Add wxEVT_WEBVIEW_CHROMIUM_MESSAGE_RECEIVED

This allows to handle IPC messages from custom JS functions in the code
using wxWebViewChromium.

include/wx/webview_chromium.h

@@ -178,6 +178,50 @@ private:
     wxDECLARE_DYNAMIC_CLASS(wxWebViewChromium);
 };
 
+class CefFrame;
+class CefProcessMessage;
+
+// Chrome-specific event sent when a message from renderer process is received.
+//
+// It provides the message received from another process and a frame that can
+// be used to send the reply back.
+class WXDLLIMPEXP_WEBVIEW wxWebViewChromiumEvent : public wxCommandEvent
+{
+public:
+    wxWebViewChromiumEvent() = default;
+
+    wxWebViewChromiumEvent(
+        wxWebViewChromium& webview,
+        CefFrame& frame,
+        CefProcessMessage& message
+    );
+
+    CefFrame& GetFrame() const { return *m_frame; }
+    CefProcessMessage& GetMessage() const { return *m_message; }
+
+    wxString GetMessageName() const;
+
+private:
+    CefFrame* const m_frame = nullptr;
+    CefProcessMessage* const m_message = nullptr;
+
+    wxDECLARE_DYNAMIC_CLASS_NO_ASSIGN_DEF_COPY(wxWebViewChromiumEvent);
+};
+
+wxDECLARE_EXPORTED_EVENT( WXDLLIMPEXP_WEBVIEW,
+                          wxEVT_WEBVIEW_CHROMIUM_MESSAGE_RECEIVED,
+                          wxWebViewChromiumEvent );
+
+typedef void (wxEvtHandler::*wxWebViewChromiumEventFunction)
+             (wxWebViewChromiumEvent&);
+
+#define wxWebViewChromiumEventHandler(func) \
+    wxEVENT_HANDLER_CAST(wxWebViewChromiumEventFunction, func)
+
+#define EVT_WEBVIEW_CHROMIUM_MESSAGE_RECEIVED(id, fn) \
+    wx__DECLARE_EVT1(wxEVT_WEBVIEW_CHROMIUM_MESSAGE_RECEIVED, id, \
+                     wxWebViewChromiumEventHandler(fn))
+
 #endif // wxUSE_WEBVIEW && wxUSE_WEBVIEW_CHROMIUM
 
 #endif // _WX_WEBVIEWCHROMIUM_H_

interface/wx/webview_chromium.h

@@ -254,6 +254,17 @@
 
     - SetRoot() allows to use the given directory for all application files.
 
+
+    @section events Events
+
+    wxWebViewChromiumEvent is a specific event generated when a message from
+    the renderer process (in which any user-defined JavaScript functions are
+    executing) is received in the browser process (containing UI). Such
+    messages are sent using `CefFrame::SendProcessMessage(PID_BROWSER)` from
+    the renderer process, but describing Chromium IPC in details is out of
+    scope of this document, please see Chromium documentation for more
+    information.
+
     @since 3.3.0
     @library{wxwebview}
     @category{webview}
@@ -292,3 +303,63 @@ public:
      */
     void SetRoot(const wxFileName& rootDir);
 };
+
+
+/**
+    Event class for events generated exclusively by wxWebViewChromium.
+
+    See wxWebViewEvent for other events also generated by wxWebViewEvent.
+
+    Currently there is a single event type corresponding to this event:
+    `wxEVT_WEBVIEW_CHROMIUM_MESSAGE_RECEIVED`. To use it (this example assumes
+    that the required CEF headers are included):
+
+    @code
+    webview->Bind(
+        wxEVT_WEBVIEW_CHROMIUM_MESSAGE_RECEIVED,
+        [this](wxWebViewChromiumEvent& event) {
+            if ( event.GetMessageName() == "MyCustomRequest" ) {
+                CefRefPtr<CefListValue> arguments = event.GetMessage().GetArgumentList();
+                CefRefPtr<CefProcessMessage> response = CefProcessMessage::Create("MyCustomResponse");
+
+                // ... do whatever is needed to construct the response ...
+
+                event.GetFrame().SendProcessMessage(PID_RENDERER, response);
+            } else {
+                // Not our message.
+                event.Skip();
+            }
+        }
+    );
+    @endcode
+
+    @since 3.3.0
+    @library{wxwebview}
+    @category{webview}
+**/
+class wxWebViewChromiumEvent : public wxCommandEvent
+{
+public:
+    /**
+        Get the associated browser frame.
+
+        This object can be used to call `SendProcessMessage(PID_RENDERER)` on
+        it to send the reply back to the renderer process.
+    */
+    CefFrame& GetFrame() const;
+
+    /**
+        Get the actual message.
+
+        Message arguments can be used in the event handler to get information
+        associated with this message.
+    */
+    CefProcessMessage& GetMessage() const;
+
+    /**
+        Get the message name.
+
+        This is just a convenient wrapper for `GetMessage().GetName()`.
+    */
+    wxString GetMessageName() const;
+};

src/common/webview_chromium.cpp

@@ -289,6 +289,11 @@ public:
     virtual CefRefPtr<CefLoadHandler> GetLoadHandler() override  { return this; }
     virtual CefRefPtr<CefRequestHandler> GetRequestHandler() override { return this; }
 
+    virtual bool OnProcessMessageReceived(CefRefPtr<CefBrowser> browser,
+        CefRefPtr<CefFrame> frame,
+        CefProcessId source_process,
+        CefRefPtr<CefProcessMessage> message) override;
+
     // CefDisplayHandler methods
     virtual void OnLoadingStateChange(CefRefPtr<CefBrowser> browser,
         bool isLoading, bool canGoBack,
@@ -1369,6 +1374,24 @@ void wxWebViewChromium::SetRoot(const wxFileName& rootDir)
     );
 }
 
+bool
+ClientHandler::OnProcessMessageReceived(CefRefPtr<CefBrowser> WXUNUSED(browser),
+    CefRefPtr<CefFrame> frame,
+    CefProcessId WXUNUSED(source_process),
+    CefRefPtr<CefProcessMessage> message)
+{
+    // This is not supposed to happen, but test for it nevertheless.
+    if ( !frame || !message )
+    {
+        wxLogTrace(TRACE_CEF, "Ignoring null OnProcessMessageReceived() args");
+        return false;
+    }
+
+    wxWebViewChromiumEvent event(m_webview, *frame, *message);
+
+    return m_webview.HandleWindowEvent(event);
+}
+
 // CefDisplayHandler methods
 void ClientHandler::OnLoadingStateChange(CefRefPtr<CefBrowser> WXUNUSED(browser),
                                          bool WXUNUSED(isLoading),
@@ -1847,4 +1870,30 @@ private:
 
 wxIMPLEMENT_DYNAMIC_CLASS(wxWebViewChromiumModule, wxModule);
 
+// ----------------------------------------------------------------------------
+// wxWebViewChromiumEvent
+// ----------------------------------------------------------------------------
+
+wxIMPLEMENT_DYNAMIC_CLASS(wxWebViewChromiumEvent, wxCommandEvent);
+
+wxDEFINE_EVENT( wxEVT_WEBVIEW_CHROMIUM_MESSAGE_RECEIVED, wxWebViewChromiumEvent );
+
+wxWebViewChromiumEvent::wxWebViewChromiumEvent(
+    wxWebViewChromium& webview,
+    CefFrame& frame,
+    CefProcessMessage& message
+) : wxCommandEvent(wxEVT_WEBVIEW_CHROMIUM_MESSAGE_RECEIVED, webview.GetId()),
+    m_frame(&frame),
+    m_message(&message)
+{
+    SetEventObject(&webview);
+}
+
+wxString wxWebViewChromiumEvent::GetMessageName() const
+{
+    wxCHECK_MSG( m_message, {}, "No message" );
+
+    return m_message->GetName().ToWString();
+}
+
 #endif // wxUSE_WEBVIEW && wxUSE_WEBVIEW_CHROMIUM