Unable to make it work in pure C (com_ptr is apparently mandatory but it should not be)

[valinet]

Description
I cannot make the library work in a pure C project despite the package description on NuGet saying "This package is necessary for Win32 C/C++ applications." and the documentation stating "The Windows Implementation Library and Windows Runtime C++ Template Library are optional and make working with COM easier for the example.".

Version
SDK: 1.0.774.44
Runtime: 89.0.774.63
Framework: Win32
OS: Windows 10 Version 20H2 (OS Build 19042.867)

Repro Steps
Take the example from https://docs.microsoft.com/en-us/microsoft-edge/webview2/gettingstarted/win32:

#include <Windows.h>
#include <stdio.h>
#include <wrl.h>
#include <wil/com.h>
#include "WebView2.h"

#define APPLICATION_NAME TEXT("WebView2")

static wil::com_ptr<ICoreWebView2Controller> webviewController;
static wil::com_ptr<ICoreWebView2> webviewWindow;

LRESULT CALLBACK WindowProc(
    _In_ HWND   hwnd,
    _In_ UINT   uMsg,
    _In_ WPARAM wParam,
    _In_ LPARAM lParam
)
{
    switch (uMsg)
    {
    case WM_DPICHANGED:
    {
        RECT* const newWindowSize = (RECT*)(lParam);
        SetWindowPos(hwnd,
            NULL,
            newWindowSize->left,
            newWindowSize->top,
            newWindowSize->right - newWindowSize->left,
            newWindowSize->bottom - newWindowSize->top,
            SWP_NOZORDER | SWP_NOACTIVATE);
        return TRUE;
    }
    case WM_SIZE:
    {
        if (webviewController != NULL) {
            RECT bounds;
            GetClientRect(hwnd, &bounds);
            webviewController->put_Bounds(bounds);
        };
        break;
    }
    case WM_DESTROY:
    {
        PostQuitMessage(0);
        break;
    }
    default:
    {
        return DefWindowProc(
            hwnd,
            uMsg,
            wParam,
            lParam
        );
    }
    }
    return 0;
}

int WINAPI wWinMain(
    HINSTANCE hInstance,
    HINSTANCE hPrevInstance,
    PWSTR pCmdLine,
    int nCmdShow
)
{
    SetProcessDpiAwarenessContext(
        DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2
    );

    WNDCLASS wndClass = { 0 };
    wndClass.style = CS_HREDRAW | CS_VREDRAW;
    wndClass.lpfnWndProc = WindowProc;
    wndClass.cbClsExtra = 0;
    wndClass.cbWndExtra = 0;
    wndClass.hInstance = hInstance;
    wndClass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndClass.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wndClass.lpszMenuName = NULL;
    wndClass.lpszClassName = APPLICATION_NAME;
    RegisterClass(&wndClass);

    HWND hWnd = CreateWindowEx(
        0,
        APPLICATION_NAME,
        APPLICATION_NAME,
        WS_OVERLAPPEDWINDOW,
        100, 100, 800, 800,
        NULL,
        NULL,
        hInstance,
        NULL
    );

    ShowWindow(
        hWnd,
        nCmdShow
    );
    UpdateWindow(hWnd);

    CreateCoreWebView2EnvironmentWithOptions(NULL, NULL, NULL,
        Microsoft::WRL::Callback<ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandler>(
            [hWnd](HRESULT result, ICoreWebView2Environment* env) -> HRESULT {

                // Create a CoreWebView2Controller and get the associated CoreWebView2 whose parent is the main window hWnd
                env->CreateCoreWebView2Controller(hWnd, Microsoft::WRL::Callback<ICoreWebView2CreateCoreWebView2ControllerCompletedHandler>(
                    [hWnd](HRESULT result, ICoreWebView2Controller* controller) -> HRESULT {
                        if (controller != nullptr) {
                            webviewController = controller;
                            webviewController->get_CoreWebView2(&webviewWindow);
                        }

                        // Add a few settings for the webview
                        // The demo step is redundant since the values are the default settings
                        ICoreWebView2Settings* Settings;
                        webviewWindow->get_Settings(&Settings);
                        Settings->put_IsScriptEnabled(TRUE);
                        Settings->put_AreDefaultScriptDialogsEnabled(TRUE);
                        Settings->put_IsWebMessageEnabled(TRUE);
                        Settings->put_AreDevToolsEnabled(FALSE);
                        //Settings->put_AreDefaultContextMenusEnabled(FALSE);
                        Settings->put_IsStatusBarEnabled(FALSE);

                        // Resize WebView to fit the bounds of the parent window
                        RECT bounds;
                        GetClientRect(hWnd, &bounds);
                        webviewController->put_Bounds(bounds);
                        webviewController->put_ZoomFactor(0.8);

                        // Schedule an async task to navigate to Bing
                        webviewWindow->Navigate(HOME_PAGE);

                        // Step 4 - Navigation events

                        // Step 5 - Scripting

                        // Step 6 - Communication between host and web content

                        return S_OK;
                    }).Get());
                return S_OK;
            }).Get());

    MSG msg;
    BOOL bRet;
    while ((bRet = GetMessage(
        &msg,
        NULL,
        0,
        0)) != 0)
    {
        // An error occured
        if (bRet == -1)
        {
            break;
        }
        else
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
    }

    return (int)msg.wParam;
}

And compile it as a C++ file. It works fine. Now, replace the com_ptrs with regular pointers. So, from:

static wil::com_ptr<ICoreWebView2Controller> webviewController;
static wil::com_ptr<ICoreWebView2> webviewWindow;

To this:

static ICoreWebView2Controller* webviewController;
static ICoreWebView2* webviewWindow;

Compile as C++ again. It does not work, the WebView2 never appears on the window. This is probably the cause I am unable to make a C port of the C++ example above work too. COM calls work just fine (the callbacks) apparently, but similarly, the WebView2 is never added to the window.

So, it seems to me that com_ptr is somehow required despite that it shouldn't be so. Furthermore, this library should work from C too, I can see no reason why it wouldn't.

Here is the C port of the code above that I am trying to get working:

#include <initguid.h>
#include <Windows.h>
#include <stdio.h>
#include <conio.h>
#include <shlwapi.h>
#pragma comment(lib, "Shlwapi.lib")
#include <Shlobj_core.h>
#include "WebView2.h"

#define APPLICATION_NAME TEXT("WebView2")

#define error_printf printf

ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandler* envHandler;
ICoreWebView2CreateCoreWebView2ControllerCompletedHandler* completedHandler;
HWND hWnd = NULL;
ICoreWebView2Controller* webviewController = NULL;
ICoreWebView2* webviewWindow = NULL;
BOOL bEnvCreated = FALSE;

ULONG HandlerRefCount = 0;
ULONG HandlerAddRef(IUnknown* This)
{
    return ++HandlerRefCount;
}
ULONG HandlerRelease(IUnknown* This)
{
    --HandlerRefCount;
    if (HandlerRefCount == 0)
    {
        if (completedHandler)
        {
            free(completedHandler->lpVtbl);
            free(completedHandler);
        }
        if (envHandler)
        {
            free(envHandler->lpVtbl);
            free(envHandler);
        }
    }
    return HandlerRefCount;
}
HRESULT HandlerQueryInterface(
    IUnknown* This,
    IID* riid,
    void** ppvObject
)
{
    *ppvObject = This;
    HandlerAddRef(This);
    return S_OK;
}
HRESULT HandlerInvoke(
    IUnknown* This,
    HRESULT errorCode,
    void* arg
)
{
    if (!bEnvCreated)
    {
        bEnvCreated = TRUE;
        char ch;
        completedHandler = malloc(sizeof(ICoreWebView2CreateCoreWebView2ControllerCompletedHandler));
        if (!completedHandler)
        {
            error_printf(
                "%s:%d: %s (0x%x).\n",
                __FILE__,
                __LINE__,
                "Cannot allocate ICoreWebView2CreateCoreWebView2ControllerCompletedHandler",
                GetLastError()
            );
            ch = _getch();
            return GetLastError();
        }
        completedHandler->lpVtbl = malloc(sizeof(ICoreWebView2CreateCoreWebView2ControllerCompletedHandlerVtbl));
        if (!completedHandler->lpVtbl)
        {
            error_printf(
                "%s:%d: %s (0x%x).\n",
                __FILE__,
                __LINE__,
                "Cannot allocate ICoreWebView2CreateCoreWebView2ControllerCompletedHandlerVtbl",
                GetLastError()
            );
            ch = _getch();
            return GetLastError();
        }
        completedHandler->lpVtbl->AddRef = HandlerAddRef;
        completedHandler->lpVtbl->Release = HandlerRelease;
        completedHandler->lpVtbl->QueryInterface = HandlerQueryInterface;
        completedHandler->lpVtbl->Invoke = HandlerInvoke;

        ICoreWebView2Environment* env = arg;
        env->lpVtbl->CreateCoreWebView2Controller(
            env,
            hWnd,
            completedHandler
        );
    }
    else
    {
        ICoreWebView2Controller* controller = arg;

        if (controller != NULL) {
            webviewController = controller;
            webviewController->lpVtbl->get_CoreWebView2(
                webviewController,
                &webviewWindow
            );
        }

        ICoreWebView2Settings* Settings;
        webviewWindow->lpVtbl->get_Settings(
            webviewWindow,
            &Settings
        );
        Settings->lpVtbl->put_IsScriptEnabled(
            Settings,
            TRUE
        );
        Settings->lpVtbl->put_AreDefaultScriptDialogsEnabled(
            Settings,
            TRUE
        );
        Settings->lpVtbl->put_IsWebMessageEnabled(
            Settings,
            TRUE
        );
        Settings->lpVtbl->put_AreDevToolsEnabled(
            Settings,
            FALSE
        );
        Settings->lpVtbl->put_AreDefaultContextMenusEnabled(
            Settings,
            TRUE
        );
        Settings->lpVtbl->put_IsStatusBarEnabled(
            Settings,
            TRUE
        );

        RECT bounds;
        GetClientRect(hWnd, &bounds);
        webviewController->lpVtbl->put_Bounds(
            webviewController,
            bounds
        );

        webviewWindow->lpVtbl->Navigate(
            webviewWindow,
            L"https://google.com/"
        );
    }

    return S_OK;
}

LRESULT CALLBACK WindowProc(
    _In_ HWND   hWnd,
    _In_ UINT   uMsg,
    _In_ WPARAM wParam,
    _In_ LPARAM lParam
)
{
    switch (uMsg)
    {
    /*case WM_NCCALCSIZE:
    {
        return 0;
    }*/
    case WM_DPICHANGED:
    {
        RECT* const newWindowSize = (RECT*)(lParam);
        SetWindowPos(
            hWnd,
            NULL,
            newWindowSize->left,
            newWindowSize->top,
            newWindowSize->right - newWindowSize->left,
            newWindowSize->bottom - newWindowSize->top,
            SWP_NOZORDER | SWP_NOACTIVATE);
        return TRUE;
    }
    case WM_SIZE:
    {
        if (webviewController != NULL) {
            RECT bounds;
            GetClientRect(hWnd, &bounds);
            webviewController->lpVtbl->put_Bounds(
                webviewController,
                bounds
            );
        };
        break;
    }
    default:
    {
        return DefWindowProc(
            hWnd,
            uMsg,
            wParam,
            lParam
        );
    }
    }
    return 0;
}

int WINAPI wWinMain(
    _In_ HINSTANCE hInstance,
    _In_opt_ HINSTANCE hPrevInstance,
    _In_ LPWSTR lpCmdLine,
    _In_ int nShowCmd
)
{
    int ch;

    FILE* conout;
    AllocConsole();
    freopen_s(
        &conout,
        "CONOUT$",
        "w",
        stdout
    );

    HRESULT hr;

    if (!SetProcessDpiAwarenessContext(
        DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2
    ))
    {
        error_printf(
            "%s:%d: %s (0x%x).\n",
            __FILE__,
            __LINE__,
            "SetProcessDpiAwarenessContext",
            GetLastError()
        );
        ch = _getch();
        return GetLastError();
    }

    hr = CoInitialize(NULL);
    if (FAILED(hr))
    {
        error_printf(
            "%s:%d: %s (0x%x).\n",
            __FILE__,
            __LINE__,
            "CoInitialize",
            hr
        );
        ch = _getch();
        return hr;
    }

    WNDCLASS wndClass = { 0 };
    wndClass.style = CS_HREDRAW | CS_VREDRAW;
    wndClass.lpfnWndProc = WindowProc;
    wndClass.cbClsExtra = 0;
    wndClass.cbWndExtra = 0;
    wndClass.hInstance = hInstance;
    wndClass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndClass.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wndClass.lpszMenuName = NULL;
    wndClass.lpszClassName = APPLICATION_NAME;

    hWnd = CreateWindowEx(
        0,
        (LPCWSTR)(
            MAKEINTATOM(
                RegisterClass(&wndClass)
            )
            ),
        APPLICATION_NAME,
        WS_OVERLAPPEDWINDOW,
        100, 100, 800, 800,
        NULL,
        NULL,
        hInstance,
        NULL
    );
    if (!hWnd)
    {
        error_printf(
            "%s:%d: %s (0x%x).\n",
            __FILE__,
            __LINE__,
            "CreateWindowEx",
            GetLastError()
        );
        ch = _getch();
        return GetLastError();
    }

    ShowWindow(hWnd, nShowCmd);

    envHandler = malloc(sizeof(ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandler));
    if (!envHandler)
    {
        error_printf(
            "%s:%d: %s (0x%x).\n",
            __FILE__,
            __LINE__,
            "Cannot allocate ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandler",
            GetLastError()
        );
        ch = _getch();
        return GetLastError();
    }
    envHandler->lpVtbl = malloc(sizeof(ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandlerVtbl));
    if (!envHandler->lpVtbl)
    {
        error_printf(
            "%s:%d: %s (0x%x).\n",
            __FILE__,
            __LINE__,
            "Cannot allocate ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandlerVtbl",
            GetLastError()
        );
        ch = _getch();
        return GetLastError();
    }
    envHandler->lpVtbl->AddRef = HandlerAddRef;
    envHandler->lpVtbl->Release = HandlerRelease;
    envHandler->lpVtbl->QueryInterface = HandlerQueryInterface;
    envHandler->lpVtbl->Invoke = HandlerInvoke;
    
    UpdateWindow(hWnd);

    CreateCoreWebView2EnvironmentWithOptions(
        NULL,
        NULL,
        NULL,
        envHandler
    );

    MSG msg;
    BOOL bRet;
    while ((bRet = GetMessage(
        &msg,
        NULL,
        0,
        0)) != 0)
    {
        // An error occured
        if (bRet == -1)
        {
            break;
        }
        else
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
    }

    return 0;
}

[ysc3839]

I guess you forget add reference to webviewController:

        if (controller != NULL) {
            webviewController = controller;
			// missing webviewController->lpVtbl->AddRef(...); here
            webviewController->lpVtbl->get_CoreWebView2(
                webviewController,
                &webviewWindow
            );
        }

[valinet]

Finally. It makes so much sense. I am tired, my mistake. But honestly, finally someone that actually looked on my code a bit and came with the solution. I had a thread on StackOverflow, everyone was commenting with generics but no one was actually looking a bit on the particular case. A million thanks for taking the time, and apologies to the team for mislabeling this as a bug.

[ysc3839]

And you don't need to alloc lpVtbl at runtime, since the function pointers do not change after linking. You can (and should) put them in a static const struct.

[valinet]

Indeed, you are right. Never quite did this, haven't thought of it, but, again, it makes too much sense. I ended up with forward declaring my Handler... functions and then:

static const ICoreWebView2CreateCoreWebView2ControllerCompletedHandlerVtbl completedHandlerVtbl = {
    HandlerQueryInterface,
    HandlerAddRef,
    HandlerRelease,
    HandlerInvoke
};
static const ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandlerVtbl envHandlerVtbl = {
    HandlerQueryInterface,
    HandlerAddRef,
    HandlerRelease,
    HandlerInvoke
};
static const ICoreWebView2CreateCoreWebView2ControllerCompletedHandler completedHandler = {
    &completedHandlerVtbl
};
static const ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandler envHandler = {
    &envHandlerVtbl
};

Thank you very much for your tips. It helps improve my C skill and understand from top to bottom, that's the main reason I write this example in C. Thank you.

[champnic]

Big thanks @ysc3839!

Sounds like this issue is resolved so I'll close for now. @valinet Please let us know if you have any further questions or issues, thanks!

[pspmoe]

I ended up with forward declaring my Handler... functions and then:

@valinet Hello! Could you please provide the final complete version of this example? I am trying to use WebView2 in Kotlin/Native. But I am a C/C++ beginner and it is difficult for me to understand this code.