[Accepted with Revisions] SDL 0250 - Next RPC Indication for the HMI

[theresalech]

Hello SDL community,

The review of the revised proposal "SDL 0250 - Next RPC Indication for the HMI" begins now and runs through January 14, 2020. Previous reviews of the proposal took place October 2 - 15, 2019 and October 30 - November 19, 2019. The original review of this proposal took place October 2 - 15, 2019. The proposal is available here:

https://github.com/smartdevicelink/sdl_evolution/blob/master/proposals/0250-NextRpcIndication.md

Reviews are an important part of the SDL evolution process. All reviews should be sent to the associated Github issue at:

#827

What goes into a review?

The goal of the review process is to improve the proposal under review through constructive criticism and, eventually, determine the direction of SDL. When writing your review, here are some questions you might want to answer in your review:

• Is the problem being addressed significant enough to warrant a change to SDL?
• Does this proposal fit well with the feel and direction of SDL?
• If you have used competitors with a similar feature, how do you feel that this proposal compares to those?
• How much effort did you put into your review? A glance, a quick reading, or an in-depth study?
  Please state explicitly whether you believe that the proposal should be accepted into SDL.

More information about the SDL evolution process is available at

https://github.com/smartdevicelink/sdl_evolution/blob/master/process.md

Thank you,
Theresa Lech

Program Manager - Livio
theresa@livio.io

[Jack-Byrne]

@MichaelCrimando Are you familiar with this accepted but not yet implemented proposal: Template Improvements: Additional SubMenus?

The additional submenus proposal allows for deeper submenus so the developer doesn't have to simulate menu depth by using multiple perform interactions.

Also there is a proposal that is implemented in SDLCore 6.0.0 that allows for in app menu tiles views.

I believe the pictured flow in the proposal could be accomplished using additional submenu depth and menu tiles without the need for the HMI anticipating future RPCs. Also the performance of using submenus over perform interactions would be much better and not require any loading screen.

[MichaelCrimando]

Hey @JackLivio

That is a great proposal and very similar but executed in a different way. That is great for apps that want to PRE load all their choice sets. The proposal that I've created is great for apps that want to POST load all their choice sets. Plus the proposal here also applies to things like softbuttons given from a Show RPC, ScrollableMessage or PerformInteraction

[joeygrover]

So reading the proposal the only use case that is really given is for a "Loading" screen to be displayed while waiting to receive an RPC of a certain function ID.

First to Jack's point, submenus do not have to be PRE loaded. They can be added at any time and I would expect that some of them are added POST load because of the new proposal. PRE loading all those choices will take forever if VR synonyms are attached, so it is likely that the sub menus are added as a skeleton and apps add to the menus as they are selected which mimics the chaining of choice set functionality. The choice set chaning that happens was an apps way to get around a lot of initial driver distraction requirements and the flow itself is very clunky. Obviously this doesn't address the soft buttons or ScrollableMessage use case though.

Regarding the solution itself, I think it still needs some work. The next function ID check works in best case scenarios, but what if multiple Shows are sent. For example, the manager layer will check if an image will need to be uploaded to Core before a Show is sent with that image name. If it does, it sends a Show without the image field to start, then once the file is uploaded, sends another show. Is it acceptable for the loading screen or wait dialog to be dismissed on the first show? Has the author through about other information that could be included for a more precise check? For example, message ID, correlation ID, etc?

For alternatives, what about being more accurate with the use case given of showing a loading screen? Possibly a new RPC that triggers a loading screen, and then uses the dismiss ability recently introduced. I really want to make sure we understand the use case to craft the right solution. Because another alternative could be to include the full RPC to process in sort of a SelectionListener if we want to speed things up, but again if it's only to show a loading screen that's overkill.

Furthermore, has the author looked into the implications this will have on the manager layer for the mobile libraries? Changes should be included in this proposal so it can be agreed upon if the proposal is accepted.

[BrettyWhite]

In addition to what joey said, there are multiple places in the managers (file, soft button, text and graphic, menu, and especially choice set) that have asynchronous calls and that will pre-load menus for example without images, then automatically resend when the images are uploaded. Just something to keep in mind that RPCs may be sent asynchronously and automatically without the developer ever knowing.

[MichaelCrimando]

Hey @joeygrover,

Those are some great points.

Going along with that, if you post load everything, you dont get the indicators (usually arrows) that something is next. Now if I understand what @BrettyWhite is saying, that could maybe be handled by Core where it knows something is coming next show it shows the indicator but doesn't bother to load anything yet.

Plus this functionality enables specfic loading screens that can be popupluated as the items load in. If Core wanted to get fancy, it could potentially load in only the first 10 items really fast, and work on the next items in the background. This is similar to how iPhone apps load long lists while keeping performance great.

Further, we have a need for the HMI to start pre-exposing things in the HMI before the user actually interacts with anything. If the HMI knows what comes next, and it's the type of RPC it's looking for, it can know what to expect and simulate the user pressing a certain button on the screen in order to get the required info from the app.
Here's one example from Tidal. The first item in the in-app menu for Tidal is "My Mixes"

Now a benefit that the additional Submenus proposal can provide is that it can improve performance in going back and forth in menu structures. However, apps would have to take the time to reorganize their menu structure from PerformInteraction style to Menu style. In addition, addCommand items can only have 1 text field and 1 image. Choice items can have 3 text fields and 2 images, so apps might not want to move from PerformInteraction styles. Also I don't know if this is handled on the Core side, but submenus are completely locked out while driving on SYNC3 for MY16-19 vehicles. Apps would then have to maintain 2 different styles of menu structure depending on what version of SYNC it's on.

The motivation of this proposal is trying to address three issues that exist today:

1. Better HMI possibilities: can show forward and backward arrows ... which is a feature of sub menus by the nature of sub menus. Choices could benefit from the feature but actually SDL-0148 made sub menus compete with choice sets... Seems like the proposal prioritizes sub menus as it says that on older head units it can automatically translate those sub-submenus into Choice Sets
2. Smart Driver Distraction: if a softbutton or choice would lead to a screen that's normally locked ... this feature doesn't exist yet for choices and the proposal would enable us to do so. It enables the system to detect use cases with many steps. For sub menus it also exist today assuming pre-loading by the app.
3. The HMI can have a much smoother experience with native HMI loading screens which is true for choice sets when initializing the app. Also it helps the "loading"-screen practice

I think the motivation of this proposal is that head units are slow especially with voice and that user interaction can only start once all the content is loaded. Knowing that the use case continues with a choice/menu conmand is very helpful to improve the experience. The proposal says that the HMI could show some loading indication. It's very helpful for the proposal understanding but I want to note that it'll be the SDL integrator responsibility on how the HMI should do this and that it should be out of scope. For instance when I tap on a choice which has a next RPC indication I could think of the HMI to make the choice change to show a "loading circle" as the choice image... again this is the decision of the HMI.

@MichaelCrimando already mentioned background loading which I believe is where we should have some focus. As of right now apps don't know what menu level or what menu entries are visible (except the root level with OnHMIStatus.systemContext = MENU). I think the method of table views in iOS would be a really big benefit to SDL app menus. AddSubMenu should have a parameter to tell how many entries this sub menu will contain but they entries don't need to be created. The HMI will do it's UI and tell the app if the menu is visible and what menu entries the app needs to create (e.g. extending OnHMIStatus with menu id).

The same could be done for PerformInteraction which would already start and show only choices and choice images that are visible. I believe this would require a larger API change.

Regarding the parameter nextFunctionInfo I am wondering about what should happen if the app fails to perform the next function. I'm thinking of specifying a timeout as an HMI requirement. Also I think it might be sufficient if choices would just provide an indication as a flag/bool. Then the HMI would wait for any kind of overlay RPC from the app (another PerformInteraction or Alert, ScrollableMessage, Slider etc.).

[joeljfischer]

PRE loading all those choices will take forever if VR synonyms are attached, so it is likely that the sub menus are added as a skeleton and apps add to the menus as they are selected which mimics the chaining of choice set functionality.

Currently this is not possible. There is no callback when a submenu is pressed; therefore, the entire menu structure has to be preloaded IIRC. This is a major deficiency of the current menu setup.

Has the author through about other information that could be included for a more precise check? For example, message ID, correlation ID, etc?

I don't think that either messageID nor correlationID would work very well in this scenario. The manager layer handles these ids, so a complicated system of "reserving" an ID for a particular message and then the developer indicating that some screen manager call is meant for a "reserved" ID would have to take place, and this would be extremely complicated.

For alternatives, what about being more accurate with the use case given of showing a loading screen? Possibly a new RPC that triggers a loading screen, and then uses the dismiss ability recently introduced.

This already exists within Alert (the progressIndicator boolean parameter), and is probably a better solution, but doesn't handle showing the "arrow" functionality.

Going along with that, if you post load everything, you dont get the indicators (usually arrows) that something is next.

This could be added to Choice and SoftButton through a boolean parameter, but Choices should probably move over to menus for cases where they present another PerformInteraction if possible.

Plus this functionality enables specfic loading screens that can be popupluated as the items load in. If Core wanted to get fancy, it could potentially load in only the first 10 items really fast, and work on the next items in the background. This is similar to how iPhone apps load long lists while keeping performance great.

This is not currently possible given the scheme of PerformInteraction. Everything must be pre-loaded, ironically. This would be more possible if we created additional RPCs to enable it, but it's currently not possible.

Further, we have a need for the HMI to start pre-exposing things in the HMI before the user actually interacts with anything. If the HMI knows what comes next, and it's the type of RPC it's looking for, it can know what to expect and simulate the user pressing a certain button on the screen in order to get the required info from the app.

This is unclear to me, could you elaborate? The diagram is unclear.

In addition, addCommand items can only have 1 text field and 1 image. Choice items can have 3 text fields and 2 images, so apps might not want to move from PerformInteraction styles.

This is true. We should expand AddCommand to enable further functionality if possible.

Also I don't know if this is handled on the Core side, but submenus are completely locked out while driving on SYNC3 for MY16-19 vehicles. Apps would then have to maintain 2 different styles of menu structure depending on what version of SYNC it's on.

I think you're missing the point here. The fact that submenus are locked out while driving doesn't mean that developers should circumvent that lock out by using PerformInteraction. In fact, PerformInteraction depth should be similarly locked out. However, your point is good in terms of the app would have to maintain both if they were using beyond two menu depth (unless we worked around it in the manager layer). But, that doesn't help this proposal at all either.

As of right now apps don't know what menu level or what menu entries are visible (except the root level with OnHMIStatus.systemContext = MENU). I think the method of table views in iOS would be a really big benefit to SDL app menus.

Agreed, I've had a task sitting in my backlog for a few months now to think about this. Your ideas here are pretty good. I think that this task (of making menus load more dynamically) is more worthwhile than this proposal in general.

---

I think that the only functionality this proposal offers is two-fold:

First, to "disable" some soft buttons when driver distraction says that those buttons' effects will be locked out. This is a decent improvement, but I'm not sure that it's worth the effort.

Second, to show "better" loading screens, i.e. instead of an Alert with progressIndicator=true, they could show the PerformInteraction or ScrollableMessage without the data and a loading indicator, then load it in. I think that this could be better accomplished by the dynamic loading of PerformInteraction and AddCommand / AddSubmenu.

[MichaelCrimando]

@joeljfischer just to elaborate on a couple of points

Currently with Tidal, the in-app menu lists "My Mix, My Albums, My Playlists, My Tracks, and Explore"
So on 8" SYNC it goes something like this - Home screen -> Menu -> Perform Interaction

So what the HMI on a future headunit with a larger screen size could do with this proposal is look at the in-app menu and see that the first menu item will lead to a performInteraction (or submenu... but that part isn't new). It can send an onCommand to the app, and have the upcoming performInteraction hang out in the side bar like so: (ignoring performInteraction timeout)

Further, the HMI could do something effectively like "Hey the first item in the menu will launch a scrollableMessage, so skip that one. However the second item in the menu will launch a performInteraction so send OnCommand for that"

Just a side note I have: you could use a bool flag for this functionality, however the proposal give you that same information (is a RPC next?) and more (WHICH RPC is next?).

Submenu is locked out completely on MY16-19 on SYNC vehicles which makes it pretty useless in the car vs PerformInteraction is page limited. I actually did the proper work to make sure that submenu is page limited like PerformInteraction is so apps can actually use it.

[theresalech]

A major point of discussion during the Steering Committee meeting with regards to this proposal was that it suggests using PerformInteraction in a way that was not intended. It was clarified that the original intention of PerformInteraction was for very dynamic pieces of data that need to be loaded at run time, like POI searches. The author noted that application developers are currently using PerformInteraction to simulate menu depth, and therefore this proposal improves that experience, but it was then questioned by SDLC Members and the Project Maintainer if we should instead focus on improving menus so developers can use those as intended. While there was discussion about this proposal as a short term solution, it was noted that this would likely instead result in two different solutions that both need to be maintained, and could be confusing to developers.

Ultimately, the Steering Committee voted to defer this proposal, and keep it in review until our next meeting. SDLC Members and the Project Maintainer can continue discussion on the review issue, focusing on the motivations for the proposal outside of menu replacement items.

[MichaelCrimando]

I believe I addressed all the main comments with PR #843