Improve scroll responsiveness.

1) mUsePagingTouchSlop set to false.
   Applist scroll now scrolls with the same
   thresholds used by homescreen scrolling.

2) Early start of scroll as soon as we
   detect that it's okay to scroll.
   Eliminates waiting for next vsync
   and starts scrolling in the current cycle.
   instead of the next.

Above changes help in reducing first touch to
first displacement latencies in scroll usecases.
Improves scroll responsiveness.

Change-Id: Ib45a361b9b6275e64d0a5b5603aa15fdd386a5f8

1 files changed, 50 insertions, 44 deletions

diff --git a/src/com/cyanogenmod/trebuchet/PagedView.java b/src/com/cyanogenmod/trebuchet/PagedView.java
index 42ae9687e..d8fccbf12 100644
--- a/src/com/cyanogenmod/trebuchet/PagedView.java
+++ b/src/com/cyanogenmod/trebuchet/PagedView.java
@@ -174,7 +174,7 @@ public abstract class PagedView extends ViewGroup implements ViewGroup.OnHierarc
 
     // It true, use a different slop parameter (pagingTouchSlop = 2 * touchSlop) for deciding
     // to switch to a new page
-    protected boolean mUsePagingTouchSlop = true;
+    protected boolean mUsePagingTouchSlop = false;
 
     // If true, the subclass should directly update scrollX itself in its computeScroll method
     protected boolean mDeferScrollUpdate = false;
@@ -1216,21 +1216,23 @@ public abstract class PagedView extends ViewGroup implements ViewGroup.OnHierarc
                 if (mUsePagingTouchSlop ? xPaged : xMoved) {
                     // Scroll if the user moved far enough along the X axis
                     mTouchState = TOUCH_STATE_SCROLLING;
-                    mTotalMotionX += Math.abs(mLastMotionX - x);
-                    mLastMotionX = x;
                     mLastMotionXRemainder = 0;
                     mTouchX = mScrollX;
                     pageBeginMoving();
+                    // Early scroll by starting as soon as we detect it's okay to scroll
+                    // instead of waiting for vsync.
+                    initiateScroll(ev);
                 }
             } else {
                 if (mUsePagingTouchSlop ? yPaged : yMoved) {
                     // Scroll if the user moved far enough along the X axis
                     mTouchState = TOUCH_STATE_SCROLLING;
-                    mTotalMotionY += Math.abs(mLastMotionY - y);
-                    mLastMotionY = y;
                     mLastMotionYRemainder = 0;
                     mTouchY = mScrollY;
                     pageBeginMoving();
+                    // Early scroll by starting as soon as we detect it's okay to scroll
+                    // instead of waiting for vsync.
+                    initiateScroll(ev);
                 }
             }
             // Either way, cancel any pending longpress
@@ -1238,6 +1240,48 @@ public abstract class PagedView extends ViewGroup implements ViewGroup.OnHierarc
         }
     }
 
+    protected void initiateScroll(MotionEvent ev) {
+        final int pointerIndex = ev.findPointerIndex(mActivePointerId);
+        final float x = ev.getX(pointerIndex);
+        final float deltaX = mLastMotionX + mLastMotionXRemainder - x;
+        final float y = ev.getY(pointerIndex);
+        final float deltaY = mLastMotionY + mLastMotionYRemainder - y;
+
+        mTotalMotionX += Math.abs(deltaX);
+        mTotalMotionY += Math.abs(deltaY);
+
+        // Only scroll and update mLastMotionX if we have moved some discrete amount.  We
+        // keep the remainder because we are actually testing if we've moved from the last
+        // scrolled position (which is discrete).
+        if (Math.abs(!mVertical ? deltaX : deltaY) >= 1.0f) {
+            if (!mVertical) {
+                mTouchX += deltaX;
+                mSmoothingTime = System.nanoTime() / NANOTIME_DIV;
+                if (!mDeferScrollUpdate) {
+                    scrollBy((int) deltaX, 0);
+                    if (DEBUG) Log.d(TAG, "onTouchEvent().Scrolling: " + deltaX);
+                } else {
+                    invalidate();
+                }
+                mLastMotionX = x;
+                mLastMotionXRemainder = deltaX - (int) deltaX;
+            } else {
+                mTouchY += deltaY;
+                mSmoothingTime = System.nanoTime() / NANOTIME_DIV;
+                if (!mDeferScrollUpdate) {
+                    scrollBy(0, (int) deltaY);
+                    if (DEBUG) Log.d(TAG, "onTouchEvent().Scrolling: " + deltaY);
+                } else {
+                    invalidate();
+                }
+                mLastMotionY = y;
+                mLastMotionYRemainder =- deltaY - (int) deltaY;
+            }
+        } else {
+            awakenScrollBars();
+        }
+    }
+
     protected void cancelCurrentPageLongPress() {
         if (mAllowLongPress) {
             mAllowLongPress = false;
@@ -1389,45 +1433,7 @@ public abstract class PagedView extends ViewGroup implements ViewGroup.OnHierarc
         case MotionEvent.ACTION_MOVE:
             if (mTouchState == TOUCH_STATE_SCROLLING) {
                 // Scroll to follow the motion event
-                final int pointerIndex = ev.findPointerIndex(mActivePointerId);
-                final float x = ev.getX(pointerIndex);
-                final float deltaX = mLastMotionX + mLastMotionXRemainder - x;
-                final float y = ev.getY(pointerIndex);
-                final float deltaY = mLastMotionY + mLastMotionYRemainder - y;
-
-                mTotalMotionX += Math.abs(deltaX);
-                mTotalMotionY += Math.abs(deltaY);
-
-                // Only scroll and update mLastMotionX if we have moved some discrete amount.  We
-                // keep the remainder because we are actually testing if we've moved from the last
-                // scrolled position (which is discrete).
-                if (Math.abs(!mVertical ? deltaX : deltaY) >= 1.0f) {
-                    if (!mVertical) {
-                        mTouchX += deltaX;
-                        mSmoothingTime = System.nanoTime() / NANOTIME_DIV;
-                        if (!mDeferScrollUpdate) {
-                            scrollBy((int) deltaX, 0);
-                            if (DEBUG) Log.d(TAG, "onTouchEvent().Scrolling: " + deltaX);
-                        } else {
-                            invalidate();
-                        }
-                        mLastMotionX = x;
-                        mLastMotionXRemainder = deltaX - (int) deltaX;
-                    } else {
-                        mTouchY += deltaY;
-                        mSmoothingTime = System.nanoTime() / NANOTIME_DIV;
-                        if (!mDeferScrollUpdate) {
-                            scrollBy(0, (int) deltaY);
-                            if (DEBUG) Log.d(TAG, "onTouchEvent().Scrolling: " + deltaY);
-                        } else {
-                            invalidate();
-                        }
-                        mLastMotionY = y;
-                        mLastMotionYRemainder = deltaY - (int) deltaY;
-                    }
-                } else {
-                    awakenScrollBars();
-                }
+                initiateScroll(ev);
             } else {
                 determineScrollingStart(ev);
             }