Added the concept of a 'flick' gesture. This uses the VelocityTracker object in Android and passes the velocity info down as an SDL joystick trackball event. We can then reinterpret this event in whatever way we like, such as up/down swipes in the deck editor (that was my initial thought, at any rate).

TBD:  right now every up finger generates this event.  We probably want to throttle it to only be an event if the velocity exceeds some arbitrary threshold;  similarly, if we generate a flick event, we probably don't want to simultaneously generate a finger up action (ie JGE_BTN_OK).

JGE/Dependencies/SDL/src/core/android/SDL_android.cpp

@@ -128,6 +128,13 @@ extern "C" void Java_org_libsdl_app_SDLActivity_onNativeTouch(
     Android_OnTouch(index, action, x, y, p);
 }
 
+extern "C" void Java_org_libsdl_app_SDLActivity_onNativeFlickGesture(
+                                    JNIEnv* env, jclass jcls,
+                                    jfloat xVelocity, jfloat yVelocity)
+{
+    Android_OnFlickGesture(xVelocity, yVelocity);
+}
+
 // Accelerometer
 extern "C" void Java_org_libsdl_app_SDLActivity_onNativeAccel(
                                     JNIEnv* env, jclass jcls,

JGE/Dependencies/SDL/src/video/android/SDL_androidtouch.c

@@ -119,4 +119,18 @@ void Android_OnTouch(int index, int action, float x, float y, float p)
     }
 }
 
+void Android_OnFlickGesture(float xVelocity, float yVelocity)
+{
+    // cheap hack, translate this to a joystick ball event instead of its own proper event
+    
+    SDL_Event event;
+    event.jball.type = SDL_JOYBALLMOTION;
+    event.jball.which = 0;
+    event.jball.ball = 0;
+    event.jball.xrel = (int) xVelocity;;
+    event.jball.yrel = (int) yVelocity;
+
+    SDL_PushEvent(&event);
+}
+
 /* vi: set ts=4 sw=4 expandtab: */

JGE/Dependencies/SDL/src/video/android/SDL_androidtouch.h

@@ -24,4 +24,6 @@
 
 extern void Android_OnTouch(int index, int action, float x, float y, float p);
 
+extern void Android_OnFlickGesture(float xVelocity, float yVelocity);
+
 /* vi: set ts=4 sw=4 expandtab: */

JGE/src/SDLmain.cpp

@@ -208,7 +208,11 @@ public:
 				<< ", dDist " << Event->mgesture.dDist
 				<< ", numFingers " << Event->mgesture.numFingers);
 			break;
-		}
+
+        case SDL_JOYBALLMOTION:
+            DebugTrace("Flick gesture detected");
+            break;
+        }
 	}
 
 	void OnUpdate();

projects/mtg/Android/src/org/libsdl/app/SDLActivity.java

@@ -95,6 +95,7 @@ public class SDLActivity extends Activity {
     public static native void onNativeKeyUp(int keycode);
     public static native void onNativeTouch(int index, int action, float x, 
                                             float y, float p);
+	public static native void onNativeFlickGesture(float xVelocity, float yVelocity);
     public static native void onNativeAccel(float x, float y, float z);
     public static native void nativeRunAudioThread();
 
@@ -245,6 +246,8 @@ class SDLSurface extends SurfaceView implements SurfaceHolder.Callback,
     // Sensors
     private static SensorManager mSensorManager;
 
+	private static VelocityTracker mVelocityTracker;
+
     // Startup    
     public SDLSurface(Context context) {
         super(context);
@@ -467,6 +470,32 @@ class SDLSurface extends SurfaceView implements SurfaceHolder.Callback,
 	        SDLActivity.onNativeTouch(index, action, x, y, p);
 		}
         
+		// account for 'flick' type gestures by monitoring velocity
+		if (event.getActionIndex() == 0)
+		{
+			if (event.getAction() == MotionEvent.ACTION_DOWN)
+			{
+				mVelocityTracker = VelocityTracker.obtain();
+				mVelocityTracker.clear();
+				mVelocityTracker.addMovement(event);
+			}
+			else if (event.getAction() == MotionEvent.ACTION_MOVE)
+			{
+				mVelocityTracker.addMovement(event);
+			}
+			else if (event.getAction() == MotionEvent.ACTION_UP)
+			{
+				mVelocityTracker.addMovement(event);
+
+				// calc velocity
+				mVelocityTracker.computeCurrentVelocity(1000);
+				
+				SDLActivity.onNativeFlickGesture(mVelocityTracker.getXVelocity(), mVelocityTracker.getYVelocity());
+
+				mVelocityTracker.recycle();
+			}
+		}
+
 		return true;
     }