Empty displayCapabilities in setDisplayLayout response prevents display update

[djs98052]

Bug Report

While processing the response to setDisplayLayout, the sdl_displayLayoutResponse method assumes the presence of response.displayCapabilities while the protocol specification indicates this is an optional field in the response. If the response contains an empty displayCapabilities field, then the cached value for displayCapabilities gets overwritten and subsequent attempts to update the display fail because the capabilities of the display cannot be determined.

Reproduction Steps

1. Call screenManager.setDisplayLayout
2. Call screenManager.beginUpdates()
3. Call screenManager.title = "Title"
4. Call screenManager.endUpdates()

Expected Behavior

Title is shown on the screen

Observed Behavior

Title is not shown on the screen

OS & Version Information

• iOS Version: Simulator 11.4, iPhone 8+ 12.4
• SDL iOS Version: 6.4.1
• Testing Against: Emulator

Test Case, Sample Code, and / or Example App

smartDeviceLinkManager.sdlManager.send(request: setLayoutRequest) { _, response, error in
    guard response?.success.boolValue ?? false == true else {
        logError("Error setting display layout: \(String(describing: error))")
        return
    }
    let screenManager = self.smartDeviceLinkManager.sdlManager.screenManager
    screenManager.beginUpdates()
    screenManager.title = NSLocalizedString("My Title", comment: "")
    screenManager.primaryGraphic = self.logoArtwork
    screenManager.softButtonObjects = [self.meetingListButton, self.meetingRoomButton]
    screenManager.endUpdates()
}

[joeljfischer]

After investigation, this particular example appears to not be an issue. We always send the templateTitle even if the head unit doesn't support it. The emulator you are using probably does not support a template title.

With that said, in the course of the investigation, we found that the underlying issue is valid for other text fields and image fields.

[joeljfischer]

@djs98052 do you remember which emulator you were using?