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diff --git a/doc/WindowManagerTMC.md b/doc/WindowManagerTMC.md new file mode 100644 index 0000000..8294186 --- /dev/null +++ b/doc/WindowManagerTMC.md @@ -0,0 +1,549 @@ +Introduction +============ + +This WindowManager implements simple layout switching of applications on +multiple layers and with different layer layouts. + +Intended audience +----------------- + +This documentation is intended for developers and system integrators who +need to know, how the window manager works and how it is to be used. + +Scope of this Document +---------------------- + +This document covers the window manager that was implemented for TMC and +delivered to the Automotive Grade Linux (AGL) project. It includes its +implementation details, concepts of operation, configuration and usage. + +It does not include + +- documentation of the underlying architecture, see + [HMI-Framework](https://wiki.automotivelinux.org/hmiframework). + +- documentation of the AGL application framework and its technologies, + see [AGL Application + Framework](https://wiki.automotivelinux.org/agl-distro/app-framework). + +It is highly recommended to have a good understanding of these documents +and projects before using the window manager. + +Known Issues +------------ + +Currently there are a couple of known issues: + +- Weston seems not to redraw the screen correctly. When the window + manager makes scene changes in quick succession, Weston seems not to + redraw the screen correctly and also not send wl\_surface::enter + events, which in turn leaves applications "dead" - i.e. not + rendering or showing up. We developed a simple secondary + ivi-controller client application **redraw\_fixer** (See + [redraw\_fixer](#_redraw_fixer) for more) that listens for specific + scene-change events and issues other commands that should prompt a + correct redraw - however, this does not work in all instances. + +- Only single-surface Qt applications are support through the + AFBClient library. This is a limitation of how Qt creates surface + IDs for the ivi-application interface. + +External libraries +------------------ + +This project includes a copy of version 2.1.1 the excellent [C++11 JSON +library by Niels Lohmann](https://github.com/nlohmann/json). + +Client Library +-------------- + +A client library implementation that internally uses the *libafbwsc*, is +provided in the subdirectory `client-lib/` with its own documentation +directory. + +The client library is built together with the window manager itself. + +Concepts +======== + +The window manager implements a couple of concepts in order to allow +efficient implementation. + +Layers +------ + +Layers are entities that are stacked on top of each other. Each layer +has an ID which is used for the ivi-controller interface, but this ID +also implicitly specifies its stacking order, from lowest to highest. + +Layers are always full-screen. We do not use layer dimensions as a way +to setup the scene, rather - each layer has a layout attached to it, +which specifies an area that is used by surfaces to draw on. + +Additionally, layers will generally leave surfaces on below layers +activated, and only disable surfaces on layers the are above the +currently used layer. + +It is possible to deactivate these surfaces on lower layers explicitly +using the `DeactivateSurface` API call. + +Surfaces +-------- + +Surfaces are *placed* on layers according to their name. The surface +will then be resized to dimensions, according to the layer’s layout +configuration. + +Binding API +=========== + +The binding API consists of a couple of AFB *verbs* - that is; function +calls to the Window Manager. + +Verbs (Functions) +----------------- + +Each function returns a reply containing at least a failed or successful +result of the call, additionally, when calls return something, it is +noted. The notation used has the following meaning: + + FunctionName(argument_name: argument_type)[: function_return_type] + +Where the return type may be omitted if it is void. + +- `RequestSurface(drawing_name: string): int` Request a surface ID for + the given name. This name and ID association will live until the + surface is destroyed (or e.g. the application exits). Each surface + that is managed by the window manager needs to call this function + first! + +- `ActivateSurface(drawing_name: string)` This function requests the + activation of a surface. It usually is not called by the + application, but rather by the application framework or + the HomeScreen. + +- `DeactivateSurface(drawing_name: string)` Request deactivation of + a surface. This function is not usually called by applications + themselves, but rather by the application framework or + the HomeScreen. + +- `EndDraw(drawing_name: string)` Signals the window manager, that the + surface is finished drawing. This is useful for consistent + flicker-free layout switches, see the Architecture document + for details. + +There are a couple of non-essential (mostly for debugging and +development) API calls: + +- `list_drawing_names(): json` List known surface *name* to + *ID* associations. + +- `ping()` Ping the window manager. Does also dispatch pending events + if any. + +- `debug_status(): json` Returns a json representation of the current + layers and surfaces known to the window manager. This represents the + wayland-ivi-extension object’s properties. + +- `debug_surfaces(): json` Returns a json representation of all + surfaces known to the window manager. This represents the + wayland-ivi-extension properties of the surfaces. + +- `debug_layers(): json` Returns the current layer configuration, as + configured through *layers.json*. + +- `debug_terminate()` Terminates the afb-daemon running the window + manager binding, if the environment variable + `WINMAN_DEBUG_TERMINATE` is set. + +Events +------ + +The window manager broadcasts certain events (to all applications) that +signal information on the state of the surface regarding the current +layout. + +- `Active(drawing_name: string)` Signal that the surface with the name + `drawing_name` is now active. + +- `Inactive(drawing_name: string)` Signal that the surface with the + name `drawing_name` is now inactive. This usually means, the layout + got changed, and the surface is now considered inactive + (or sleeping). + +- `Visible(drawing_name: string)` Signal applications, that the + surface with name `drawing_name` is now visible. + +- `Invisible(drawing_name: string)` Signal applications that the + surface with name `drawing_name` is now invisible. + +- `SyncDraw(drawing_name: string)` Signal applications, that the + surface with name `drawing_name` needs to redraw its content - this + usually is sent when the surface geometry changed. + +- `FlushDraw(drawing_name: string)` Signal to applications, that the + surface with name `drawing_name` can now be swapped to its newly + drawn content as the window manager is ready to activate a new + layout (i.e. a new surface geometry). + +Binding API Usage +----------------- + +For a detailed description on how the binding API is supposed to be +used, refer to the Architecture document. + +Configuration +============= + +The window manager is configured with the *layers.json* configuration +file, by default it is searched in `/etc/layers.json` but through the +use of the environment variable `LAYERS_JSON` the WM can be instructed +to use different file. Note, that the WM will not run unless this +configuration is found and valid. + +A sample configuration is provided with the window manager +implementation, this sample is installed to /etc/layers.json. + +Configuration Items +------------------- + +This section describes configuration items available through +`layers.json`. It will do this, by first providing an example, and then +going into its components. + +### main\_surface + + "main_surface": { + "surface_role": "HomeScreen", + }, + +The `main_surface` object describes a surface that will internally be +treated as the main surface - usually this mean *HomeScreen*. The only +special handling this surface receives, is that it is not allowed to +deactivate it. Placement of this surface on an layer is done by the +other configuration described below. + +- `surface_role` this configuration item specifies the name of the + main surface. Set this to e.g. `HomeScreen`. + +### mappings + +This configuration item is a list of surface-name to layer mappings. + +#### surface to layer mapping + + "mappings": [ + { + "role": "^HomeScreen$", + "name": "HomeScreen", + "layer_id": 1000, + "area": { "type": "full" }, + }, + { + "role": "^App.*", + "name": "apps", + "layer_id": 1001, + "area": { "type": "rect", + "rect": { "x": 0, + "y": 100, + "width": -1, + "height": -201 } }, + "split_layouts": [] + } + ] + +Each mapping defines the following items to map corresponding surfaces +to a layer. + +- `role` defines a regular expression that application drawing names + are matched against. If applications match tis regular expression, + the surface will be visible on this layer. + +- `name` is just a name definition for this layer, it has no + functional use apart from identifying a layer with a name. + +- `layer_id` specifies which ID this layer will use. + +- `area` is an object that defines the area assigned to surfaces. + +- `split_layouts` is an optional item, that - if present - defines a + number of possible split-screen layouts for this layer. + +#### Area + +Areas can be either `full` or `rect`, whereas `full` means a full-screen +layer, this is mostly useful for the main\_surface or HomeScreen layer. +`rect` declares a layer drawing area specified as a rectangle with start +coordinates `x` and `y` as well as its dimensions `width` and `height`. + +The dimensions can be specified relative to the screen dimensions. For +this negative values for width and height mus be used. + +For example, a full-screen surface can have the following `rect` +definition: + + "rect": { "x": 0, + "y": 0, + "width": -1, + "height": -1 } + +A surface that leaves a 200pixel margin on the top and bottom can use +the following `rect` definition: + + "rect": { "x": 0, + "y": 200, + "width": -1, + "height": -401 } + +So the expression for the actual surface dimensions when using +screen-size-relative values will be: + + actual_width = screen_width + 1 + width + actual_height = screen_height + 1 + height + +Or in other words, to leave an `N` wide border around a surface, the +actual value in the dimension configuration needs to be `-N - 1`, and +appropriate offsets need to be set for `x` and `y`. + +#### split\_layouts + +This configuration item allows the specification of split-screen layouts +on layers for certain surfaces. + +A split screen layout always has a *main* surface and a *sub* surface. +In order to enter a split screen layout, first the *main* surface of the +layout must be activated, and then the *sub* surface. In order to +disable the split layout, one of the two participating surface must be +deactivated (or a surface on a layer below the current one must be +activated). + + "split_layouts": [ + { + "name": "Media Player", + "main_match": "^App MPlayer Main$", + "sub_match": "^App MPlayer Sub", + } + ] + +A split layout object has the following attributes: + +- `name` defines its name, it has no actual function other then a way + to identify this split layout. + +- `main_match` is a regular expression that matches for the *main* + surface of this split layout. + +- `sub_match` is a regular expression that matches for the *sub* + surface of this layout. + +In the above example only the surface with drawing name +`App MPlayer Main` will be used as the *main* surface, but all surfaces +that begin with `App MPlayer Sub` can be used as a *sub* surface for +this layout. + +The names must still match the layer’s role match! + +Building and Running +==================== + +Dependencies +------------ + +This project is intended to be build with the 4.0 release of AGL. + +Build dependencies are as follows: + +- afb-daemon >= 1.0 + +- libsystemd >= 222 + +- wayland-client >= 1.11 + +- cmake >= 3.6.1 + +Build Configuration +------------------- + +Use cmake to configure a build tree: + + mkdir build + cd build + cmake .. + make + [sudo] make install + +A couple of build options to configure the build are available: + +- `ENABLE_DEBUG_OUTPUT:BOOL` Compiles including very verbose debug + output from the window manager, use --verbose three times on an + afb-daemon instance to see the debug messages. + +- `ENABLE_SCOPE_TRACING:BOOL` Enables a simple scope tracing mechanism + used for a rather small portion of the window manager code. However, + it is used quite extensively in the AFBClient implementation. + +By default these options will be disabled. + +Utilities +========= + +With the actual window manager implementation, two general utilities are +provided. + +wm-request +---------- + +A shell script, that wraps `afb-client-demo` and issues commands to the +window manager using the AFB exposed API. It will call synchronously to +the WM, and output any events that are happening in the meantime. +Replies are printed to stdout using an failed/success annotation and a +dump of the actual json reply from the AFB. When found on the system, it +will use `pygmentize` to apply syntax highlighting to the returned JSON. + +### Examples + + $ wm-request list_drawing_names + ON-REPLY 1:winman/list_drawing_names: OK + { + "response":{ + "App1":1, + "App2":2, + "HomeScreen":3, + "OnScreen":4 + }, + "jtype":"afb-reply", + "request":{ + "status":"success", + "info":"success" + } + } + $ wm-request activatesurface App1 + ON-REPLY 1:winman/activatesurface: OK + { + "response":{ + }, + "jtype":"afb-reply", + "request":{ + "status":"success", + "info":"success" + } + } + $ wm-request activatesurface AppThatDoesNotExist + ON-REPLY 1:winman/activatesurface: ERROR + { + "jtype":"afb-reply", + "request":{ + "status":"failed", + "info":"Surface does not exist" + } + } + +redraw\_fixer +------------- + +This utility is intended to be ran alongside the compositor, it will +listen for certain events regarding surfaces, and issue a couple of +other commands, to hopefully trigger a redraw of the surface in the +compositor. + +It will print messages for each acted-upon event, and exit when the +compositor exits. + +Implementation Notes +==================== + +The window manager is implemented as a app-framework-binder binding. +That means, the build produces one shared object that exports a binding +interface. + +Binding code generation +----------------------- + +The binding API is rather simple; functions receive a json object +describing arguments and return a json object describing the result or +an error. In order to simplify development, the +`generate-binding-glue.py` script was added, that contains a description +of the API as a python dictionary. This script generates the header +`afb_binding_api.hpp` and the afb binding functions as +`afb_binding_glue.inl`. Where the latter is included in `main.cpp`. + +Each function for the AFB binding that is generated does the following: + +- Lock the binding mutex, so that we serialize all access to + the binding. + +- Do some debug logging (if wanted). + +- Check the binding state, i.e. the compositor might have exited + unexpectedly at which point it would not make sense to continue. + +- Extract the arguments from the json object that is provided (doing + some primitive type checking). + +- Call the afb\_binding\_api method corresponding to this binding + function + +- Check the afb\_binding\_api’s function return value, log an error + state and return the result to the afb request. + +The generated functions do also check for any "loose" exception that +comes out of the afb\_binding\_api call (which in turn might call the +actual non-trivial implementation in `App`). However, **IF** an +exception is thrown and not handled inside the afb\_binding\_call, that +internal state of the window manager might be broken at this time (hence +the talkative error log). + +Structure +--------- + +The implementation is loosely split across the following source files: + +- `main.cpp`: The program entry point as used by the afb-daemon. This + file defines the afbBindingV2 symbol tat is used by the afb-daemon + in order to load a binding. It also defines the wayland fd event + dispatcher and some globals to be used (as context for the afb calls + we receive). + +- `afb_binding_api.cpp`: The implementation of the afb + binding functions. The actual functions are generated by + `generate-binding-glue.py` which generates a **.inl** file that is + included by `main.cpp`. + +- `app.cpp` / `app.hpp`: This is the main application + logic implementation. + +- `config.cpp` / `config.hpp`: Very simple configuration + item interface. + +- `controller_hooks.hpp`: hook functions called by the wayland + controller to call into the App instance. Only a very limited number + of events are passed to the Application, which allowed the usage of + such a simple interface. + +- `json_helper.cpp` / `json_helper.hpp`: Smaller json related + helper functions. + +- `layers.cpp` / `layers.hpp`: Actually hold all the data from + layers.json configuration, do some transformations and service the + App implementation. + +- `layout.cpp` / `layout.hpp`: Very simple layout state for the + implementation of split layouts and tracking of the + surfaces involved. + +- `policy.hpp`: PolicyManager implementation stub. Gets passed the + current and new layout on layout switch and can decide upon it being + valid or not. + +- `result.hpp`: Simple result class around + `std::experimental::optional` that additionally can hold a + `char const *` to describe the error. + +- `util.cpp` / `util.hpp`: general utility functions and structs - and + preprocessor definitions (e.g. `log*()` to AFB logging functions. + +- `wayland.cpp` / `wayland.hpp`: A C++ object-oriented + libwayland-client wrapper. It is instanced in `main.cpp` and handles + all our wayland needs. + + |