android: add README

Change-Id: I7a2b3cb487b4dfe290bff36e3766357fbbc84fba

1 files changed, 40 insertions, 136 deletions

diff --git a/android/README b/android/README
index 5e8db7c9caf5..d7fdf7731422 100644
--- a/android/README
+++ b/android/README
@@ -1,136 +1,40 @@
-Android-specific notes
-
-Note that this document has not necessarily been updated to match
-reality...
-
-For instructions on how to build for Android, see README.cross.
-
-* Getting something running on an emulated device
-
-	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
-
-In order to have proper acceleration, you need the 32-bit libGL.so:
-
-        sudo zypper in Mesa-libGL-devel-32bit
-
-	Where <Name> is the literal name of the AVD that you entered.
-
-	Then:
-
-	cd android/experimental/LOAndroid3
-	ant debug install
-	adb logcat
-
-	And if all goes well - you should have some nice debug output to enjoy
-when you start the app. 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. If using the
-emulator, you can do:
-
-	adb shell stop; adb shell start
-
-but on a (non-rooted) device you probably just need to reboot it. On the other
-hand, this phenomenon might not happen on actual devices.
-
-* What about using a real device?
-
-	That works fine, too.
-
-* Debugging
-
-	First of all, you need to configure the build with --enable-debug or
---enable-dbgutil.  You may want to provide --enable-selective-debuginfo too,
-like --enable-selective-debuginfo="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).
-
-	You also want to avoid --with-android-package-name (or when you use
-that, you must set it to "org.libreoffice"), otherwise ndk-gdb will complain
-that
-
-ERROR: Could not extract package's data directory. Are you sure that
-       your installed application is debuggable?
-
-	When you have all this, install the .apk to the device, and:
-
-	cd android/experimental/LOAndroid3
-	<android-ndk-r10d>/ndk-gdb --adb=<android-sdk-linux>/platform-tools/adb --start
-
-	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
-
-* Debuggint the Java part
-
-At the moment the code is not organized in a way that would make Eclipse or
-Android Studio happy as-is, so the quickest way 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.
-
-* 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/....
-
-
-* Detailed explanation
-
-Note: the below talk about unit tests is obsolete; we no longer have
-any makefilery etc to build unit tests for Android.
-
-Unit tests are the first thing we want to run on Android, to get some
-idea how well, if at all, the basic LO libraries work. We want to
-build even unit tests as normal Android apps, i.e. packaged as .apk
-files, so that they run in a sandboxed environment like that of
-whatever eventual end-user Android apps there will be that use LO
-code.
-
-Sure, we could quite easily build unit tests as plain Linux
-executables (built against the Android libraries, of course, not
-GNU/Linux ones), push them to the device or emulator with adb and run
-them from adb shell, but that would not be a good test as the
-environment such processs run in is completely different from that in
-which real end-user apps with GUI etc run. We have no intent to
-require LibreOffice code to be used only on "rooted" devices etc.
-
-All Android apps are basically Java programs. They run "in" a Dalvik
-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
-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 (DocumentLoader,
-LibreOffice4Android and LibreOfficeDesktop) are not based on
-NativeActivity any more. 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.
+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.
+
+LOAndroid3 (in experimental)
+****************************
+
+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. 
+
+TiledRendering
+**************
+
+Tiled rendering is a technique that splits the document to bitmaps of same size 
+(typically 256x256) which are fetched on demand. 
+
+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 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.