interface ICoreWebView2Controller2

Artikel
11/18/2024

interface ICoreWebView2Controller2
  : public ICoreWebView2Controller

A continuation of the ICoreWebView2Controller interface.

Summary

Members	Descriptions
get_DefaultBackgroundColor	Gets the `DefaultBackgroundColor` property.
put_DefaultBackgroundColor	The `DefaultBackgroundColor` property is the color WebView renders underneath all web content.

Applies to

Product	Introduced
WebView2 Win32	1.0.774.44
WebView2 Win32 Prerelease	1.0.790

Members

get_DefaultBackgroundColor

Gets the DefaultBackgroundColor property.

public HRESULT get_DefaultBackgroundColor(COREWEBVIEW2_COLOR * value)

put_DefaultBackgroundColor

The DefaultBackgroundColor property is the color WebView renders underneath all web content.

public HRESULT put_DefaultBackgroundColor(COREWEBVIEW2_COLOR value)

This means WebView renders this color when there is no web content loaded such as before the initial navigation or between navigations. This also means web pages with undefined css background properties or background properties containing transparent pixels will render their contents over this color. Web pages with defined and opaque background properties that span the page will obscure the DefaultBackgroundColor and display normally. The default value for this property is white to resemble the native browser experience.

The Color is specified by the COREWEBVIEW2_COLOR that represents an RGBA value. The A represents an Alpha value, meaning DefaultBackgroundColor can be transparent. In the case of a transparent DefaultBackgroundColor WebView will render hosting app content as the background. This Alpha value is not supported on Windows 7. Any A value other than 255 will result in E_INVALIDARG on Windows 7. It is supported on all other WebView compatible platforms.

Semi-transparent colors are not currently supported by this API and setting DefaultBackgroundColor to a semi-transparent color will fail with E_INVALIDARG. The only supported alpha values are 0 and 255, all other values will result in E_INVALIDARG. DefaultBackgroundColor can only be an opaque color or transparent.

This value may also be set by using the WEBVIEW2_DEFAULT_BACKGROUND_COLOR environment variable. There is a known issue with background color where setting the color by API can still leave the app with a white flicker before the DefaultBackgroundColor takes effect. Setting the color via environment variable solves this issue. The value must be a hex value that can optionally prepend a 0x. The value must account for the alpha value which is represented by the first 2 digits. So any hex value fewer than 8 digits will assume a prepended 00 to the hex value and result in a transparent color. get_DefaultBackgroundColor will return the result of this environment variable if used. This environment variable can only set the DefaultBackgroundColor once. Subsequent updates to background color must be done through API call.

void ViewComponent::SetBackgroundColor(COLORREF color, bool transparent)
{
    m_webViewColor.R = GetRValue(color);
    m_webViewColor.G = GetGValue(color);
    m_webViewColor.B = GetBValue(color);
    m_webViewColor.A = transparent ? 0 : 255;
    wil::com_ptr<ICoreWebView2Controller2> controller2 =
        m_controller.query<ICoreWebView2Controller2>();
    controller2->put_DefaultBackgroundColor(m_webViewColor);
}

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