Re: [Devel] Preferences and Persistence design 0.3.0
Hi Andre, That seems like a workable design to me. I will update the design document to incorporate it and will try to send out a new draft by the end of the week, although I am prioritising the Sensors and Actuators design over Preferences and Persistence at the moment. Philip On Tue, 2016-01-12 at 12:05 +0000, Barkowski Andre (CM-CI1/PRM1) wrote:
ok lets focus on the last topic ("seamless integration" of common and specific entities into one UI).
First of all lets keep both possibilities: a) UI is entirely provided by oem-settings b) UI is entirely provided by the application developer lets recommend / enforce to use a), lets see b) as last way with maximum flexibility.
now lets look to push the limits for a). It's not black or white, let's can extend its applicability.
I am with you, we should prevent the mentioned approach, based on a "client-server protocol for embedding the UI" "Application developers would have to cooperate in implementing it, as the application-provided settings program would have to be a client in a client–server protocol for embedding the UI"
Lets go for a pretty easy approach, there is an entry listed in the oem-settings on an app, but the "value" of this entry gets modified by an executable. This executable gets launched rendered and it provides a return code. That’s all. Again see this like a "Wizard", e.g. to configure email accounts. The Wizard is a standalone executable, provided by the app.
May be to make it more clear let me describe a potential look&feel for better understanding. Lets assume all apps are listed in one system settings application with their name and icon - similar like in iOS.
Once you choose an App, the releated UI slides in, showing again a list of entries reflecting the configurable items.
Configurations may have further sub chapters, which again slides in and shows a collection of configurable entities in its own list-view (like a standard list of list approach). It optionally shows an own / current value at the calling scree entry (see the first entry in above view for "search engine" which shows the current one "DuckDuckGo" but also indicates that there is a submenu available which helps to change it)
Once you have a complex app-specific thing, lets put it into one entry, lets (optional) show the last value and lets run it as a standalone wizard with its own set of UIs (based on ApertisSettingsList). On other entry can then link to another executable. The result is similar like the first seen at the entry for "search engine", the only difference is that an own executable gets launched to guide the user. And lets keep the capability to define one return value optionally.
e.g. like this:
So finally, we do have a split in one responsibility per "subview" (and its successors) , it is not "mixed" in a way that _one_ view gets composed by several clients. In addition, this capability can also be used by an OEM-settings Apps (completely realized for/by the OEM) for very complex interactions not fitting in the prepared ApertisSettingsList scope).
Hope you get what I mean.
With that we have a good coverage - the majority of cases we cover with approach a) [UI is entirely provided by oem-settings] - for special cases we can add sub views in own executables (wizards) like explained above [see above] - for very rare case, we enable flexibility to implement the complete UI entirely by the application developer.
To be honest, there needs to be a very good reason to go for the last option, especially in our business environment where the Apps are created driven by a business-to-business relationship of the OEM with the service provider, and it is the OEM who like to keep the control of that portion outside of the scope of the App (caused by the ui-customization interest explained before). So typically, as part of the business contract the app-developer will be driven to prevent using option 3. So we are less App developer / capability driven than business requirement driven. Nevertheless, let's keep the last option as an exception of the rule of thumb and with that for flexibility.
Rgds Andre
-----Ursprüngliche Nachricht----- Von: Philip Withnall [mailto:philip.withnall@collabora.co.uk] Gesendet: Montag, 11. Januar 2016 19:10 An: Barkowski Andre (CM-CI1/PRM1) <Andre.Barkowski@de.bosch.com>; devel@lists.apertis.org Betreff: Re: AW: AW: AW: [Devel] Preferences and Persistence design 0.3.0
Hi Andre,
On Mon, 2016-01-11 at 15:20 +0000, Barkowski Andre (CM-CI1/PRM1) wrote:
it sounds to me that your proposal is fitting to the "responsibility" split (OEM vs App developer), so from that perspective my answer to your question "Does that fit better with what you have in mind?" would be yes. But let me reflect from other perspectives, the packaging & deployment & control & seamless integration
OK.
I prefer, that the "code" implementing the OEM-settings is deployed with the OS (essential software) outside of the App-package. With that, all code included in the App-package belongs to and gets provided by the App-Developer. Customization within Apps gets realized based on using prepared widgets / css scheming / etc, all in scope of the OS. With that oem-setting app belongs to the OS (essential software), and the App is only providing some data/model to it. But we do not have to adopt _all_ packages to replace the OEM specific settings implementation included in them. From my point of view it looks like your proposal fulfills that (since there is an application "oem-settings", created and distributed with the essential software), are we on the same page ?
Yes, precisely.
From "control" point of view, I would like to "enforce" the central solution, the using the exception only the complex parts. Launching the "oem-settings" application - instead of using some homegrown App internal solution w/o need - should _not_ be delegated to the App. It should be part of the system software (essential software) to launch it and to cover all common use-cases. Again, are we on the same page, its _not_ the App who decided/launches the oem-settings on the first hand (but the OEM settings App, who implements the umbrella) ?
Yes, we agree here too. In my suggestion, the settings UI for each application is launched by the system settings application, which is written by the OEM. The executable which provides the settings UI for an application is specified in the application’s manifest, which is also under the control of the OEM.
In regard to seamless integration, the "uncommon cases" should be go down to a granularity of a single entry within the settings. So some common, one 1 or more uncommon, again 1 or more common and so forth. I would not like to have a black or white decision, either all are common or the get replaced completely by a proprietary implementation. This is why I referred to Wizards. Its one entry in the settings app, but instead of modifying its value within the App based on an easy standard type, a dedicated executable is used for it. However, finally its seamless included into one view. Again, I have the feeling your proposal fits to that, but like to be on the same page.
I don’t think we are on the same page here. In my most recent proposal, an application’s settings UI is either entirely provided by oem- settings, or entirely provided by the application developer. If it’s implemented by the application developer, they can use ApertisSettingsList (for example) to ensure a look and feel which is consistent with oem-settings. However, they could choose to use something else.
The problem with providing a ‘mixed’ solution – where oem-settings displays the simple settings for an application, and some code provided by the application developer displays the one or two more complex settings – is that of privilege separation. oem-settings necessarily has permissions to write to all GSettings keys for all applications — it is part of the trusted computing base (TCB) for settings management. If code provided by application developers is allowed to run within oem-settings, it also gains those privileges, which violates the security policy we want for settings.
Therefore code from the application developer would have to run in a separate process and have its UI embedded into oem-settings. I provided a couple of options for how to implement this in the most recent version of the document (‘Alternative model 1’ in §5.1.5 of version 0.3.0 of the document). It’s possible, but is a very complex solution for a rare situation. Application developers would have to cooperate in implementing it, as the application-provided settings program would have to be a client in a client–server protocol for embedding the UI. This means that there would need to be app store validation of how they implemented the protocol, plus testing.
What I suggest is to go with the black and white solution – not implement embedding – and instead make it easy for application developers to use ApertisSettingsList (and other widgets which replicate the look and feel of oem-settings) in their application settings UIs. Subject these applications to app store validation checks (which I suspect would end up being no more complex than the alternative of validating an application’s settings UI can be embedded).
If we are on the same page in regard to the 3 scopes mentioned above, I don't have any issue with the proposal. Hope you are also happy with the outcome.
I’ll start updating the design document once we’ve discussed the topic above.
And thanks for your clarification that GSettings will not allow a setting to be changed if it is not writable. That’s good to know. Also the recommendation to check is as part of app store validation. I fear we will forget all this valuable hints for store validation, because at least I do not collect this hints in a structured way. Hope you are doing that in some way.
The design documents which Simon and I have worked on recently all have any relevant app store validation checks listed in them. We have a task open for collating these and adding any additional checks we can think of (for older design documents).
Philip
-----Ursprüngliche Nachricht----- Von: Philip Withnall [mailto:philip.withnall@collabora.co.uk] Gesendet: Montag, 11. Januar 2016 15:12 An: Barkowski Andre (CM-CI1/PRM1) <Andre.Barkowski@de.bosch.com <mailto:Andre.Barkowski@de.bosch.com> >; dev el@lists.apertis.org <mailto:el@lists.apertis.org> Betreff: Re: AW: AW: [Devel] Preferences and Persistence design 0.3.0
Hi Andre,
On Fri, 2016-01-08 at 16:40 +0000, Barkowski Andre (CM-CI1/PRM1) wrote:
-----Ursprüngliche Nachricht----- Von: Philip Withnall [mailto:philip.withnall@collabora.co.uk] Gesendet: Freitag, 8. Januar 2016 11:04 An: Barkowski Andre (CM-CI1/PRM1) <Andre.Barkowski@de.bosch.com <mailto:Andre.Barkowski@de.bosch.com> >; dev el@lists.apertis.org <mailto:el@lists.apertis.org> Betreff: Re: AW: [Devel] Preferences and Persistence design 0.3.0
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.
I see. I think we could handle this using much of the same code as suggested in my previous e-mail (i.e. the ApertisSettingsList widget), but have that code written by the OEM as an application which takes the name of a GSettings schema as a parameter, and automatically generates and displays a UI for all the settings in that schema. For clarity, let’s call it oem-settings.
Each application’s manifest could contain a key which gives the name of an executable to run to display that application’s settings. For the common cases, that would be: oem-settings com.appauthor.MyApp i.e. it would run the OEM’s settings application to generate a settings UI for the application (com.appauthor.MyApp).
For the uncommon cases, where the application needs a particularly complex settings UI, the manifest key would be set to a settings program provided by the application developer. This could use a combination of ApertisSettingsList and custom widgets, as suggested in my previous e-mail, to build whatever UI the developer needs. It could also launch the application itself, with a special argument to show the settings dialogue, if that’s how the developer has implemented their settings.
In these uncommon cases, the OEM will be able to control the appearance of the application’s settings dialogue to a certain extent by setting the CSS of ApertisSettingsList. However, as you say (lower down in your e-mail, I think), the OEM won’t be able to control everything. I don’t think there is a way to reconcile this other than through app store validation of the code for the settings UI. If the application developer is allowed to execute //any// code in order to build the settings UI, they can (if they try hard enough) flaunt the OEM’s desired look and feel.
For all cases, the system settings application would initially present a list of all applications which have this key set in their manifest — I guess as an icon against the application name, as in iOS. When the user selects an application, the settings executable given in the manifest would be executed — whether that be the oem-settings application, or something provided by the application developer.
Does that fit better with what you have in mind?
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.
I see.
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.
OK. Thank you for the clear explanation.
- 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.
I should clarify here: GSettings will not allow a setting to be changed if it is not writable. If a vendor has used the vendor lockdown system to fix the value of a specific key, that key will no longer be writable. An application should use g_settings_is_writable() to check whether to display that key in the UI; but even if it fails to check that, any edits it makes to the key will fail.
Any Apertis-provided widgets like ApertisSettingsList would check g_settings_is_writable(), so this is only relevant to the minority of application developers who are writing their own settings UIs, and it could be something which is checked as part of app store validation.
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.
As above.
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 wizards. Andre: yes, but only for very special cases, not as the general approach.
Agreed.
Philip
-----Ursprüngliche Nachricht----- Von: Devel [mailto:devel-bounces@lists.apertis.org] Im Auftrag von Philip Withnall Gesendet: Freitag, 27. November 2015 13:05 An: devel@lists.apertis.org <mailto:devel@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
Hi Philip, Great, sounds like we have a got trade off found. Looking forward to your update. Rgds Andre -----Ursprüngliche Nachricht----- Von: Philip Withnall [mailto:philip.withnall@collabora.co.uk] Gesendet: Montag, 18. Januar 2016 17:17 An: Barkowski Andre (CM-CI1/PRM1) <Andre.Barkowski@de.bosch.com>; devel@lists.apertis.org Betreff: Re: AW: AW: AW: AW: [Devel] Preferences and Persistence design 0.3.0 Hi Andre, That seems like a workable design to me. I will update the design document to incorporate it and will try to send out a new draft by the end of the week, although I am prioritising the Sensors and Actuators design over Preferences and Persistence at the moment. Philip On Tue, 2016-01-12 at 12:05 +0000, Barkowski Andre (CM-CI1/PRM1) wrote:
ok lets focus on the last topic ("seamless integration" of common and specific entities into one UI).
First of all lets keep both possibilities: a) UI is entirely provided by oem-settings b) UI is entirely provided by the application developer lets recommend / enforce to use a), lets see b) as last way with maximum flexibility.
now lets look to push the limits for a). It's not black or white, let's can extend its applicability.
I am with you, we should prevent the mentioned approach, based on a "client-server protocol for embedding the UI" "Application developers would have to cooperate in implementing it, as the application-provided settings program would have to be a client in a client–server protocol for embedding the UI"
Lets go for a pretty easy approach, there is an entry listed in the oem-settings on an app, but the "value" of this entry gets modified by an executable. This executable gets launched rendered and it provides a return code. That’s all. Again see this like a "Wizard", e.g. to configure email accounts. The Wizard is a standalone executable, provided by the app.
May be to make it more clear let me describe a potential look&feel for better understanding. Lets assume all apps are listed in one system settings application with their name and icon - similar like in iOS.
Once you choose an App, the releated UI slides in, showing again a list of entries reflecting the configurable items.
Configurations may have further sub chapters, which again slides in and shows a collection of configurable entities in its own list-view (like a standard list of list approach). It optionally shows an own / current value at the calling scree entry (see the first entry in above view for "search engine" which shows the current one "DuckDuckGo" but also indicates that there is a submenu available which helps to change it)
Once you have a complex app-specific thing, lets put it into one entry, lets (optional) show the last value and lets run it as a standalone wizard with its own set of UIs (based on ApertisSettingsList). On other entry can then link to another executable. The result is similar like the first seen at the entry for "search engine", the only difference is that an own executable gets launched to guide the user. And lets keep the capability to define one return value optionally.
e.g. like this:
So finally, we do have a split in one responsibility per "subview" (and its successors) , it is not "mixed" in a way that _one_ view gets composed by several clients. In addition, this capability can also be used by an OEM-settings Apps (completely realized for/by the OEM) for very complex interactions not fitting in the prepared ApertisSettingsList scope).
Hope you get what I mean.
With that we have a good coverage - the majority of cases we cover with approach a) [UI is entirely provided by oem-settings] - for special cases we can add sub views in own executables (wizards) like explained above [see above] - for very rare case, we enable flexibility to implement the complete UI entirely by the application developer.
To be honest, there needs to be a very good reason to go for the last option, especially in our business environment where the Apps are created driven by a business-to-business relationship of the OEM with the service provider, and it is the OEM who like to keep the control of that portion outside of the scope of the App (caused by the ui-customization interest explained before). So typically, as part of the business contract the app-developer will be driven to prevent using option 3. So we are less App developer / capability driven than business requirement driven. Nevertheless, let's keep the last option as an exception of the rule of thumb and with that for flexibility.
Rgds Andre
-----Ursprüngliche Nachricht----- Von: Philip Withnall [mailto:philip.withnall@collabora.co.uk] Gesendet: Montag, 11. Januar 2016 19:10 An: Barkowski Andre (CM-CI1/PRM1) <Andre.Barkowski@de.bosch.com>; devel@lists.apertis.org Betreff: Re: AW: AW: AW: [Devel] Preferences and Persistence design 0.3.0
Hi Andre,
On Mon, 2016-01-11 at 15:20 +0000, Barkowski Andre (CM-CI1/PRM1) wrote:
it sounds to me that your proposal is fitting to the "responsibility" split (OEM vs App developer), so from that perspective my answer to your question "Does that fit better with what you have in mind?" would be yes. But let me reflect from other perspectives, the packaging & deployment & control & seamless integration
OK.
I prefer, that the "code" implementing the OEM-settings is deployed with the OS (essential software) outside of the App-package. With that, all code included in the App-package belongs to and gets provided by the App-Developer. Customization within Apps gets realized based on using prepared widgets / css scheming / etc, all in scope of the OS. With that oem-setting app belongs to the OS (essential software), and the App is only providing some data/model to it. But we do not have to adopt _all_ packages to replace the OEM specific settings implementation included in them. From my point of view it looks like your proposal fulfills that (since there is an application "oem-settings", created and distributed with the essential software), are we on the same page ?
Yes, precisely.
From "control" point of view, I would like to "enforce" the central solution, the using the exception only the complex parts. Launching the "oem-settings" application - instead of using some homegrown App internal solution w/o need - should _not_ be delegated to the App. It should be part of the system software (essential software) to launch it and to cover all common use-cases. Again, are we on the same page, its _not_ the App who decided/launches the oem-settings on the first hand (but the OEM settings App, who implements the umbrella) ?
Yes, we agree here too. In my suggestion, the settings UI for each application is launched by the system settings application, which is written by the OEM. The executable which provides the settings UI for an application is specified in the application’s manifest, which is also under the control of the OEM.
In regard to seamless integration, the "uncommon cases" should be go down to a granularity of a single entry within the settings. So some common, one 1 or more uncommon, again 1 or more common and so forth. I would not like to have a black or white decision, either all are common or the get replaced completely by a proprietary implementation. This is why I referred to Wizards. Its one entry in the settings app, but instead of modifying its value within the App based on an easy standard type, a dedicated executable is used for it. However, finally its seamless included into one view. Again, I have the feeling your proposal fits to that, but like to be on the same page.
I don’t think we are on the same page here. In my most recent proposal, an application’s settings UI is either entirely provided by oem- settings, or entirely provided by the application developer. If it’s implemented by the application developer, they can use ApertisSettingsList (for example) to ensure a look and feel which is consistent with oem-settings. However, they could choose to use something else.
The problem with providing a ‘mixed’ solution – where oem-settings displays the simple settings for an application, and some code provided by the application developer displays the one or two more complex settings – is that of privilege separation. oem-settings necessarily has permissions to write to all GSettings keys for all applications — it is part of the trusted computing base (TCB) for settings management. If code provided by application developers is allowed to run within oem-settings, it also gains those privileges, which violates the security policy we want for settings.
Therefore code from the application developer would have to run in a separate process and have its UI embedded into oem-settings. I provided a couple of options for how to implement this in the most recent version of the document (‘Alternative model 1’ in §5.1.5 of version 0.3.0 of the document). It’s possible, but is a very complex solution for a rare situation. Application developers would have to cooperate in implementing it, as the application-provided settings program would have to be a client in a client–server protocol for embedding the UI. This means that there would need to be app store validation of how they implemented the protocol, plus testing.
What I suggest is to go with the black and white solution – not implement embedding – and instead make it easy for application developers to use ApertisSettingsList (and other widgets which replicate the look and feel of oem-settings) in their application settings UIs. Subject these applications to app store validation checks (which I suspect would end up being no more complex than the alternative of validating an application’s settings UI can be embedded).
If we are on the same page in regard to the 3 scopes mentioned above, I don't have any issue with the proposal. Hope you are also happy with the outcome.
I’ll start updating the design document once we’ve discussed the topic above.
And thanks for your clarification that GSettings will not allow a setting to be changed if it is not writable. That’s good to know. Also the recommendation to check is as part of app store validation. I fear we will forget all this valuable hints for store validation, because at least I do not collect this hints in a structured way. Hope you are doing that in some way.
The design documents which Simon and I have worked on recently all have any relevant app store validation checks listed in them. We have a task open for collating these and adding any additional checks we can think of (for older design documents).
Philip
-----Ursprüngliche Nachricht----- Von: Philip Withnall [mailto:philip.withnall@collabora.co.uk] Gesendet: Montag, 11. Januar 2016 15:12 An: Barkowski Andre (CM-CI1/PRM1) <Andre.Barkowski@de.bosch.com <mailto:Andre.Barkowski@de.bosch.com> >; dev el@lists.apertis.org <mailto:el@lists.apertis.org> Betreff: Re: AW: AW: [Devel] Preferences and Persistence design 0.3.0
Hi Andre,
On Fri, 2016-01-08 at 16:40 +0000, Barkowski Andre (CM-CI1/PRM1) wrote:
-----Ursprüngliche Nachricht----- Von: Philip Withnall [mailto:philip.withnall@collabora.co.uk] Gesendet: Freitag, 8. Januar 2016 11:04 An: Barkowski Andre (CM-CI1/PRM1) <Andre.Barkowski@de.bosch.com <mailto:Andre.Barkowski@de.bosch.com> >; dev el@lists.apertis.org <mailto:el@lists.apertis.org> Betreff: Re: AW: [Devel] Preferences and Persistence design 0.3.0
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.
I see. I think we could handle this using much of the same code as suggested in my previous e-mail (i.e. the ApertisSettingsList widget), but have that code written by the OEM as an application which takes the name of a GSettings schema as a parameter, and automatically generates and displays a UI for all the settings in that schema. For clarity, let’s call it oem-settings.
Each application’s manifest could contain a key which gives the name of an executable to run to display that application’s settings. For the common cases, that would be: oem-settings com.appauthor.MyApp i.e. it would run the OEM’s settings application to generate a settings UI for the application (com.appauthor.MyApp).
For the uncommon cases, where the application needs a particularly complex settings UI, the manifest key would be set to a settings program provided by the application developer. This could use a combination of ApertisSettingsList and custom widgets, as suggested in my previous e-mail, to build whatever UI the developer needs. It could also launch the application itself, with a special argument to show the settings dialogue, if that’s how the developer has implemented their settings.
In these uncommon cases, the OEM will be able to control the appearance of the application’s settings dialogue to a certain extent by setting the CSS of ApertisSettingsList. However, as you say (lower down in your e-mail, I think), the OEM won’t be able to control everything. I don’t think there is a way to reconcile this other than through app store validation of the code for the settings UI. If the application developer is allowed to execute //any// code in order to build the settings UI, they can (if they try hard enough) flaunt the OEM’s desired look and feel.
For all cases, the system settings application would initially present a list of all applications which have this key set in their manifest — I guess as an icon against the application name, as in iOS. When the user selects an application, the settings executable given in the manifest would be executed — whether that be the oem-settings application, or something provided by the application developer.
Does that fit better with what you have in mind?
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.
I see.
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.
OK. Thank you for the clear explanation.
- 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.
I should clarify here: GSettings will not allow a setting to be changed if it is not writable. If a vendor has used the vendor lockdown system to fix the value of a specific key, that key will no longer be writable. An application should use g_settings_is_writable() to check whether to display that key in the UI; but even if it fails to check that, any edits it makes to the key will fail.
Any Apertis-provided widgets like ApertisSettingsList would check g_settings_is_writable(), so this is only relevant to the minority of application developers who are writing their own settings UIs, and it could be something which is checked as part of app store validation.
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.
As above.
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 wizards. Andre: yes, but only for very special cases, not as the general approach.
Agreed.
Philip
-----Ursprüngliche Nachricht----- Von: Devel [mailto:devel-bounces@lists.apertis.org] Im Auftrag von Philip Withnall Gesendet: Freitag, 27. November 2015 13:05 An: devel@lists.apertis.org <mailto:devel@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
participants (2)
-
Barkowski Andre (CM-CI1/PRM1) -
Philip Withnall