webkit_web_view_get_snapshot_finish无法返回表面并返回错误

Question

我正在尝试获取WebKitWebView的快照。

调用GAsyncReadyCallback，但是调用后返回cairo_surface_t *并将GError *传递给webkit_web_view_get_snapshot_finish为空。

//.cpp
void ExampleProgram::TakeSnapshot()
{
    webkit_web_view_get_snapshot (m_webView,
                                  WEBKIT_SNAPSHOT_REGION_FULL_DOCUMENT,
                                  WEBKIT_SNAPSHOT_OPTIONS_NONE,
                                  NULL,
                                  (GAsyncReadyCallback)onTakeWebviewSnapshotFinished,
                                  NULL);
}

void ExampleProgram::onTakeWebviewSnapshotFinished(WebKitWebView* webView, GParamSpec* pspec)
{
   GAsyncResult * result;
   GError *error = NULL;
   cairo_surface_t * surface = webkit_web_view_get_snapshot_finish(webView, result, &error);
}

//.h
void TakeSnapshot();
static void onCaptureFullWebviewFinished(WebKitWebView* webView, GParamSpec* pspec);