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diff --git a/android/README.md b/android/README.md new file mode 100644 index 000000000000..cfce3ddaa942 --- /dev/null +++ b/android/README.md @@ -0,0 +1,326 @@ +LibreOffice Android +******************* + +Bootstrap +********* + +Contains common code for all projects on Android to bootstrap LibreOffice. In +addition it is a home to LibreOfficeKit (LOK - see libreofficekit/README) JNI +classes. + +stuff in source directory +************************* + +LibreOffice Android application - the code is based on Fennec (Firefox for Android). +It uses OpenGL ES 2 for rendering of the document tiles which are gathered from +LibreOffice using LOK. The application contains the LibreOffice core in one shared +library: liblo-native-code.so, which is bundled together with the application. + +Architecture and Threading +************************** + +The application implements editing support using 4 threads: +1. The Android UI thread, we can't perform anything here that would take a considerable + amount of time. +2. An OpenGL thread which contains the OpenGL context and is responsible for drawing + all layers (including tiles) to the screen. +3. A thread (LOKitThread), that performs LibreOfficeKit calls, which may take more time + to complete. In addition it also receives events from the soffice thread (see below) + when the callback emits an event. Events are stored in a blocking queue (thread + processes events in FCFS order, goes to sleep when no more event is available and + awakens when there are events in the queue again). +4. A native thread created by LibreOfficeKit (we call it the soffice thread), where + LibreOffice itself runs. It receives calls from LOKitThread, and may emit callback + events as necessary. + +LOKitThread +*********** + +LOKitThread (org.libreoffice.LOKitThread) communicates with LO via JNI (this can +be done only for one thread) and processes events (defined in org.libreoffice.LOEvent) +triggered from UI. + +Application Overview +******************** + +LibreOfficeMainActivity (org.libreoffice.LibreOfficeMainActivity) is the entry point +of the application - everything starts up and tears down from here (onCreate, onResume, +onPause, onStart, onStop, onDestroy). + +Document view +------------- + +From here on one of the most interesting pieces are the classes around document view, +which includes listening to touch events, recalculating the viewport, tiled handling +and rendering the layers to the document. + +Viewport - the viewport is the currently visible part of the document. It is defined + by view rectangle and zoom. + +Layers - document view is rendered using many layers. Such layers are: document + background, scroll handles, and also the document tiles. + +Document view classes +--------------------- + +- LayerView (org.mozilla.gecko.gfx.LayerView) is the document view of the application. + It uses the SurfaceView (android.view.SurfaceView) as the main surface to draw on + using OpenGL ES 2. + +- GLController (org.mozilla.gecko.gfx.GLController) - holder of the OpenGL context. + +- RenderControllerThread (org.mozilla.gecko.gfx.RenderControllerThread) executes the + rendering requests through LayerRenderer. + +- LayerRenderer (org.mozilla.gecko.gfx.LayerRenderer) renders all the layers. + +- GeckoLayerClient (org.mozilla.gecko.gfx.GeckoLayerClient) is the middle man of the + application, which connects all the bits together. It is the document view layer + holder so the any management (including tiled rendering) usually go through this + class. It listens to draw requests and viewport changes from PanZoomController + (see "Touch events"). + +Touch events, scrolling and zooming +----------------------------------- + +The main class that handles the touch event, scrolling and zooming is JavaPanZoomController +org.mozilla.gecko.gfx.JavaPanZoomController (implementation of PanZoomController interface). +When the user performs a touch action, the document view needs to change, which means the +viewport changes. JavaPanZoomController changes the viewport and signals the change through +PanZoomTarget (org.mozilla.gecko.gfx.PanZoomTarget). + +TiledRendering +-------------- + +Tiled rendering is a technique that splits the document to bitmaps of same size (typically +256x256) which are fetched on demand. + +In the application the ComposedTileLayer (org.mozilla.gecko.gfx.ComposedTileLayer) is the +layer responsible for tracking and managing the tiles. Tiles are in this case also layers +(sub layers?) implemented in SubTile (org.mozilla.gecko.gfx.SubTile), where each one is +responsible for one tile bitmap (actually OpenGL texture once it has been uploaded). + +When the viewport changes, the request for tile rechecking is send to LOKitThread (see +LOKitThread#tileReevaluationRequest), where the tiles are rechecked, add and removed if +necessary. + +CompositeTileLayer is actually an abstract class, which has two implementations. One is +DynamicTileLayer (org.mozilla.gecko.gfx.DynamicTileLayer), which is used for main tile +view of the document, and FixedZoomTileLayer (org.mozilla.gecko.gfx.FixedZoomTileLayer), +which just renders the tiles at a fixed zoom level. This is then used as a background +low resolution layer. + +Tile invalidation +----------------- + +Tile can change in LibreOffice when user changes the content (adds, removes text or changes +the properties). In this case, an invalidation rectangle is signaled from LibreOffice, which +includes a rectangle that needs to be invalidated. In this case LOKitThread gets this request +via callback, and rechecks all tiles if they need to be invalidated. For more details see +LOKitThread#tileInvalidation). + +Editing +******* + +For editing there are 2 coarse tasks that the LibreOffice app must do: +1. send input events to LibreOffice core (keyboard, touch and mouse) +2. listen to messages (provided via callback) from LibreOffice core and react accordingly + +In most cases when an input event happens and is send to the LO core, then a message from +LO core follows. For example: when the user writes to the keyboard, key event is sent and +an invalidation request from LO core follows. When user touches an image, a mouse event is +sent, and a "new graphic selection" message from LO core follows. + +All keyboard and touch events are sent to LOKitThread as LOEvents. In LOKitThread they are +processed and sent to LibreOffice core. The touch events originate in JavaPanZoomController, +the keyboard events in LOKitInputConnectionHandler (org.libreoffice.LOKitInputConnectionHandler), +however there are other parts too - depending on the need. + +InvalidationHandler (org.libreoffice.InvalidationHandler) is the class that is responsible +to process messages from LibreOffice core and to track the state. + +Overlay +******* + +Overlay elements like cursor and selections aren't drawn by the LO core, instead the core +only provides data (cursor position, selection rectangles) and the app needs to draw them. +DocumentOverlay (org.libreoffice.overlay.DocumentOverlay) and DocumentOverlayView +(org.libreoffice.overlay.DocumentOverlayView) are the classes that provide the overlay over +the document, where selections and the cursor is drawn. + + +Icons +***** + +App uses material design icons available at [1]. + + +[1] - https://www.google.com/design/icons/ + +Emulator and debugging notes +**************************** + +For instructions on how to build for Android, see README.cross. + +* Getting something running + +Attach your device, so 'adb devices' shows it. Then run: + + cd android/source + make install + adb logcat + +and if all goes well, you should have some nice debug output to enjoy when you +start the app. + +* Using the emulator + +Create an AVD in the android UI, don't even try to get the data partition size +right in the GUI, that is doomed to producing an AVD that doesn't work. +Instead start it from the console: + + LD_LIBRARY_PATH=$(pwd)/lib emulator-arm -avd <Name> -partition-size 500 + +where <Name> is the literal name of the AVD that you entered. + +[ In order to have proper acceleration, you need the 32-bit libGL.so: + + sudo zypper in Mesa-libGL-devel-32bit + +and run emulator-arm after the installation. ] + +Then you can run ant/adb as described above. + +After a while of this loop you might find that you have lost a lot of +space on your emulator's or device's /data volume. You can do: + + adb shell stop; adb shell start + +Debugging +--------- + +First of all, you need to configure the build with --enable-debug or +--enable-dbgutil. You may want to provide --enable-symbols to limit debuginfo, +like --enable-symbols="sw/" or so, in order to fit into the memory +during linking. + +Building with all symbols is also possible but the linking is currently +slow (around 10 to 15 minutes) and you need lots of memory (around 16GB + some +swap). + +* Using ndk-gdb + +Direct support for using ndk-gdb has been removed from the build system. It is +recommended that you give the lldb debugger a try that has the benefit of being +nicely integrated into Android Studio (see below for instructions). +If you nevertheless want to continue using ndk-gdb, use the following steps +that are described in more detail here: https://stackoverflow.com/a/10539883 + + - add android:debuggable="true" to AndroidManifest.xml + - push gdbserver to device, launch and attach to application + - forward debugging port from host to device + - launch matching gdb on host and run following setup commands: + - set solib-search-path obj/local/<appAbi> + - file obj/local/<appAbi>/liblo-native-code.so + - target remote :<portused> + +Pretty printers aren't loaded automatically due to the single shared +object, but you can still load them manually. E.g. to have a pretty-printer for +rtl::OString, you need: + + (gdb) python sys.path.insert(0, "/master/solenv/gdb") + (gdb) source /master/instdir/program/libuno_sal.so.3-gdb.py + +* Using Android Studio (and thus lldb) + +Note that lldb might not yield the same results as ndk-gdb. If you suspect a +problem with lldb, you can try to manually use ndk-gdb as described above. +Using lldb from within Android Studio is more comfortable though and works like this: + + - open android/source/build.gradle in Android Studio via File|New → Import Project + - make sure you select the right build variant (strippedUIDebug is what you want) + - use Run|Edit Configurations to create a new configuration of type "Android Native" + - on tab "General" pick module "source" + - on tab "Native Debugger" add android/obj/local/<hostarch> to + the Symbol directories + - on the LLDB startup commands tab add + "command script import /path/to/solenv/lldb/libreoffice/LO.py" + to get some pretty printing hooks for the various string classes + +Then you can select your new configuration and use Run | Debug to launch it. +Note that lldb doesn't initially stop execution, so if you want to add +breakpoints using lldb prompt, you manually have to pause execution, then you +can switch to the lldb tab and add your breakpoints. However making use of the +editor just using File|Open .. to open the desired file in Android Studio and +then toggling the breakpoint by clicking on the margin is more comfortable. + +* Debugging the Java part + +Open android/source/build.gradle in Android studio via File|New → Import +Project and you can use Android Studio's debugging interface. +Just make sure you pick the correct build variant (strippedUIDebug) + +The alternative is to use the jdb command-line debugger. Steps to use it: + +1) Find out the JDWP ID of a debuggable application: + + adb jdwp + +From the list of currently active JDWP processes, the last number is the just +started debuggable application. + +2) Forward the remote JDWP port/process ID to a local port: + + adb forward tcp:7777 jdwp:31739 + +3) Connect to the running application: + + jdb -sourcepath src/java/ -attach localhost:7777 + +Assuming that you're already in the LOAndroid3 directory in your shell. + +* Debugging the missing services + +Android library only include essential services that are compiled for +LibreOffice in order to reduce the size of the apk. When developing, +some services might become useful and we should add those services +to the combined library. + +In order to identify missing services, we need to be able to receive +SAL_INFO from cppuhelper/source/shlib.cxx in logcat and therefore identify +what services are missing. To do so, you may want add the following +when configuring the build. + + --enable-symbols="cppuhelper/ sal/" + +[TODO: This is nonsense. --enable-symbols enables the -g option, not SAL_INFO. +Perhaps this was a misunderstanding of meaning of --enable-selective-debuginfo, +the old name for the option.] + +Which services are combined in the android lib is determined by + + solenv/bin/native-code.py + +* Common Errors / Gotchas + +lo_dlneeds: Could not read ELF header of /data/data/org.libreoffice...libfoo.so + This (most likely) means that the install quietly failed, and that +the file is truncated; check it out with adb shell ls -l /data/data/... + +* Startup details + +All Android apps are basically Java programs. They run "in" a Dalvik +(or on Android 5 or newer - ART) virtual machine. Yes, you can also +have apps where all *your* code is native code, written in a compiled +language like C or C++. But also such apps are actually started +by system-provided Java bootstrapping code (NativeActivity) running +in a Dalvik VM. + +Such a native app (or actually, "activity") is not built as a +executable program, but as a shared object. The Java NativeActivity +bootstrapper loads that shared object with dlopen. + +Anyway, our current "experimental" apps are not based on NativeActivity. +They have normal Java code for the activity, and just call out to a single, +app-specific native library (called liblo-native-code.so) to do all the +heavy lifting. |