apparmor picture_files_read

  • I'm working on an app that needs permissions to access the user's Pictures directory. I'm programming with C++ and SDL. I set this in my apparmor file:

    "policy_groups": [
    "policy_version": 16.04

    I am able to access the app's directory here:
    I can read and write to that directory.

    However, I am not able to read files from this directory:

    Is there something I have over looked?

    Thank you for your help.

  • @Craig Hi Craig,

    Short answer, please read this page :

    Developers should typically use the content_exchange policy group and API to access picture files instead

    You might want to use :

    I don't know about how to use the reserved rights but I'll advise to follow the common rules and use the content hub.

  • @AppLee Thank you. I read those pages before and I read them again. I added hooks in my manifest.json and a contenthub.json file. I see my app listed when I open Gallery, select a photo and click the share icon.

    I'm programming my app in C++ and SDL2. So my question is: How can I get my app to open the content hub so a user can select a photo from their Gallery?

  • @Craig have you tried Telegram AppDev group ?, or maybe create a new topic for this issue

  • @AppLee I'm getting my C++/SDL app to receive pictures from the content hub as you suggested. I hope this can serve as a half-way tutorial for others out there. But it's not complete. Here is what I have so far:

    In my manifest.json, I have "content-hub" in the hooks section:

    "hooks": {
    	"SDLTest": {
    		"apparmor": "SDLTest.apparmor",
    		"desktop": "SDLTest.desktop",
    		"content-hub": "SDLTest-contenthub.json"

    In SDLTest-contenthub.json I have "pictures":

    "destination": [

    In SDLTest.apparmor I have "content_exchange":

    "policy_groups": [
    "policy_version": 16.04

    After I run "clickable", I open the Gallery app, select a photo and click on the link icon, I see my app listed. After I selected my app, I used "adb shell" and found the photo I selected on my phone at this system path:

    And I had read/write access to the photos with C++. This part works great so far!

    But all I need to understand now is how to I get my app to LAUNCH Gallery when a user clicks a button inside my app. I'm using purely C++ and SDL. I imagine it would work something like this:

    if ( event.type == SDL_FINGERDOWN ) {

    Detailed instructions would be appreciated. You wont bore me.

  • @Craig I dont think that its supported for an App to launch another app. You could export a picture and then the suer canchoose Gallery as a target. But so far just launching a specific app is not possible. Its also hard to make this stable since what if Gallery app is not installed, has been renamed etc ?

  • @Craig
    Hi, and good job on this.
    Now you want to use the content hub the other way around and export a picture from your app.

    You'll have to add ContentHandler.Source to your SDLTest-contenthub.json
    You should read this :

    As Flo wrote, you cannot force an app, the user has to select the destination app.

  • @Flohack What about when the Messaging app launches the content hub so I can attach an image to a text message?

  • @Craig
    What Florian meant is that an app cannot directly opens another one (even less a specific one).
    You have to go through the Content Hub to do so, but it's not the messaging app opening the gallery...

  • @AppLee Why would I want to export a picture from my app when that's not what it needs to do? It needs to acquire a picture from the content hub, namely Gallery or File Manager. Sorry, maybe I didn't make it clear what I'm trying to do.

  • @AppLee Sorry, I must not be using the right vocabulary. Basically, like how the Messaging app opens the content hub and you can choose from Gallery or File Manager, then a photo is sent to a directory where the Messaging app can access it. How can I get my C++ app to open/launch/etc the content hub? I have already added the required code for my app to be listed as a "destination" in the content hub. I just need to understand how to create an event/link/etc in C++ that will open the content hub for my app's users. Thank you!

  • @Craig
    Oh sorry, I ddin't fully understand your question.

    So you can refer there :
    You can call the ContentPeerPicker in your code to display the app choice to import a Picture from.

  • @AppLee I read that Importing section, thanks. What language is that written in? Qml? My app is written in C++. Is there a way to open the content hub with C++? Or is there some headers I can put in my C++ program that will enable a new function to do that? I can't seem to find documentation for C++.

  • @Craig
    Yes it's QML, I don't know about C++ only.
    Can you consider some QML for the front part of your app ?
    It's not difficult to learn and use.

  • @AppLee Okay, I tried it. I did "clickable create" and selected the C++ binary option.

    When I run "clickable" the main.cpp file calls qml/Main.qml and it says "Hello World!" on my touch device.

    Now, I tried to swap the code in Main.qml for this code here:
    The code just below "Example usage for importing content:"

    When I run "clickable", clickable reports: /bin/sh: 1: Syntax error: "(" unexpected

    Is there a mistake in the documented code? What do I need to put in the Main.qml file so it brings up the content hub?


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