application:openFile: did report error when trying to open own file type

Question

My application has it's own unique file type. When the file is double-clicked by the user and the application was not running, the application starts but reports the following error:

My application base on Chromium (CEF). I neither use application:applicationWillFinishLaunching nor application:applicationDidFinishLaunching for any setup parts but it seems that application:openFile did get called before the application is fully launched.

Questions

• Is there a way to wait until the application is fully initialized to be able to open/handle the file correctly
• Is there another method which can be called after the application is fully initialized

My AppDelegate implementation is as follow:

// ****************************************************************************
// application:openFile
// ****************************************************************************

- (BOOL)application:(NSApplication *)theApplication openFile:(NSString *)filename
{
  return [self processFile:filename];
}

// ****************************************************************************
// processFile
// ****************************************************************************

- (BOOL)processFile:(NSString *)file
{
  std::string fileName([file UTF8String]);
  au::arcwork::Handler* handler = au::arcwork::Handler::GetInstance();
  handler->OnOpenFile(fileName);
  return YES;
}

Answer 1

After lot of research and debugging I came up with a solution how to implement application:openFile for Chromium based applications on OS X. First of all, there are 3 parts/layers which have to be solved.

1. Cocoa part with application:openFile
2. Chromium part with browser initialization code
3. JavaScript part with its initialization part

Beginning with 1:

The Apple documentation for application:openFile already describes in the Discussion part, that application:openFile is called before applicationDidFinishLaunching. This means, that If you rely on a full initialized client (I can't imagine how's not?), you have to store the URL of the file somewhere, e.g. ivar/property in application:openFile or like in my example below in a std::vector of my Chromium handler. Only if the application if fully initialized and a browser window is displayed, then you're able to directly call the Chromium handler method that in turn calls the appropriate JavaScript function!

// ***
// application:openFile
// ***

- (BOOL)application:(NSApplication *)theApplication openFile:(NSString *)filename {
  AUApplication * clientApp = (AUApplication *)theApplication;
  NSWindow* targetWindow = [clientApp findTargetWindow];
  //Check if browser window is up and running
  if (targetWindow) {
    [self processFile:filename];
  }
  else {
    //This method saves the file URL to open the file 
    //when the application+JavaScript is fully initialized
    au::test::Handler* handler = au::test::Handler::GetInstance();
    handler->AddPendingFile([filename UTF8String]); 
  }
  return YES;
}

// ***
// processFile
// ***

- (BOOL)processFile:(NSString *)file
{
  //This method calls the JavaScript function to open the file
  std::string fileName([file UTF8String]);
  au::test::Handler* handler = au::test::Handler::GetInstance();
  handler->OnOpenFile(fileName); 
  return YES;
}

The 2 part:

On Chromium side you have to store the file URL in a appropriate structure. I'm using std::vector for that. The file URL is saved in the Chromium method OnLoadEnd. Here Chromium have loaded your HTML+JavaScript parts in the browser. But be careful. The initialization of JavaScript is not done yet! In my example below I have to assign a JavaScript property to store the file URL.

// ***
// Handler::OnLoadEnd
// ***

void Handler::OnLoadEnd(CefRefPtr<CefBrowser> browser,
               CefRefPtr<CefFrame> frame,
               int httpStatusCode) {
  if (!m_pendingOpenFiles.empty()) {
    std::string file(m_pendingOpenFiles[0]);
    std::cout << "Pending file for later opening: " << file << std::endl;
    //This method below is calling a JavaScript function to assign
    //a property `pendingFile`
    OnPendingFile(file);
    //Don't forget to pop the file URL afterwards 
    //or use another store container instead of `std::vector`
    //if you don't plan to implement `application:openFiles` as well!!!
    m_pendingOpenFiles.pop_back();
  }
}

The 3 part:

On JavaScript side you have to check after the application initialization if the property pendingFile is assigned or not to open the file appropriately.