Reporting range of visible tasks

Also fixes task position being incorrectly reported specifically for
swipe events due to using stale getCurrentPage().

Bug: 72222505
Test: Manual
Change-Id: Ic79b67f8a6ffbfabc397b411b14afc309405197e
diff --git a/src/com/android/launcher3/PagedView.java b/src/com/android/launcher3/PagedView.java
index 5cc2e8f..62b581f 100644
--- a/src/com/android/launcher3/PagedView.java
+++ b/src/com/android/launcher3/PagedView.java
@@ -152,6 +152,8 @@
     // Similar to the platform implementation of isLayoutValid();
     protected boolean mIsLayoutValid;
 
+    private int[] mTmpIntPair = new int[2];
+
     public PagedView(Context context) {
         this(context, null);
     }
@@ -1600,4 +1602,33 @@
 
         boolean shouldIncludeView(View view);
     }
+
+    public int[] getVisibleChildrenRange() {
+        float visibleLeft = 0;
+        float visibleRight = visibleLeft + getMeasuredWidth();
+        float scaleX = getScaleX();
+        if (scaleX < 1 && scaleX > 0) {
+            float mid = getMeasuredWidth() / 2;
+            visibleLeft = mid - ((mid - visibleLeft) / scaleX);
+            visibleRight = mid + ((visibleRight - mid) / scaleX);
+        }
+
+        int leftChild = -1;
+        int rightChild = -1;
+        final int childCount = getChildCount();
+        for (int i = 0; i < childCount; i++) {
+            final View child = getPageAt(i);
+
+            float left = child.getLeft() + child.getTranslationX() - getScrollX();
+            if (left <= visibleRight && (left + child.getMeasuredWidth()) >= visibleLeft) {
+                if (leftChild == -1) {
+                    leftChild = i;
+                }
+                rightChild = i;
+            }
+        }
+        mTmpIntPair[0] = leftChild;
+        mTmpIntPair[1] = rightChild;
+        return mTmpIntPair;
+    }
 }