Allow the user to scroll a webpage by touching a textfield.

Fix for http://b/issue?id=1703971.  Because the browser overlays
the WebTextView over textfields, it intercepts all the touch
events, which was preventing the page from scrolling.  This
change passes the move events back to the WebView to make
the page scroll.

core/java/android/webkit/WebTextView.java

@@ -31,6 +31,7 @@ import android.text.Spannable;
 import android.text.TextPaint;
 import android.text.TextUtils;
 import android.text.method.MovementMethod;
+import android.text.method.Touch;
 import android.util.Log;
 import android.view.Gravity;
 import android.view.KeyCharacterMap;
@@ -71,6 +72,12 @@ import java.util.ArrayList;
     // need to send down the DOM events.
     private String          mPreChange;
     private Drawable        mBackground;
+    // Variables for keeping track of the touch down, to send to the WebView
+    // when a drag starts
+    private float           mDragStartX;
+    private float           mDragStartY;
+    private long            mDragStartTime;
+    private boolean         mDragSent;
     // Array to store the final character added in onTextChanged, so that its
     // KeyEvents may be determined.
     private char[]          mCharacter = new char[1];
@@ -365,6 +372,65 @@ import java.util.ArrayList;
         updateCachedTextfield();
     }
 
+    @Override
+    public boolean onTouchEvent(MotionEvent event) {
+        int initialScrollX = -1;
+        int initialScrollY = -1;
+        int selectionStart = -1;
+        int selectionEnd = -1;
+        int action = event.getAction();
+        if (action == MotionEvent.ACTION_MOVE) {
+            Spannable buffer = getText();
+            initialScrollX = Touch.getInitialScrollX(this, buffer);
+            initialScrollY = Touch.getInitialScrollY(this, buffer);
+            selectionStart = Selection.getSelectionStart(buffer);
+            selectionEnd = Selection.getSelectionEnd(buffer);
+        }
+        super.onTouchEvent(event);
+        switch (action) {
+        case MotionEvent.ACTION_DOWN:
+            // This event may be the start of a drag, so store it to pass to the
+            // WebView if it is.
+            mDragStartX = event.getX();
+            mDragStartY = event.getY();
+            mDragStartTime = event.getEventTime();
+            mDragSent = false;
+            break;
+        case MotionEvent.ACTION_MOVE:
+            if (mScrollX != initialScrollX
+                    || mScrollY != initialScrollY) {
+                // TextView scrolled, so return true.
+                // FIXME: Need to make the webkit text scroll to reflect this
+                return true;
+            }
+            if (Selection.getSelectionStart(getText()) != selectionStart
+                    || Selection.getSelectionEnd(getText()) != selectionEnd) {
+                // Selection changed, so return true
+                return true;
+            }
+            if (mWebView != null) {
+                // Only want to set the initial state once.
+                if (!mDragSent) {
+                    mWebView.initiateTextFieldDrag(mDragStartX, mDragStartY,
+                            mDragStartTime);
+                    mDragSent = true;
+                }
+                return mWebView.textFieldDrag(event);
+            }
+            return false;
+        case MotionEvent.ACTION_UP:
+        case MotionEvent.ACTION_CANCEL:
+            // Necessary for the WebView to reset its state
+            if (mWebView != null && mDragSent) {
+                mWebView.onTouchEvent(event);
+            }
+            break;
+        default:
+            break;
+        }
+        return true;
+    }
+
     @Override
     public boolean onTrackballEvent(MotionEvent event) {
         if (isPopupShowing()) {

core/java/android/webkit/WebView.java

@@ -4494,6 +4494,38 @@ public class WebView extends AbsoluteLayout
         nativeSelectBestAt(rect);
     }
 
+    /**
+     * Set our starting point and time for a drag from the WebTextView.
+     */
+    /*package*/ void initiateTextFieldDrag(float x, float y, long eventTime) {
+        if (!inEditingMode()) {
+            return;
+        }
+        mLastTouchX = x + (float) (mWebTextView.getLeft() - mScrollX);
+        mLastTouchY = y + (float) (mWebTextView.getTop() - mScrollY);
+        mLastTouchTime = eventTime;
+        if (!mScroller.isFinished()) {
+            mScroller.abortAnimation();
+            mPrivateHandler.removeMessages(RESUME_WEBCORE_UPDATE);
+        }
+        mSnapScrollMode = SNAP_NONE;
+        mVelocityTracker = VelocityTracker.obtain();
+        mTouchMode = TOUCH_DRAG_START_MODE;
+    }
+
+    /**
+     * Given a motion event from the WebTextView, set its location to our
+     * coordinates, and handle the event.
+     */
+    /*package*/ boolean textFieldDrag(MotionEvent event) {
+        if (!inEditingMode()) {
+            return false;
+        }
+        event.offsetLocation((float) (mWebTextView.getLeft() - mScrollX),
+                (float) (mWebTextView.getTop() - mScrollY));
+        return onTouchEvent(event);
+    }
+
     /*package*/ void shortPressOnTextField() {
         if (inEditingMode()) {
             View v = mWebTextView;