SkAR Java: minor refactoring to TapHelper (now GestureHelper)

Bug: skia:
Change-Id: I1983c6cb1727e86fec91a0c9a5706f26070b1b49
Reviewed-on: https://skia-review.googlesource.com/144021
Reviewed-by: Mike Reed <reed@google.com>

5 files changed, 29 insertions, 21 deletions

diff --git a/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/PaintUtil.java b/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/PaintUtil.java
index b9aaa01730..7665d365ba 100644
--- a/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/PaintUtil.java
+++ b/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/PaintUtil.java
@@ -35,9 +35,11 @@ public class PaintUtil {
      */
     public static ColorFilter createLightCorrectionColorFilter(float[] colorCorr) {
         float[] colorCorrCopy = Arrays.copyOf(colorCorr, 4);
+
         for (int i = 0; i < 3; i++) {
             colorCorrCopy[i] *= colorCorrCopy[3] / MIDDLE_GRAY_GAMMA;
         }
+
         ColorMatrix m = new ColorMatrix();
         m.setScale(colorCorrCopy[0], colorCorrCopy[1], colorCorrCopy[2], 1);
         return new ColorMatrixColorFilter(m);
diff --git a/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/examples/helloskar/app/CanvasARSurfaceView.java b/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/examples/helloskar/app/CanvasARSurfaceView.java
index 40c789d0a2..efe8acfa1d 100644
--- a/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/examples/helloskar/app/CanvasARSurfaceView.java
+++ b/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/examples/helloskar/app/CanvasARSurfaceView.java
@@ -57,6 +57,5 @@ public class CanvasARSurfaceView extends SurfaceView implements SurfaceHolder.Ca
     }
 
     @Override
-    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
-    }
+    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {}
 }
diff --git a/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/examples/helloskar/app/FingerPainting.java b/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/examples/helloskar/app/FingerPainting.java
index e4aaf5784b..ac97dfbf77 100644
--- a/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/examples/helloskar/app/FingerPainting.java
+++ b/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/examples/helloskar/app/FingerPainting.java
@@ -19,17 +19,14 @@ package com.google.skar.examples.helloskar.app;
 import android.graphics.Color;
 import android.graphics.Path;
 import android.graphics.PointF;
-import android.util.Log;
 
-import com.google.skar.examples.helloskar.helpers.TapHelper;
+import com.google.skar.examples.helloskar.helpers.GestureHelper;
 
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
-import java.util.ArrayList;
-
 public class FingerPainting {
     public static class BuiltPath {
         public Path path;
@@ -87,7 +84,7 @@ public class FingerPainting {
      * @param holdTap       ScrollEvent associated with the hit test that calls this function
      * @return              true if point was computed and added. False otherwise.
      */
-    public boolean computeNextPoint(float[] hitLocation, TapHelper.ScrollEvent holdTap) {
+    public boolean computeNextPoint(float[] hitLocation, GestureHelper.ScrollEvent holdTap) {
         if (isEmpty()) {
             // If finger painting is empty, then first point is origin. Model matrix
             // of the finger painting is the model matrix of the first point
diff --git a/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/examples/helloskar/app/HelloCanvasAR.java b/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/examples/helloskar/app/HelloCanvasAR.java
index d883c693a2..78791fae93 100644
--- a/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/examples/helloskar/app/HelloCanvasAR.java
+++ b/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/examples/helloskar/app/HelloCanvasAR.java
@@ -57,8 +57,8 @@ import com.google.ar.core.examples.java.helloskar.R;
 import com.google.skar.examples.helloskar.helpers.CameraPermissionHelper;
 import com.google.skar.examples.helloskar.helpers.DisplayRotationHelper;
 import com.google.skar.examples.helloskar.helpers.FullScreenHelper;
+import com.google.skar.examples.helloskar.helpers.GestureHelper;
 import com.google.skar.examples.helloskar.helpers.SnackbarHelper;
-import com.google.skar.examples.helloskar.helpers.TapHelper;
 
 import com.google.skar.examples.helloskar.rendering.BackgroundRenderer;
 import com.google.skar.examples.helloskar.rendering.DrawManager;
@@ -105,7 +105,7 @@ public class HelloCanvasAR extends AppCompatActivity implements GLSurfaceView.Re
     private boolean installRequested;
     private final SnackbarHelper messageSnackbarHelper = new SnackbarHelper();
     private DisplayRotationHelper displayRotationHelper;
-    private TapHelper tapHelper;
+    private GestureHelper tapHelper;
 
     // Temporary matrix allocated here to reduce number of allocations for each frame.
     private final float[] anchorMatrix = new float[16];
@@ -138,7 +138,7 @@ public class HelloCanvasAR extends AppCompatActivity implements GLSurfaceView.Re
         holder = arSurfaceView.getHolder();
 
         // Set up tap listener.
-        tapHelper = new TapHelper(this);
+        tapHelper = new GestureHelper(this);
         glSurfaceView.setOnTouchListener(tapHelper);
 
         // Set up renderer.
@@ -439,9 +439,9 @@ public class HelloCanvasAR extends AppCompatActivity implements GLSurfaceView.Re
      */
     private void handleHoldTaps(Frame frame, Camera camera) {
         // Building finger painting
-        TapHelper.ScrollEvent holdTap = tapHelper.holdPoll();
+        GestureHelper.ScrollEvent holdTap = tapHelper.holdPoll();
         if (holdTap != null && camera.getTrackingState() == TrackingState.TRACKING) {
-            for (HitResult hit : frame.hitTest(holdTap.e)) {
+            for (HitResult hit : frame.hitTest(holdTap.event)) {
                 // Check if any plane was hit, and if it was hit inside the plane polygon
                 Trackable trackable = hit.getTrackable();
                 // Creates an anchor if a plane or an oriented point was hit.
diff --git a/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/examples/helloskar/helpers/TapHelper.java b/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/examples/helloskar/helpers/GestureHelper.java
index 6dcfd8fb13..2cd195fdb1 100644
--- a/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/examples/helloskar/helpers/TapHelper.java
+++ b/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/examples/helloskar/helpers/GestureHelper.java
@@ -25,32 +25,35 @@ import java.util.concurrent.ArrayBlockingQueue;
 import java.util.concurrent.BlockingQueue;
 
 /**
- * Helper to detect taps using Android GestureDetector, and pass the taps between UI thread and
+ * Helper to detect gestures using Android GestureDetector, and pass the taps between UI thread and
  * render thread.
  */
-public final class TapHelper implements OnTouchListener {
+
+public final class GestureHelper implements OnTouchListener {
     private final GestureDetector gestureDetector;
     private final BlockingQueue<MotionEvent> queuedSingleTaps = new ArrayBlockingQueue<>(16);
     private final BlockingQueue<ScrollEvent> queuedFingerHold = new ArrayBlockingQueue<>(16);
     private boolean isScrolling = false;
     private boolean previousScroll = true;
 
+    // Struct holding a MotionEvent obtained from onScroll() callbacks, and a boolean evaluating to
+    // true if the MotionEven was the start of the scrolling motion
     public static class ScrollEvent {
-        public MotionEvent e;
+        public MotionEvent event;
         public boolean isStartOfScroll;
 
         public ScrollEvent(MotionEvent e, boolean isStartOfScroll) {
-            this.e = e;
+            this.event = e;
             this.isStartOfScroll = isStartOfScroll;
         }
     }
 
     /**
-     * Creates the tap helper.
+     * Creates the gesture helper.
      *
      * @param context the application's context.
      */
-    public TapHelper(Context context) {
+    public GestureHelper(Context context) {
         gestureDetector =
                 new GestureDetector(
                         context,
@@ -63,13 +66,15 @@ public final class TapHelper implements OnTouchListener {
                             }
 
                             @Override
-                            public boolean onScroll (MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
+                            public boolean onScroll (MotionEvent e1, MotionEvent e2,
+                                                     float distanceX, float distanceY) {
                                 // Queue motion events when scrolling
                                 if (e2.getPointerCount() == 1 && e1.getPointerCount() == 1) {
                                     previousScroll = isScrolling;
                                     isScrolling = true;
 
-                                    queuedFingerHold.offer(new ScrollEvent(e2, isStartedScrolling()));
+                                    queuedFingerHold.offer(new ScrollEvent(e2,
+                                                                           isStartedScrolling()));
 
                                     return true;
                                 }
@@ -93,13 +98,18 @@ public final class TapHelper implements OnTouchListener {
         return queuedSingleTaps.poll();
     }
 
+    /**
+     * Polls for a scrolling motion.
+     *
+     * @return if a scrolling event was queued, a ScrollEvent for the gesture. Otherwise null
+     */
     public ScrollEvent holdPoll() { return queuedFingerHold.poll(); }
 
     @Override
     public boolean onTouch(View view, MotionEvent motionEvent) {
         boolean val = gestureDetector.onTouchEvent(motionEvent);
 
-        // If finger is up + is scrolling: don't scroll anymore, and empty Touch Hold queue
+        // If finger is up + is scrolling: don't scroll anymore, and empty touch hold queue
         if (motionEvent.getAction() == MotionEvent.ACTION_UP && isScrolling) {
             previousScroll = true;
             isScrolling = false;