cWebView2 — RC6-compatible WebView2 wrapper for VB6

A drop-in replacement of vbRichClient6's cWebView2 class, implemented in pure VB6 directly against the official Microsoft WebView2 COM API. No RC6.dll dependency, no dependency on the WebView2 SDK typelib — the only redistributable is WebView2Loader.dll, located at runtime in the exe's External subfolder, next to the exe, or in any parent folder, targeting the Evergreen WebView2 Runtime installed on the machine.

Layout

Path	Purpose
src/cWebView2.cls	The public class — RC6-compatible properties, methods and events (~120KB compiled)
src/cWebView2Callback.cls	Implements every native callback interface (completed-handlers, event handlers, environment options) and forwards to cWebView2's Friend sinks
typelib/VBWebView2Impl.odl / .tlb	Hand-written companion type library with VB6-safe redeclarations of the WebView2 interfaces (see below)
WebView2Loader.dll	Microsoft's loader shim (x86), resolves the installed Evergreen runtime
test/Form1.frm	Manual test harness, grown alongside the implementation
test/Project1.vbp	Test exe project — references only stdole2.tlb and VBWebView2Impl.tlb
contrib/dll/VbWebView2.vbp	ActiveX DLL project packaging the classes as VbWebView2.dll (binary compatibility kept via VbWebView2.cmp)
contrib/dll/test/Project1.vbp	Test exe consuming the compiled VbWebView2.dll
doc/WebView2.idl	The official WebView2 SDK IDL, kept as read-only reference only
doc/RC6.idl	vbRichClient6 IDL, kept as API-surface reference only

How it works

VB6 cannot Implements (or in places even call) the WebView2 SDK interfaces because they use automation-hostile types: raw BOOL, LPWSTR/LPCWSTR, unsigned ints, and even plain IUnknown* parameters. VBWebView2Impl.odl redeclares every interface the code touches under an IVB... name with the exact same IID as the SDK original — so QueryInterface and vtable calls to/from native code resolve correctly — but with VB6-safe types:

• BOOL → long (0 = False, nonzero = True)
• LPWSTR/LPCWSTR → long (raw pointer, converted with StrPtr / SysReAllocString helpers; strings the API documents as caller-owned are freed with CoTaskMemFree)
• UINT32/UINT64/enums/HRESULT params → long
• interface pointers not otherwise needed → VB6IUnknown, a locally-declared marker interface binary-identical to IUnknown (VB6 rejects the imported stdole IUnknown as a parameter type in Implements members)
• interface version chains (ICoreWebView2_2..11, ICoreWebView2Settings2..6, ICoreWebView2Controller unchanged) are flattened onto their base vtable and published under the newest IID actually needed
• unused members that precede needed ones are still declared, purely to keep vtable slots aligned
• every interface is forward-declared once near the top of the file (mktyplib supports bare interface IFoo; declarations), so any interface can reference any other regardless of which one is fully defined first further down

The tlb is compiled with MKTYPLIB.EXE VBWebView2Impl.odl (VC98).

RC6's synchronous call style (BindTo, Navigate, jsRun, ... block until done or timeout) is reproduced by spinning the thread message pump (PeekMessage/DispatchMessage + CoWaitForMultipleHandles) until the native async completion fires. Completions are correlated by Currency tokens so nested and interleaved calls cannot cross wires.

jsRun/jsProp/jsCallByName run over an RC6-style SetFuncObj bridge: an injected script hands a JS function table ({run, cbn, propGet, propLet}) to the host as a live IDispatch proxy; the wrapper resolves and calls those with raw GetIDsOfNames/Invoke (via IVBDispatch, LCID LOCALE_USER_DEFAULT — JS scripting proxies reject LCID 0), and the JS glue reports the result back through a nested RaiseResultEvent. That result — including live JS object proxies, not the JSON copies ExecuteScript yields — is what makes jsCallByName work. The nested RaiseResultEvent is not dispatched reentrantly (WebView2 queues the incoming host-object call), so the bridge pumps the message loop for it, with the jsCallTimeOutSeconds timeout.

Because WebView2 serialises callbacks — no callback (including the bridge's result) is delivered while another is on our stack — a blocking jsRun from inside an event handler would otherwise deadlock. So notification events (NavigationCompleted, DocumentComplete, TitleChanged, DOMContentLoaded, JSMessage, ...) are deferred: their args are captured synchronously and the event is raised one message-loop tick later, from a fire-once timer, on a clean stack where jsRun/jsProp/jsCallByName work. This matches RC6, where NavigationCompleted/DocumentComplete likewise fire after Navigate returns (the internal done-flag stays synchronous, so blocking Navigate is unaffected). Cancelable/answerable events (NavigationStarting, PermissionRequested, ScriptDialogOpening, NewWindowRequested, AcceleratorKeyPressed, WebResourceRequested, ContextMenuRequested, DownloadStarting, MoveFocusRequested, BasicAuthenticationRequested) are raised inline because the native side reads their ByRef answer back — jsRun cannot be used in those (nor can it in RC6), use jsRunAsync there instead.

RC6 compatibility notes

• The instance registers its cWebView2Callback as host object vbHost and injects a global vbH() accessor on document creation, so existing RC6-style page script like vbH().RaiseMessageEvent('title_change', document.title) works unchanged. The callback only forwards a handful of methods (RaiseMessageEvent, RaiseContextMenuEvent) to the owning cWebView2 — script never obtains a direct reference to the cWebView2 instance itself. A contextmenu listener is injected the same way to raise UserContextMenu.
• Default user data folder is %LOCALAPPDATA%\<EXENAME>, matching RC6, instead of the native default <exe>.WebView2 next to the executable.
• JSMessage fires from both the RC6 channel (vbH().RaiseMessageEvent) and native chrome.webview.postMessage; JSON object content is decoded into the oJSONContent parameter.
• AddObject "Name", Obj also publishes a global window.Name alias of the synchronous host-object proxy, so page script can call Name.MethodName(...) directly, like with RC6. The native chrome.webview.hostObjects[.sync].Name forms remain available (the async proxy returns Promises).
• Return values verified against live RC6: BindTo returns 1 on success and 0 on failure (details go to the debug console); Navigate/ NavigateToString/NavigateWithWebResourceRequest return 1 whenever the navigation completed within the wait — even when it landed on an error page — and Empty on timeout.

Deliberate deviations from RC6

• CapturePreview returns a Byte() array with the raw PNG/JPEG data (RC6 returned a Cairo surface).
• WebResourceRequested is a simplified allow/deny gate — deny answers the request with a synthesized 403, no response-body rewriting.
• GotFocus/LostFocus Reason is a best-effort heuristic (primed by SetFocus, defaults to FocusReason_PROGRAMMATIC).
• CallDevToolsProtocolMethod blocks and returns the CDP response, decoded like jsRun's result, instead of RC6's fire-and-forget signature (RC6's own IDL has no retval either, but discarding the CDP response is rarely useful).
• BindTo's AllowSingleSignOnUsingOSPrimaryAccount is Boolean, not RC6's Long.
• BindTo has four trailing optional parameters beyond RC6's signature — ExclusiveUserDataFolderAccess, IsCustomCrashReportingEnabled, EnableTrackingPrevention (default True, matching WebView2's own default) and AreBrowserExtensionsEnabled — surfacing ICoreWebView2EnvironmentOptions2/3/5/6. Options4's custom scheme registration is not exposed (no RC6 counterpart, different shape of feature entirely — an array of registration objects, not a simple flag).

Building

1. MKTYPLIB.EXE typelib\VBWebView2Impl.odl whenever the odl changes.
2. Build test\Project1.vbp with VB6 (VB6.EXE /make).
3. Ship WebView2Loader.dll with the compiled exe — it is located at runtime in the exe's External subfolder, next to the exe, or in any parent folder. The Evergreen WebView2 Runtime must be installed on the target machine (preinstalled on Windows 11).

Status

All RC6 cWebView2 properties, methods and events are implemented and verified against live pages (navigation, JS interop incl. blocking/async calls, live JS object proxies and JSON marshaling, host objects, web messages, settings, script dialogs, permissions, new-window, accelerator keys, focus, web-resource filtering, response introspection, frames, downloads, capture). Notes:

• jsRun/jsProp/jsCallByName run over the SetFuncObj bridge (see How it works) and return live JS object proxies, so jsCallByName dispatches on objects obtained from jsRun/jsProp exactly as in RC6. Like RC6, jsProp("window") returns Empty (WebView2 won't marshal the global window object) — expose a named object instead; nested objects (jsProp("window.x")) come back live and callable. jsProp reads dotted property paths only; arbitrary expressions fall back to ExecuteScript evaluation.
• jsRun/jsProp/jsCallByName work inside deferred event handlers (see How it works) but not inside cancelable events (NavigationStarting, etc.) — use jsRunAsync there, same as RC6.
• GetMostRecentInstallPath — resolves the runtime version through the loader, fills the VersionString out-param and returns %ProgramFiles(x86)%\Microsoft\<EdgeChannel>\Application\<version> when that folder exists (matching live RC6 output), empty string otherwise.

Additions beyond RC6 parity

Methods with no RC6 counterpart, exposed because the native plumbing is cheap and the features are frequently requested:

• PrintToPdf(ResultFilePath, [SecondsToWaitForPrintComplete], [Landscape], [ScaleFactor], [PageWidth/PageHeight], [margins], [ShouldPrintBackgrounds], [ShouldPrintSelectionOnly], [ShouldPrintHeaderAndFooter], [HeaderTitle], [FooterUri]) — blocking (or fire-and-forget at 0 seconds), returns True/False, Empty on timeout. Settings ride ICoreWebView2Environment6.CreatePrintSettings; the call itself uses the PrintToPdf slot already present in the _11 flatten.
• AddBrowserExtension(ExtensionFolderPath) — installs an unpacked extension into the profile, returns the extension Id (empty string on failure). Requires BindTo's AreBrowserExtensionsEnabled:=True (a fourth RC6-surplus optional parameter, surfacing ICoreWebView2EnvironmentOptions6 — must be decided before environment creation, and all cWebView2 instances sharing a user data folder must agree on it).
• GetBrowserExtensions() — returns a Collection of per-extension Collections (Id, Name, IsEnabled keys), keyed by extension Id. Extension APIs need a recent Evergreen runtime; on older runtimes the internal Profile7 QI fails soft and these return empty results.
• SetVirtualHostNameToFolderMapping(HostName, FolderPath, [AccessKind]) / ClearVirtualHostNameToFolderMapping(HostName) — serve a local folder as https://<HostName>/.... AccessKind defaults to HostResourceAccess_DENY (the mapped origin still serves its own content; other origins can't read it — Microsoft's recommended default). Mappings persist for the browser instance's lifetime: set once after BindTo, then Navigate "https://<HostName>/...". The host name must be a bare name — no scheme or slashes.
• Stop_ — cancels in-flight navigation/loading, WebBrowser.Stop style (trailing underscore because Stop is a VB6 keyword).
• PostWebMessageAsString/PostWebMessageAsJson — host-to-page messaging; page script receives via chrome.webview.addEventListener('message', ...).
• ContainsFullScreenElement — detect HTML fullscreen (resize/borderless the host form).
• IsBuiltInErrorPageEnabled — the one base setting RC6 didn't surface.
• IsMuted (get/let), IsDocumentPlayingAudio — tab audio control.
• Default download dialog control — OpenDefaultDownloadDialog/ CloseDefaultDownloadDialog/IsDefaultDownloadDialogOpen, DefaultDownloadDialogCornerAlignment and DefaultDownloadDialogMargin.
• Profile properties — PreferredColorScheme (dark mode), DefaultDownloadFolderPath, PreferredTrackingPreventionLevel, ProfileName, ProfilePath, IsInPrivateModeEnabled.
• StatusBarText, BrowserVersion — runtime/status introspection; OpenTaskManagerWindow — browser diagnostics.
• CallDevToolsProtocolMethodForSession — CDP against a specific target session, same blocking semantics as CallDevToolsProtocolMethod.
• SetBoundsAndZoomFactor, NotifyParentWindowPositionChanged (also called internally on resize/move), HosthWnd is now writable (re-hosting).
• TrySuspend/ResumeFromSuspend/IsSuspended — release memory while in the background; TrySuspend hides the webview first (a native precondition), ResumeFromSuspend makes it visible again.
• ClearBrowsingData(DataKinds), ClearBrowsingDataInTimeRange(DataKinds, StartTime, EndTime), ClearBrowsingDataAll — clear cache/cookies/history etc per eWebView2BrowsingDataKinds flags; blocking with the usual fire-and-forget at 0 seconds.
• Cookie management — GetCookies([URI]) returns a Collection of per-cookie Collections (Name, Value, Domain, Path, IsSession, Expires, IsSecure, IsHttpOnly, SameSite keys); AddOrUpdateCookie(Name, Value, Domain, [Path], [Expires], ...) (zero Expires = session cookie); DeleteCookies(Name, URI) (both required — cookies are matched by name and URI natively); DeleteAllCookies.
• PrintToPdfStream([settings...]) — same settings as PrintToPdf but returns the PDF as a Byte() array, no file involved. ShowPrintUI opens the browser or system print dialog.

A handful of native WebView2/WebBrowser-style events with no RC6 counterpart are also exposed, since the native plumbing is either free (already needed for something else) or fills a gap the JS-bridge-based events can't:

• ContentLoading(IsErrorPage) — fires before NavigationCompleted, akin to WebBrowser's early loading moment.
• HistoryChanged() — back/forward stack changed; pair with CanGoBack/CanGoForward.
• WindowCloseRequested() — page called window.close().
• ZoomFactorChanged() — native counterpart to the ZoomFactor property.
• MoveFocusRequested(Reason, Handled) — Tab/Shift+Tab reached the edge of the web content; Reason reuses eWebView2FocusReason.
• DOMContentLoaded() — the classic DOM-ready moment, between ContentLoading and DocumentComplete.
• StatusBarTextChanged(Text) — hover-link/status text, pairs with the StatusBarText property.
• ContainsFullScreenElementChanged() — page entered/left HTML fullscreen; read ContainsFullScreenElement to react.
• BasicAuthenticationRequested(URI, Challenge, UserName, Password, Cancel) — supply credentials for HTTP basic/proxy auth via the ByRef params. Note Chromium's flow: the challenged navigation first completes with WebErrorStatus 17 (VALID_AUTHENTICATION_CREDENTIALS_REQUIRED), then the authenticated retry loads.
• ContextMenuRequested(PageURI, LinkURI, SelectionText, ScreenX, ScreenY, Handled) — the native context-menu event, richer than the JS-injected UserContextMenu (which only reports coordinates): carries link/selection info and can actually suppress the browser's context menu via Handled. Deliberately simplified — no custom menu item injection/CustomItemSelected, matching the WebResourceRequested simplified-gate precedent. UserContextMenu is unchanged and still fires alongside it.

ContextMenuRequested required flattening ICoreWebView2_5.._11 (only _11's ContextMenuRequested is used; the rest are unused placeholders kept solely to preserve vtable alignment), same technique as the earlier _4 flatten.