How are url scheme and file types handlers found/registered on macOS? - objective-c

I am creating a plug-in in Objective-C to a third-party macOS app. I want to register and handle url scheme (like myscheme://somedatahere) and file types - for example, when a user double click on a file our plug-in should be notified.
As my product is just a plug-in to a third-party app, the code has no access to the app's NSApplication instance nor to its events. As such, I need to create a helper app and bundle it inside the plug-in bundle/package to register and handle that. Please let me know if these presumptions are incorrect.
The plug-in bundle is being installed inside the Library/Application Support (the user typically downloads the plug-in into the Downloads folder, double click it and then the host app's handler copies the plug-in into the Application Support folder). The app handling urls and file types will be placed inside the plug-in bundle. The location was chosen by the host app.
I have several uncertainties I failed to find answers for:
How does the macOS finds apps capable of handling a particular url scheme and file types?
Does macOS finds it somewhat automatically or should I call something?
If it is found automatically, will it work even if the app is located inside a plug-in package outside of the Applications directory?

You can find the answers you are looking for the in the Launch Services documentation.
If you check the section "Application Registration", you will see that:
A built-in background tool, run whenever the system is booted or a new user logs in, automatically searches the Applications folders in the system, network, local, and user domains and registers any new applications it finds there.
The Finder automatically registers all applications as it becomes aware of them, such as when they are dragged onto the user’s disk or when the user navigates to a folder containing them.
So, if your helper app is installed into /Library/Application Support by the user manually dragging-and-dropping, it looks like Launch Services will see it and register the URL scheme.
Otherwise, the documentation continues to cover the manual case:
In spite of these automatic registration utilities, it may sometimes be necessary to register an application explicitly with Launch Services. For example, although developers are encouraged to package their applications so that they can be installed by simply dragging them onto the user’s disk, some applications may require more elaborate custom installer software. In such cases, the installer should call one of the Launch Services registration functions LSRegisterFSRef or LSRegisterURL to register the application explicitly.

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So I have an application that has dependencies, web drivers for Selenium. I want to include the drivers in my program, or optionally just ask the user what browser they would like to use this application with, and include the proper driver. But during install, I would like to save the file path of the driver to load the selenium web driver. I thought about creating a .txt file when the user specifies their path into that folder, and using that. But all the "create an application installer" guides I've come across just use another app to create their installer. There is really no installation, there is just a light weight .exe main program, and then the web drivers. But I need to configure the web driver in the program.

How to program a sandboxed application in Yosemite

I was trying to program a simple TODO app for Yosemite with sandboxing. Apple has its tutorials for the same but they are not very elaborate. I wanted to know sandbox APIs like sandbox_init() and APIs for console logs (heard sandboxed apps use some special APIs). Could someone please point me to some open source app with sandboxing on Yosemite, so that I could see the APIs that it is using.
You don't need to use sandbox_init() etc. in order to create a sandboxed app.
Roughly, you need to understand:
Use the APIs to find well known directories and don't assume that /Users/username/Documents is the Documents folder, for example.
The app has no access to user files and must gain access via NSOpenPanel.
If the app wants to retain access it has already gained then it needs to create and store bookmark URLs, which can be reloaded during a later invocation.
If the sandboxed app spawns a child process, then that child process needs it's own set of entitlements.
Once you understand that it's normally just a case of setting Use Sandbox in the app capabilities and you're off.

make an AIR desktop application the default web browser

I would like to make my AIR desktop browser be the default web browser on a system, how can I go about and do this ?
I would also like to know how I can retrieve the link that has been clicked (in an email for example) to interact with the application.
thanks !
As far as I'm aware this is impossible in AIR. You can associate your app with file types using the air-app.xml descriptor or by calling NativeApplication.setAsDefaultApplication() (Read about it here). Opening files after using either of these methods will trigger your application to launch with an InvokeEvent (Read Here). You can read a good tutorial for this here.
However, if I understand correctly, you also want your app to take over any HTTP requests from inside any other app. To do this you have to override the protocol default application, which requires a registry edit and (I believe) that AIR can't do that. You may be able to write an external script in C or Java to do that for you (This might help with that).

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I am attempting to write a small, lightweight client, using vb.net winforms, that can install without needing elevated privileges. Before I ask my questions, let me give you a bit of an idea of what it is supposed to do.
The app will start when Windows loads, set like this from the install, with a system/notification tray icon that can be clicked on to load up specific functionality. The application install from a website, or possibly a file share, haven't quite decided yet. This client will initially request user credentials for one of our web programs, and it will talk to an already built web service to determine what functionalities of our services they have licensed access to. After this, credentials will be encrypted and saved to the users pc locally. Every five minutes, the client will pass the credentials to the websites they have access to and check to see the status of jobs that are being processed, and download available reports if needed.
So, here is what I am trying to understand. If I configure this app as a ClickOnce application, once it installs from the url or shared drive, the user will not need to do anything else, correct? Or do they have to visit that url every time they boot up to reinstall/run the client?
Another thing, I wanted to get some opinions on the best ways to do some of the things this app will be doing. I have a good idea of where I am going with it, but I have no idea of which solution to go with yet.
For instance, what is the best way to store user passed credentials on their system for a "remember me"?
Also, is the best way to have the client install with automatically starting on windows startup to configure it to create a shortcut of itself in the windows startup folder?
I am trying to keep this as lightweight as possible, and using a very small GUI, so it shouldn't be too intrusive, so any ideas on how to ensure that, while keeping it from needing admin privs to install, will also help.
If I configure this app as a ClickOnce application, once it installs
from the url or shared drive, the user will not need to do anything
else, correct? Or do they have to visit that url every time they boot
up to reinstall/run the client?
Well if they need to reinstall it, they would have to download the setup.exe file again, but why would users need to do that? CilckOnce supports automatic updates. Visiting url is certainly not needed for running the program.
what is the best way to store user passed credentials on their system
for a "remember me"?
Probably storing them as application settings. Haven't used visual studio 2012, but in visual studio 2010 you have to right-click on project in solutions explorer, go to project propeties and then create variables in Settings tab. Then you can access those variables in code using My.Settings.variableName. Not sure about security though, if you need any.
As for privileges, I think you just need a privilege to install a program. Maybe you should publish a primitive clickOnce application and experiment with it and that will answer all your other questions about clickOnce.

Updating OSX right click context menu with new service item

I have created an application that exposes a OSX service for certain file by adding an NSService entry into my applications info.plist (as in http://www.macosxautomation.com/services/learn/), but I find that upon installing my application on a new machine the service doesn't show up quickly in the finder right click context menu.
I know that this is because pasteboard services hasn't re-indexed the /Applications folder and "discovered" the newly installed service.
I also know that I can force a re-index and discovery by manually running /System/Library/CoreServices/pbs.
The question here is what is the best way to ensure that my service shows up as quickly as possible for users who are installing my application for the first time.
I could execute a system call to "/System/Library/CoreServices/pbs" when my application starts up --If the user immediately starts my application--, but that only partly solves the problem (in addition I wonder if there is a better Cocoa API based way of doing this).
If my application is generally only accessed via the context menu, a user will never think to go out and start the application in the first place. They will only think it is broken when the context menu isn't there.
I am not distributing my application with an installer. I am simply providing a bundle that can be dragged and dropped into /Applications (as I believe Apple usually suggests).
Is there a way to expedite the process of service discovery when doing an installation in this fashion, so that there isn't any period of time where the user is without the newly installed service?
As a side note, it appears that the problem may not exist in 10.8 (or at least be as pronounced). Apple may have made this indexing happen more quickly in their most recent release.
I've actually ended up using
system("killall pbs;/System/Library/CoreServices/pbs -flush");
in one of my apps, just as you describe, though it's a long time ago, when 10.5 was in question as well.
You might want to try this function, however:
void NSUpdateDynamicServices(void)
which according to the documentation acts just like flushing pbs, but is a cleaner solution.
Also, if (according to your description), the app is nothing but a service, consider making it a really just a service - see (Installing the Service)
To build a standalone service, use the extension .service and store it in Library/Services.