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diff --git a/docs/5_Component_Documentation/1_agl-compositor.md b/docs/5_Component_Documentation/1_agl-compositor.md index 23e3a1a..437e6a7 100644 --- a/docs/5_Component_Documentation/1_agl-compositor.md +++ b/docs/5_Component_Documentation/1_agl-compositor.md @@ -138,6 +138,59 @@ presenting. Please consult the [protocol file](https://gerrit.automotivelinux.org/gerrit/gitweb?p=src/agl-compositor.git;a=blob_plain;f=protocol/agl-shell.xml;hb=refs/heads/master) as that is the authoritative way of getting the latest version. +#### V2 updates + +Version 2 of the agl-shell protocol, while it is is not obligatory to be +supported by the shell client, it adds two new events: bound_ok and bound_fail +events. + +It has been observed that in some cases where we do not explicitly have a knob +in the toolkit to tell whether the application is a regular one (which doesn't +need to bind to the agl-shell protocol) or a one that needs to implement +agl-shell protocol might result in terminating the wayland connection. + +That happens because we can't have multiple clients bind to the agl-shell +protocol interface and was particularly visible when using regular +flutter applications with other shell clients (Qt homescreen, or WAM/chromum), +basically mashing together different kind of toolkits in the same image. Once +a client has already bound to the agl-shell protocol interface any other client +that attempts to do same will get its wayland connection severed and the +application will be terminated. + +These two events provide a race-free method in which the clients can tell if +they're in charge (of being the shell client) or their just regular +applications. Explicitly implementing this protocol if you have other means to +specify which type of application it is running wouldn't be required nor +necessary. But by using the protocol we can provide the same thing, +programmatically, without fearing that the wayland connection might be +severed, and implicitly taking down the application. + +#### V3 updates + +Version 3 of the agl-shell protocol adds 4 more events to signal out when the +application state was changed: started, activated, deactivated and terminated. + +Version 3 update was mostly prompted by an issue with start-up of applications +but also is part of the first steps to reduce and simplify a bit more +activation handling in the compositor. Specifically with this protocol update, +we can correctly orchestrate start-up and activation of applications. + +At the moment of adding this protocol update, the default compositor behaviour +is to display/activate applications as soon they're started, a feature which +we've called activate-by-default (and which is turned on by default). +But users can choose to disable that in such a way that activation is entirely +driven the shell client. + +Implicitly having this activate-by-default papered over various +issue when don't have that activation by default turned on. Supporting both +use-cases (activate-by-default, on and off) turned out to be cluster of +problems and regression over time. Not only that the amount of complexity in +the compositor is unwarranted and can simplified by telling the shell client +handle any window management interaction on its own. + +Further more, with this protocol update we also includes some events already +present in the agl-shell-desktop protocol like deactivate and terminate. + ### agl-shell-desktop This extension is targeted at keeping some of the functionally already |