How to setup font rendering in MSHTML

Question

I'm learning to host a browser in my WinApi application using MSHTML and it's IWebBrowser2 and IHTMLDocument2. The first problem is blurry text, the left part of a picture is my app, and the right part is IE:

So, how to setup font rendering?

Answer 1

1. Your screen setting looks like 150% scaling so make sure that application is marked as DPI aware (edit manifest or select option in IDE).

2. In IDocHostUIHandler::GetHostInfo implementation add DOCHOSTUIFLAG_DPI_AWARE to dwFlags.

HRESULT DocHostUIHandler::GetHostInfo( DOCHOSTUIINFO* pInfo )
{
    pInfo->cbSize = sizeof(DOCHOSTUIINFO);
    pInfo->dwFlags =
            DOCHOSTUIFLAG_NO3DBORDER
            | DOCHOSTUIFLAG_DPI_AWARE
            | DOCHOSTUIFLAG_DISABLE_SCRIPT_INACTIVE;
    pInfo->dwDoubleClick = DOCHOSTUIDBLCLK_DEFAULT;
    return S_OK;
}

3. Change emulated IE version by setting registry key (not essential for high DPI, rather for better CSS support).

BOOL FixIeCompatMode()
{
    DWORD fix_version = 11001;

    // Get full path to application
    WCHAR app_path[ PATH_MAX ];
    DWORD result = GetModuleFileName( NULL, app_path, PATH_MAX );
    if ( result == 0 || result == PATH_MAX )
        return FALSE;

    // Find application name part (without path)
    WCHAR* app_name = app_path + wcslen( app_path );
    while ( app_name > app_path && app_name[ -1 ] != '\\' )
        --app_name;

    // Create or open FEATURE_BROWSER_EMULATION key
    HKEY hKey;
    WCHAR* reg_path = L"Software\\Microsoft\\Internet Explorer\\Main\\FeatureControl\\FEATURE_BROWSER_EMULATION";
    if ( RegCreateKey( HKEY_CURRENT_USER, reg_path, &hKey) != ERROR_SUCCESS )
        return FALSE;

    // Add registy entry for our application e.g
    // DisplayHTML.exe = 11001
    // You can check it (or delete) with regedit
    BOOL set = RegSetValueEx(
                 hKey,
                 app_name,
                 0,
                 REG_DWORD,
                 (void*)&fix_version,
                 sizeof(fix_version) ) == ERROR_SUCCESS )
    RegCloseKey( hKey );
    return set;
}

// Somewhere in your startup code (before creating WebView)
FixIeCompatMode();

Edit:

FixIeCompatMode sets WebBrowser emulation mode. Depending on value assigned to fix_version WebBrowser emulates different versions of IE.

Internet Feature Controls

• 11001: Internet Explorer 11. Webpages are displayed in IE11 edge mode, regardless of the declared !DOCTYPE directive. Failing to declare a !DOCTYPE directive causes the page to load in Quirks.
• 11000: IE11. Webpages containing standards-based !DOCTYPE directives are displayed in IE11 edge mode. Default value for IE11.
• 10001: Internet Explorer 10. Webpages are displayed in IE10 Standards mode, regardless of the !DOCTYPE directive.
• 10000: Internet Explorer 10. Webpages containing standards-based !DOCTYPE directives are displayed in IE10 Standards mode. Default value for Internet Explorer 10.
• 9999: Windows Internet Explorer 9. Webpages are displayed in IE9 Standards mode, regardless of the declared !DOCTYPE directive. Failing to declare a !DOCTYPE directive causes the page to load in Quirks.
• 9000: Internet Explorer 9. Webpages containing standards-based !DOCTYPE directives are displayed in IE9 mode. Default value for Internet Explorer 9. In Internet Explorer 10, Webpages containing standards-based !DOCTYPE directives are displayed in IE10 Standards mode.
• 8888: Webpages are displayed in IE8 Standards mode, regardless of the declared !DOCTYPE directive. Failing to declare a !DOCTYPE directive causes the page to load in Quirks.
• 8000: Webpages containing standards-based !DOCTYPE directives are displayed in IE8 mode. Default value for Internet Explorer 8. Important In Internet Explorer 10, Webpages containing standards-based !DOCTYPE directives are displayed in IE10 Standards mode.
• 7000: Webpages containing standards-based !DOCTYPE directives are displayed in IE7 Standards mode. Default value for applications hosting the WebBrowser Control.

What Happens if I Set the FEATURE_BROWSER_EMULATION Document Mode Value Higher than the IE Version on the Client?

Obviously, the browser control can only support a document mode that is less than or equal to the IE version installed on the client.
Using the FEATURE_BROWSER_EMULATION key works best for enterprise line of business apps where there is a deployed and support version of the browser. In the case you set the value to a browser mode that is a higher version than the browser version installed on the client, the browser control will choose the highest document mode available.

If FEATURE_BROWSER_EMULATION is omitted some !DOCTYPE directives (e.g <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">) could activate old IE 7.0 emulation with many drawbacks (e.g. worse CSS support).

You can check it (or delete) with regedit.