ImageCaptureCore via Mac Catalyst: ICCameraFile requestReadData(atOffset:length:completion:) always passes nil Data object to completion block

Number:rdar://FB7663990 Date Originated:2020-04-14
Status:Open Resolved:
Product:Image I/O Product Version:macOS 10.15.4
Classification: Reproducible:100%
(Note that this ticket refers specifically to `requestReadData(atOffset:length:completion:)` on Catalyst. See FB7663947 for the related iPadOS ticket. To my knowledge, `requestReadData(atOffset:length:completion:)` has never worked on Catalyst, unlike iPadOS, where it has worked until iPadOS 13.4.)

On Mac Catalyst, ICCameraFile's `requestReadData(atOffset:length:completion:)` method does not read data from the camera file.

When `requestReadData` is called with an offset of 0 and a length corresponding to the size of the file, the completion block is executed with a nil Data object. (The error is also nil.) The expected result is a Data object with the actual contents of the camera file (and a nil error).

The attached project reproduces this sample issue. (There is no app UI; see the messages logged to the console.) This project:

- Instantiates an ICDeviceBrowser, sets its delegate, and starts its browser.
- When an ICCameraDevice (such as an SD card) is connected, the code automatically sets its delegate, and opens a session.
- When the ICCameraDeviceDelegate's `deviceDidBecomeReady(withCompleteContentCatalog:)` delegate method is called, `requestReadData(atOffset:length:completion:)` is called with on the first ICCameraFile object. (Using the first ICCameraFile is arbitrary; the results are the same regardless of which file is chosen.)
- The `requestReadData(atOffset:length:completion:)` completion block is subsequently called with a nil Data object, and a nil Error object.

For Open Radar: The minimum code sample to reproduce this is at


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