iOS Dynamically loaded custom fonts in WidgetKit not working on real device (simulator is fine). Sandbox chronod deny file-read-data for font file.

Project structure is:
App target + widget extension + widget intent extension
All share a common appgroup group.com.x.y and all file handling is done using

Code Block 
FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: "group.com.x.y")

so that only the shared container is used.

Using the Main app target, a font "Chewy-Regular.ttf" is downloaded and saved to the shared AppGroup container.

Font can now be loaded via

Code Block 
CTFontManagerRegisterFontsForURL

and displayed in a Main App Text view

Code Block 
Text("Testing...").font(Font.custom("Chewy-Regular", size: 20))

Now add a Widgetkit widget instance that uses this font.

In 'getTimeLine() and getSnapShot() of IntentTimelineProvider we load the font again via CTFontManagerRegisterFontsForURL (this needs to happen again probably because widget runs in a separate process from the main app?).

On simulator, the widget will show the correct font.
BUT
On iPhone7 real device, the widget will show the 'redacted placeholder view'. It seems that something is crashing.

I see in the device console :

Code Block 
error	14:39:07.567120-0800	chronod	No configuration found for configured widget identifier: D9BF75EE-4A04-441A-8C85-1507F7ECE379
fault	14:39:07.625600-0800	widgetxExtension	-[EXSwiftUI_Subsystem beginUsing:withBundle:] unexpectedly called multiple times.
error	14:39:07.672733-0800	chronod	Encountered an error reading the view archive for <private>; error: <private>
error	14:39:07.672799-0800	chronod	[co.appevolve.onewidget.widgetx:widgetx:small:1536744920620481560@148.0/148.0/20.2] reload: could not decode view
error	14:39:07.674984-0800	kernel	Sandbox: chronod(2128) deny(1) file-read-metadata /private/var/mobile/Containers/Shared/AppGroup/9B524570-1765-4C24-9E0C-15BC3982F0DC/downloadedFonts/Chewy/Chewy-Regular.ttf
error	14:39:07.675762-0800	kernel	Sandbox: chronod(2128) deny(1) file-read-data /private/var/mobile/Containers/Shared/AppGroup/9B524570-1765-4C24-9E0C-15BC3982F0DC/downloadedFonts/Chewy/Chewy-Regular.ttf
error	14:39:07.708914-0800	chronod	[u 8D2C83B3-A6CB-432E-A9D4-9BC8F7056B10:m (null)] [<private>(<private>)] Connection to plugin invalidated while in use.
fault	14:39:07.710284-0800	widgetxExtension	-[EXSwiftUI_Subsystem beginUsing:withBundle:] unexpectedly called multiple times.
error	14:39:07.803468-0800	chronod	Encountered an error reading the view archive for <private>; error: <private>

It seems that it's a permission issue, and the textview can't access the font file it needs when the widget is rendering.

Notes:

1) Font is definitely registered because I can see them in

Code Block 
for fontFamily in UIFont.familyNames {
            for fontName in UIFont.fontNames(forFamilyName: fontFamily) {
                print(fontName)
                ...

in both the Main App target and the Widget Extension target

2) If I make make the font part of the app bundle and add to 'Fonts provided by application' , the are loaded absolutely fine in the Main App and the Widget on simulator and iPhone 7 real device.

3) I do see this error sometimes in the Widget extension target log, don't know if it's related.

Code Block 
widgetxExtension[1385:254599] [User Defaults] Couldn't read values in CFPrefsPlistSource<0x28375b880> (Domain: group.co.appevolve.onewidget, User: kCFPreferencesAnyUser, ByHost: Yes, Container: (null), Contents Need Refresh: Yes): Using kCFPreferencesAnyUser with a container is only allowed for System Containers, detaching from cfprefsd

4) I suspected something to do with app groups, so I tried to copy the font into the Widget Extension container and load from there, but had the same result.


Please help! Thank you.