[Devel] Preferences and Persistence design 0.3.0

Barkowski Andre (CM-CI1/PRM1) Andre.Barkowski at de.bosch.com
Fri Jan 8 16:40:08 GMT 2016

Hi Philip,
please find my comments enclosed in green


-----Ursprüngliche Nachricht-----
Von: Philip Withnall [mailto:philip.withnall at collabora.co.uk] 
Gesendet: Freitag, 8. Januar 2016 11:04
An: Barkowski Andre (CM-CI1/PRM1) <Andre.Barkowski at de.bosch.com>; devel at lists.apertis.org
Betreff: Re: AW: [Devel] Preferences and Persistence design 0.3.0

Hi Andre,

Sorry for my delayed response. Instead of diving straight into updating
the document, I feel this topic (§5.1.5, user interfaces) needs a
little more discussion. I think we are broadly on the same page,
although your e-mail has introduced a couple more use cases which the
design currently doesn’t cover. I will try to explain below.

In various places below I have said that the design covers a particular
point. On re-reading the design when writing this e-mail, I realise
there are places where it could be restructured to be clearer. I will
try to do that.

On Mon, 2015-11-30 at 16:18 +0000, Barkowski Andre (CM-CI1/PRM1) wrote:
> Enclosed my feedback. 
> - secrets & passwords ==> move to security paper
> Its ok for me to move this scope to the security paper, with that we
> can also add more context to it like discussed in another thread.
> (see enclosed email).
> But please do not forget a reflection of rollback and its impact the
> "user secrets and password" approach and where to add this reflection
> (this paper - e.g in chapter 5 approach - or the security paper -
> which I feel would may fit better). 

OK, I will expand the section on this in the Security design. I will
leave the current section in the Preferences and Persistence design as
a pointer to the Security design.

Andre: ok.

> I have the feeling we are not on the same page so far. To make it
> easier to understand, let's call it "an iOS like" solution. There is
> a settings App, bundled with the system like an App-Launcher
> Application - providing the preferences to the User. An App carries
> stuff to be configured in some way, e.g. a manifest, this gets
> interpreted by some "Settings App" and shown to the User in a
> consistent way. 

This is actually quite similar to what we have so far in the design: a
GSettings schema (‘manifest file’) which specifies all the preferences
for a given application. The design assumes some central preferences
application, like iOS, which has sub-pages for each application.

Andre: ok.

The design currently gives a couple of options for how those sub-pages
are implemented, but the differences are technical rather than user-
facing. In all cases, the intention is that the preferences application
lists applications, the user selects one, and all the preferences for
that application are displayed.

Andre: the difference is responsibility & deployment. The settings App belongs 
to the system chrome, gets defined by the OEM and we expect to write (by us) one
new implementation per product. But we keep the Apps out of that scope. They 
are not ruling how it looks like (by providing the UI implementation aka look & feel),
they are only defining the data. In a model/view/control pattern, their focus is limited
to the model. 

However, no general rule w/o exception, we would like to keep the flexibility for 
special topics/data, which may need some more complex interaction to gets defined. But this
doesn't change the overall approach, it only extends it. This would mean for very special 
entities (a very small quantity and with that an exception and not the rule of thumb), Apps
can provide a UI which gets used to modify a value (e.g. like a wizard). For this part 
we again think about how to customize it to the maximum degree, but we accept limits.

Where the design currently differs from this is that it advises
//against// automatically generating the preferences UI from the
GSettings schema file. This is advice borne out of the experiences of
various of us, who have seen and worked with auto-generated preferences
UIs. They are almost universally not a pleasure to use, unless they
list a very small number of very simple preferences (on the order of a
couple of checkboxes, for example). You can think of this as a
model–view–controller split: in all such patterns, it is rarely
possible to satisfactorily generate the view from the model.

Andre: yes, I see, but I don't share this recommendation against it.
Its not black or white, the majority is very simple and on top 
we provide flexibility for the exceptions and last but not least we have the 
need for OEM customization. 

Instead, it advises creating preferences UIs using code. This allows
for ultimate flexibility in how the UI works, which can make for a much
more pleasant user experience. 

Andre: again, I see but don't share it because it does not fit to our business model.
Which user experience is pleasant decides the OEM, even if we find it very disappointing.
With that we are talking about different kind of "flexibility". Since the majority of preferences 
is quite easy, the "flexibility for Apps" is only important for some special entities, 
but since we adopt the look&feel of each and every product accordant to the OEM interest, 
we do need "flexibility for OEM". And therefore we restrict flexibility for Apps. 
However, for parts with very good reasons, we will provide it, but not as a rule of thumb.

And implementing it using code is not the issue what I am talking about, the responsibility is the topic. 
The system chrome application providing the UI for the App settings (which has been created based on code) 
will be done by the product team, not the App Developer. With that we keep the maximum level of flexibility for 
the settings app (belonging to the system chrome) in our own hands (i.e. the product team, out of the App Developer hands)
And like said a new implementation will be done for each new product. 
Its the same for the App-Launcher, the status bar / Home screen, etc.. 
But its not based on code to provide flexibility for the configuration, its based on code to provide flexibility for 
the OEM, even for the standard / easy stuff. The complex, very App specific stuff can not realized outside the scope of 
the App responsibility, so we keep this in their hands with limitations in customization
(even though we push also the limits as much as possible to enable customization for that part to a maximum degree)

However, the approach which I explain is not going for one way without enabling the other one.
So we have to enable both, minimize the part which is in the hands of the App Dev and maximize the 
part which is out of their scope. 

The amount of code needed does not need
to be large at all: there are various GSettings convenience APIs which
mean binding a particular setting to a particular widget is typically 1
line of code.

Andre: great.

I think the main attraction of creating preference UIs using code,
rather than auto-generating them is that it provides a simple
progression path: if version 1 of an application has a couple of
boolean preferences, it makes sense to auto-generate the preferences UI
for them. However, if version 2 adds some more complex preferences
which cannot have their UI auto-generated, the application developer
has to reimplement the entire preferences UI in code, including the old

Andre: see above, its not black or white as also the flexibility for App 
Developers is not the first/only priority in our business environment.

So instead I propose a new solution (which is not in the current
version of the design): write preference UIs in code, but Apertis
should provide a widget which can auto-generate the UI for a specific
set of preferences from the GSettings schema for the application. Let’s
call the widget ApertisSettingsList.

This means that version 1 of the application above would implement its
preferences UI in a small amount of code to instantiate
the ApertisSettingsList widget for its two boolean preferences. Version
2 would keep this widget, and add additional widgets to the UI for the
new, complex, preferences.

Wizards could be implemented as a similar progression.

Andre: like said, I do not have an issue with realizing the settings based on code,
the topic is the responsibility of code as also the differnent kind of flexibility.

I would like to go for a solution, where the majority of flexibility / code is in the hands
of the product team, which adopts it accordant to OEM interest, and the minority is in the 
hand of the App developer.

In your sample above, its still too much responsibility in the scope of the App-developer.
The "ApertisSettingsList" is not able to cover enough customization from my point of view, 
we would need more like a a setings applications, complety in the responsibility of the product 
team, providing an implementation of all the easy / standard stuff accordant to the OEM interest, and
hook to Apps for special entities, which then gets limited customization capabilities based on 
widget customization.

> - A user do not has to step into an app and to search for it to
> configure it, it’s at a central place. 

This is already handled in the design.
Andre: ok

> - We also do not have to coordinate all the different kinds of
> possibilities to incorporate it within Apps (at different places and
> in different way) 

The design already covers this by specifying a standard way for an
application to be launched so that it shows its preferences immediately
(§5.1.5¶2; ActivateAction).

> - An OEM can decide to remove configurable parts in his product, so
> that only a subset gets published to the user for a specific device. 

This is already handled by the vendor lockdown system supported by
GSettings. Applications can check whether a preference is locked down
by calling the g_settings_is_writable() method. I will mention that in
the document.

Andre: "can" check is not sufficient. We need to deliver the product w/o 
contacting the App-developer to adopt this part. Again, it’s a matter of 
responsibilities. So the code is in responsibility of the product team to the maximum
degree. For the remaining stuff we try to push the limits as much as possible, so "can"
would be ok for that.

> - An OEM can also change the look and feel of the Settings-App and it
> keeps consistent, no need to change the App

This can be handled by applying CSS classes to the preferences windows
in applications, which allows the OEM to override the CSS for that
class and have the changes be applied to all preferences windows
without needing to modify applications. This is something covered by
the UI Customisation design. I will mention that in this document too.

Andre: like said above, this is sufficient for the special cases but not enough 
flexibility for the general one. 

> - One can optionally re-organize / combine  configurations of same
> kind over all Apps into one view (e.g. similar like "privacy"
> settings)

This should be possible for the simple preferences supported by
ApertisSettingsList by creating a new view which instructs that widget
to display the desired preferences from //several// GSettings schemas.

Note that it would not be possible for preferences whose UIs cannot be

Andre: see above

> - We can easily add Search capabilities (over all Apps), to help
> Users to find the topic of interest independent of their
> organization 

This can be implemented by searching the summaries and descriptions of
installed GSettings schemas.

Andre: yes, GSettings is not an issue. 

> Often there are "configurations" which modifies the App behavior but
> used by the system-integrator at point in time of product creation.
> By intention, they are not transported to the Used for configuration.
> It limits the capability of the User, but also reduces complexity.
> Its maybe used for variant handling. However, it is highly OEM
> specific, since another OEM my decide differently which configuration
> capabilities to provide to the User.

This is already handled by the combination of vendor lockdown and
vendor overrides, as provided by GSettings.

Andre: I am not talking about the GSettings capabilities, I am talking about 
the code responsibility for the presentation, and who will change what in case
an OEM adoption is running into issues. The Settings App / UI shall be in the 
responsibility of the product team to the maximum degree and interact with the
OEM for adoption, but not with each and every App developer to check if its 
Code has issues with the new presentation solution.

> But to be honest, settings configured by the central Settings App are
> not covering all App internals. There are settings changed
> dynamically during usage, e.g. Sat-View/Hybrid-View/Standard-View in
> a Map, routing parameter like fast/short/eco etc or even stored
> Favorites. This will be done App-internally, and typically spread
> over the App-UI to be at the place where it is needed (instead of
> collected and presented all together at a single place). These App
> internals are managed by the App itself. Also for this the prepared
> (preferences & setting) services can be used by the App-developer,
> and we provide prepared basic widgets, to keep the UI consistent and
> to customize it easily (and we should have some words about it in the
> document) but when I say we have to have a central App for the App
> settings, then I am talking about the "static" ones. 

Indeed, the design recommends that preferences are integrated into the
application UI where appropriate. This is definitely a use case we want
to support.

> For that we use some basic data structures like "bool", "int",
> "string" etc and provide widgets as visual representation of it. Lets
> compare it with the iOS way.

Since I haven’t mentioned it so far, both the iOS approach and the
Android approach are relevant here (and I will include them in the
document as background research):

iOS uses settings bundles, which are lists of preferences from which a
UI is auto-generated. They support very simple data types, and can be
loaded by the application or by a central preferences application.

Android uses preferences fragments, which are implemented in code as
part of the application, and are launched by the preferences UI when
needed, using a special launch argument to get the application to
display that fragment (or present it as a separate Settings Activity).

Both approaches result in roughly the same user experience.

So as it stands, our design is aligned more with the Android approach
than the iOS approach.

Andre: yip, but it looks like the iOS approach is fitting better to our business needs.

> In addition, there could be a sequence needed to ease the input of
> values, e.g. a wizard  (e.g. to configure an email account). This
> should be provided by the App-Developer. An isolated executable
> (Agent), using some PopUp-Sequence and finally set the key-value
> pairs shown in the settings App. With that, the Wizard gets shipped
> with the App, but launched by the Settings Apps. 

The wizard, as you describe it, is effectively what we have in mind for
all preferences UIs — you could think of them as similar to one-page

Andre: yes, but only for very special cases, not as the general approach.

> Once we do have both mechanisms - the wizard together with the
> standard key/value types - , we have a great tradeoff between the 80%
> of easy to use Standard stuff and the 20% complex parts not fitting
> well into the standard patterns. And being well prepared to handle it
> in a central App, we can easily cover a look & feel where it behaves
> like bundled to each App (for example a dedicated "Settings Hard
> Key", which shall show only the Settings of the App (in Foreground at
> the point in time of key press), by initiating a flip Animation and
> showing the App-Settings at the Back-Side of the current App Screen.
> That said, from a solution for central handling we can derive a
> decentralized setup, but not as easy vice versa. So lets go for the
> one covering the wider scope.

I will add the settings hard key to the document as a requirement and
figure out how to integrate it into the design.

> However, even if we support the central solution, an App developer
> may decide not to use it. In this case, App settings - which still
> exists but not exposed centrally - are somehow internally handled, in
> an app-specific way. Its not consistent, etc, but its possible. And
> we shall support this too. Its like different levels of integration,
> similar like with the different level of prepared UI elements (from
> basic widgets via container to complete views/templates) - we
> recommend the deepest integration but if the App developer decides
> not to use it he can go for it but then he has to take the burden for
> build in functionality. So for "settings", we may expose a "settings
> key pressed" signal to the App for the case it does not participate
> on the central handling. Or the OEM customization in look&feel but
> also in scope. Or the "search settings" functionality. An App
> Developer can even decide not to use our low level services to handle
> key-value pairs and uses its own. In this case, he has to take care
> about under voltage etc, 


> With that in mind, I do have the feeling that the explanations on
> page 26, like 
> - disadvantages
> - ways to embed UI from an application (A) into the system
> preferences app (B)
> are not perfectly fitting.

Hopefully this e-mail has managed to clarify my reasoning behind page
26 a little more. At the moment I am leaning towards recommending
‘alternative model 2’ as the default recommendation. 

Andre: yes, thx for that. However, it doesn't convince me and I hope
you see why in our OEM business flexibility for App Developers is 
not the only driving goal.

> Could you please reflect the things said above
> - different kind of App settings (which ones are in-app handled,
> which ones are central)
> - going for the widest scope solution (central handling,
> incorporation of wizards)
> - flexibility in tailoring for a specific product (customization, de-
> centralized setup)

I will ensure those are covered in the next iteration of the document,
but would appreciate your thoughts on my explanations above first, to
make sure we’re on the same page.

> And also 
> - reflect the iOS User Interface approach for presenting the App
> settings

Will do (and the Android one).


> -----Ursprüngliche Nachricht-----
> Von: Devel [mailto:devel-bounces at lists.apertis.org] Im Auftrag von
> Philip Withnall
> Gesendet: Freitag, 27. November 2015 13:05
> An: devel at lists.apertis.org <mailto:devel at lists.apertis.org> 
> Betreff: [Devel] Preferences and Persistence design 0.3.0
> Hi all,
> Please find attached version 0.3.0 of the Preferences and Persistence
> design, plus a document showing the changes between version 0.2.3 and
> 0.3.0.
> This version includes more background research, some alternative
> designs for the system preferences application (§5.1.5) and
> clarifications of recommendations for storing secrets and passwords.
> Is this one OK to upload to the wiki?
> Philip
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