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diff --git a/libwindowmanager/doc/LibWindowmanager.txt b/libwindowmanager/doc/LibWindowmanager.txt new file mode 100644 index 0000000..87394af --- /dev/null +++ b/libwindowmanager/doc/LibWindowmanager.txt @@ -0,0 +1,238 @@ += LibWindowmanager Library User Guide +:doctype: book +:toc: +:icons: +:data-uri: +:lang: en +:encoding: utf-8 + +== Introduction +The LibWindowmanager library provides a simple interface to manipulate and +query the state of the window manager application framework binding. +It is needs to be integrated and called from the client application. + +=== Intended audience +This document is intended to be useful to application developers. + +=== Scope of this Document +This document describes the singleton class interface to the _Window +Manager_ binding service. + +== class LibWindowmanager +This is the public interface of the class `LibWindowmanager`. Private members +and methods are not reproduced as they will not affect usage of the +class by client applications. + +--------------------------- +class LibWindowmanager +{ +public: + static LibWindowmanager &instance(); + + int init(int port, char const *token); + + // WM API + int requestSurface(const char *label); + int activateSurface(const char *label); + int deactivateSurface(const char *label); + int endDraw(const char *label); + + enum EventType { + Event_Active, + Event_Inactive, + Event_Visible, + Event_Invisible, + Event_SyncDraw, + Event_FlushDraw, + }; + + void set_event_handler(enum EventType et, + std::function<void(char const *label)> f); +}; +--------------------------- + +=== Errors +Methods returning an `int` signal successful operation when returning +`0`. In case of an error, an error value is returned as a negative errno +value. E.g. `-EINVAL` to signal that some input value was invalid. + +Additionally, logging of error messages is done on the standard error +file descriptor to help debugging the issue. + +=== Labels +Surface labels are any valid strings. For `requestSurface()` these strings +must match the _Window Manager_ configuration in order to be allowed to +be displayed on one layer or the other. For all other calls the label +must match the exact name of a requested surface. + +=== Methods + +==== LibWindowmanager::init(port, token) +Initialize the Binding communication. + +The `token` parameter is a string consisting of only alphanumeric characters. +If these conditions are not met, the LibWindowmanager instance will not initialize, +i.e. this call will return `-EINVAL`. + +The `port` parameter is the port the afb daemon is listening on, +an invalid port will lead to a failure of the call and return `-EINVAL`. + +==== LibWindowmanager::requestSurface(label) +This method requests a surface with the label given from the _Window +Manager_. It will return `0` for a successful surface request, and +`-errno` on failure. Additionally, on the standard error, messages are +logged to help debgging the issue. + +==== LibWindowmanager::activateSurface(label) +This method is mainly intended for _manager_ applications that control +other applications (think an application manager or the _HomeScreen_). It +instructs the window manager to activate the surface with the given +_label_. + +This method only is effective after the actual window or surface was +created by the application. + +==== LibWindowmanager::deactivateSurface(label) +This method is mainly intended for _manager_ applications that control +other applications. It instructs the window manager to deactivate the +surface associated with the given label. Note, that deactivating a +surface also means to implicitly activate another (the last active or +if not available _main surface_ or _HomeScreen_.) + +This method only is effective after the actual window or surface was +created by the application. + +==== LibWindowmanager::endDraw(label) +This function is called from a client application when it is done +drawing its surface content. + +It is not crucial to make this call at every time a drawing is finished - +it is mainly intended to allow the window manager to synchronize drawing +in case of layout switch. The exact semantics are explained in the next +<<_events,Events>> Section. + +==== LibWindowmanager::set_event_handler(et, func) +This method needs to be used to register event handlers for the WM +events described in the EventType enum. Only one hendler for each +EventType is possible, i.e. if it is called multiple times with the same +EventType the previous handler will be replaced. + +The `func` handler functions will receive the label of the surface this +event is targeted at. + +See Section <<_events,Events>> for mor detailed information about event +delivery to client applications. + +=== Usage + +==== Initialization of LibWindowmanager +Before usage of the LibWindowmanager, the method `init()` must be +called once, it will return `-errno` in case of en error and log diagnostic +messages to stderr. + +==== Request a surface +When creating a surface with _Qt_ - it is necessary to request a surface +from the WM, internally this will communicate with the window manager +binding. Only after `requestSurface()` was successful, a surface should +be created. + +This is also true for _QML_ aplications, where only after the +`requestSurface()` should the load of the resource be done. The method +returns `0` after the surface was requested successfully. + +===== Workings of requestSurface() +`LibWindowmanager::requestSurface()` calls the AFB binding verb +`requestsurface` of the `windowmanager` API. This API call will return a +numeric ID to be used when creating the surface. This ID is never +explicitly returned to the client application, instead, it is set in the +application environment in order for _Qt_ to then use it when creating the +surface. + +.Remarks +******************************** +With the current _Qt_ implementation this means, that only one surface +will be available to client applications, as subsequent windows will +increment this numeric ID internally - which then will lead to IDs that +cannot be known by the window manager as there is no direct +communication from _Qt_ to the WM. +******************************** + +=== Events +Events are a way for the _Window Manager_ to propagate information to +client applications. It was vital for the project to implement a number +of events, that mirror functionality that is already present in the +wayland protocol. + +All events have the surface `label` as argument - a way to enable future +multi-surface applications. + +.Remarks +************************** +As already stated above, this is currently not possible with the way +_Qt_ implements its surface ID setting. +************************** + +==== Active and Inactive Events +These events signal an application that it was activated or deactivated +respectively. Usually this means it was switched visible - which means +the surface will now be on the screen and therefor continue to render. + +==== Visible and Invisible +These events signal an application that it was switched to be visible or +invisible respectively. These events too are handled implicitly through +the wayland protocol by means of `wl_surface::enter` and +`wl_surface::leave` events to the client. + +==== SyncDraw and FlushDraw +These events instruct applications that they should redraw their surface +contents - again, this is handled implicitly by the wayland protocol. + +`SyncDraw` is sent to the application when it has to redraw its surface. + +`FlushDraw` is sent to the application when it should swap its buffers, +that is _signal_ the compositor that its surface contains new content. + +=== Example Use Case +In order to enable application to use the `WM` surface registration +function the above described steps need to be implemented. + +As a minimal example the usage and initialization can look like the +following. + +----------------------- + // Assume a program argc and argv. + QGuiApplication app(argc, argv); + + auto &wm = LibWindowmanager::instance(); + + // initialize the LibWindowmanager binding. + if(wm.init(1234, "wmtest") != 0) { + exit(EXIT_FAILURE); + } + + // Request a surface label from the WM. + char const *surface_label = "AppMediaPlayer"; + if (wm.requestSurface(surface_label) != 0) { + exit(EXIT_FAILURE); + } + + // Register an Active event handler. + wm.set_event_handler(Event_Active, + [](char const *label) { + qDebug() << "Surface" << label << "got activated"; + }); + + // Initialize application window + // ... + + // request to activate the surface, this should usually + // not be done by the client application. + if (wm.activateSurface(surface_label) != 0) { + fprintf(stderr, "Could not activate the surface\n"); + exit(EXIT_FAILURE); + } + + // e.g. exec the qt application + app.exec(); + +// vim:set ft=asciidoc tw=72: |