How to set/coding in CEF to allow flash on current page

[QtHarry]

When I visited http://get.adobe.com/it/flashplayer/about/, the chrome displayed "Flash was blocked on this page", but I can set Flash to "Allow" by the information menu and let flash be played successfully.
At least in chrome flash can be set to allow manually, but how to do this in CEF? I visited the same url in cefclient or cefsimple app, the flash was blocked, how to set flash to allow? Thanks.

[magreenblatt]

If you are on Windows or macOS install the "Opera and Chromium PPAPI" version from https://get.adobe.com/flashplayer/otherversions/ and then run CEF with the `--enable-system-flash` command-line flag.

[QtHarry]

Thanks magreenblatt.
I'ved installed ppapi flash plugin, for normal flash website, there is no problem, flash content can be played. But for http://get.adobe.com/it/flashplayer/about/, the flash is blocked.
I can see the difference between chrome and cef (cefclient or cefsimple app) is that, in chrome, flash can be set to allow through menu, but how to set it in cef?

[JimmyO]

Hello,

i also have some trouble with blocked flash.
Any solution to enable the blocked flash in software or as commandline paramater for cefclient.exe.
Thanks
Jimmy

[magreenblatt]

See CefRequestContextHandler::OnBeforePluginLoad documentation.

[JimmyO]

Hello,

Where can i found then CefRequestContextHandler::OnBeforePluginLoad documentation ?

I've add a CefRequestContextHandler and overwrite the function OnBeforePluginLoad.
The function OnBeforePluginLoad is called, but
a) mime_type is only applicaton/pdf and no flash ?
b) and the default policy is ALLOWED.
But i don't see any flag for enable the plugin.

Please can you give me more information about this. I'm new in CEF.

Thanks

[ndesktop]

OnBeforePluginLoad is implemented by CefRequestContextHandler.
You need to derive a class from CefRequestContextHandler, and instantiate it in your client handler GetRequestContext.
Something like this:

// declaration in client_handler.h

Code: Select all

class ClientHandler
  : public CefClient
...
  , public CefRequestContextHandler
{
...
  critical_section_t _csSharedRequestContext; // protection for m_SharedRequestContext
  CefRefPtr<CefRequestContext> m_SharedRequestContext;
...
    public:
        CefRefPtr<CefRequestContext> GetRequestContext(
            ClientHandler* client_handler);
        void CloseRequestContext();
...
};


Browser creation:

Code: Select all

... function to create a CefBrowser
   return CefBrowserHost::CreateBrowser(
            info,
            static_cast<CefRefPtr<CefClient>>(m_Handler),
            url, settings,
            GetRequestContext( pClientHandler )  // <== here we create (the "de facto" singleton) context and pass client handler to our ClientRequestContextHandler implementation
        );


// client handler GetRequestContext implementation

Code: Select all

CefRefPtr<CefRequestContext> ClientHandler::GetRequestContext(
    ClientHandler* client_handler)
{
    DCHECK(CefCurrentlyOn(TID_UI));

...

    //  all browsers are sharing the same request context (for now)
    critical_section_lock_t lock(&_csSharedRequestContext);
    if(m_SharedRequestContext.get() == nullptr)
    {
        m_SharedRequestContext =
            CefRequestContext::CreateContext(
                CefRequestContext::GetGlobalContext(),
                new ClientRequestContextHandler(this)
            );
    }
    DCHECK(m_SharedRequestContext.get());
    return m_SharedRequestContext;
}

void ClientHandler::CloseRequestContext()  // call this on shutdown - lifetime it's up to you
{
    critical_section_lock_t lock(&_csSharedRequestContext);
    m_SharedRequestContext = nullptr;
}


ClientRequestContextHandler implementation:

Code: Select all

        class ClientRequestContextHandler
            : public CefRequestContextHandler {
        private:
            ClientHandler* m_handler; // weak ref
        public:
            ClientRequestContextHandler(ClientHandler* handler)
                : m_handler(handler)
            {}
            ~ClientRequestContextHandler()
            {
                m_handler = nullptr;
            }
        public:
            CefRefPtr<CefCookieManager> GetCookieManager() override {
                return NULL;
            }
            bool OnBeforePluginLoad(const CefString& mime_type,
                const CefString& plugin_url, bool is_main_frame,
                const CefString& top_origin_url,
                CefRefPtr<CefWebPluginInfo> plugin_info,
                PluginPolicy* plugin_policy) override {
                // simply forward it to client handler
                if(m_handler) {
                    if(m_handler->OnBeforePluginLoad(mime_type,
                                plugin_url, is_main_frame, top_origin_url,
                                plugin_info, plugin_policy)) {
                        //  handled by client handler
                        return true;
                    }
                }
                return __super::OnBeforePluginLoad(mime_type,
                    plugin_url, is_main_frame, top_origin_url,
                    plugin_info, plugin_policy);
            }
            void OnUnloadablePlugin(const CefString& url,
                const CefString& mime_type) override
            {
                if(m_handler) {
                    m_handler->OnUnloadablePlugin(url, mime_type);
                }
            }
        private:
            IMPLEMENT_REFCOUNTING(ClientRequestContextHandler);
        };


And finally the proxied implementation in client handler (trimmed of sample):

Code: Select all

bool ClientHandler::OnBeforePluginLoad(
    const CefString& mime_type,
    const CefString& plugin_url,
    bool is_main_frame,
    const CefString& policy_url,
    CefRefPtr<CefWebPluginInfo> info,
    CefRequestContextHandler::PluginPolicy* plugin_policy)
{
    METHOD_GUARD_(CefRequestHandler, OnBeforePluginLoad, false)

    if(plugin_policy == nullptr)
        return false;

    const char* kFlashMimeType = "application/x-shockwave-flash";

    if(info.get()) {
        CefRefPtr<CefListValue> mime_types = info->GetMimeTypes();
        if(mime_types.get() != 0) {
            size_t cMimeTypes = mime_types->GetSize();
            for(size_t c = 0; c < cMimeTypes; c++)
            {
                CefString sMimeType = mime_types->GetString(c);
                if(sMimeType == kFlashMimeType) {
                   *plugin_policy = PLUGIN_POLICY_ALLOW;
                   return true; // explicitely allowed by us
                }
            }
        }
    }

...
    return false; // no verdict from us, let the default behavior flow
}


[ndesktop]

Also, launch your app with --enable-system-flash. I don't know what version are you using and Flash is on the verge of being obsoleted.
Maybe by default is not even allowing it, that's why you receive only application/pdf which is the internal Chromium PDF viewer (chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai/).