Revert "Revert "support scroll backward to minus one screen via voice/switch access""

This reverts commit 3ad4ace203c73aebac98010812703dbb6879d55d.

Reason for revert: roll forward and bugfixes

Change-Id: Icd56cdeddb3baf9819700cc567c04af0905825ef

2 files changed, 22 insertions, 7 deletions

diff --git a/src/com/android/launcher3/PagedView.java b/src/com/android/launcher3/PagedView.java
index a99c7c28f..5c790f379 100644
--- a/src/com/android/launcher3/PagedView.java
+++ b/src/com/android/launcher3/PagedView.java
@@ -1548,7 +1548,7 @@ public abstract class PagedView<T extends View & PageIndicator> extends ViewGrou
             snapToPage(getNextPage() - 1);
             return true;
         }
-        return false;
+        return onOverscroll(-getMeasuredWidth());
     }
 
     public boolean scrollRight() {
@@ -1556,7 +1556,15 @@ public abstract class PagedView<T extends View & PageIndicator> extends ViewGrou
             snapToPage(getNextPage() + 1);
             return true;
         }
-        return false;
+        return onOverscroll(getMeasuredWidth());
+    }
+
+    protected boolean onOverscroll(int amount) {
+        if (!mAllowOverScroll) return false;
+        onScrollInteractionBegin();
+        overScroll(amount);
+        onScrollInteractionEnd();
+        return true;
     }
 
     @Override
@@ -1576,8 +1584,9 @@ public abstract class PagedView<T extends View & PageIndicator> extends ViewGrou
     public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {
         super.onInitializeAccessibilityNodeInfo(info);
         final boolean pagesFlipped = isPageOrderFlipped();
-        info.setScrollable(getPageCount() > 1);
-        if (getCurrentPage() < getPageCount() - 1) {
+        int offset = (mAllowOverScroll ? 0 : 1);
+        info.setScrollable(getPageCount() > offset);
+        if (getCurrentPage() < getPageCount() - offset) {
             info.addAction(pagesFlipped ?
                 AccessibilityNodeInfo.AccessibilityAction.ACTION_SCROLL_BACKWARD
                 : AccessibilityNodeInfo.AccessibilityAction.ACTION_SCROLL_FORWARD);
@@ -1585,7 +1594,7 @@ public abstract class PagedView<T extends View & PageIndicator> extends ViewGrou
                 AccessibilityNodeInfo.AccessibilityAction.ACTION_PAGE_LEFT
                 : AccessibilityNodeInfo.AccessibilityAction.ACTION_PAGE_RIGHT);
         }
-        if (getCurrentPage() > 0) {
+        if (getCurrentPage() >= offset) {
             info.addAction(pagesFlipped ?
                 AccessibilityNodeInfo.AccessibilityAction.ACTION_SCROLL_FORWARD
                 : AccessibilityNodeInfo.AccessibilityAction.ACTION_SCROLL_BACKWARD);
@@ -1593,7 +1602,6 @@ public abstract class PagedView<T extends View & PageIndicator> extends ViewGrou
                 AccessibilityNodeInfo.AccessibilityAction.ACTION_PAGE_RIGHT
                 : AccessibilityNodeInfo.AccessibilityAction.ACTION_PAGE_LEFT);
         }
-
         // Accessibility-wise, PagedView doesn't support long click, so disabling it.
         // Besides disabling the accessibility long-click, this also prevents this view from getting
         // accessibility focus.
@@ -1612,7 +1620,7 @@ public abstract class PagedView<T extends View & PageIndicator> extends ViewGrou
     @Override
     public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
         super.onInitializeAccessibilityEvent(event);
-        event.setScrollable(getPageCount() > 1);
+        event.setScrollable(mAllowOverScroll || getPageCount() > 1);
     }
 
     @Override
diff --git a/src/com/android/launcher3/Workspace.java b/src/com/android/launcher3/Workspace.java
index f9201d04c..1cb15db98 100644
--- a/src/com/android/launcher3/Workspace.java
+++ b/src/com/android/launcher3/Workspace.java
@@ -1035,6 +1035,13 @@ public class Workspace extends PagedView<WorkspacePageIndicator>
     }
 
     @Override
+    protected boolean onOverscroll(int amount) {
+        // Enforce overscroll on -1 direction
+        if ((amount > 0 && !mIsRtl) || (amount < 0 && mIsRtl)) return false;
+        return super.onOverscroll(amount);
+    }
+
+    @Override
     protected boolean shouldFlingForVelocity(int velocityX) {
         // When the overlay is moving, the fling or settle transition is controlled by the overlay.
         return Float.compare(Math.abs(mOverlayTranslation), 0) == 0 &&