Fix invisible scroll thumb blocks clicks.

The current issue is that Views that have either the horizontal or
vertical scroll bars enabled will intercept mouse interactions that
entire the region where the scrolling thumb would be even if the View
cannot actually scroll because it's content isn't larger than it.

This is fixed by only intercepting mouse interactions in the scroll
thumb region if there is something to scroll.

Bug: 110375792
Test: None yet

Change-Id: Ib638b4ac88375f55bc80ba2a66d945a16ecd6d22

diff --git a/core/java/android/view/View.java b/core/java/android/view/View.java
index 0e5527d..546ea87 100644 (file)
--- a/core/java/android/view/View.java
+++ b/core/java/android/view/View.java
@@ -6119,14 +6119,18 @@ public class View implements Drawable.Callback, KeyEvent.Callback,
         }
         x += getScrollX();
         y += getScrollY();
-        if (isVerticalScrollBarEnabled() && !isVerticalScrollBarHidden()) {
+        final boolean canScrollVertically =
+                computeVerticalScrollRange() > computeVerticalScrollExtent();
+        if (isVerticalScrollBarEnabled() && !isVerticalScrollBarHidden() && canScrollVertically) {
             final Rect touchBounds = mScrollCache.mScrollBarTouchBounds;
             getVerticalScrollBarBounds(null, touchBounds);
             if (touchBounds.contains((int) x, (int) y)) {
                 return true;
             }
         }
-        if (isHorizontalScrollBarEnabled()) {
+        final boolean canScrollHorizontally =
+                computeHorizontalScrollRange() > computeHorizontalScrollExtent();
+        if (isHorizontalScrollBarEnabled() && canScrollHorizontally) {
             final Rect touchBounds = mScrollCache.mScrollBarTouchBounds;
             getHorizontalScrollBarBounds(null, touchBounds);
             if (touchBounds.contains((int) x, (int) y)) {
@@ -6141,18 +6145,18 @@ public class View implements Drawable.Callback, KeyEvent.Callback,
     }
 
     private boolean isOnVerticalScrollbarThumb(float x, float y) {
-        if (mScrollCache == null) {
+        if (mScrollCache == null || !isVerticalScrollBarEnabled() || isVerticalScrollBarHidden()) {
             return false;
         }
-        if (isVerticalScrollBarEnabled() && !isVerticalScrollBarHidden()) {
+        final int range = computeVerticalScrollRange();
+        final int extent = computeVerticalScrollExtent();
+        if (range > extent) {
             x += getScrollX();
             y += getScrollY();
             final Rect bounds = mScrollCache.mScrollBarBounds;
             final Rect touchBounds = mScrollCache.mScrollBarTouchBounds;
             getVerticalScrollBarBounds(bounds, touchBounds);
-            final int range = computeVerticalScrollRange();
             final int offset = computeVerticalScrollOffset();
-            final int extent = computeVerticalScrollExtent();
             final int thumbLength = ScrollBarUtils.getThumbLength(bounds.height(), bounds.width(),
                     extent, range);
             final int thumbOffset = ScrollBarUtils.getThumbOffset(bounds.height(), thumbLength,
@@ -6168,18 +6172,19 @@ public class View implements Drawable.Callback, KeyEvent.Callback,
     }
 
     private boolean isOnHorizontalScrollbarThumb(float x, float y) {
-        if (mScrollCache == null) {
+        if (mScrollCache == null || !isHorizontalScrollBarEnabled()) {
             return false;
         }
-        if (isHorizontalScrollBarEnabled()) {
+        final int range = computeHorizontalScrollRange();
+        final int extent = computeHorizontalScrollExtent();
+        if (range > extent) {
             x += getScrollX();
             y += getScrollY();
             final Rect bounds = mScrollCache.mScrollBarBounds;
             final Rect touchBounds = mScrollCache.mScrollBarTouchBounds;
             getHorizontalScrollBarBounds(bounds, touchBounds);
-            final int range = computeHorizontalScrollRange();
             final int offset = computeHorizontalScrollOffset();
-            final int extent = computeHorizontalScrollExtent();
+
             final int thumbLength = ScrollBarUtils.getThumbLength(bounds.width(), bounds.height(),
                     extent, range);
             final int thumbOffset = ScrollBarUtils.getThumbOffset(bounds.width(), thumbLength,