android: properly merge README with new content

Change-Id: I740c654f5844ef4cb7cbc5387c7b8a56e326e532

1 files changed, 76 insertions, 35 deletions

diff --git a/android/README b/android/README
index 5e8db7c9caf5..617e86bc9c2b 100644
--- a/android/README
+++ b/android/README
@@ -1,4 +1,46 @@
+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.
+
 Android-specific notes
+**********************
 
 Note that this document has not necessarily been updated to match
 reality...
@@ -7,67 +49,67 @@ 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
+        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=$(pwd)/lib emulator-arm -avd <Name> -partition-size 500
+        LD_LIBRARY_PATH=$(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.
+        Where <Name> is the literal name of the AVD that you entered.
 
-	Then:
+        Then:
 
-	cd android/experimental/LOAndroid3
-	ant debug install
-	adb logcat
+        cd android/experimental/LOAndroid3
+        ant debug install
+        adb logcat
 
-	And if all goes well - you should have some nice debug output to enjoy
+        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
+        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.
+        That works fine, too.
 
 * Debugging
 
-	First of all, you need to configure the build with --enable-debug or
+        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
+        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
+        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:
+        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
+        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:
+        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
+        (gdb) python sys.path.insert(0, "/master/solenv/gdb")
+        (gdb) source /master/instdir/program/libuno_sal.so.3-gdb.py
 
 * Debuggint the Java part
 
@@ -77,28 +119,27 @@ debugger. Steps to use it:
 
 1) Find out the JDWP ID of a debuggable application:
 
-	adb jdwp
+        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
+        adb forward tcp:7777 jdwp:31739
 
 3) Connect to the running application:
 
-	jdb -sourcepath src/java/ -attach localhost:7777
+        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
+        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
@@ -120,17 +161,17 @@ 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.
+(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 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.
+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.