From d5af944f414588b4f964d176ebc9193f082daf7c Mon Sep 17 00:00:00 2001
From: Pinyao Ting <pinyaoting@google.com>
Date: Fri, 13 Sep 2019 15:35:48 -0700
Subject: [PATCH] support scroll backward to minus one screen via voice/switch
 access

Bug: 140406263
Test: Manual
Change-Id: I604b12f8ba8706cbabc28acafd6c151166832f22
---
 src/com/android/launcher3/PagedView.java | 22 +++++++++++++++-------
 src/com/android/launcher3/Workspace.java |  7 +++++++
 2 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/src/com/android/launcher3/PagedView.java b/src/com/android/launcher3/PagedView.java
index f9a326f4e2..4f5b1cd673 100644
--- a/src/com/android/launcher3/PagedView.java
+++ b/src/com/android/launcher3/PagedView.java
@@ -1543,7 +1543,7 @@ public abstract class PagedView<T extends View & PageIndicator> extends ViewGrou
             snapToPage(getNextPage() - 1);
             return true;
         }
-        return false;
+        return onOverscroll(-getMeasuredWidth());
     }
 
     public boolean scrollRight() {
@@ -1551,7 +1551,15 @@ 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
@@ -1571,8 +1579,9 @@ 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);
@@ -1580,7 +1589,7 @@ 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);
@@ -1588,7 +1597,6 @@ 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.
@@ -1607,7 +1615,7 @@ 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 f9201d04c7..1cb15db98e 100644
--- a/src/com/android/launcher3/Workspace.java
+++ b/src/com/android/launcher3/Workspace.java
@@ -1034,6 +1034,13 @@ 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.