Thanks to Denis Bernard!
Also, changed the Android manifest so the app doesn't quit with orientation
changes, and made testgles.c exit properly on Android.
This bumps the build SDK level to 12 (up from 10). Runtime requirements remain
the same (at API level < 12 joystick support is disabled).
Also enables building SDL for armv7 and x86.
Denis Bernard
Background information: http://developer.android.com/reference/android/hardware/SensorEvent.html#values
Steps to reproduce: compile testjoystick.c as an android app (change screen size according to your device). While running the app, also run:
adb logcat -c; adb logcat -s 'SDL:*' 'SDL/APP:*'
When tilting the device left/right, the joystick moves in the opposite direction of what one would expect. Or at least, the behaviour is not consistent with the Y axis.
Also when the device sits on a table (obviously not moving), the Z axis value oscillates between -32000 and +32000 (by overflow):
I/SDL/APP ( 1994): Joystick 0 axis 2 value: 32511
I/SDL/APP ( 1994): Joystick 0 axis 2 value: 32575
I/SDL/APP ( 1994): Joystick 0 axis 2 value: 32383
I/SDL/APP ( 1994): Joystick 0 axis 2 value: -32386
I/SDL/APP ( 1994): Joystick 0 axis 2 value: -32450
I/SDL/APP ( 1994): Joystick 0 axis 2 value: -32578
This is caused by the accelerometer yielding a constant value around 9.81 for Z and feeding something like 0.9 to 1.1 to the joystick driver, resulting in the overflow.
Proposed fix in SDLActivity.java (swap X and subtract G from Z reading)
Denis Bernard
Background information: http://android-developers.blogspot.fr/2010/09/one-screen-turn-deserves-another.html and http://developer.android.com/reference/android/hardware/SensorEvent.html
Right now, the Android accelerometer event handler feeds raw accelerometer data to the SDL Joystick driver. The result is that for landscape-only applications, the axis need to be swapped if running on a portrait device (like a phone), and vice-versa: running a portrait only app on a landscape device like a tablet.
The purpose of this patch is to perform coordinate remapping of the accelerometer data before feeding it to the SDL joystick driver so that the X axis of the joystick is always aligned with the X axis of the display, same for the Y axis.
This has been tested on applications that support screen orientation changes as well as applications with fixed screen orientations, both on phones and tablets.
On Android available touch devices are now added with video initialization (like
the keyboard). This fixes SDL_GetNumTouchDevices() returning 0 before any touch
events happened although there is a touch screen available. The adding of touch
devices after a touch event was received is still active to allow connecting
devices later (if this is possible) and to provide a fallback if the new init
did not work somehow. For the implementation JNI was used and API level 9 is
required. There seems to be nothing in the Android NDK's input header (input.h)
to implement everything on C side without communication with Java side.
If the app is in landscape mode and the user presses the power button, a pause
is followed immediately by a surfaceChanged event because the lock screen
is shown in portrait mode. This triggers a "false" resume.
So, we just pause and resume following the onWindowFocusChanged events.
Also, wait for SDL_APP_WILLENTERBACKGROUND and SDL_APP_DIDENTERBACKGROUND before
blocking the event pump.
