Remove the handle headroom if the challenge is open.

This change also moves to an absolute-distance model of
tracking the panel instead of a delta model; this allows us
to make the decision about the handle size in only one place
(when first detecting the gesture) instead of requiring us
to mix it into the arithmetic everywhere.

Also fixes the drag-too-slowly-and-the-panel-doesn't-move
problem.

Change-Id: I9bdbadd968134ad5ad67eaef9539536fb5cfe1a1
Proto-Id: I0c2f484da89f063995384c263aa9f5f03339ed7c

Author: dsandler

policy/src/com/android/internal/policy/impl/keyguard/SlidingChallengeLayout.java

@@ -82,7 +82,8 @@ public class SlidingChallengeLayout extends ViewGroup implements ChallengeLayout
     private VelocityTracker mVelocityTracker;
     private int mMinVelocity;
     private int mMaxVelocity;
-    private float mLastTouchY;
+    private float mGestureStartY; // where did you touch the screen to start this gesture?
+    private int mGestureStartChallengeBottom; // where was the challenge at that time?
     private int mDragHandleSize; // handle hitrect extension into the challenge view
     private int mDragHandleHeadroom; // extend the handle's hitrect this far above the line
     private int mDragHandleEdgeSlop;
@@ -469,7 +470,7 @@ public boolean onInterceptTouchEvent(MotionEvent ev) {
         final int action = ev.getActionMasked();
         switch (action) {
             case MotionEvent.ACTION_DOWN:
-                mLastTouchY = ev.getY();
+                mGestureStartY = ev.getY();
                 break;
 
             case MotionEvent.ACTION_CANCEL:
@@ -484,11 +485,12 @@ public boolean onInterceptTouchEvent(MotionEvent ev) {
                     final float y = ev.getY(i);
 
                     if (!mIsBouncing &&
-                            (isInDragHandle(x, y) || crossedDragHandle(x, y, mLastTouchY) ||
+                            (isInDragHandle(x, y) || crossedDragHandle(x, y, mGestureStartY) ||
                             (isInChallengeView(x, y) && mScrollState == SCROLL_STATE_SETTLING)) &&
                             mActivePointerId == INVALID_POINTER) {
                         mActivePointerId = ev.getPointerId(i);
-                        mLastTouchY = y;
+                        mGestureStartY = ev.getY();
+                        mGestureStartChallengeBottom = getChallengeBottom();
                         mDragging = true;
                     } else if (isInChallengeView(x, y)) {
                         mBlockDrag = true;
@@ -547,10 +549,12 @@ public boolean onTouchEvent(MotionEvent ev) {
                         final float x = ev.getX(i);
                         final float y = ev.getY(i);
 
-                        if ((isInDragHandle(x, y) || crossedDragHandle(x, y, mLastTouchY) ||
+                        if ((isInDragHandle(x, y) || crossedDragHandle(x, y, mGestureStartY) ||
                                 (isInChallengeView(x, y) && mScrollState == SCROLL_STATE_SETTLING))
                                 && mActivePointerId == INVALID_POINTER) {
+                            mGestureStartY = y;
                             mActivePointerId = ev.getPointerId(i);
+                            mGestureStartChallengeBottom = getChallengeBottom();
                             mDragging = true;
                             break;
                         }
@@ -570,20 +574,25 @@ public boolean onTouchEvent(MotionEvent ev) {
                         showChallenge(0);
                         return true;
                     }
-                    final float y = Math.max(ev.getY(index),
-                            getChallengeOpenedTop() - mDragHandleHeadroom);
-                    final float delta = y - mLastTouchY;
-                    final int idelta = (int) delta;
-                    // Don't lose the rounded component
-                    mLastTouchY = y + delta - idelta;
-
-                    moveChallengeBy(idelta);
+                    final float y = ev.getY(index);
+                    final float pos = Math.min(y - mGestureStartY,
+                            getChallengeOpenedTop());
+
+                    moveChallengeTo(mGestureStartChallengeBottom + (int) pos);
                 }
                 break;
         }
         return true;
     }
 
+    /**
+     * We only want to add additional vertical space to the drag handle when the panel is fully
+     * closed.
+     */
+    private int getDragHandleHeadroom() {
+        return isChallengeShowing() ? 0 : mDragHandleHeadroom;
+    }
+
     private boolean isInChallengeView(float x, float y) {
         if (mChallengeView == null) return false;
 
@@ -595,16 +604,16 @@ private boolean isInDragHandle(float x, float y) {
         if (mChallengeView == null) return false;
 
         return x >= mDragHandleEdgeSlop &&
-                y >= mChallengeView.getTop() - mDragHandleHeadroom &&
+                y >= mChallengeView.getTop() - getDragHandleHeadroom() &&
                 x < getWidth() - mDragHandleEdgeSlop &&
                 y < mChallengeView.getTop() + mDragHandleSize;
     }
 
-    private boolean crossedDragHandle(float x, float y, float lastY) {
+    private boolean crossedDragHandle(float x, float y, float initialY) {
         final int challengeTop = mChallengeView.getTop();
         return  x >= 0 &&
                 x < getWidth() &&
-                lastY < (challengeTop - mDragHandleHeadroom) &&
+                initialY < (challengeTop - getDragHandleHeadroom()) &&
                 y > challengeTop + mDragHandleSize;
     }
 
@@ -734,7 +743,7 @@ public void draw(Canvas c) {
             debugPaint.setColor(0x40FF00CC);
             // show the isInDragHandle() rect
             c.drawRect(mDragHandleEdgeSlop,
-                    mChallengeView.getTop() - mDragHandleHeadroom,
+                    mChallengeView.getTop() - getDragHandleHeadroom(),
                     getWidth() - mDragHandleEdgeSlop,
                     mChallengeView.getTop() + mDragHandleSize,
                     debugPaint);
@@ -790,8 +799,7 @@ private boolean moveChallengeTo(int bottom) {
             return false;
         }
 
-        final int bottomMargin = ((LayoutParams) mChallengeView.getLayoutParams()).bottomMargin;
-        final int layoutBottom = getHeight() - getPaddingBottom() - bottomMargin;
+        final int layoutBottom = getLayoutBottom();
         final int challengeHeight = mChallengeView.getHeight();
 
         bottom = Math.max(layoutBottom,
@@ -814,20 +822,32 @@ private boolean moveChallengeTo(int bottom) {
         return true;
     }
 
+    /**
+     * The bottom edge of this SlidingChallengeLayout's coordinate system; will coincide with
+     * the bottom edge of mChallengeView when the challenge is fully opened.
+     */
+    private int getLayoutBottom() {
+        final int bottomMargin = (mChallengeView == null)
+                ? 0
+                : ((LayoutParams) mChallengeView.getLayoutParams()).bottomMargin;
+        final int layoutBottom = getHeight() - getPaddingBottom() - bottomMargin;
+        return layoutBottom;
+    }
+
+    /**
+     * The bottom edge of mChallengeView; essentially, where the sliding challenge 'is'.
+     */
     private int getChallengeBottom() {
         if (mChallengeView == null) return 0;
 
         return mChallengeView.getBottom();
     }
 
+    /**
+     * The top edge of the challenge if it were fully opened.
+     */
     private int getChallengeOpenedTop() {
-        final int paddedBottom = getHeight() - getPaddingBottom();
-        if (mChallengeView == null) return paddedBottom;
-
-        final int bottomMargin = ((LayoutParams) mChallengeView.getLayoutParams()).bottomMargin;
-        final int layoutBottom = paddedBottom - bottomMargin;
-
-        return layoutBottom - mChallengeView.getHeight();
+        return getLayoutBottom() - ((mChallengeView == null) ? 0 : mChallengeView.getHeight());
     }
 
     private void moveChallengeBy(int delta) {