Re-add double tap to the Browser. It only works if WebView uses wide viewport.

It is also controlled by ENABLE_DOUBLETAP_ZOOM flag. Currently the default
is on.

Double tap will toggle between current zoom level and all the way zoom out,
in another word, zoom overview mode.

While in zoom overview mode, don't display zoom control while panning. You
can click to follow the link. If clicking on a text input box, it should
bring it back to the normal mode so that it will be easy to edit text.

While in zoom overview mode, the page is zoomed to fit the width in the
view. While the text paragraph are wrapped to the matching normal mode scale.
So there is no reflow when we switching between two modes.

2 files changed, 203 insertions, 25 deletions

diff --git a/core/java/android/webkit/WebView.java b/core/java/android/webkit/WebView.java
index 19df87feb7a9..358fc9ec2bdf 100644
--- a/core/java/android/webkit/WebView.java
+++ b/core/java/android/webkit/WebView.java
@@ -351,6 +351,9 @@ public class WebView extends AbsoluteLayout
     VelocityTracker mVelocityTracker;
     private int mMaximumFling;
 
+    // use this flag to control whether enabling the new double tap zoom
+    static final boolean ENABLE_DOUBLETAP_ZOOM = true;
+
     /**
      * Touch mode
      */
@@ -370,6 +373,7 @@ public class WebView extends AbsoluteLayout
     private static final int SCROLL_ZOOM_OUT = 11;
     private static final int LAST_SCROLL_ZOOM = 11;
     // end of touch mode values specific to scale+scroll
+    private static final int TOUCH_DOUBLE_TAP_MODE = 12;
 
     // Whether to forward the touch events to WebCore
     private boolean mForwardTouchEvents = false;
@@ -394,6 +398,8 @@ public class WebView extends AbsoluteLayout
      */
     // pre-computed square of ViewConfiguration.getScaledTouchSlop()
     private int mTouchSlopSquare;
+    // pre-computed square of ViewConfiguration.getScaledDoubleTapSlop()
+    private int mDoubleTapSlopSquare;
     // pre-computed density adjusted navigation slop
     private int mNavSlop;
     // This should be ViewConfiguration.getTapTimeout()
@@ -450,6 +456,7 @@ public class WebView extends AbsoluteLayout
     private static final int NEVER_REMEMBER_PASSWORD    = 2;
     private static final int SWITCH_TO_SHORTPRESS       = 3;
     private static final int SWITCH_TO_LONGPRESS        = 4;
+    private static final int RELEASE_SINGLE_TAP         = 5;
     private static final int REQUEST_FORM_DATA          = 6;
     private static final int SWITCH_TO_CLICK            = 7;
     private static final int RESUME_WEBCORE_UPDATE      = 8;
@@ -482,7 +489,7 @@ public class WebView extends AbsoluteLayout
         "NEVER_REMEMBER_PASSWORD", //        = 2;
         "SWITCH_TO_SHORTPRESS", //           = 3;
         "SWITCH_TO_LONGPRESS", //            = 4;
-        "5",
+        "RELEASE_SINGLE_TAP", //             = 5;
         "REQUEST_FORM_DATA", //              = 6;
         "SWITCH_TO_CLICK", //                = 7;
         "RESUME_WEBCORE_UPDATE", //          = 8;
@@ -521,6 +528,16 @@ public class WebView extends AbsoluteLayout
     // initial scale in percent. 0 means using default.
     private int mInitialScale = 0;
 
+    // while in the zoom overview mode, the page's width is fully fit to the
+    // current window. The page is alive, in another words, you can click to
+    // follow the links. Double tap will toggle between zoom overview mode and
+    // the last zoom scale.
+    boolean mInZoomOverview = false;
+    // ideally mZoomOverviewWidth should be mContentWidth. But sites like espn,
+    // engadget always have wider mContentWidth no matter what viewport size is.
+    int mZoomOverviewWidth = 0;
+    float mLastScale;
+
     // default scale. Depending on the display density.
     static int DEFAULT_SCALE_PERCENT;
     private float mDefaultScale;
@@ -762,9 +779,11 @@ public class WebView extends AbsoluteLayout
         setLongClickable(true);
 
         final ViewConfiguration configuration = ViewConfiguration.get(getContext());
-        final int slop = configuration.getScaledTouchSlop();
+        int slop = configuration.getScaledTouchSlop();
         mTouchSlopSquare = slop * slop;
         mMinLockSnapReverseDistance = slop;
+        slop = configuration.getScaledDoubleTapSlop();
+        mDoubleTapSlopSquare = slop * slop;
         final float density = getContext().getResources().getDisplayMetrics().density;
         // use one line height, 16 based on our current default font, for how
         // far we allow a touch be away from the edge of a link
@@ -1124,6 +1143,9 @@ public class WebView extends AbsoluteLayout
             b.putInt("scrollX", mScrollX);
             b.putInt("scrollY", mScrollY);
             b.putFloat("scale", mActualScale);
+            if (mInZoomOverview) {
+                b.putFloat("lastScale", mLastScale);
+            }
             return true;
         }
         return false;
@@ -1168,6 +1190,13 @@ public class WebView extends AbsoluteLayout
                 // onSizeChanged() is called, the rest will be set
                 // correctly
                 mActualScale = scale;
+                float lastScale = b.getFloat("lastScale", -1.0f);
+                if (lastScale > 0) {
+                    mInZoomOverview = true;
+                    mLastScale = lastScale;
+                } else {
+                    mInZoomOverview = false;
+                }
                 invalidate();
                 return true;
             }
@@ -3060,6 +3089,11 @@ public class WebView extends AbsoluteLayout
                 float y = mLastTouchY + (float) (mScrollY - lp.y);
                 mWebTextView.fakeTouchEvent(x, y);
             }
+            if (mInZoomOverview) {
+                // if in zoom overview mode, call doDoubleTap() to bring it back
+                // to normal mode so that user can enter text.
+                doDoubleTap();
+            }
         }
         else { // used by plugins
             imm.showSoftInput(this, 0);
@@ -3634,7 +3668,9 @@ public class WebView extends AbsoluteLayout
         // update mMinZoomScale if the minimum zoom scale is not fixed
         if (!mMinZoomScaleFixed) {
             mMinZoomScale = (float) getViewWidth()
-                    / Math.max(ZOOM_OUT_WIDTH, mContentWidth);
+                    / Math.max(ZOOM_OUT_WIDTH, mDrawHistory ? mHistoryPicture
+                            .getWidth() : (mZoomOverviewWidth > 0 ?
+                                    mZoomOverviewWidth : mContentWidth));
         }
 
         // we always force, in case our height changed, in which case we still
@@ -3755,6 +3791,15 @@ public class WebView extends AbsoluteLayout
                     nativeMoveSelection(viewToContent(mSelectX)
                             , viewToContent(mSelectY), false);
                     mTouchSelection = mExtendSelection = true;
+                } else if (mPrivateHandler.hasMessages(RELEASE_SINGLE_TAP)) {
+                    mPrivateHandler.removeMessages(RELEASE_SINGLE_TAP);
+                    if (deltaX * deltaX + deltaY * deltaY < mDoubleTapSlopSquare) {
+                        mTouchMode = TOUCH_DOUBLE_TAP_MODE;
+                    } else {
+                        // commit the short press action for the previous tap
+                        doShortPress();
+                        // continue, mTouchMode should be still TOUCH_INIT_MODE
+                    }
                 } else {
                     mTouchMode = TOUCH_INIT_MODE;
                     mPreventDrag = mForwardTouchEvents;
@@ -3764,7 +3809,8 @@ public class WebView extends AbsoluteLayout
                     }
                 }
                 // Trigger the link
-                if (mTouchMode == TOUCH_INIT_MODE) {
+                if (mTouchMode == TOUCH_INIT_MODE
+                        || mTouchMode == TOUCH_DOUBLE_TAP_MODE) {
                     mPrivateHandler.sendMessageDelayed(mPrivateHandler
                             .obtainMessage(SWITCH_TO_SHORTPRESS), TAP_TIMEOUT);
                 }
@@ -3810,7 +3856,8 @@ public class WebView extends AbsoluteLayout
                     if (mTouchMode == TOUCH_SHORTPRESS_MODE
                             || mTouchMode == TOUCH_SHORTPRESS_START_MODE) {
                         mPrivateHandler.removeMessages(SWITCH_TO_LONGPRESS);
-                    } else if (mTouchMode == TOUCH_INIT_MODE) {
+                    } else if (mTouchMode == TOUCH_INIT_MODE
+                            || mTouchMode == TOUCH_DOUBLE_TAP_MODE) {
                         mPrivateHandler.removeMessages(SWITCH_TO_SHORTPRESS);
                     }
 
@@ -3836,7 +3883,7 @@ public class WebView extends AbsoluteLayout
                                 .sendMessage(EventHub.SET_SNAP_ANCHOR, 0, 0);
                     }
                     WebSettings settings = getSettings();
-                    if (settings.supportZoom()
+                    if (settings.supportZoom() && !mInZoomOverview
                             && settings.getBuiltInZoomControls()
                             && !mZoomButtonsController.isVisible()
                             && (canZoomScrollOut() ||
@@ -3905,7 +3952,7 @@ public class WebView extends AbsoluteLayout
                     mUserScroll = true;
                 }
 
-                if (!getSettings().getBuiltInZoomControls()) {
+                if (!getSettings().getBuiltInZoomControls() && !mInZoomOverview) {
                     boolean showPlusMinus = mMinZoomScale < mMaxZoomScale;
                     boolean showMagnify = canZoomScrollOut();
                     if (mZoomControls != null && (showPlusMinus || showMagnify)) {
@@ -3929,7 +3976,22 @@ public class WebView extends AbsoluteLayout
             case MotionEvent.ACTION_UP: {
                 mLastTouchUpTime = eventTime;
                 switch (mTouchMode) {
+                    case TOUCH_DOUBLE_TAP_MODE: // double tap
+                        mPrivateHandler.removeMessages(SWITCH_TO_SHORTPRESS);
+                        doDoubleTap();
+                        break;
                     case TOUCH_INIT_MODE: // tap
+                        if (ENABLE_DOUBLETAP_ZOOM) {
+                            mPrivateHandler.removeMessages(SWITCH_TO_SHORTPRESS);
+                            if (!mPreventDrag) {
+                                mPrivateHandler.sendMessageDelayed(
+                                        mPrivateHandler.obtainMessage(
+                                        RELEASE_SINGLE_TAP),
+                                        ViewConfiguration.getDoubleTapTimeout());
+                            }
+                            break;
+                        }
+                        // fall through
                     case TOUCH_SHORTPRESS_START_MODE:
                     case TOUCH_SHORTPRESS_MODE:
                         mPrivateHandler.removeMessages(SWITCH_TO_SHORTPRESS);
@@ -4365,6 +4427,9 @@ public class WebView extends AbsoluteLayout
             mInvInitialZoomScale = 1.0f / oldScale;
             mInvFinalZoomScale = 1.0f / mActualScale;
             mZoomScale = mActualScale;
+            if (!mInZoomOverview) {
+                mLastScale = scale;
+            }
             invalidate();
             return true;
         } else {
@@ -4470,6 +4535,9 @@ public class WebView extends AbsoluteLayout
     public boolean zoomIn() {
         // TODO: alternatively we can disallow this during draw history mode
         switchOutDrawHistory();
+        // Center zooming to the center of the screen.
+        mZoomCenterX = getViewWidth() * .5f;
+        mZoomCenterY = getViewHeight() * .5f;
         return zoomWithPreview(mActualScale * 1.25f);
     }
 
@@ -4480,6 +4548,9 @@ public class WebView extends AbsoluteLayout
     public boolean zoomOut() {
         // TODO: alternatively we can disallow this during draw history mode
         switchOutDrawHistory();
+        // Center zooming to the center of the screen.
+        mZoomCenterX = getViewWidth() * .5f;
+        mZoomCenterY = getViewHeight() * .5f;
         return zoomWithPreview(mActualScale * 0.8f);
     }
 
@@ -4571,6 +4642,50 @@ public class WebView extends AbsoluteLayout
         }
     }
 
+    private void doDoubleTap() {
+        if (mWebViewCore.getSettings().getUseWideViewPort() == false) {
+            return;
+        }
+        mZoomCenterX = mLastTouchX;
+        mZoomCenterY = mLastTouchY;
+        mInZoomOverview = !mInZoomOverview;
+        if (mInZoomOverview) {
+            float newScale = (float) getViewWidth()
+                    / (mZoomOverviewWidth > 0 ? mZoomOverviewWidth
+                            : mContentWidth);
+            if (Math.abs(newScale - mActualScale) < 0.01) {
+                mInZoomOverview = !mInZoomOverview;
+                // as it is already full screen, do nothing.
+                return;
+            }
+            if (getSettings().getBuiltInZoomControls()) {
+                if (mZoomButtonsController.isVisible()) {
+                    mZoomButtonsController.setVisible(false);
+                }
+            } else {
+                if (mZoomControlRunnable != null) {
+                    mPrivateHandler.removeCallbacks(mZoomControlRunnable);
+                }
+                if (mZoomControls != null) {
+                    mZoomControls.hide();
+                }
+            }
+            zoomWithPreview(newScale);
+        } else {
+            // mLastTouchX and mLastTouchY are the point in the current viewport
+            int contentX = viewToContent((int) mLastTouchX + mScrollX);
+            int contentY = viewToContent((int) mLastTouchY + mScrollY);
+            int left = nativeGetBlockLeftEdge(contentX, contentY);
+            if (left != NO_LEFTEDGE) {
+                // add a 5pt padding to the left edge. Re-calculate the zoom
+                // center so that the new scroll x will be on the left edge.
+                mZoomCenterX = left < 5 ? 0 : (left - 5) * mLastScale
+                        * mActualScale / (mLastScale - mActualScale);
+            }
+            zoomWithPreview(mLastScale);
+        }
+    }
+
     // Called by JNI to handle a touch on a node representing an email address,
     // address, or phone number
     private void overrideLoading(String url) {
@@ -4791,6 +4906,8 @@ public class WebView extends AbsoluteLayout
                     if (mTouchMode == TOUCH_INIT_MODE) {
                         mTouchMode = TOUCH_SHORTPRESS_START_MODE;
                         updateSelection();
+                    } else if (mTouchMode == TOUCH_DOUBLE_TAP_MODE) {
+                        mTouchMode = TOUCH_DONE_MODE;
                     }
                     break;
                 }
@@ -4802,6 +4919,13 @@ public class WebView extends AbsoluteLayout
                     }
                     break;
                 }
+                case RELEASE_SINGLE_TAP: {
+                    if (!mPreventDrag) {
+                        mTouchMode = TOUCH_DONE_MODE;
+                        doShortPress();
+                    }
+                    break;
+                }
                 case SWITCH_TO_CLICK:
                     // The user clicked with the trackball, and did not click a
                     // second time, so perform the action of a trackball single
@@ -4854,6 +4978,7 @@ public class WebView extends AbsoluteLayout
                     break;
                 case NEW_PICTURE_MSG_ID:
                     // called for new content
+                    final int viewWidth = getViewWidth();
                     final WebViewCore.DrawData draw =
                             (WebViewCore.DrawData) msg.obj;
                     final Point viewSize = draw.mViewPoint;
@@ -4861,16 +4986,12 @@ public class WebView extends AbsoluteLayout
                         // use the same logic in sendViewSizeZoom() to make sure
                         // the mZoomScale has matched the viewSize so that we
                         // can clear mZoomScale
-                        if (Math.round(getViewWidth() / mZoomScale) == viewSize.x) {
+                        if (Math.round(viewWidth / mZoomScale) == viewSize.x) {
                             mZoomScale = 0;
                             mWebViewCore.sendMessage(EventHub.SET_SNAP_ANCHOR,
                                     0, 0);
                         }
                     }
-                    if (!mMinZoomScaleFixed) {
-                        mMinZoomScale = (float) getViewWidth()
-                                / Math.max(ZOOM_OUT_WIDTH, draw.mWidthHeight.x);
-                    }
                     // We update the layout (i.e. request a layout from the
                     // view system) if the last view size that we sent to
                     // WebCore matches the view size of the picture we just
@@ -4888,6 +5009,25 @@ public class WebView extends AbsoluteLayout
                     if (mPictureListener != null) {
                         mPictureListener.onNewPicture(WebView.this, capturePicture());
                     }
+                    if (mWebViewCore.getSettings().getUseWideViewPort()) {
+                        mZoomOverviewWidth = Math.max(draw.mMinPrefWidth,
+                                draw.mViewPoint.x);
+                    }
+                    if (!mMinZoomScaleFixed) {
+                        mMinZoomScale = (float) viewWidth
+                                / Math.max(ZOOM_OUT_WIDTH,
+                                mZoomOverviewWidth > 0 ? mZoomOverviewWidth
+                                        : mContentWidth);
+                    }
+                    if (!mDrawHistory && mInZoomOverview) {
+                        // fit the content width to the current view. Ignore
+                        // the rounding error case.
+                        if (Math.abs((viewWidth * mInvActualScale)
+                                - mZoomOverviewWidth) > 1) {
+                            zoomWithPreview((float) viewWidth
+                                    / mZoomOverviewWidth);
+                        }
+                    }
                     break;
                 case WEBCORE_INITIALIZED_MSG_ID:
                     // nativeCreate sets mNativeClass to a non-zero value
@@ -4916,7 +5056,7 @@ public class WebView extends AbsoluteLayout
                         }
                     }
                     break;
-                case DID_FIRST_LAYOUT_MSG_ID:
+                case DID_FIRST_LAYOUT_MSG_ID: {
                     if (mNativeClass == 0) {
                         break;
                     }
@@ -4943,15 +5083,17 @@ public class WebView extends AbsoluteLayout
                     if (width == 0) {
                         break;
                     }
+                    final WebSettings settings = mWebViewCore.getSettings();
                     int initialScale = msg.arg1;
                     int viewportWidth = msg.arg2;
                     // start a new page with DEFAULT_SCALE zoom scale.
                     float scale = mDefaultScale;
+                    mInZoomOverview = false;
                     if (mInitialScale > 0) {
                         scale = mInitialScale / 100.0f;
                     } else  {
-                        if (initialScale < 0) break;
-                        if (mWebViewCore.getSettings().getUseWideViewPort()) {
+                        if (initialScale == -1) break;
+                        if (settings.getUseWideViewPort()) {
                             // force viewSizeChanged by setting mLastWidthSent
                             // to 0
                             mLastWidthSent = 0;
@@ -4961,11 +5103,21 @@ public class WebView extends AbsoluteLayout
                             // than the view width, zoom in to fill the view
                             if (viewportWidth > 0 && viewportWidth < width) {
                                 scale = (float) width / viewportWidth;
+                            } else {
+                                if (settings.getUseWideViewPort()) {
+                                    mInZoomOverview = ENABLE_DOUBLETAP_ZOOM;
+                                }
                             }
+                        } else if (initialScale < 0) {
+                            // this should only happen when
+                            // ENABLE_DOUBLETAP_ZOOM is true
+                            mInZoomOverview = true;
+                            scale = -initialScale / 100.0f;
                         } else {
                             scale = initialScale / 100.0f;
                         }
                     }
+                    mLastScale = scale;
                     setNewZoomScale(scale, false);
                     // As we are on a new page, remove the WebTextView.  This
                     // is necessary for page loads driven by webkit, and in
@@ -4973,6 +5125,7 @@ public class WebView extends AbsoluteLayout
                     // the WebTextView was visible.
                     clearTextEntry();
                     break;
+                }
                 case MOVE_OUT_OF_PLUGIN:
                     if (nativePluginEatsNavKey()) {
                         navHandledKey(msg.arg1, 1, false, 0, true);
@@ -5542,4 +5695,7 @@ public class WebView extends AbsoluteLayout
     private native void     nativeUpdateCachedTextfield(String updatedText,
             int generation);
     private native void     nativeUpdatePluginReceivesEvents();
+    // return NO_LEFTEDGE means failure.
+    private static final int NO_LEFTEDGE = -1;
+    private native int      nativeGetBlockLeftEdge(int x, int y);
 }
diff --git a/core/java/android/webkit/WebViewCore.java b/core/java/android/webkit/WebViewCore.java
index 4993fcf05741..36c5f0c87c31 100644
--- a/core/java/android/webkit/WebViewCore.java
+++ b/core/java/android/webkit/WebViewCore.java
@@ -96,7 +96,8 @@ final class WebViewCore {
 
     private boolean mViewportUserScalable = true;
 
-    private int mRestoredScale = WebView.DEFAULT_SCALE_PERCENT;
+    private int mRestoredScale = 0;
+    private int mRestoredScreenWidthScale = 0;
     private int mRestoredX = 0;
     private int mRestoredY = 0;
 
@@ -1340,9 +1341,8 @@ final class WebViewCore {
             Log.w(LOGTAG, "skip viewSizeChanged as w is 0");
             return;
         }
-        if (mSettings.getUseWideViewPort()
-                && (w < mViewportWidth || mViewportWidth == -1)) {
-            int width = mViewportWidth;
+        if (mSettings.getUseWideViewPort()) {
+            int width;
             if (mViewportWidth == -1) {
                 if (mSettings.getLayoutAlgorithm() ==
                         WebSettings.LayoutAlgorithm.NORMAL) {
@@ -1362,9 +1362,15 @@ final class WebViewCore {
                      */
                     width = Math.max(w, nativeGetContentMinPrefWidth());
                 }
+            } else {
+                width = Math.max(w, mViewportWidth);
             }
-            nativeSetSize(width, Math.round((float) width * h / w), w, scale,
-                    w, h);
+            // while in zoom overview mode, the text are wrapped to the screen
+            // width matching mWebView.mLastScale. So that we don't trigger
+            // re-flow while toggling between overview mode and normal mode.
+            nativeSetSize(width, Math.round((float) width * h / w),
+                    Math.round(mWebView.mInZoomOverview ? w * scale
+                            / mWebView.mLastScale : w), scale, w, h);
         } else {
             nativeSetSize(w, h, w, scale, w, h);
         }
@@ -1409,6 +1415,7 @@ final class WebViewCore {
         public Region mInvalRegion;
         public Point mViewPoint;
         public Point mWidthHeight;
+        public int mMinPrefWidth;
     }
 
     private void webkitDraw() {
@@ -1424,6 +1431,9 @@ final class WebViewCore {
             // Send the native view size that was used during the most recent
             // layout.
             draw.mViewPoint = new Point(mCurrentViewWidth, mCurrentViewHeight);
+            if (WebView.ENABLE_DOUBLETAP_ZOOM && mSettings.getUseWideViewPort()) {
+                draw.mMinPrefWidth = nativeGetContentMinPrefWidth();
+            }
             if (DebugFlags.WEB_VIEW_CORE) Log.v(LOGTAG, "webkitDraw NEW_PICTURE_MSG_ID");
             Message.obtain(mWebView.mPrivateHandler,
                     WebView.NEW_PICTURE_MSG_ID, draw).sendToTarget();
@@ -1734,9 +1744,10 @@ final class WebViewCore {
 
             if (mRestoredScale > 0) {
                 Message.obtain(mWebView.mPrivateHandler,
-                        WebView.DID_FIRST_LAYOUT_MSG_ID, mRestoredScale, 0,
+                        WebView.DID_FIRST_LAYOUT_MSG_ID,
+                        mRestoredScreenWidthScale > 0 ?
+                        -mRestoredScreenWidthScale : mRestoredScale, 0,
                         scaleLimit).sendToTarget();
-                mRestoredScale = 0;
             } else {
                 // if standardLoad is true, use mViewportInitialScale, otherwise
                 // pass -1 to the WebView to indicate no change of the scale.
@@ -1764,8 +1775,8 @@ final class WebViewCore {
                 }
             }
 
-            // reset restored offset
-            mRestoredX = mRestoredY = 0;
+            // reset restored offset, scale
+            mRestoredX = mRestoredY = mRestoredScale = mRestoredScreenWidthScale = 0;
         }
     }
 
@@ -1777,6 +1788,17 @@ final class WebViewCore {
     }
 
     // called by JNI
+    private void restoreScreenWidthScale(int scale) {
+        if (!WebView.ENABLE_DOUBLETAP_ZOOM || !mSettings.getUseWideViewPort()) {
+            return;
+        }
+
+        if (mBrowserFrame.firstLayoutDone() == false) {
+            mRestoredScreenWidthScale = scale;
+        }
+    }
+
+    // called by JNI
     private void needTouchEvents(boolean need) {
         if (mWebView != null) {
             Message.obtain(mWebView.mPrivateHandler,