEW2_WEB_RESOURCE_CONTEXT_IMAGE )
CWebView2Ptr( hwnd )->AddWebResourceRequested( cast( any ptr, new CWebView2WebResourceRequestedEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2WebResourceRequestedEventArgs ptr ) as HRESULT

Called for each request the page makes that matches a filter added with AddWebResourceRequestedFilter; with no filter it is never called. The handler can read or change the request, or answer it itself with put_Response and a response made by the environment's CreateWebResourceResponse. Attach it with AddWebResourceRequested.

Parameter	Meaning
sender	The web view.
args	get_Request, put_Response, GetDeferral, get_ResourceContext (a COREWEBVIEW2_WEB_RESOURCE_CONTEXT).

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type ResourceRequested extends CWebView2WebResourceRequestedEventHandler
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2WebResourceRequestedEventArgs ptr ) as HRESULT
end type
function ResourceRequested.Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2WebResourceRequestedEventArgs ptr ) as HRESULT
    ' // answer every filtered request with 403, so no image is loaded
    dim pResponse as ICoreWebView2WebResourceResponse ptr
    dim pEnv as ICoreWebView2Environment ptr = CWebView2Ptr( hwnd )->GetEnvironmentPtr()
    if pEnv->CreateWebResourceResponse( NULL, 403, "Blocked", "", @pResponse ) = S_OK then
        args->put_Response( pResponse )
        pResponse->Release()
    end if
    return S_OK
end function

Microsoft Learn: ICoreWebView2WebResourceRequestedEventHandler

CWebView2WindowCloseRequestedEventHandler

Implements ICoreWebView2WindowCloseRequestedEventHandler: a request from the page to close the window.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->AddWindowCloseRequested( cast( any ptr, new CWebView2WindowCloseRequestedEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2 ptr, byval args as IUnknown ptr ) as HRESULT

Called when the page's script calls window.close. WebView2 does not close anything itself; the program decides. Attach it with AddWindowCloseRequested.

Parameter	Meaning
sender	The web view.
args	args is not used by this event; WebView2 passes NULL.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type CloseRequested extends CWebView2WindowCloseRequestedEventHandler
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as IUnknown ptr ) as HRESULT
end type
function CloseRequested.Invoke( byval sender as ICoreWebView2 ptr, byval args as IUnknown ptr ) as HRESULT
    PostMessageW( hwnd, WM_CLOSE, 0, 0 )
    return S_OK
end function

Microsoft Learn: ICoreWebView2WindowCloseRequestedEventHandler

CWebView2ExecuteScriptCompletedHandler

Implements ICoreWebView2ExecuteScriptCompletedHandler: the result of a script.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

CWebView2Ptr( hwnd )->ExecuteScript( "document.title", cast( any ptr, new CWebView2ExecuteScriptCompletedHandler ) )

Invoke

virtual function Invoke( byval errorCode as HRESULT, byval resultObjectAsJson as LPCWSTR ) as HRESULT

Called once when a script run with ExecuteScript has finished. The result is the value of the script's last expression, as JSON: a string comes back in quotes ("My page"), a number as its digits, and undefined or an error as null.

Parameter	Meaning
errorCode	S_OK, or why the script could not run.
resultObjectAsJson	The result as JSON, valid during the call only.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type ScriptDone extends CWebView2ExecuteScriptCompletedHandler
    declare function Invoke( byval errorCode as HRESULT, byval resultObjectAsJson as LPCWSTR ) as HRESULT
end type
function ScriptDone.Invoke( byval errorCode as HRESULT, byval resultObjectAsJson as LPCWSTR ) as HRESULT
    if errorCode = S_OK then SetWindowTextW( hwnd, resultObjectAsJson )
    return S_OK
end function

Microsoft Learn: ICoreWebView2ExecuteScriptCompletedHandler

CWebView2AddScriptToExecuteOnDocumentCreatedCompleteHandler

Implements ICoreWebView2AddScriptToExecuteOnDocumentCreatedCompletedHandler: the id of a script added to every document.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

CWebView2Ptr( hwnd )->AddScriptToExecuteOnDocumentCreated( "window.fromHost = true;", cast( any ptr, new CWebView2AddScriptToExecuteOnDocumentCreatedCompleteHandler ) )

Invoke

virtual function Invoke( byval errorCode as HRESULT, byval resultObjectAsJson as LPCWSTR ) as HRESULT

Called once when a script given to AddScriptToExecuteOnDocumentCreated has been registered. Despite its name, the second parameter is not JSON: it is the id of the added script, the value RemoveScriptToExecuteOnDocumentCreated takes to remove it again. The class name ends in CompleteHandler, without the d of the interface name.

Parameter	Meaning
errorCode	S_OK, or why the script could not be added.
resultObjectAsJson	The id of the script, valid during the call only.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

dim shared g_ustrScriptId as ustring
type ScriptAdded extends CWebView2AddScriptToExecuteOnDocumentCreatedCompleteHandler
    declare function Invoke( byval errorCode as HRESULT, byval resultObjectAsJson as LPCWSTR ) as HRESULT
end type
function ScriptAdded.Invoke( byval errorCode as HRESULT, byval resultObjectAsJson as LPCWSTR ) as HRESULT
    if errorCode = S_OK then g_ustrScriptId = *resultObjectAsJson
    return S_OK
end function

Microsoft Learn: ICoreWebView2AddScriptToExecuteOnDocumentCreatedCompletedHandler

CWebView2AddCapturePreviewCompletedHandler

Implements ICoreWebView2CapturePreviewCompletedHandler: the end of a screenshot of the page.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim pStream as IStream ptr
if CreateStreamOnHGlobal( NULL, TRUE, @pStream ) = S_OK then
    CWebView2Ptr( hwnd )->CapturePreview( COREWEBVIEW2_CAPTURE_PREVIEW_IMAGE_FORMAT_PNG, pStream, cast( any ptr, new CWebView2AddCapturePreviewCompletedHandler ) )
    pStream->lpVtbl->Release( pStream )
end if

Invoke

virtual function Invoke( byval errorCode as HRESULT ) as HRESULT

Called once when CapturePreview has written the image of the visible page to the stream it was given. The class name starts with Add, which the interface name does not have.

Parameter	Meaning
errorCode	S_OK when the image has been written to the stream.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type Captured extends CWebView2AddCapturePreviewCompletedHandler
    declare function Invoke( byval errorCode as HRESULT ) as HRESULT
end type
function Captured.Invoke( byval errorCode as HRESULT ) as HRESULT
    SetWindowText( hwnd, iif( errorCode = S_OK, "Page captured", "Capture failed" ) )
    return S_OK
end function

Microsoft Learn: ICoreWebView2CapturePreviewCompletedHandler

CWebView2DevToolsProtocolEventReceivedEventHandler

Implements ICoreWebView2DevToolsProtocolEventReceivedEventHandler: a DevTools Protocol event.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim pReceiver as ICoreWebView2DevToolsProtocolEventReceiver ptr
dim token as EventRegistrationToken
if CWebView2Ptr( hwnd )->GetDevToolsProtocolEventReceiver( "Log.entryAdded", @pReceiver ) = S_OK then
    pReceiver->add_DevToolsProtocolEventReceived( cast( any ptr, new CWebView2DevToolsProtocolEventReceivedEventHandler ), @token )
end if

Invoke

virtual function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2DevToolsProtocolEventReceivedEventArgs ptr ) as HRESULT

Called each time the DevTools Protocol event it is attached to is raised. Get the receiver for one event name with GetDevToolsProtocolEventReceiver, attach the handler with the receiver's add_DevToolsProtocolEventReceived, and turn the event's domain on with CallDevToolsProtocolMethod (for example Log.enable). Keep the receiver to remove the handler later.

Parameter	Meaning
sender	The web view.
args	get_ParameterObjectAsJson, the event's parameters as JSON.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type DevToolsEvent extends CWebView2DevToolsProtocolEventReceivedEventHandler
    declare function Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2DevToolsProtocolEventReceivedEventArgs ptr ) as HRESULT
end type
function DevToolsEvent.Invoke( byval sender as ICoreWebView2 ptr, byval args as ICoreWebView2DevToolsProtocolEventReceivedEventArgs ptr ) as HRESULT
    dim pwszJson as LPWSTR
    if args->get_ParameterObjectAsJson( @pwszJson ) = S_OK then
        OutputDebugStringW( pwszJson )
        CoTaskMemFree( pwszJson )
    end if
    return S_OK
end function

Microsoft Learn: ICoreWebView2DevToolsProtocolEventReceivedEventHandler

CWebView2ZoomFactorChangedEventHandler

Implements ICoreWebView2ZoomFactorChangedEventHandler: a change of the zoom factor.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->AddZoomFactorChanged( cast( any ptr, new CWebView2ZoomFactorChangedEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2Controller ptr, byval args as IUnknown ptr ) as HRESULT

Called when the zoom factor of the web view changes, whether the user zoomed with Ctrl and the mouse wheel or the program set it. The sender is the controller, not the web view. Attach it with AddZoomFactorChanged.

Parameter	Meaning
sender	The controller; get_ZoomFactor gives the new factor (1 is 100 %).
args	args is not used by this event; WebView2 passes NULL.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type ZoomChanged extends CWebView2ZoomFactorChangedEventHandler
    declare function Invoke( byval sender as ICoreWebView2Controller ptr, byval args as IUnknown ptr ) as HRESULT
end type
function ZoomChanged.Invoke( byval sender as ICoreWebView2Controller ptr, byval args as IUnknown ptr ) as HRESULT
    dim dZoom as double
    sender->get_ZoomFactor( @dZoom )
    SetWindowText( hwnd, "Zoom " & int( dZoom * 100 + 0.5 ) & " %" )
    return S_OK
end function

Microsoft Learn: ICoreWebView2ZoomFactorChangedEventHandler

CWebView2MoveFocusRequestedEventHandler

Implements ICoreWebView2MoveFocusRequestedEventHandler: a request to move the focus out of the web view.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->AddMoveFocusRequested( cast( any ptr, new CWebView2MoveFocusRequestedEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2Controller ptr, byval args as ICoreWebView2MoveFocusRequestedEventArgs ptr ) as HRESULT

Called when the user tabs out of the last element of the page (or Shift+Tabs out of the first), so that the program can give the focus to its next control. Set put_Handled once the focus has been moved. Attach it with AddMoveFocusRequested.

Parameter	Meaning
sender	The controller.
args	get_reason (a COREWEBVIEW2_MOVE_FOCUS_REASON) and put_Handled.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type FocusOut extends CWebView2MoveFocusRequestedEventHandler
    declare function Invoke( byval sender as ICoreWebView2Controller ptr, byval args as ICoreWebView2MoveFocusRequestedEventArgs ptr ) as HRESULT
end type
function FocusOut.Invoke( byval sender as ICoreWebView2Controller ptr, byval args as ICoreWebView2MoveFocusRequestedEventArgs ptr ) as HRESULT
    dim nReason as COREWEBVIEW2_MOVE_FOCUS_REASON
    args->get_reason( @nReason )
    if nReason = COREWEBVIEW2_MOVE_FOCUS_REASON_NEXT then
        SetFocus( GetDlgItem( hwnd, 101 ) )
        args->put_Handled( TRUE )
    end if
    return S_OK
end function

Microsoft Learn: ICoreWebView2MoveFocusRequestedEventHandler

CWebView2FocusChangedEventHandler

Implements ICoreWebView2FocusChangedEventHandler: the web view gaining or losing the focus.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim as EventRegistrationToken tokGot, tokLost
CWebView2Ptr( hwnd )->AddGotFocus( cast( any ptr, new CWebView2FocusChangedEventHandler ), @tokGot )
CWebView2Ptr( hwnd )->AddLostFocus( cast( any ptr, new CWebView2FocusChangedEventHandler ), @tokLost )

Invoke

virtual function Invoke( byval sender as ICoreWebView2Controller ptr, byval args as IUnknown ptr ) as HRESULT

One class for two events: attach an object with AddGotFocus and another with AddLostFocus. Invoke is not told which of the two it is answering, so give the type a field that says.

Parameter	Meaning
sender	The controller.
args	args is not used by this event; WebView2 passes NULL.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type FocusChanged extends CWebView2FocusChangedEventHandler
    declare function Invoke( byval sender as ICoreWebView2Controller ptr, byval args as IUnknown ptr ) as HRESULT
    m_bGot as boolean
end type
function FocusChanged.Invoke( byval sender as ICoreWebView2Controller ptr, byval args as IUnknown ptr ) as HRESULT
    SetWindowText( hwnd, iif( m_bGot, "The page has the focus", "The page lost the focus" ) )
    return S_OK
end function

Microsoft Learn: ICoreWebView2FocusChangedEventHandler

CWebView2AcceleratorKeyPressedEventHandler

Implements ICoreWebView2AcceleratorKeyPressedEventHandler: a shortcut key pressed in the web view.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->AddAcceleratorKeyPressed( cast( any ptr, new CWebView2AcceleratorKeyPressedEventHandler ), @token )

Invoke

virtual function Invoke( byval sender as ICoreWebView2Controller ptr, byval args as ICoreWebView2AcceleratorKeyPressedEventArgs ptr ) as HRESULT

Called for keys that may be shortcuts (function keys, keys with Ctrl or Alt, Escape) while the web view has the focus, for each key-down and key-up. Setting put_Handled keeps the key from the page and from the browser's own shortcuts, such as F5 for reload. Attach it with AddAcceleratorKeyPressed.

Parameter	Meaning
sender	The controller.
args	get_KeyEventKind (a COREWEBVIEW2_KEY_EVENT_KIND), get_VirtualKey, get_KeyEventLParam, get_PhysicalKeyStatus, put_Handled.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type KeyPressed extends CWebView2AcceleratorKeyPressedEventHandler
    declare function Invoke( byval sender as ICoreWebView2Controller ptr, byval args as ICoreWebView2AcceleratorKeyPressedEventArgs ptr ) as HRESULT
end type
function KeyPressed.Invoke( byval sender as ICoreWebView2Controller ptr, byval args as ICoreWebView2AcceleratorKeyPressedEventArgs ptr ) as HRESULT
    dim nKind as COREWEBVIEW2_KEY_EVENT_KIND, nKey as UINT
    args->get_KeyEventKind( @nKind )
    args->get_VirtualKey( @nKey )
    if nKind = COREWEBVIEW2_KEY_EVENT_KIND_KEY_DOWN andalso nKey = VK_F5 then args->put_Handled( TRUE )   ' no reload
    return S_OK
end function

Microsoft Learn: ICoreWebView2AcceleratorKeyPressedEventHandler

CWebView2NewBrowserVersionAvailableEventHandler

Implements ICoreWebView2NewBrowserVersionAvailableEventHandler: the installation of a newer WebView2 runtime.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

dim token as EventRegistrationToken
CWebView2Ptr( hwnd )->GetEnvironmentPtr()->add_NewBrowserVersionAvailable( cast( any ptr, new CWebView2NewBrowserVersionAvailableEventHandler ), @token )

Invoke

virtual function Invoke( byval webviewEnvironment as ICoreWebView2Environment ptr, byval args as IUNknown ptr ) as HRESULT

Called when a newer WebView2 runtime has been installed while the program runs. The web view goes on using the old one until every web view of the environment is closed and a new environment is created. CWebView2 has no method for this event: attach the handler to the environment with add_NewBrowserVersionAvailable.

Parameter	Meaning
webviewEnvironment	The environment.
args	args is not used by this event; WebView2 passes NULL.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type NewRuntime extends CWebView2NewBrowserVersionAvailableEventHandler
    declare function Invoke( byval webviewEnvironment as ICoreWebView2Environment ptr, byval args as IUNknown ptr ) as HRESULT
end type
function NewRuntime.Invoke( byval webviewEnvironment as ICoreWebView2Environment ptr, byval args as IUNknown ptr ) as HRESULT
    dim pwszVersion as LPWSTR
    if webviewEnvironment->get_BrowserVersionString( @pwszVersion ) = S_OK then
        SetWindowText( hwnd, "Restart to use WebView2 " & *pwszVersion )
        CoTaskMemFree( pwszVersion )
    end if
    return S_OK
end function

Microsoft Learn: ICoreWebView2NewBrowserVersionAvailableEventHandler

CWebView2CallDevToolsProtocolMethodCompletedHandler

Implements ICoreWebView2CallDevToolsProtocolMethodCompletedHandler: the result of a DevTools Protocol method.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 0. The destructor does nothing of its own; it runs when Release brings the count to 0, after WebView2 has let go of the handler.

Example

CWebView2Ptr( hwnd )->CallDevToolsProtocolMethod( "Browser.getVersion", "{}", cast( any ptr, new CWebView2CallDevToolsProtocolMethodCompletedHandler ) )

Invoke

virtual function Invoke( byval errorCode as HRESULT, byval returnObjectAsJson as LPCWSTR ) as HRESULT

Called once when a method run with CallDevToolsProtocolMethod has returned.

Parameter	Meaning
errorCode	S_OK, or why the method failed.
returnObjectAsJson	What the method returned, as JSON, valid during the call only.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type DevToolsDone extends CWebView2CallDevToolsProtocolMethodCompletedHandler
    declare function Invoke( byval errorCode as HRESULT, byval returnObjectAsJson as LPCWSTR ) as HRESULT
end type
function DevToolsDone.Invoke( byval errorCode as HRESULT, byval returnObjectAsJson as LPCWSTR ) as HRESULT
    if errorCode = S_OK then SetWindowTextW( hwnd, returnObjectAsJson )
    return S_OK
end function

Microsoft Learn: ICoreWebView2CallDevToolsProtocolMethodCompletedHandler

CWebView2ExecuteScriptWithResultCompletedHandler

Implements ICoreWebView2ExecuteScriptWithResultCompletedHandler: the result of a script, with any exception.

Constructor, Destructor

constructor
virtual destructor

Creates the handler with refCount set to 1. The destructor does nothing of its own; it runs when Release brings the count to 0.

Example

dim p21 as ICoreWebView2_21 ptr
if CWebView2Ptr( hwnd )->GetWebViewPtr()->QueryInterface( @IID_ICoreWebView2_21, cast( any ptr ptr, @p21 ) ) = S_OK then
    p21->ExecuteScriptWithResult( "6 * 7", cast( any ptr, new CWebView2ExecuteScriptWithResultCompletedHandler ) )
    p21->Release()
end if

Invoke

virtual function Invoke( byval errorCode as HRESULT, byval result as ICoreWebView2ExecuteScriptResult ptr ) as HRESULT

Called once when a script run with ExecuteScriptWithResult of ICoreWebView2_21 has finished. Unlike ExecuteScript it tells success from failure and gives the exception a script threw. CWebView2 has no method for it: ask the web view for ICoreWebView2_21.

This class is the one whose refCount starts at 1, not 0; the source notes that WebView2 does not take a reference to this handler.

Parameter	Meaning
errorCode	S_OK, or why the script could not run.
result	get_Succeeded, get_ResultAsJson, TryGetResultAsString, get_Exception; borrowed for the call.

Returns S_OK. Return S_OK from your own Invoke as well.

Example

type ScriptResult extends CWebView2ExecuteScriptWithResultCompletedHandler
    declare function Invoke( byval errorCode as HRESULT, byval result as ICoreWebView2ExecuteScriptResult ptr ) as HRESULT
end type
function ScriptResult.Invoke( byval errorCode as HRESULT, byval result as ICoreWebView2ExecuteScriptResult ptr ) as HRESULT
    dim bSucceeded as LONG, pwszJson as LPWSTR
    result->get_Succeeded( @bSucceeded )
    if bSucceeded <> 0 andalso result->get_ResultAsJson( @pwszJson ) = S_OK then
        SetWindowTextW( hwnd, pwszJson )
        CoTaskMemFree( pwszJson )
    end if
    return S_OK
end function

Microsoft Learn: ICoreWebView2ExecuteScriptWithResultCompletedHandler

See also

• sys/win/webview2
• CWebView2, whose Add and Remove methods attach and detach these handlers
• WebView2 interfaces and types, the interfaces sender and args are, and every other handler interface
• File dialog events, the same pattern for the Open and Save dialogs
• Microsoft Learn: WebView2 Win32 reference