Fixed bug 1368 - Enabling joystick subsystem cause an infinite loop

morgan.devel@gmail.com 2012-01-13 00:32:23 PST

The android version of SDL_SYS_JoystickUpdate doesn't check if there is
actually new data and always generate the SDL_JOYAXISMOTION event.
Consequently, doing a while(SDL_PollEvent()) will result in an endless loop.

The attached patch fix this issue.

It also scale the incoming values properly in the Sint16 range. The scale from
[-gravity;+gravity] is done directly in the java part because one may want to
map the sensor values with a non-linear method for example.

android-project/src/org/libsdl/app/SDLActivity.java

@@ -565,9 +565,9 @@ public void onAccuracyChanged(Sensor sensor, int accuracy) {
 
     public void onSensorChanged(SensorEvent event) {
         if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
-            SDLActivity.onNativeAccel(event.values[0],
-                                      event.values[1],
-                                      event.values[2]);
+            SDLActivity.onNativeAccel(event.values[0] / SensorManager.GRAVITY_EARTH,
+                                      event.values[1] / SensorManager.GRAVITY_EARTH,
+                                      event.values[2] / SensorManager.GRAVITY_EARTH);
         }
     }
 

src/core/android/SDL_android.cpp

@@ -70,7 +70,7 @@ static jmethodID midAudioQuit;
 
 // Accelerometer data storage
 static float fLastAccelerometer[3];
-
+static bool bHasNewData;
 
 /*******************************************************************************
                  Functions called by JNI
@@ -111,6 +111,8 @@ extern "C" void SDL_Android_Init(JNIEnv* env, jclass cls)
     midAudioQuit = mEnv->GetStaticMethodID(mActivityClass,
                                 "audioQuit", "()V");
 
+    bHasNewData = false;
+
     if(!midCreateGLContext || !midFlipBuffers || !midAudioInit ||
        !midAudioWriteShortBuffer || !midAudioWriteByteBuffer || !midAudioQuit) {
         __android_log_print(ANDROID_LOG_WARN, "SDL", "SDL: Couldn't locate Java callbacks, check that they're named and typed correctly");
@@ -156,7 +158,8 @@ extern "C" void Java_org_libsdl_app_SDLActivity_onNativeAccel(
 {
     fLastAccelerometer[0] = x;
     fLastAccelerometer[1] = y;
-    fLastAccelerometer[2] = z;   
+    fLastAccelerometer[2] = z;
+    bHasNewData = true;
 }
 
 // Quit
@@ -224,12 +227,20 @@ extern "C" void Android_JNI_SetActivityTitle(const char *title)
     }
 }
 
-extern "C" void Android_JNI_GetAccelerometerValues(float values[3])
+extern "C" SDL_bool Android_JNI_GetAccelerometerValues(float values[3])
 {
     int i;
-    for (i = 0; i < 3; ++i) {
-        values[i] = fLastAccelerometer[i];
+    SDL_bool retval = SDL_FALSE;
+
+    if (bHasNewData) {
+        for (i = 0; i < 3; ++i) {
+            values[i] = fLastAccelerometer[i];
+        }
+        bHasNewData = false;
+        retval = SDL_TRUE;
     }
+
+    return retval;
 }
 
 //

src/core/android/SDL_android.h

@@ -31,7 +31,7 @@ extern "C" {
 extern SDL_bool Android_JNI_CreateContext(int majorVersion, int minorVersion);
 extern void Android_JNI_SwapWindow();
 extern void Android_JNI_SetActivityTitle(const char *title);
-extern void Android_JNI_GetAccelerometerValues(float values[3]);
+extern SDL_bool Android_JNI_GetAccelerometerValues(float values[3]);
 
 // Audio support
 extern int Android_JNI_OpenAudioDevice(int sampleRate, int is16Bit, int channelCount, int desiredBufferFrames);

src/joystick/android/SDL_sysjoystick.c

@@ -86,12 +86,14 @@ void
 SDL_SYS_JoystickUpdate(SDL_Joystick * joystick)
 {
     int i;
+    Sint16 value;
     float values[3];
 
-    Android_JNI_GetAccelerometerValues(values);
-
-    for ( i = 0; i < 3; i++ ) {
-        SDL_PrivateJoystickAxis(joystick, i, values[i]);
+    if (Android_JNI_GetAccelerometerValues(values)) {
+        for ( i = 0; i < 3; i++ ) {
+            value = (Sint16)(values[i] * 32767.0f);
+            SDL_PrivateJoystickAxis(joystick, i, value);
+        }
     }
 }